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Biochar Application for the remediation of salt-affected soils: Challenges and Opportunities
Abstract
Soil salinization and sodification are two commonly occurring major threats to soil productivity in arable croplands. Salt-affected soils are found in >100 countries, and their distribution is extensive and widespread in arid and semi-arid regions of the world. In order to meet the challenges of global food security, it is imperative to bring barren salt-affected soils under cultivation. Various inorganic and organic amendments are used to reclaim the salt-affected lands. The selection of a sustainable ameliorant is largely determined by the site-specific geographical and soil physicochemical parameters. Recently, biochar (solid carbonaceous residue, produced under oxygen-free or oxygen-limited conditions at temperatures ranging from 300 to 1000°C) has attracted considerable attention as a soil amendment. An emerging pool of knowledge shows that biochar addition is effective in improving physical, chemical and biological properties of salt-affected soils. However, some studies have also found an increase in soil salinity and sodicity with biochar application at high rates. Further, the high cost associated with production of biochar and high application rates remains a significant challenge to its widespread use in areas affected by salinity and sodicity. Moreover, there is relatively limited information on the long-term behavior of salt-affected soils subjected to biochar applications. The main objective of the present paper was to review, analyze and discuss the recent studies investigating a role of biochar in improving soil properties and plant growth in salt-affected soils. This review emphasizes that using biochar as an organic amendment for sustainable and profitable use of salt-affected soils would not be practicable as long as low-cost methods for the production of biochar are not devised.
... In India, floods damage ~ 64 lakh hectares of agricultural land in two months itself (June and July). Salinization has degraded ~ 1/3rd of irrigated lands primarily due to enhanced soil moisture evaporation (due to heat stress and droughts) and back-water effect in coastal areas (due to sea level rise and frequent storm surges) (Saifullah et al. 2018). Salinization injures soil properties and minimizes biomass production by decreasing nutrient uptake, damaging photosynthesis, and initiating oxidative stress (Gunarathne et al. 2020). ...
... A considerable amount of investigations on the impact of droughts and salinization on soil-plants and their mitigation by biochar amendment have been performed in the last decade (Ali et al. 2017;Saifullah et al. 2018;Mansoor et al. 2021). However, there is a dearth of a holistic review incorporating impacts of climate change-associated extreme weather events on soil-plants and how the adverse impacts of extreme weather (especially high temperature, droughts, and floods) on soil-plants could be mitigated by biochar amendment. ...
... Correspondingly, salt-stress keeps on building up, degrades arable lands, and damages the global economy. Long-term management of salinization-exposed soils requires efficient strategies to boost crop yield and increase farm income (Saifullah et al. 2018). Accordingly, the development of salt-tolerant crops and farming techniques has been advocated to increase crop production and revenue (Kaus 2020). ...
There has been more than 75% rise in the number of extreme weather events such as drought and flood during 2000–2019 compared to 1980–1999 due to the adverse effects of climate change, causing significant deterioration of the soil and water quality. Simultaneously, the growing human population has been exerting pressure on available water and soil resources due to overuse or unplanned use. While greenhouse gas emissions have intensified, the fertility of agricultural soils has declined globally due to the exposure of soils to frequent flooding, desertification, and salinization (resulting from extreme weather events). The current review aims to give an overview of damages caused to the soil–plant system by extreme weather events and provide a perspective on how biochar can repair the damaged system. Biochar is known to improve soil fertility, increase crop productivity and mitigate greenhouse gas emissions via sustainable recycling of bio-waste. Beneficial properties of biochar such as alkaline pH, high cation exchange capacity, abundant surface functional groups, remarkable surface area, adequate porosity, excellent water holding capacity, and sufficient nutrient retention capacity can help repair the adverse effects of extreme weather events in the soil–plant system. This paper recommends some cautious future approaches that can propel biochar’s use in improving the soil–plant systems and promoting sustainable functioning of extreme weather-affected areas via mitigation of the adverse effects.
Graphical Abstract
... Biochar has the potential for remediating saline soil. As a carbon-rich material with plant nutrients and functional groups (Nguyen et al. 2017;Saifullah et al. 2018), biochar is a multi-functional material capable of improving soil properties (He et al. 2020;Gunarathne et al. 2020). For example, Xiao et al. (2020a), Zhu et al. (2020), and Sun et al. (2017) all reported that the application of a small dosage of biochar (2-10‰) reduced NH 3 volatilization and increased NH 4 + -N and NO 3 − -N content in a coastal saline soil via nutrient release and retention. ...
... Despite the numerous reporting of biochar benefits, it has not been widely used in agriculture in general and in YRD in particular because of two challenges: (1) its high cost and the high dose required (Saifullah et al. 2018); and (2) the beneficial effect of biochar amendment on salt-affected soil has primarily been obtained from laboratory or greenhouse studies instead of field trials (Al-Wabel et al. 2018;Saifullah et al. 2018). Field trial in YRD (Liang et al. 2020) is rare, where climate and soil conditions are complex. ...
... Despite the numerous reporting of biochar benefits, it has not been widely used in agriculture in general and in YRD in particular because of two challenges: (1) its high cost and the high dose required (Saifullah et al. 2018); and (2) the beneficial effect of biochar amendment on salt-affected soil has primarily been obtained from laboratory or greenhouse studies instead of field trials (Al-Wabel et al. 2018;Saifullah et al. 2018). Field trial in YRD (Liang et al. 2020) is rare, where climate and soil conditions are complex. ...
To test the hypothesis that by alleviating the salt stress in salt-affected soil, biochar could maintain crop yields even if fertilizer use is reduced by 25% in the Yellow River Delta (YRD). A field trial was conducted to assess the effect of biochar use alone (3, 6, and 12 t ha−1) and in combination with reduced fertilization (25% reduction) on alleviating salt stress, enhancing nutrient supply, and increasing crop yields in wheat–maize rotation. Porous biochar at 12 t ha−1 dose significantly decreased the bulk density of saline soil and increased its saturated hydraulic conductivity (Ks) and water content at wheat and maize harvest over the control (CK). Being rich in K+ (493.9 mmol kg−1), the biochar reduced sodium adsorption ratio (SAR) and Cl−/√SO42− at wheat harvest by 50% and 73%, respectively, and helped the uptake of K+ by crops over Na+, resulting in a higher K/Na ratio of grains in treatments as compared to the control. Similar trends were found when biochar (12 t ha−1) was applied together with 75% of conventional fertilization (CF: 375 kg ha−1). This combined biochar and fertilizers increased soil NH4+-N, Olsen-P, nutrient supply, and crop yields compared to 75% CF. Excessive Na+ and soil compaction limited crop yields in YRD. Biochar amendment reduced soil bulk density and increased saturated hydraulic conductivity (Ks). They, in turn, enhanced salt leaching and made salt compositions more favorable to crop growth. Compared with 75% CF, co-application of 6–12 t ha−1 biochar and 75% CF increased crop yields.
... However, soil microbial activity may be affected by any change in soil pH [11][12][13]. A significant positive relationship was found between inoculum population density, BC feed stuff and BC pH [14,15]. Some studies have found that increasing soil acidity (pH) increases microbial biomass (for example, from pH 3.75 to 7.1). ...
... BC differs from soil organic carbon (SOC) structurally and chemically because it contains far more aromatic C with a stable structure than other carbonous materials such as lignin [25,26]. Soil microbiomes benefit from a high concentration of BC in the form of C, N, K, P and other elements [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Furthermore, when compared to other carbon sources, BC is readily and easily available to soil microbes, allowing them to begin their activities more quickly [28,29]. ...
... Salinity-alkali induces various types of soil degradations, such as compaction, inhibited aeration, nutrient deficiency, and reduction of microbial activities and functions (Saifullah et al., 2018). Extreme soil pH can directly affect plant root function, alter nutrient availability and disturb the balance of ions and mineral nutrition (Peng et al., 2008). ...
... Owing to the excellent cationic adsorption and desorption properties of FCNs, the saline ions move with water to the subsoil after irrigation, which accelerate the leaching of salt and reduce the topsoil salinity (Yan et al., 2021). In addition, the reduced SBD reveals that FCNs can increase soil porosity, which is resulted from the enhanced root development and vigor improving soil structure and creating water channels (Saifullah et al., 2018). In turn, the increased soil porosity and soil hydraulic conductivity promote water movement in soil, thus contribute to the absorption of nutrients and water by roots, as well as accelerate the leaching of salts (Cui et al., 2021). ...
High salinity and alkalinity of saline-alkali soil lead to soil deterioration, the subsequent osmotic stress and ion toxicity inhibited crops growth and productivity. In this research, 8 mg kg⁻¹ and 16 mg kg⁻¹ functional carbon nanodots (FCNs) can alleviate the adverse effects of saline-alkali on tomato plant at both seedling and harvest stages, thanks to their up-regulation effects on soil properties and plant physiological processes. On one hand, FCNs stimulate the plant potential of tolerance to saline-alkali and disease resistance through triggering the defense response of antioxidant system, enhancing the osmotic adjustment, promoting the nutrient uptake, transportation and utilization, and up-regulating the photosynthesis, thereby improve tomato growth and productivity in saline-alkali soils. On the other hand, FCNs application contributes to the improvement of soil physicochemical properties and fertilities, as well as decline soil salinity and alkalinity, which are related to plant growth and fruit quality. This research also focuses on the dose-dependent effects of FCNs on their regulation effects and toxicity to tomato growth under stress or non-stress. These findings recommend that FCNs could be applied as potential amendments to ameliorate the saline-alkali soil and improve the tomato tolerance and productivity in the Yellow River Delta.
... Soil salinity stress is one of the major abiotic stresses affecting agricultural production in arid and semi-arid regions worldwide (Ali et al.,2016;Kamal et al., 2016;Helmi et al., 2018;Saifullah et al., 2018;Farid et al., 2019). Global agricultural yields are reduced by salinity, which has a severe influence on soil qualities and the ecological balance of large regions of land (Farid et al., 2014, Shrivastava and Kumar, 2015, Farid et al., 2020. ...
... Pyrolysis is the heat breakdown of organic compounds in the absence or restricted presence of oxygen (Wang et al., 2017;Bassouny and Abbas, 2019;Tolba et al., 2021). Novac et al., (2009) found that biochar enhances soil physical, chemical, and biological properties (Saifullah et al., 2018;Elshony et al., 2019). ...
The wheat plant was previously cultivated on a salty soil treated with biochar and/or sprayed with K, either in its regular form or the nano one, with nanoparticles of Si and organic fertilizer dominated by amino acids in this experiment. Soil samples collected after harvesting wheat were utilized in this experiment to examine the effects of the aforementioned treatments on its qualities. Although biochar improved the soil pH, it had a substantial impact on lowering the soil salinity indicated as electrical conductivity, according to the results (EC in dSm-1). However, the use of biochar might raise the soil organic matter (SOM) and, as a result, the cation exchange capacity of the soil (CEC). Adding to this, it seems that biochar may have increased the amount of N, P, and K that was accessible. This impact was amplified when biochar was administered together with the K. The application of K considerably lowered soil pH. The pH of the soil was significantly lowered by using K nanoparticles. K fertilizer, particularly when given in its nano-form, may help to reduce soil salinity a little. When K was combined with charcoal or nanoparticles, this impact was amplified. Although it increased the SOM, it also contributed to raising N, P, and K concentrations in the soil. In addition to N, P, and K, the nanoparticles put to the soil improved the CEC and increased the OM content.
... Crop productivity of the salt-affected soil can be improved due to the improvement of the physical, chemical, and biological properties of the biochar-added soil (Alkharabsheh et al. 2021;Hammer et al. 2015). Furthermore, Saifullah et al. (2018) demonstrated that biochar addition can reduce the EC of the salt-affected soil by facilitating leaching and adsorption of Na. Nonetheless, Singh et al. (2018) found that adding biochar to the salt-affected soil increased its EC. ...
... These two latent factors reflected the two primary constraints of the acidic and salt-affected soil. While many studies reported that biochar addition lowered the EC of the salt-affected soils (Hammer et al. 2015;Saifullah et al. 2018), the current study found that biochar addition increased the EC of the acidic and salt-affected soil, which was consistent with another study (Singh et al. 2018). Furthermore, the current study found that the biocharadded soil was significantly enhanced with the exchangeable K concentration. ...
... Crop productivity of the salt-affected soil can be improved due to the improvement of the physical, chemical, and biological properties of the biochar-added soil (Alkharabsheh et al. 2021;Hammer et al. 2015). Furthermore, Saifullah et al. (2018) demonstrated that biochar addition can reduce the EC of the salt-affected soil by facilitating leaching and adsorption of Na. Nonetheless, Singh et al. (2018) found that adding biochar to the salt-affected soil increased its EC. ...
... These two latent factors reflected the two primary constraints of the acidic and salt-affected soil. While many studies reported that biochar addition lowered the EC of the salt-affected soils (Hammer et al. 2015;Saifullah et al. 2018), the current study found that biochar addition increased the EC of the acidic and salt-affected soil, which was consistent with another study (Singh et al. 2018). Furthermore, the current study found that the biocharadded soil was significantly enhanced with the exchangeable K concentration. ...
High salinity and severe acidity are the two primary constraints of acidic and salt-affected soil, leading to phytotoxicity of sodium (Na), aluminum (Al), and iron (Fe), as well as phosphorous (P) deficiency. Biochar, having high alkalinity and adsorption capacity, can be a potential bio-amendment to ameliorate these constraints. The current study aimed to assess the impacts of biochar addition on these constraints and the quality of the soil. A pot experiment was set up in a greenhouse using acidic and salt-affected soil mixed with five biochar rates (0 (T1), 2.5 (T2), 5 (T3), 10 (T4), and 20 (%, w/w, T5)); and experimental soil samples were taken on days 5, 15, 30, 60, and 100 to analyze for 11 parameters. The results showed that biochar addition (T5) enhanced electrical conductivity (EC), pH, and the concentration of exchangeable Na and potassium (K) by 24, 90, 13, and 1064 (%), whereas it reduced the concentration of Al and Fe by 93 and 66 (%), as compared to T1. The non-occluded P of the biochar-added soil was raised by 109 (%) in T5, relative to T1. The increased amount of exchangeable Na and K could originate from the added biochar, which may re-absorb Na after 2 months. The reduced magnitude of exchangeable Al and Fe could be involved in the increased pH, leading to the enhanced non-occluded P. In brief, biochar may worsen soil EC but mitigate the acidity-related constraints, leading to an enhancement of soil quality, eventually.
... Crop productivity of the salt-affected soil can be improved due to the improvement of the physical, chemical, and biological properties of the biochar-added soil (Alkharabsheh et al. 2021;Hammer et al. 2015). Furthermore, Saifullah et al. (2018) demonstrated that biochar addition can reduce the EC of the salt-affected soil by facilitating leaching and adsorption of Na. Nonetheless, Singh et al. (2018) found that adding biochar to the salt-affected soil increased its EC. ...
... These two latent factors reflected the two primary constraints of the acidic and salt-affected soil. While many studies reported that biochar addition lowered the EC of the salt-affected soils (Hammer et al. 2015;Saifullah et al. 2018), the current study found that biochar addition increased the EC of the acidic and salt-affected soil, which was consistent with another study (Singh et al. 2018). Furthermore, the current study found that the biocharadded soil was significantly enhanced with the exchangeable K concentration. ...
High salinity and severe acidity are the two primary constraints of acidic and salt-affected soil, leading to phytotoxicity of sodium (Na), aluminum (Al), and iron (Fe), as well as phosphorous (P) deficiency. Biochar, having high alkalinity and adsorption capacity, can be a potential bio-amendment to ameliorate these constraints. The current study aimed to assess the impacts of biochar addition on these constraints and the quality of the soil. A pot experiment was set up in a greenhouse using acidic and salt-affected soil mixed with five biochar rates (0 (T1), 2.5 (T2), 5 (T3), 10 (T4), and 20 (%, w/w, T5)); and experimental soil samples were taken on days 5, 15, 30, 60, and 100 to analyze for 11 parameters. The results showed that biochar addition (T5) enhanced electrical conductivity (EC), pH, and the concentration of exchangeable Na and potassium (K) by 24, 90, 13, and 1064 (%), whereas it reduced the concentration of Al and Fe by 93 and 66 (%), as compared to T1. The non-occluded P of the biochar-added soil was raised by 109 (%) in T5, relative to T1. The increased amount of exchangeable Na and K could originate from the added biochar, which may re-absorb Na after 2 months. The reduced magnitude of exchangeable Al and Fe could be involved in the increased pH, leading to the enhanced non-occluded P. In brief, biochar may worsen soil EC but mitigate the acidity-related constraints, leading to an enhancement of soil quality, eventually.
... The PB decreased the EC values, whereas the BB increased it as compared to the control. This may be attributed to salt adsorption, and its preservation resulted in a lower EC value of soil solution and/or movement of saline water downward, which reflected in a reduction EC value in the surface layer [2,28,30]. Our results clearly showed that all feedstock biochar reduced the risk of toxic metals by stabilizing them in insoluble forms. ...
... PB had higher alkalinity, total dissolved salts, and O, Si, K, and Ca content than those of BB, which may explain the more significant reduction in HMs solubility. Organic amendments affect the mobility, and bioavailability of soil HMS depends on the specific metal, soil type, and the amendment characteristics such EC, CEC, and pH [30,47]. ...
Citation: Awad, M.; Liu, Z.; Skalicky, M.; Dessoky, E.S.; Brestic, M.; Mbarki, S.; Rastogi, A.; EL Sabagh, A.
... Our results are in accordance with previous studies as it has been reported that when biochar was applied at higher rates, it increased sodicity. The increase in sodicity resulted in decline in growth [61]. Other researchers have also reported that the application rate of biochar is an important component to determine the effectiveness of biochar [62,63]. ...
... Excessive amount of biochar results in increased salinity [65]. Higher application rate of biochar can also increase sodicity of soil [61]. Moreover it can also deteriorate soil health conditions by increasing the values of EC and pH [66]. ...
Salinity is a global problem, and almost more than 20% of the total cultivated area of the world is affected by salt stress. Phytoremediation is one of the most suitable practices to combat salinity and recently biochar has showed the tremendous potential to alleviate salt-affected soils and enhance vegetation. Trees improve the soil characteristics by facilitating the leaching of salts and releasing organic acids in soil. Moreover, in the presence of trees, higher transpiration rates and lower evaporation rates are also helpful in ameliorating salt affected soils. This study was designed to check the effect of different levels of biochar on the morph-physiological characteristics of three important agroforestry tree species: Eucalyptus camaldulensis , Vachellia nilotica , and Dalbergia sissoo , in saline soils. Farmyard manure biochar was applied at the rate of 3% (w/w), 6% (w/w), and 9% (w/w) to find appropriate levels of biochar for promoting the early-stage trees growth under saline conditions. Results of the current study revealed that maximum shoot length (104.77 cm), shoot dry weight (23.72 g), leaves dry weight (28.23 g), plant diameter (12.32 mm), root length (20.89 cm), root dry weight (18.90 g), photosynthetic rate (25.33 μ moles CO 2 m ⁻² s ⁻¹ ) and stomatal conductance (0.12 mol H 2 O m ⁻² s ⁻¹ ) were discovered in the plants of Eucalyptus camaldulensis at the rate of 6% (w/w). All tree species showed better results for growth and physiological characteristics when biochar was applied at the rate of 6% (w/w). In comparison, a decreasing trend in growth parameters was found in the excessive amount of biochar when the application rate was increased from 6% (w/w) to 9% (w/w) for all three species. So, applying an appropriate level of biochar is important for boosting plant growth in saline soils. Among different tree species, Vachellia nilotica and Eucalyptus camaldulensis both showed very promising results to remediate salt affected soils with Vachellia nilotica showing maximum potential to absorb sodium ions.
... Biochar, a carbon-rich substance possibly produced from agricultural residues, can be used as an organic amendment to reduce the salinity of the salt-affected soils (Saifullah et al., 2018;Xiao and Meng, 2020). The authors also summarized various benefits brought to salt-affected soils through biochar addition, including reduced Na concentration and EC of the biochar-added soil. ...
... The biochar EC varied greatly, depending on feedstock and pyrolysis temperature, ranging from 0.04 (Rajkovich et al., 2011) to as high as 54.2 dS m -1 (Smider and Singh, 2014). Consequently, Saifullah et al. (2018) hypothesized that the EC of salt-affected soil could be increased or decreased, basically depending on the relative EC of the soil solution and of the biochar. Relative to the solution, high-EC biochar may increase the solution EC, while low-EC biochar may reduce the solution EC. ...
... Coastal soils are important reserve land resources for food production; however, there is an area of 3.4-9.8 billion m 2 of them degrading every year worldwide [1,2]. Coastal soils face a series of problems, including high pH value and salinity, low water and nutrient retention capacity, poor air and water permeability, and low soil organic carbon concentrations [3][4][5]. These problems restricted the sustainable development of agriculture and food safety [6]. ...
The high salinity and nutrient deficiency in degraded coastal soil restricts crop growth and grain production. The development of effective and novel technology for coastal soil remediation is of great requirement. The effect of wood waste biochar (WB) on the growth and biological nitrogen fixation of wild soybean (Glycine max subsp. soja Siebold & Zucc.), a legume with high economic values and salt tolerance in coastal soil, were explored using a 42-day pot experiment. With the optimal rate of WB addition (1.5%, w/w), the biomass and plant height of wild soybean increased by 55.9% and 28.3%, respectively. WB addition enhanced the photosynthesis (chlorophyll content) and biological nitrogen fixation (nodule number) of the wild soybean. These results may attribute to the improvement of the soil properties including the SOM, NO3−-N content, and WHC. In addition, the shifted bacterial community following WB addition in the coastal soil favored the nitrogen fixation of wild soybean, which was evidenced by the increased abundance of nifH gene and Pseudarthrobacter, Azospirillum, and Rhizobiales. The results of our study suggested the potential of using biochar-based technology to reclaim the coastal degraded soils and enhance the crop growth to ensure food security.
... Borage (Borago officinalis L.; Boraginaceae), as a moderately salt-tolerant crop, represents an important medicinally cultivar that has about 20% γ-linolenic acid in the fixed indicate that Bi can induce encouraging impacts via enhancing the physio-biochemical and biological trials of saline soils, including enrichment minerals nutrients and recover soil bulk density, stabilization of soil structure, accelerating water-holding capacity, and high cation exchange capability and microbial activity [24,25]. Furthermore, Bi may have the capacity to decrease salt injury following three mechanisms [22,26]: (1) transient binding of sodium (Na + ) on its exchange position, and hence decreasing Na + uptake; (2) rising potassium (K + ) in soil solution, and so preserving Na + /K + ionic balance to lessen Na + uptake; and (3) rising soil moisture content, which may cause dilution effect and eventually causes a decline in Na + uptake. Finally, a small number of researchers have illustrated the effect of Bi on oxidative anxiety and antioxidant capacity in salt-affected plants [27]. ...
Salinity is persistently a decisive feature confining agricultural sustainability and food security in arid and semi-arid regions. Biochar (Bi) has been advocated as a means of lessening climate changes by sequestering carbon, concurrently supplying energy and rising crop productivity under normal or stressful conditions. Melatonin (Mt) has been shown to mediate numerous biochemical pathways and play important roles in mitigating multi-stress factors. However, their integrated roles in mitigating salt toxicity remain largely inexpressible. A completely randomized design was conducted to realize the remediation potential of Bi and/or Mt in attenuation salinity injury on borage plants by evaluating its effects on growth, water status, osmotic adjustment, antioxidant capacity, ions, and finally the yield. Salinity stress significantly decreased the plant growth and attributed yield when compared with non-salinized control plants. The depression effect of salinity on borage productivity was associated with the reduction in photosynthetic pigment and ascorbic acid (AsA) concentrations, potassium (K+) percentage, K+-translocation, and potassium/sodium ratio as well as catalase (CAT) activity. Additionally, borage plants’ water status was disrupted by salinity through decreasing water content (WC), relative water content (RWC), and water retention capacity (WTC), as well as water potential (Ψw), osmotic potential (Ψs), and turgor potential (Ψp). Moreover, salinity stress evoked oxidative bursts via hyper-accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA), as well as protein carbonyl, which is associated with membrane dysfunction. The oxidative burst was connected with the hyper-accumulation of sodium (Na+) and chloride (Cl−) in plant tissues, coupled with osmolytes’ accumulation and accelerating plants’ osmotic adjustment (OA) capacity. The addition of Bi and/or Mt had a positive effect in mitigating salinity on borage plants by reducing Cl−, Na+, and Na+-translocation, and oxidative biomarkers as well as Ψw, Ψs, and Ψp. Moreover, Bi and/or Mt addition to salt-affected plants increased plant growth and yield by improving plant water status and OA capacity associated with the activation of antioxidant capacity and osmolytes accumulation as well as increased photosynthetic pigments, K+, and K+/Na+ ratio. Considering these observations, Bi and/or Mt can be used as a promising approach for enhancing the productivity of salt-affected borage plants due to their roles in sustaining water relations, rising solutes synthesis, progressing OA, improving redox homeostasis, and antioxidant aptitude.
... Each way of treating agricultural biomass waste has its own set of advantages and disadvantages with varying benefits. Biomass waste can be recycled to produce biochar for a variety of applications (Haris et al., 2021;Nguyen et al., 2021;Nan et al., 2021), including salt-affected soil remediation (Gunarathne et al., 2020;Saifullah et al., 2018). Nevertheless, the effectiveness of the pathway of recycling agricultural biomass waste could be dependent on the linkage between agricultural biomass waste, biochar characteristics, and biochar's sodium adsorption capacity which is insufficiently discussed in the literature. ...
Agricultural biomass wastes, which may pollute the environment yet are inefficiently managed worldwide, can be recycled into biochar, which is subsequently used to remediate salt-affected environments. This creates value-added or dual benefits of treating the wastes while reclaiming saline water/soil for sustainable development. Nevertheless, a lack of knowledge about the linkage between biochar characteristics and sodium adsorption capacity may restrict the wastes from being recycled. The current study aimed to examine physicochemical, nano/microstructural, and functional-group characteristics of biochar and to assess its sodium isothermal-adsorption properties. Four biochars made from rice husk (RH-BC), corn stalks (CS-BC), longan branch (LA-BC), and coconut coir (CC-BC) were used for an isothermal-adsorption experiment. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Brauner-Emmett-Teller surface area (BET area), pore size distribution, and Fourier Transform Infrared spectroscopy (FTIR) were used to characterize biochars, which were additionally analyzed for 9 parameters. RH-BC had the highest BET area (151 m² g⁻¹) and porosity, whereas LA-BC exhibited the lowest BET area (10.6 m² g⁻¹), and LA-BC was more condensed. Functional groups, necessary for cation adsorption, were found in biochars. The maximum adsorption capacity of RH-BC (33.9 mg g⁻¹), estimated by the Langmuir isotherm model, was the highest while that of CC-BC (15.5 mg g⁻¹) was the lowest. The Dubinin-Radushkevich isotherm model showed that the Na adsorption mechanism was dominantly a physical process. The current study provides a feasible value-added and sustainable strategy of recycling agricultural biomass wastes with dual benefits of waste treatment and salt-affected environment remediation, applicable worldwide.
... Biochar balances air porosity in soils and water holding capacity, thus it promotes benefits in plant growth in saline soils by reducing oxidation stress and osmotic stress (de Vasconcelos, 2020). Several studies observed that the application of biochar has been shown to be effective in reducing salinity stress by improving soil physicochemical and biological properties directly related to Na removals (Dahlawi et al., 2018). Heavy metal accumulation in the soil is another concern threatening agricultural production. ...
Cashmere production offers a new source of income for remote farmers in Central Asia where goats have long been raised. Between 2008-2018 we established a selected breeding flock to preserve, assess and improve the economic and genetic potential of cashmere-bearing indigenous goats in Kyrgyzstan. Significant effects of year, age and the sex of goats affected cashmere weight, while year and age of goat affected cashmere length and year affected cashmere fiber diameter. The best statistical model explained about 60% of the variation in both cashmere weight and length and about 30% of the variation in fiber diameter. No particular measurement year trend could be detected for any trait. Between years, cashmere weight varied between 103-150 g, fiber diameter between 15.8-17.6 m and length between 32-48 mm. Key words:Coat color, Indigenous goats, Fiber diameter, Fiber length, Genetic improvement
... Biochar can promote the formation of soil organic matter and the recycling and transformation of degraded substances and nutrients (Hua et al. 2014). Its effect on enzyme activity can be explained by the improvement of soil organic matter, soil nutrient status, microbial diversity, and community structure (Saifullah et al. 2018;Azadi and Raiesi 2021). ...
The purpose of this study was to assess the effects of wetland plant biochars on the enzyme activity in heavy metal contaminated soil. The biochars were produced from Phragmites australis (PB), Suaeda salsa (SB), and Tamarix chinensis (TB) under different pyrolysis temperatures and times. The detected pyrolysis products showed that the ash, pH, electrical conductivity, and carbon content of the biochars increased significantly, while the production rate of the biochars decreased with increasing pyrolysis temperature and time. The results of the adsorption experiments indicated that biochar addition could effectively reduce the concentration of Pb and/or Cd in the Pb²⁺/Cd²⁺ single or mixed solutions, but the Pb²⁺ and Cd²⁺ in the mixed solution indicated a competitive adsorption. A 30-day incubation experiment was conducted using salt marsh soil amended with different biochar application rates to investigate the short-term effects of biochar addition on Pb and Cd immobilization. The PB and SB significantly immobilized Pb within the first 15 days, but Pb remobilized within the next 15-day period. In contrast, TB addition did not significantly fix Pb. Moreover, biochar addition promoted the conversion of Cd from the residue to the less immobile fractions. The addition of three types of plant biochar had no significant effect on the urease activity in wetland soil but significantly increased soil sucrase activity. PB and SB significantly promoted catalase activity, while TB significantly inhibited soil catalase activity. According to the adsorption effect, the fixation effect, and the promotion of enzyme activities, the Suaeda salsa biochars are suitable for the remediation of heavy metal pollution in wetland soils.
... The organic form of soil carbon is predominantly dependent upon carbon inputs through vegetation growth including plant roots, litterfall and anthropogenic activities (Kooch et al. 2019;Meena et al. 2020). Sodic soil contains low soil organic carbon (OC) content, because of underutilization by the farming communities and less biomass production due to patchy and poor crop growth (Bhardwaj et al. 2019;Saifullah et al. 2018). Apparently, less supply of biological substrates in sodic soils restricts buildup of OC content relatively more than unfavourable soil conditions (Singh 2016). ...
Soil sodification through irrigation with alkali groundwater is quite extensive in arid to semi-arid regions of the world. Therefore, the long-term effects of alkali and partially neutralized water irrigations were quantified on sandy loam soils. The experiment was conducted in semi-controlled concrete lysimeters of 2 × 2 × 2 m3 with drainage outlets at bottom and filled with sandy loam soils. These were irrigated with five types of irrigation water, i.e. good quality water (GQW), synthetic alkali water (SAW) having the residual sodium carbonate (RSC) ~ 5 me L−1 (SAW1), SAW of RSC ~ 10 me L−1 (SAW2), SAW2 partially neutralized up to RSC ~ 5 me L−1 with gypsum (SAW2 + GYP) and SAW2 partially neutralized up to RSC ~ 5 me L−1 with sulphuric acid (SAW2 + SA). Perpetual irrigation with residual alkalinity water deteriorated soil quality through increasing its soil pH, electrical conductivity and total inorganic carbon content and diminishing soil microbial activities, total organic carbon (TOC) and its active pools. Increased soil pH further induced negative effect on soil microbial activities and TOC as well as its active pool. Conversely, availability of phosphorous and potassium increased but nitrogen availability remained unaffected. Irrigation with increasing RSC water caused proportionate deterioration in soil quality. Partial neutralization of irrigation water RSC from ~ 10 to ~ 5 me L−1 with gypsum or sulphurous amendments did not suffice for sustaining long-term soil quality. It suggested substantial revision in existing recommendation of alkali water neutralization for irrigation to achieve the land degradation neutrality, food security and sustainability.
... Especially the long-term effect on soil microbes, the enzymes that are likely to be of great concern should be modified and investigated in high-surface biochar [174]. Long-term behavioral care should focus on amending the contaminated soil (e.g., serpentine soil) with modified biochar in various ways to analyze various aspects such as fertility, mineralogy, toxicity, and texture [193]. ...
Serpentine soils are contaminants of naturally occurring metal-rich agricultural and fallow lands due to erosion of the serpentine site with consequences and deterioration of soil, water quality, and water sources in the ecosystem. The harsh climatic conditions due to the high concentration of potential toxic elements, organic pollutants, and acidity make it difficult to cultivate and establish vegetation on serpentine or adjacent land. Recently, biochar amendments have emerged in the area of soil remediation technology with the suitability and potential to promote seed emergence, plant growth, biomass productivity, and vegetation cover on contaminated soils such as serpentine soil. By enhancing the buffering capacity of the soil through pH, soil nutrients and water holding capacity stimulate the diversity and function of microbes. In this review, we have conferred the physicochemical aspects of serpentine soil, heavy metal contaminants, and their consequences, especially in crop production and phytotoxicity. Another, the assessment of biochar preparation using various types of feedstock, their characteristics, and the application for the amendment of serpentine soils has been deliberated. The restoration of sites with a high fraction of heavy metal contaminents and organic pollutants associated with serpentine soils using biochar has been highlighted for its importance. In line with the possibility of expanding the cultivated area, future research directions have been suggested in field trials, advances in biochar production, and environmental risk assessment. In addition, the applicable mechanisms have prerequisites to accelerate the efficiency of biochar amendments.
... significantly promotes maize growth. Previous studies have shown that biochar addition could improve the soil structure and nutrient balance, especially for enhancing the total concentration and bioavailable fractions of nutrients for plant growth (Saifullah et al., 2018). The ballmilled P-loaded biochar (BPBC700) prepared in this paper could further induce increasing CEC, OC, nutrients (e.g., N, P, K), soil porosity and buffering capacity, which are the factors mainly responsible for enhancing maize growth. ...
Pyrolytic biochar is a good material for remediating soils contaminated with heavy metals; however, it exhibits strong alkalinity, which easily causes soil alkalization and fertility reduction. Herein, a series of novel biochar materials (BPBCs) were prepared by combined ball milling and phosphorus (P)-loading. The optimized BPBC were fabricated in the basis of Cd and Pb adsorption capacities of the biochar, with pyrolysis at 700 °C, ball milling for 12 h and the addition of 5% red P (BPBC700). Ball milling could effectively grind pristine biochar into submicron particles and nanoscale P particles could be uniformly loaded on BPBC700. Moreover, the oxidative conversion of red P into phosphorus oxides, phosphoric acid and (hydro)phosphates was promoted due to reactions with the carbonates, alkaline minerals and O-containing functional groups of biochar. These reactions also decreased the biochar and soil pH to nearly neutral by acid-base neutralization. Pot experiments showed that BPBC700 had better effects than the pristine or ball-milled biochar in improving soil properties (e.g., cation exchange capacity and organic carbon), increasing the concentrations of soil nutrients (e.g., N and P), promoting alkaline phosphatase, catalase and urease activities, decreasing soil mobility and plant accumulation of Cd and Pb, and alleviating Cd and Pb stress on maize plants. Thus, BPBC is a promising and ecofriendly amendment to enhance its adsorption ability on Cd and Pb, soil quality and plant productivity in contaminated soil.
... Biochar is produced by heating any organic waste materials at high temperatures through the process of pyrolysis. It is rich in organic matter and influential in improving physical, chemical (by increasing Ca, Mg and K, CEC, etc.), and saline-sodic and sodic soils [62]. In addition to this, biochar has been shown to maximize porosity, resulting in improved available water and reduced bulk density of saline-sodic and sodic soils [61]. ...
Ethiopia’s irrigated agriculture productivity has been threatened by severe salinity and
sodicity problems which have resulted in significantly lower yields, food insecurity, and environmental degradation. The destructive effects of poor irrigation water management with the absence of drainage and anticipated future climate changes can accelerate the formation of salt-affected soil, potentially expanding the problem to currently unaffected regions. This paper synthesizes the available information on the causes, extent, and effects of salt-affected soils on soil and crop production and suggests chemical, biological, and physical reclamation and management approaches for tackling salinity and sodicity problems. The mitigation approaches (e.g., the addition of amendments,
plantation of salt-tolerant crops, appropriate irrigation and drainage management, phytoremediation, and bioremediation) have successfully tackled soil salinity and sodicity problems in many parts of the world. These approaches have further improved the socioeconomic conditions of farming communities in salt-affected areas. The paper also discusses the effectiveness of these mitigation strategies under Ethiopian conditions. The policy interventions for reclamation of soil salinity and sodicity that indicates future research attention to restoring agricultural sustainability are also foci of this paper.
... Moreover, due to the higher density of seawater, the groundwater in coastal cultivated land is easy to be invaded by seawater, which leads to soil salinization (Akter et al., 2020;Badaruddin et al., 2015). In this case, irrigation and water conservancy measures, chemical improvement measures and biological improvement measures have been applied in coastal areas (Saifullah et al., 2018;Fei et al., 2019;Anapali et al., 2001). The evaluation of improved soil properties is the key to guide soil improvement in coastal land (Lal and Augustin, 2012). ...
Coastal soil is an important reserve land resource. The accurate prediction of soil hydraulic properties plays an important role in understanding the improvement of soil properties after reclamation in coastal areas. With the development of modern mathematical theory, the pore-solid fractal (PSF) model has become an important basis for simulating soil hydraulic properties. The accuracy of PSF model depends on the accurate acquisition of changepoints and fractal dimensions. Previous studies have found that micro-CT scanning combined with image processing could accurately obtain fractal dimensions. However, we still need soil water retention data to determine changepoints, which greatly limits the application of fractal models for estimating soil hydraulic properties. In this case, we determined the relationship between changepoints and soil physical and chemical properties and established a genetic algorithm-support vector regression (GA-SVR) model to predict changepoints. Then an improved PSF model was adopted to predict soil water retention curve in coastal areas of Jiangsu Province based on image processing. The results showed that soil physical and chemical properties changed the soil water movement and changepoints by affecting soil pore distribution. In coastal saline soil, four parameters (BD, silt, EC, SOM) were selected to predict changepoints. The mass fractal dimension (Dm) was mainly influenced by the porosity and the heterogeneity of pore space. The porosity, pore diameter and specific surface area were the determining factors of DS value. Reclamation activities in coastal reclamation area changed Dm value but had no clear effect on DS value. By combining predicted changepoints, measured water content at the suction of changepoints and fractal dimensions, the accuracy of the PSF model had been greatly improved.
... As a resource, biochar is not inexhaustible. The high cost associated with the production of biochar and the high application rates are significant challenges to its widespread use in rainfed areas (Dahlawi et al. 2018). Thus, determining the amount of biochar application to obtain economically beneficial crop production with quality is highly important. ...
The inability of humans and many farm animals to synthesize certain amino acids has long triggered tremendous interest in increasing the levels of these so-called essential amino acids in crop plants. Hence, a two-year field experiment was conducted to evaluate the effects of straw mulch (8 t ha−1) and biochar applied at various rates (0, 4, 12, 36 t ha−1) on the chlorophyll, photosynthesis, total nitrogen in soil, essential and nonessential amino acid (AA) contents of maize grain. The maize straw mulch and biochar significantly increased chlorophyll contents, photosynthesis rate of maize crop and total soil nitrogen. The application of biochar (12 t ha−1) increased the chlorophyll contents and photosynthesis rate and total soil nitrogen during both years. However, excessive biochar applications (more than 12 t ha−1) had negative effects on chlorophyll contents, photosynthesis rate of maize crop and total soil nitrogen of soil. The AAs were significantly affected by biochar, depending on the application rate. In conclusion, the application of straw mulch and biochar improved the rate of leaf chlorophyll contents, photosynthesis rate and amino acid contents in maize grain when applied at appropriate rates, but the effects were negative when biochar was overused.
... The biomass of purslane grown in both soil conditions was higher in soil amended with biochar than plants grown in soil without biochar amendment. Several studies observed improved plant growth and stress tolerance under saline conditions after biochar application [54,55]. For example, Yang et al. [56] reported increased growth, improved plant physiological properties, and a higher quinoa yield by biochar under salt stress than control plants. ...
Numerous reports confirm a positive impact of biochar amendments on soil enzyme activities, nutrient cycles, and, finally, plant growth and development. However, reports explaining the process behind such diverse observations are scarce. The aim of the present study was (1) to evaluate the effect of biochar on the growth of purslane (Portulaca oleracea L.) and nutrients; (2) to determine the response of rhizosphere enzyme activities linked to soil phosphorus cycling after bio- char amendment under non–saline and saline soil conditions. Furthermore, we investigate whether adding biochar to soil alters the abundance of P-cycling-related bacteria. Two rates of biochar (2% and 4%) were applied in pot experiments. Biochar addition of 2% significantly increased plant growth under non-saline and saline soil conditions by 21% and 40%, respectively. Moreover, applying biochar increased soil microbial activity as observed by fluorescein diacetate (FDA) hydrolase activity, as well as phosphomonoesterase activities, and the numbers of colony-forming units (CFU) of P-mobilizing bacteria. Soil amended with 2% biochar concentration increased total soil nitrogen (Nt), phosphorus (P), and total carbon (Ct) concentrations by 18%, 15%, and 90% under non-saline soil conditions and by 29%, 16%, and 90% in saline soil compared the control, respectively. The soil FDA hydrolytic activity and phosphatase strongly correlate with soil Ct, Nt, and P contents. The rhizosphere soil collected after biochar amendment showed a higher abundance of tricalcium phosphate-solubilizing bacteria than the control soil without biochar. Overall, this study demonstrated that 2% maize-derived biochar positively affects halophyte plant growth and thus could be considered for potential use in the reclamation of degraded saline soil.
... A previous study also found that the application of organic fertilizer would strengthen the activity of phosphatase and invertase [61]. Moreover, bacterial networks and interactions among taxa exhibited higher complexity after OCPF treatment, which had a positive impact on nutrient cycling and accumulation [62]. ...
Appropriate fertilization can enhance forest productivity by maintaining soil fertility and improving the structure of the bacterial community. However, there is still uncertainty surrounding the effects of combined application of organic and inorganic fertilizers on soil nutrient status and bacterial community structure. A fertilization experiment was set up in an eight-year-old teak plantation with five treatments involved: mixed organic and NPK compound fertilizers (OCF), mixed organic and phosphorus fertilizers (OPF), mixed organic, NPK and phosphorus fertilizers (OCPF), mixed NPK and phosphorus fertilizers (CPF) and no fertilization (CK). Soil chemical properties and bacterial communities were investigated, and the co-occurrence pattern of the bacterial community under different fertilization treatments was compared. The results showed that the contents of soil organic matter and nitrate nitrogen, and the soil pH values were the highest after OCPF treatment, which were 20.39%, 90.91% and 8.16% higher than CK, respectively. The richness and diversity of bacteria underwent no obvious changes, but the structure of the soil’s bacterial community was significantly altered by fertilization. Of the dominant bacteria taxa, the relative abundance increased for Gemmatimonadetes, Myxococcota, ADurb.Bin063-13 and Candidatus_Koribacter, and decreased for Chloroflexi, Proteobacteria, JG30-KF-AS9 and Acidothermus under OCPF treatment in comparison to CK. The number of nodes and edges, the average degree and the network density of bacterial community co-occurrence networks were the greatest in OCPF treatment, indicating that application of OCPF could make the network structure of soil bacteria more stable and complex. Moreover, soil pH and organic matter were significantly correlated with bacterial community structure and were considered the main influencing factors. These findings highlight that the combined application of organic, NPK and phosphorus fertilizers is highly beneficial for improving soil quality and optimizing bacterial community structure in teak plantations.
... Besides, it is as a way to modify the nutrient cycle, reduce soil nitrous oxide emissions, and enhance carbon sequestration (Singh et al. 2015). Additionally, it is beneficial in reducing the impact of salt stress by enhancing the physical and chemical properties through sodium filtration and decreasing its concentration in the soil (Dahlawi et al. 2018). It could markedly affect the soil CO 2 emissions (Oo et al. 2018) and improved the contaminated soil because of its high ability to absorb pollutants (She et al. 2018). ...
This study was carried out during two consecutive seasons, 2020 and 2021, on 12-year-old mango (Mangifera indica L.). cv. Ewaise grown in region Idku, El Beheira Governorate, Egypt. The trees were planted at 5 × 4 m apart and grafted on “Sokary” root stock to study the influence of zeolite and biochar on growth, yield, and fruit quality of “Ewaise” mango cultivar irrigated by agricultural drainage water. The trees were treated by the following treatments: zeolite or biochar solely at 1, 2, and 3 kg for tree and their different combinations such as 1 kg zeolite + 1 kg biochar; 1 kg zeolite + 2 kg biochar; 1 kg zeolite + 3 kg biochar; 2 kg zeolite + 1 kg biochar; 2 kg zeolite + 2 kg biochar; 2 kg zeolite + 3 kg biochar; 3 kg zeolite + 1 kg biochar; 3 kg zeolite + 2 kg biochar; and 3 kg zeolite + 3 kg biochar as well as control zero soil application. The obtained results showed that the soil application of zeolite or biochar gave a positive effect on improving the soil characteristics which reflects on the tree trunk thickness, shoot length and thickness, number of inflorescences, yield in kg per tree, and fruit quality. The greatest positive effect on the previous mentioned parameters was obtained by the combined application of the soil application of 2 kg zeolite + 3 kg biochar; 2 kg zeolite + 2 kg biochar; 3 kg zeolite + 2 kg biochar; and 3 kg zeolite + 3 kg biochar over the rest-applied treatments or control in the two seasons.
... Compost can alleviate soil salt stress owing to compost humic acids and their ability to chelate sodium on their carboxylic sites (Hasini et al., 2020). (Saifullah et al., 2018) mentioned that biochar can improve the soil organisms growth in salt-affected through enhance soil aggregate formation, water retention and also can serve as source releasing nutrients in soil for for microbial metabolism (Jatav et al., 2021). ...
In-situ super-stable mineralization technology with mineralizers (CaSO4, Fe2(SO4)3) and attapulgite (ATP) clay were applied to improve soda saline-alkali soil. The addition of mineralizers and the existence of OH and CO3²⁻ in soil resulted in the formation of CaFe-layered double hydroxide (CaFe-LDH) with super-stable mineralization structure (Ksp = 1.512 × 10⁻⁶¹), which was confirmed by the characterization of physicochemical properties and density functional theory (DFT) calculation. The fixation of OH⁻ and CO3²⁻ during the formation process of CaFe-LDH led to the transformation of the existing forms of OH⁻ and CO3²⁻ in soil from free to stable state, resulting in the permanent decrease of soil pH and CO3²⁻ concentration. The effect of ATP clay on the decrease of soluble Na ions in soil through electrostatic attraction and cation exchange was also indicated. Furthermore, mineralizers (1.2 t/ha CaSO4 and 0.75 t/ha Fe2(SO4)3) and ATP clay (1.2 t/ha) were applied to 1.33 ha soda saline-alkali land, and Rumex patientia L. was seeded meanwhile for the identification of improved performance. After five months of improvement, the physical and chemical properties of soil was improved that pH, electrical conductivity (EC), the concentration of CO3²⁻ and soluble Na ions, and soil bulk density decreased significantly. In addition, the emergence rate of Rumex patientia L. increased from 0% to 98.3%. All above indicated that in-situ super-stable mineralization technology with the properties of high efficiency, long-term and cost-effective (234.88 $/ha) displays excellent potential in the improvement of soda saline-alkali soil.
Biochar application in agricultural salt-affected soils has shown strong potential to amend soil and promote production. The effect of biochar on soil properties and crop yield varies with crop, soil, biochar properties and climate. Thus, it is critical to select suitable biochar and their application amounts for ameliorating salt-affected soils while improving its conditions and crop yields. The objectives of this study were to investigate the effect of biochar application rates on soil properties, water and temperature conditions and crop yields in saline-alkali soils under cotton-sugarbeet intercropping. We used a three-year (2018–2020) field experiment with biochar application rates of 0, 10, 50 and 100 t ha⁻¹ in 2018, 0, 10, 25, 50 and100 t ha⁻¹ in 2019 and 0, 10, 25 and 30 t ha⁻¹ in 2020. Soil bulk density decreased and thus porosity increased with application of biochar. Soil pH decreased with increasing biochar application amount and the rate of change ranged from −0.003 to −0.004 per ton of biochar. Biochar application at 10 t ha⁻¹ increased soil water content (SWC) and weighted planar soil water storage (WPSWS) in all three experimental years, while oversupply of biochar decreased SWC. Application of biochar moderated soil temperature fluctuations. The yield of cotton and sugarbeet first increased and then decreased with increasing amount of biochar. Considering the effects of biochar on soil water, temperature, and crop yields, 10 t ha⁻¹ biochar amount was proposed as an appropriate application rate for saline-alkali soils. The results provided valuable information on appropriate biochar rates to amend salt-affected soils and their properties while increase crop yields.
The present research was carried out in Al-Saniyah district, Al-Diwaniyah Governorate, Iraq, on a salt-affected soil (EC>4 dSm-1). To counteract the negative effects of salt on wheat plant development metrics and productivity, as well as the quantity of N, P, and K in the plant, it was developed In addition to the biocher, nano-5, amino acids and K fertiliser, the other amendments utilised for their functions were KCl and nano-K. It was thought that K would increase plant tolerance to drought. The research found that these supplements had a favourable impact on all plant development metrics, including grain production and biological output.
Soil salinization is a widespread land degredation, especially in water-stressed regions, jeopardizing agriculture sustainability. Current desalinization methodology involves excessive water consumption. Biochar has the potential to mitigate soil salinization while increasing water holding capacity. As a saline and sodic material, however, how it works and whether it can be used to sustain the agriculture at reduced water resource remain to be studied. Here, by monitoring transport of water, salts and nutrients in the profile of irrigation-silt soil during watering and evaporation in both laboratory and field in Kashgar oasis, Xinjiang, China, we find biochar exacerbates salinization upon application. This is changed, however, after several cycles of irrigation-evaporation due to strengthened salt leaching in irrigation and salt removal out of the depth through intensified top accumulation by evaporation, both resulting from increased capillary effect and thereby the enhanced movement of salts despite the competing electrical adsorption to the cations. The resulted salt distribution facilitates desalinization by removing the top 2 cm soil. Biochar also promotes evaporation after irrigation due to inceased water content and capillary suction. This is reversed once the soil cracks, a common phemomenon in irrigated land. Biochar counteracts the cracking through alleviation of soil compaction, saving tillage while lowering water evaporation, e.g., by 43% at 10% biochar. Our findings indicate that application of biochar changes salt distribution, enabling desalinization with little water consumption. Together with the effect of anti-fracturing and enhanced salt leaching, it lowers water demand substantially, providing a novel solution for agricultural sustainability in salt-affected regions.
Vachellia nilotica (L.) P.J.H. Hurther & Mabb. and Dalbergia sissoo Roxb. are two of the most important multipurpose agroforestry tree species of the Indian sub-continent, but their growth in saline soils is greatly reduced. Recently, organic amendments have showed the potential to increase plant growth in salt-affected soils; however, the influence of using these amendments for growing the above-mentioned tree species under saline conditions is not yet quantified. Therefore, an experiment was devised to analyze the interactive effects of organic amendments in saline soils on the growth of V. nilotica and D. sissoo. Under controlled conditions, a pot experiment was conducted in sandy loam saline soils (EC = 20.5 dSm−1). Organic amendments from four diverse sources: farmyard manure (FYM), poultry manure (PM), slurry (SL), and farmyard manure biochar (FYMB) were employed in this study. At the harvesting time, data regarding morphological, physiological, ionic, and biochemical parameters were obtained. The current study results indicated that both tree species reacted differently, but positively, to diverse applied amendments. The maximum increment in total above-ground biomass, total below-ground biomass, and shoot length for V. nilotica (163.8%, 116.3%, and 68.2%, respectively) was observed in FYM amended soils, while the maximum increment for D. sissoo (128%, 86%, and 107%, respectively) was observed in FYMB amended soils, as compared to control. Minimum plant growth of both species was observed in untreated soils (saline soils). Likewise, the maximum potassium ion and minimum sodium ion concentrations were present in the root and shoots of plants (both species) treated with FYMB. The use of organic amendments resulted in decreased concentrations of malondialdehyde and hydrogen peroxide, and increased concentrations of antioxidant enzymes such as SOD, POD, and CAT. Moreover, higher photosynthetic rates and stomatal conductance were observed in the plants grown in amended soils. The findings of this study can be used to include the above-mentioned high-value tree species for future afforestation programs under saline conditions.
Coastal soils in the Yellow River Delta (YRD) are characterized by high salinity and degraded physicochemical properties, which threaten agricultural production. Biochar has received growing interest as a sustainable soil amendment. However, the effects of biochar on coastal soil quality and the soil microbial response in the field are limited. In this study, the responses of soil properties and microbes to biochar amendment at low dosage (LBC, 18 ton/ha) and high dosage (HBC, 36 ton/ha) and no biochar treatment (CK) were investigated in a peanut field located in the YRD. The results elucidated that biochar-amended soils showed higher available nutrient (i.e., nitrogen, phosphorus, and potassium) contents and cation exchange capacity, but exhibited lower electrical conductivity. Generally, the bacterial community was more easily impacted than that of fungi in both LBC and HBC treatments. Furthermore, the LBC amendment not only improved the abundance of some beneficial bacteria (i.e., Sphingomonas and Nannocystis) but also increased the complexity, modularity index, and competitive interactions of the bacterial co-occurrence network. HBC-enriched Rozellomycota that is probably associated with peanut rot decreased the modularity index and competitive interactions, which might account for the decreased peanut yield under HBC treatment. It is encouraged to comprehensively consider the interaction among microorganisms when evaluating the effects of soil amendments on the soil environment, which plays a vital role in rhizosphere microecology and soil quality.
Soil contamination by heavy metals (loid)s is a considerable environmental concern, and immobilization is a promising alternative to reduce their toxicity. In recent years, modified/engineered biochars have gained enormous attention in soil remediation, and various research studies reported noticeable results concerning their abilities to immobilize heavy metal(loids). In this review, a summary from publications on the utilization of modified biochars has been discussed to address the heavy metal(loids) threat in soils. Within the pertinent summarized publications, various modified/engineered biochars were identified. The variation method of preparation revealed an intense change in surface chemistry such as develop pore volume, an increase of surface functional group, binding metals sites, which can be seen through various analytical techniques including Brunauer, Emmett and Teller (BET), X-Ray Photoelectron Spectroscopy (XPS), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and magnetism. Such analytical approaches elucidated mechanism immobilization through adsorption, precipitation, surface complexation, and cation exchange between biochar and the metal ions. Besides, the performance of the biochar on the heavy metal(loid)s also leads to considerable amelioration of the soil condition. Additionally, many factors that could influence the stability of metal ion immobilization onto biochar in the soil, such as pH and redox potential, microorganisms, climate regime, etc., are highlighted. Finally, this paper emphasizes that using modified biochar as an immobilizing agent for profitable use of heavy metal(loid)s pollution in the soil is promising and would not be practicable if a comprehensive mechanism for their long-term stability in contaminated soil is well elucidated.
Improving productivity of saline soils under drought condition is critical for sustainable agricultural development in arid areas. Whether biochar addition can interact with drought and salinity on fruit yield and quality remains unclear. A pot study was conducted to examine the effects of water, salinity and biochar addition on tomato yield and quality in a solar greenhouse of northwest China. There were twelve treatments combining two irrigation levels of high (W1) and low irrigation (W2 = 2/3 W1), three salinity levels with 0%, 0.3% and 0.6% of soil dry weight salts, referred to S0, S1, and S2, respectively, and two biochar addition levels with 0 (B0) and 1% (B1) of soil dry weight. Biochar, water, salinity, and the interaction between water and salinity were found significant affecting yield and irrigation water productivity (IWP). Biochar addition reduced yield and IWP, ranging from by 7% of W2S0 to 43% of W1S2. The difference in yield and IWP between W1 and W2 was greater for lower salinity treatments. The reduction percentage of W2, relative to W1, was 70%, 38%, and 29% for yield, 58%, 14%, and 0.9% for IWP under S0, S1, and S2, respectively. The effects of water, salinity and biochar treatments was found inconsistent for different quality parameters. Adding biochar had no significant effect on firmness, and slightly increased total soluble solids (TSS) and Vitamin C (VC) at both irrigation levels, while lower irrigation and higher salinity generally led to higher TSS and VC. The absolute slope value of the linear regression of yield and quality parameters with soil electrical conductivity was smaller under W2, relative to W1, indicating that the salinity effect was less pronounced when water stress was greater. The results are valuable in developing and evaluating remedy measures for improving saline soil productivity in arid areas.
Biochar application in reclaiming degraded soils and improving plant productivity has been recognized as a promising technology. Yet, the impacts of biochar and mixtures with compound effective microorganisms (CEM) on alfalfa growth and soil quality in coastal wetlands are poorly understood. A greenhouse experiment was set to systematically reveal the impacts of biochar and biochar combined with CEM on alfalfa growth traits, nutrient uptake, biomass, soil quality, and enzyme activities. Eight treatments were included: (1) control (CK−CEM), (2) 10-g/kg biochar (B 10 −CEM); (3) 20-g/kg biochar (B 20 −CEM); (4) 30-g/kg biochar (B 30 −CEM), (5) CEM without biochar (CK + CEM); (6) 10-g/kg biochar with CEM (B 10 + CEM), (7) 20-g/kg biochar with CEM (B 20 + CEM), (8) 30-g/kg biochar with CEM (B 30 + CEM). The utilization of biochar promoted seed germination, height, and tissue nutrient contents of alfalfa, and the combined biochar with CEM showed greater effects. Alfalfa biomass showed the maximum value in the B 20 + CEM treatment, and the biomass of root, shoot, leaf in the B 20 + CEM treatment increased by 200, 117.3, 144.6%, respectively, relative to the CK−CEM treatment. Alfalfa yield in the CK + CEM, B 10 + CEM, B 20 + CEM, B 30 + CEM treatments was 71.91, 84.11, 138.5, and 120.5% higher than those in the CK−CEM treatment. The use of biochar and CEM decreased soil salinity and elevated soil nutrient content effectively. Biochar elevated soil organic carbon (SOC) and microbial biomass carbon (MBC), NH 4 ⁺ , NO 3 – , and enzymatic activities, and the positive impacts of biochar combined with CEM were additive. The combined addition of 20-g/kg biochar with CEM showed the pronounced improvement effects on improving soil fertility and nutrient availability as well as soil enzyme activities. Path analysis indicated that the application of biochar mixture with CEM promoted alfalfa biomass by regulating plant nutrient uptake, soil quality (soil nitrogen, SOC, MBC, NH 4 ⁺ , NO 3 – ), and soil enzymatic activities (sucrase, urease, and alkaline phosphatases). Thus, incorporation of suitable biochar and CEM can serve as an effective measure to promote alfalfa productivity and restore coastal wetlands soils.
Biochar (e.g., pyrochar and hydrochar) application is a promising strategy to improve soil quality and productivity. However, the comparison of biochars with different carbonization methods and feedstocks for the plant growth in the coastal salt-affected soil remains limited. In this study, a 30-day microcosmic experiment was conducted to compare the effects of pyrochars and hydrochars derived from reed straw (RPC and RHC) and cow manure (CPC and CHC) on the peanut (Arachis hypogaea L.) seedling growth in a coastal salt-affected soil of Yellow River Delta, China. The results showed that RPC, CHC and CPC significantly elevated fresh shoot weight by 67.77%–89.37%, whereas the RHC amendment showed little effect. The malondialdehyde contents in peanut seedling leaves were significantly declined by 25.28%–35.51% with pyrochar and hydrochar amendments, which might be associated with the enhanced proline contents and K/Na ratios. The stimulation of certain phytohormones (e.g., indole-3-acetic acid, zeatin riboside, gibberellic acid 3) in peanut seedlings with pyrochar and hydrochar amendments, might be attributed to the growth enhancement. RPC, CPC and CHC improved the soil properties and fertility such as cation-exchange capacity (CEC), total nitrogen, and available potassium and water holding capacity (WHC) of the coastal salt-affected soil. However, RHC not only significantly decreased soil CEC and WHC, but also increased soil exchangeable sodium percentage. The abundances of soil beneficial bacteria, such as f_Gemmatimonadacea, Sphingomonas, Blastococcus and Lysobacter were enhanced by RPC, CHC and CPC amendments, which were mainly associated with the increased WHC and CEC. Fungal community was less sensitive to pyrochar and hydrochar amendments than bacterial community according to the relative abundance and diversity, and beneficial fungi, such as Oidiodendron and Sarocladium were enriched in the CHC soil. Overall, the application of RPC, CHC and CPC showed greater potentials for the enhancement of peanut growth in a coastal salt-affected soil.
Biochar is a pyrogenic carbonaceous material with well-developed porous structure and tunable functionality, and has triggered great interests in its agronomic and environmental benefits. However, unintended consequences related to biochar application are poorly understood. This chapter provides a systematic review on the structural development and characterization of biochar, which impact its function as a soil amendment including carbon sequestration, soil improvement, salinity and drought stress amelioration, and remediation of polluted soils. The relationships between biochar properties and its applications as well as the potential risks on plants and humans are also analyzed critically. Future research foci are suggested for green and sustainable applications of biochar.
In this chapter, the soil ecosystem is introduced as a multiphase system that (i) acts as habitat for a wide diversity of soil organisms and (ii) varies at both spatial and temporal scale. The soil formation varies according to a combination of geological factors and biological process (e.g., here included the influence of mankind) that result in an almost infinite variation in soil-forming factors. Basically, five forming factors are defined as the most important factors. These forming factors are parent material, climate, topography, time, and the activity of soil organisms (e.g., plant roots, insects, microorganisms, human influence, etc.). Considering the wide range of soil properties, i.e., physical, chemical, and biochemical variables, in this chapter we focused only on describing the most important and significant properties to soil organisms, such as soil organic carbon, soil pH, soil aggregation, and moisture. Finally, when considering the tremendous variety of soil types, the need for soil ecologist to recognize this variation must be considered to avoid stresses. Especially, if the student is considering both spatial and temporal variation into soil ecosystem. In view of this, it is important that soil ecologist must consider both soil biota and soil ecosystem characterization.
Salinization of soils and freshwater resources by natural processes and/or human activities has become an increasing issue that affects environmental services and socioeconomic relations. In addition, salinization jeopardizes agroecosystems, inducing salt stress in most cultivated plants (nutrient deficiency, pH and oxidative stress, biomass reduction), and directly affects the quality and quantity of food production. Depending on the type of salt/stress (alkaline or pH-neutral), specific approaches and solutions should be applied to ameliorate the situation on-site. Various agro-hydrotechnical (soil and water conservation, reduced tillage, mulching, rainwater harvesting, irrigation and drainage, control of seawater intrusion), biological (agroforestry, multi-cropping, cultivation of salt-resistant species, bacterial inoculation, promotion of mycorrhiza, grafting with salt-resistant rootstocks), chemical (application of organic and mineral amendments, phytohormones), bio-ecological (breeding, desalination, application of nano-based products, seed biopriming), and/or institutional solutions (salinity monitoring, integrated national and regional strategies) are very effective against salinity/salt stress and numerous other constraints. Advances in computer science (artificial intelligence, machine learning) provide rapid predictions of salinization processes from the field to the global scale, under numerous scenarios, including climate change. Thus, these results represent a comprehensive outcome and tool for a multidisciplinary approach to protect and control salinization, minimizing damages caused by salt stress.
Salt stress in soils impacts grain crop yield. Soil amendment with biochar and arbuscular mycorrhizal alone has been analyzed to improve the growth of several crops under salinity stress. However, the combined application of biochar and arbuscular mycorrhizal fungi for the remediation of salinity and improvement of crop productivity in wheat are rarely discussed and have remained unclear. Therefore, this experiment was performed to investigate the effect with biochar (150 g biochar per each treated pot containing 3 kg soil) and/or arbuscular mycorrhizal fungi (20 g AMF inoculum containing 80% mycorrhizal roots, 100–160 spores, and extraradical hyphae per each treated pot) on the productivity of wheat (Triticum aestivum L.) under four salt stress gradients; 0, 50, 100, and 150 mM NaCl. The results show salinity significantly reduced plant height (9.9% to 22.9%), shoot fresh weight (35.6% to 64.4%), enzymatic activities (34.1% to 39.3%), and photosynthetic pigments—i.e., total chlorophyll contents (75.0%) and carotenoids contents (56.2%) of plants—as compared with control. Under exclusive biochar application, the plants were moderately tolerant to salinity stress, which was evident in their growth, moderately reduced fatty acid content, partially impaired enzymatic activity, and photosynthetic pigments, while under the exclusive AMF application, the wheat plants were relatively sensitive to salinity stress, resulting in impaired growth rate, decreased unsaturated fatty acid composition, enzymatic activity, and photosynthetic pigments. Conversely, under the co-application of biochar and AMF, wheat plants partially increased plant height (14.1%), shoot fresh biomass (75.7%), root fresh biomass (24.9%), partially increased enzymatic activity (49.5%), and unimpaired photosynthetic pigments (30.2% to 54.8%) of wheat under salinity stress. Current findings concluded that exclusive incorporation of biochar, and the synergistic application of AMF and biochar, could be utilized as a promising way to reduce the deleterious effects of salinity stress in wheat production.
Soil salinity has become a major threat to land degradation worldwide. The application of organic amendments is a promising alternative to restore salt-degraded soils and alleviate the deleterious effects of soil salt ions on crop growth and productivity. The aim of present study was to explore the potential impact of biochar and vermicompost, applied individually or in combination, on soil enzyme activity and the growth, yield and quality of Hybrid Pennisetum plants suffered moderate salt stress (5.0 g kg⁻¹ NaCl in the soil). Our results showed that biochar and/or vermicompost promoted Na⁺ exclusion and K⁺ accumulation, relieved stomatal limitation, increased leaf pigment contents, enhanced electron transport efficiency and net photosynthesis, improved root activity, and minimized the oxidative damage in Hybrid Pennisetum caused by soil salinity stress. In addition, soil enzymes were also activated by biochar and vermicompost. These amendments increased the biomass and crude protein content, and decreased the acid detergent fiber and neutral detergent fiber contents in salt-stressed Hybrid Pennisetum. Biochar and vermicompost addition increased the biomass and quality of Hybrid Pennisetum due to the direct effects related to plant growth parameters and the indirect effects via soil enzyme activity. Finally, among the different treatments, the use of vermicompost showed better results than biochar alone or the biochar–compost combination did, suggesting that the addition of vermicompost to the soil is an effective and valuable method for reclamation of salt-affected soils.
Thí nghiệm được tiến hành nhằm đánh giá ảnh hưởng của lượng bón biochar đến sinh trưởng, sinh lý và năng suất của giống lạc L27 trong điều kiện mặn. Thí nghiệm hai nhân tố được bố trí theo phương pháp split-plot. Nhân tố 1 gồm 4 mức bón biochar (0, 5, 10 và 15 tấn/ha), nhân tố 2 gồm điều kiện gây mặn và không gây mặn. Công thức gây mặn được xử lý ba ngày một lần với lượng 200ml dung dịch NaCl 100mm trong vòng 30 ngày từ khi cây bắt đầu ra hoa. Kết quả thí nghiệm cho thấy mặn làm giảm đáng kể các chỉ tiêu sinh trưởng, các chỉ tiêu sinh lý cũng như khả năng hình thành nốt sần. Bên cạnh đó mặn làm tăng mức độ rò rỉ ion và độ thiếu hụt bão hòa nước dẫn đến làm giảm các yếu tố cấu thành năng suất và năng suất cá thể. Bón biochar làm tăng các chỉ tiêu sinh trưởng, chỉ tiêu sinh lý và các yếu tố cấu thành năng suất cũng như năng suất cá thể trong cả hai điều kiện gây mặn và không gây mặn. So sánh giữa các mức bón biochar, mức bón 10 tấn/ha cho các chỉ tiêu sinh trưởng, chỉ tiêu sinh lý và các yếu tố cấu thành năng suất cũng như năng suất cá thể cao hơn so với các mức bón còn lại. Từ khóa: Biochar, lạc, mặn, năng suất.
Estuarine wetlands are often located in economically developed and densely populated estuarine deltas, which are frequently disturbed and threatened by human activities. Reclamation, as an important way to alleviate the demand for local land resources, can lead to habitat destruction of natural coastal wetlands and weakening of ecological service functions, including carbon sink capacity. Research has shown that poor plant growth and weakened carbon fixation were the main reasons for the reduced carbon sequestration in a reclaimed wetland. This study aimed to examine the impacts of plant management on the improvement or restoration of carbon sink function in Chongming Dongtan reclaimed wetland, located in the Yangtze River Estuary, China. A management pattern that could effectively enhance the carbon sink function of the reclaimed wetland was selected based on analyses of the effects of different plant harvesting and management patterns (no harvesting, harvesting without returning to the field, direct straw return, and charred straw return) on the plant growth, carbon fixation, and soil respiration, combined with whole-life-cycle carbon footprint evaluation from straw harvest to field return. Compared with no harvesting, the aboveground biomass of direct straw return and charred straw return increased by about 12.3% and 15.5%, respectively (P < 0.05). Simultaneously, straw charring released the least amount of CO2 (1.94 μmol m⁻² s⁻¹) and inhibited degradation of soil organic carbon through affecting its microbial community structure. Moreover, considering the carbon budget of different patterns, the charred straw return pattern also most effectively enhanced the carbon sink function and thus could be used for subsequent improvement of carbon sequestration in reclaimed wetlands.
In midlatitude seasonally frozen areas, the freeze–thaw cycle affects the movement of soil water, which increases the uncertainty in salt transport and aggravates the risk of soil salinization. Based on this, a two-year field study was established on the Songnen Plain, a seasonally frozen area in northern China. Four treatments were set up: (i) control, (ii) corn stover, (iii) biochar, and (iv) combined (joint application of biochar and corn stover). The modified soil underwent seasonal freeze–thaw cycling, accompanied by the evaporation and infiltration of snowmelt water, and the soil salt migration and diffusion characteristics were determined. Both biochar and corn stover regulated the pore structure of the soil and enhanced the infiltration capacity of snowmelt water; notably, the maximum soil moisture contents in the corn stover, biochar and combined treatments increased by 9.33%, 22.12% and 16.37%, respectively, compared with that in the control group. However, biochar with abundant functional groups increased the cation exchange capacity and promoted the migration of salt ions (i.e., Na⁺, K⁺ and Cl⁻), and the surface soil salt content in the biochar treatment was 0.12–0.53 g/kg lower than that for the other three modes during the infiltration period. Additionally, soil water evaporation carried salts upwards, which greatly increased the salt content of the surface soil. Conversely, biochar presented a strong water-holding capacity, which reduced the ineffective evaporation of soil water, while stover acted as a barrier to hinder the return of salt. Among the treatments, the synergistic transport ability of soil salt and water was the lowest in the combined treatment. Overall, the combination of biochar and corn stover had advantages in terms of soil salt leaching and offered a healthy, effective strategy for soil salinization control in cold areas.
Drought and salt stresses adversely affect the growth and yield of plants in agricultural production. Bacillus pumilus, an important plant growth-promoting bacterium, play a significant role in improving plant tolerance to abiotic stresses. In this study, B. pumilus G5 were immobilized in polyvinyl alcohol‑sodium alginate (PVA-SA) microbeads and then applied on the Pharbitis nil under drought and salt stresses by pot experiment. Orthogonal array experiments showed that the optimal immobilization conditions of PVA-SA immobilized G5 microbeads were adsorbent 6.0%, PVA: SA 1:1 (3.0%), CaCl2 4.0%, and bacterium: embedding agent (PVA-SA) 3:4; And the G5 microbeads produced at the optimal condition exhibited better cultivable bacteria count, encapsulation rate, expansion rate and mechanical strength. Pot experiment showed that G5 microbeads significantly increased the length and diameter of root and stem, and dry weight of P. nil during experimental stage under drought and salt stress. G5 microbeads also increased the total cultivable bacteria population, the activities of invertase (INV), urease (URE), phosphatase (PHO) and catalase (CAT), and the contents of available nitrogen (AN) and available phosphorus (AP) in the rhizosphere soil of P. nil. Therefore, our study obtained the optimal process of G5 microbeads, and confirmed its effect on improved plant growth and soil chemical and biological properties of P. nil. Thus it can be used as sustainable tool for eco-friendly bio-inoculants at salinity soil within arid and semi-arid areas.
The Caatinga is one of the largest seasonally dry tropical forests in the world. With an estimated area of 600 000 km2 to 900 000 km2 , it is located in the semi-arid north-east of Brazil. The climate is demanding with constant high temperatures, erratic rainfalls, and regular droughts, resulting in general water scarcity. Moreover, the soils in the Caatinga are usually only of low to medium fertility and often shallow and stony. The water-deficient conditions, paired with poor soils, are severely challenging agricultural practice in the region. As the backbone of agriculture, soils play a crucial role in food production.
Therefore, the overall aim of this dissertation was to sustainably increase the fertility of Caatinga soils on a long-term basis to promote food security and livelihood of the local smallholders. Two important parameters that impact soil fertility were considered: nutrient retention and soil organic carbon (SOC). First of all, the effects of biochar and clay addition on the nutrient retention of an Arenosol were evaluated. Second, the influence of various factors on SOC stocks, in particular grazing, were studied. All research was conducted in the Itaparica region in the state of Pernambuco, Brazil.
For the first thematic part, two locally available and inexpensive soil amendments were selected: a traditionally produced mid-temperature biochar made of the invasive tree species Prosopis juliflora (Sw.) DC and the clayey sediment of a temporarily dry lake. In a batch equilibrium experiment, the sorption of ammonium-N (NH 4+ -N), nitrate-N (NO3- -N), potassium (K+ ), and phosphate-P (PO43- -P) was quantified for substrate mixtures of an Arenosol with increasing shares of biochar and clay, respectively. In a corresponding field experiment using the same substrates, the leaching of NH4+ -N, NO3- -N, and K+ was quantified for two consecutive periods of eight months each by using self-integrating accumulators. Both experiments showed the same tendencies. Biochar addition induced marginal to medium retention of NO3- -N, medium retention for PO43- -P, and medium to strong retention of NH4+ -N. In the field experiment, the biochar showed medium retention of K+ , while it provoked strong K+ release in the batch equilibrium experiment. In contrast, clay addition resulted in the release of NO3- -N and medium to strong retention of NH4+ -N, K+ , and PO43- -P.
Both soil amendments showed the potential to enhance the retention of nutrients and, thus, the fertility of an Arenosol. The nutrient retention capacity of the clay remained relatively stable for the 16 months of the field experiment, whereas the retention capacity of biochar significantly dropped for all nutrients by about half in the second observation period compared to the first. The reason was the comparatively low stability of this particular biochar, causing rapid decomposition under the given climatic conditions. Therefore, for future application, the long-term stability of biochar should be enhanced by higher pyrolysis temperatures.
In the second thematic part of this dissertation, SOC stocks of Caatinga soils were quantified on 45 study plots for the upper 5 cm of the soil profile and greater soil depths down to bedrock. Along a gradient of light, medium, and heavy grazing intensity, the impact of grazing on SOC stocks was assessed. Additionally, the influence of clay content, distance to the nearest permanent water body, several vegetation parameters, depth to bedrock, and altitude on SOC stocks were analysed.
The mean organic carbon content in the area was relatively low with 16.86 ± 1.28 Mg C ha −1 . Heavy grazing significantly reduced carbon stocks in the upper 5 cm of the soil profile but had no significant effect in greater soil depths. Clay content and altitude proved to be the most relevant factors influencing SOC stocks of the total soil profile and the stocks below the upper 5 cm.
In summary, grazing has adverse effects on SOC stocks and, consequently, on the fertility of the soils in the Caatinga. In particular, high grazing intensities should be avoided, and animal stocking rates should be reduced and adapted to sustainable local carrying capacities. Conclusively, based on the outcomes of the conducted research, recommendations for agriculture and future research were made.
A 30-day incubation experiment was conducted using a heavy metal-contaminated mined soil amended with date palm feedstock (FS) and its derivative biochars (BCs) at three pyrolysis temperatures of 300 (BC-300), 500 (BC-500), and 700 °C (BC-700) with different application rates (0.0, 5, 15, and 30 g kg⁻¹) to investigate their short-term effects on soil respiration (CO2–C efflux), microbial biomass carbon (MBC), soil organic carbon (SOC), mobile fraction of heavy metals (Cd, Cu, Pb, Zn, Mn, and Fe), pH, and electrical conductivity (EC). The results showed that FS and BC-300 with increasing addition rate significantly reduced soil pH, whereas SOC, CO2–C efflux, and soil MBC were increased compared to the control. On the contrary, BC-500 and BC-700 increased soil pH at early stage of incubation and have small or no effects on SOC, CO2–C efflux, and MBC. Based on the results, the date palm biochars exhibited much lower cumulative CO2–C efflux than feedstock, even with low-temperature biochar, indicating that BCs have C sequestration potential. Applying BC-700 at 15 and 30 g kg⁻¹ significantly reduced cumulative CO2–C efflux by 21.8 and 45.4% compared to the control, respectively. The incorporation of FS into contaminated soil significantly increased the mobile content of Cd and Mn, but decreased the mobile content of Cu. However, BC-300 significantly reduced the mobile content of Cd, Cu, Pb, and Zn. It could be concluded that low-temperature biochar could be used as a soil amendment for reducing heavy metal mobility in mining contaminated soil in addition to minimize soil CO2–C efflux.
Soil degradation by salinity and accumulation of trace elements such as cadmium (Cd) in the soils are expected to become one of the most critical issues hindering sustainable production and feeding the increasing population. Biochar (BC) has been known to protect the plants against soil salinity and heavy metal stress. A soil culture study was performed to evaluate the effect of BC on wheat (Triticum aestivum L.) growth, biomass, and reducing Cd and sodium (Na) uptake grown in Cd-contaminated saline soil under ambient conditions. Soil salinity decreased the plant growth, biomass, grain yield, chlorophyll contents, and gas exchange parameters and caused oxidative stress in plants compared with Cd stress alone. Salt stress increased Cd and Na uptake and reduced the potassium (K) and zinc (Zn) uptake by plants. AB-DTPA-extractable Cd and soil electrical conductivity (ECe) increased under salt stress compared to the soil without NaCl stress. Biochar application improved the plant growth and reduced the Cd and Na uptake except in plants treated with higher BC and salt stress (5.0% BC + 50 mM NaCl). Biochar application reduced the oxidative stress in plants and modified the antioxidant enzyme activities, and reduced the bioavailable Cd under salt stress. The positive effects of BC under lower salt stress while the negative effects of BC under higher BC and salt levels indicated that BC doses should be used with great care in higher soil salinity levels simultaneously contaminated with Cd to avoid the negative effects of BC on growth and metal uptake.
Drought and salt stress negatively affect soil fertility and plant growth. Application of biochar, carbon-rich material developed from combustion of biomass under no or limited oxygen supply, ameliorates the negative effects of drought and salt stress on plants. The biochar application increased the plant growth, biomass, and yield under either drought and/or salt stress and also increased photosynthesis, nutrient uptake, and modified gas exchange characteristics in drought and salt-stressed plants. Under drought stress, biochar increased the water holding capacity of soil and improved the physical and biological properties of soils. Under salt stress, biochar decreased Na+ uptake, while increased K+ uptake by plants. Biochar-mediated increase in salt tolerance of plants is primarily associated with improvement in soil properties, thus increasing plant water status, reduction of Na+ uptake, increasing uptake of minerals, and regulation of stomatal conductance and phytohormones. This review highlights both the potential of biochar in alleviating drought and salt stress in plants and future prospect of the role of biochar under drought and salt stress in plants.
The objectives of this study were to evaluate the effects of different fertilizer types and application rates on ammonia volatilization loss and to explore nitrogen distribution and nitrogen use efficiency using the ¹⁵N isotope tracing technique in different alkaline salt-affected conditions in the Songnen Plain, Northeast China. The results showed a decreasing trend in ammonia volatilization loss from ammonium nitrate and ammonium sulfate, but not that from urea, as the electrical conductivity gradient increased, whereas the reverse trend was found as the pH gradient increased. Ammonia volatilization loss increased in moderately salt-affected soil compared with that in slightly salt-affected soil, particularly during the tillering stage, regardless of the N fertilizer rate. The percentage of N absorbed by rice plants increased from urea but decreased from the soil as the amount of nitrogen was increased. Interestingly, the N retention rate in soil decreased and rice grain yield and nitrogen agronomic efficiency increased as the amount of nitrogen increased in both salt-affected soil conditions. The nitrogen application amount of highest N physiological efficiency was 225 kg·N/ha. Considering high rice production and a minimal environmental threat, we should fully consider controlling ammonia volatilization losses by adjusting the fertilizer type and the crop stage when the fertilizer is applied.
Background and aim
Biochar application to soil is widely claimed to increase plant productivity. However, the underlying mechanisms are still not conclusively described. Here, we aim to elucidate these mechanisms using stable isotope probing.
Methods
We conducted two experiments with uniquely double-labelled (¹⁵N and ¹³C) biochar and its feedstock (residue), applied separately at 15 Mg ha⁻¹. Both experiments contained three treatments: biochar amendment (Biochar), unpyrolysed residue amendment (Residue) and a no addition control (Control). Experiment I was a 119 day pot experiment seeded with Lolium perenne. Experiment II was a 71 day incubation experiment without plants in which CO2 and N2O fluxes were measured.
Results
Both Biochar and Residue significantly increased aboveground productivity compared to Control (140% and 160%, respectively). Initial N immobilisation was stimulated in Residue, whereas not in Biochar. ¹³C–CO2 analysis confirmed that biochar was significantly more recalcitrant than residue. ¹⁵N analysis showed that 2% and 0.3% of grass N was derived from the amended material in Residue and Biochar, respectively.
Conclusions
Our results suggest that biochar-induced yield increases derive from a combination of reduced N immobilization and a moderate N fertilization effect. Although in the short term biochar might offer benefits compared to residue incorporation, it is unlikely that biochar yield gains will be sustainable for the decades to centuries that biochar C can be expected to reside in soil.
Peat is used as rooting medium in greenhouse horticulture. Biochar is a sustainable alternative for the use of peat, which will reduce peat derived carbon dioxide emissions. Biochar in potting soil mixtures allegedly increases water storage, nutrient supply, microbial life and disease suppression but this depends on feedstock and the production process. The aim of this paper is to find combinations of feedstock and production circumstances which will deliver biochars with value for the horticultural end user. Low-temperature (600 °C – 750 °C) gasification was used for combined energy and biochar generation. Biochars produced were screened in laboratory tests and selected biochars were used in plant experiments. Tests included dry bulk density, total pore space, specific surface area, phytotoxicity, pH, EC, moisture characteristics and microbial stability. We conclude that biochars from nutrient-rich feedstocks are too saline and too alkaline to be applied in horticultural rooting media. Biochars from less nutrient-rich feedstocks can be conveniently neutralized by mixing with acid peat. The influence of production circumstances on specific surface area, pH, total pore space and toxicity is discussed. Biochar mildly improved the survival of beneficial micro-organisms in a mix with peat. Overall, wood biochar can replace at least 20% V/V of peat in potting soils without affecting plant growth
Biochar is pyrolysed biomass and largely consists of pyrogenic carbon (C), which takes much longer to decompose compared to the biomass it is made from. When applied to soil, it could increase agricultural productivity through nutrient retention and changing soil properties. The biochar-mediated nutrient retention capacity depends on the biochar properties, which change with time, and on soil properties. Here, we examined the effects of a wood biochar (20 t ha-1), that has aged (21 months) in a grassland field, on gross nitrogen (N) mineralisation (GNM) and 15N recovery using a 15N tracer. The field based microcosm experiment was conducted in two soil types, i.e., a Tenosol and a Dermosol, and also included a phosphorus (P) addition treatment (1 kg ha-1). Compared to control, biochar in combination with P addition significantly increased GNM in the Tenosol. Possibly, biochar and P addition enhanced nutrient availability in this nutrient limited soil thereby stimulating microbial activity and GNM. In contrast, biochar addition reduced GNM in the Dermosol, possibly by protecting soil organic matter (SOM) from decomposition through sorption onto biochar surface and enhanced formation of organo-mineral complexes in this soil that had a higher clay content (29%). Compared to control, biochar significantly increased total 15N recovery in the Tenosol (on average by 12%) and reduced leaching to sub-surface soil layers (on average by 52%). Overall, 15N recovery was greater in the Dermosol (83%) than the Tenosol (63%), but was not affected by biochar or P treatment. The increased N recovery with biochar addition in the sandy Tenosol may be due to NH4+-N retention at exchange sites on aged biochar in the soil, while such beneficial effects may not be visible in the soils with high clay content. Our results suggest that aged biochar may increase N use efficiency through reduced leaching or gaseous losses in sandy soils.
There is little knowledge about whether biochar amendment can reduce soil salinity, though increasing data have shown that biochar amendment can improve soil fertility and crop production. In this study, we hypothesized that biochar amendment could promote salt leaching, and the effect might depend on biochar properties. The aims were to evaluate the impacts of three biochars on promoting salt washing and then find possible biochars as saline soil conditioner. Three biochars derived from rice (Oryza sativa L.) straw (RSB), sunflower (Helianthus annuus) straw (SSB), and cow manure (CMB) through a slow pyrolysis process were respectively added at a rate of 5% (w/w) into 0 to 35 cm (0 to 13.8 in) soil depth of a sulfate (SO4²⁻) saline soil column. After washing with deionized water, the eluent was collected from each column and then measured for electrical conductivity (EC) and major salt ions. At the end of washing, the major salt ions were determined in each soil layer. Results showed that the biochar-amended columns discharged efflux 24 to 40 days earlier than that of the control without biochar (CK). Biochar addition saved 56 to 62 days for the EC values of the efflux to be reduced to 5 dS m⁻¹. Among the three biochars, SSB led to much lower contents of the most detrimental ions of both sodium (Na⁺) and bicarbonate (HCO3⁻) in the soil at the end of experiment, showing that SSB may be a highly potential amendment of saline soils in the Hetao region in China. Further work is required for investigating and confirming the effect of biochar amendment on different saline soils with different textures, salinities, and alkalinities in both lab and field, together with local irrigation water, and then quantifying water saving and crop production through biochar amendment in agriculture.
The 'biochar effect' depicts a phenomenon in which biochar soil amendment enhances plant performance by promoting growth and suppressing disease. Although this phenomenon has been observed in numerous studies, the mode of action that explains it is currently unknown. In order to elucidate mechanisms responsible for the 'biochar effect', we comprehensively monitored tomato plant development and resistance to the foliar fungal pathogen Botrytis cinerea, in biochar-amended and nonamended soils using native biochar and washed biochar, striped of labile chemical constituents. We concomitantly assessed bacterial community succession in the rhizosphere by high-throughput 16S rRNA gene amplicon sequencing and carbon-source utilization profiling. Biochar had little impact on plant physiological parameters. However, both native and washed biochar treatments were characterized by higher rhizosphere bacterial diversity and enhanced carbohydrate and phenolic compound utilization rates coupled to stimulation of bacteria known to degrade phenolic compounds. This study indicates that the 'biochar effect' is at least partially dictated by increased diversity and changes in metabolic potential in the rhizosphere microbiome, which is primarily triggered by the recalcitrant carbon backbone of the biochar and tightly bound compounds. It corresponds to the growing consensus that soil amendments which enhance microbial diversity have important benefits to ecosystem functioning.
Soil salinization has become a worldwide problem that imposes restrictions on crop production and food quality. This study utilizes a soil column experiment to address the potential of using mixed solid waste (vinegar residue, fly ash, and sewage sludge) as soil amendment to ameliorate saline-sodic soil and enhance crop growth. Mixed solid waste with vinegar residue content ranging from 60-90 %, sewage sludge of 8.7–30 %, and fly ash of 1.3–10 % was added to saline-sodic soil (electrical conductivity (EC1:5) = 1.83 dS m−1, sodium adsorption ratio (SAR1:5) = 129.3 (mmolc L−1)1/2, pH = 9.73) at rates of 0 (control), 130, 260, and 650 kg ha−1. Results showed that the application of waste amendment significantly reduced SAR, while increasing soil soluble K+, Ca2+, and Mg2+, at a dose of 650 kg ha−1. The wet stability of macro-aggregates (>1 mm) was improved 90.7–133.7 % when the application rate of amendment was greater than 260 kg ha−1. The application of this amendment significantly reduced soil pH. Germination rates and plant heights of oats were improved with the increasing rate of application. There was a positive correlation between the percentage of vinegar residue and the K/Na ratio in the soil solutions and roots. These findings suggest that applying a mixed waste amendment (vinegar residue, fly ash, and sewage sludge) could be a cost-effective method for the reclamation of saline-sodic soil and the improvement of the growth of salt-tolerant plants.
This study examined the influence of pyrolysis temperature on biochar characteristics and evaluated its suitability for carbon capture and energy production. Biochar was produced from corn stover using slow pyrolysis at 300, 400 and 500°C and 2 hrs holding time. The experimental biochars were characterized by elemental analysis, BET, FTIR, TGA/DTA, NMR (C-13). Higher heating value (HHV) of feedstock and biochars was measured using bomb calorimeter. Results show that carbon content of corn stover biochar increased from 45.5% to 64.5%, with increasing pyrolysis temperatures. A decrease in H:C and O:C ratios as well as volatile matter, coupled with increase in the concentration of aromatic carbon in the biochar as determined by FTIR and NMR (C-13) demonstrates a higher biochar carbon stability at 500°C. It was estimated that corn stover pyrolysed at 500°C could provide of 10.12 MJ/kg thermal energy. Pyrolysis is therefore a potential technology with its carbon-negative, energy positive and soil amendment benefits thus creating win- win scenario.
Purpose
Soil amendment with biochar can result in decreased bulk density and soil penetration resistance, and increased water-holding capacity. We hypothesized that adding biochar could moderate the reductions in infiltration rates (IR) that occur during high-intensity rainstorms in seal-prone soils, and hence result in reduced runoff and erosion rates. The objectives were to (i) evaluate biochar potential to improve infiltration and control soil erosion, and (ii) investigate the mechanisms by which biochar influences infiltration rate and soil loss.
Materials and methods
Rainfall simulation experiments were conducted on two physicochemically contrasting, agriculturally significant, erosion-prone soils of Israel that are candidates for biochar amendment: (i) non-calcareous loamy sand, and (ii) calcareous loam. Biochar produced from mixed wood sievings from wood chip production at a highest treatment temperature of 620 °C was used as the amendment at concentrations from 0 to 2 wt%.
Results and discussion
In the non-calcareous loamy sand, 2 % biochar was found to significantly increase final IR (FIR) by 1.7 times, and significantly reduce soil loss by 3.6 times, compared with the 0 % biochar control. These effects persisted throughout a second rainfall simulation, and were attributed to an increase in soil solution Ca and decrease in Na, and a subsequently decreased sodium adsorption ratio (SAR). In the calcareous loam, biochar addition had no significant effect on FIR but did reduce soil loss by 1.3 times. There were no biochar-related chemical changes in the soil solution of the calcareous loam, which corresponds to the lack of biochar impact on FIR. Surface roughness of the calcareous loam increased as a result of accumulation of coarse biochar particles, which is consistent with decreased soil loss.
Conclusions
These results confirm that biochar addition may be a tool for soil conservation in arid and semi-arid zone soils.
The influence of 15 annual applications of composted (CM) or stockpiled (SM) beef feedlot manure with straw (ST) or wood-chip (WD) bedding on electrical conductivity (EC), soluble cations and anions (Na, K, Ca, Mg, SO4-S, Cl), sodium adsorption ratio (SAR), potassium adsorption ratio (PAR), and pH of a clay loam soil (0–15 cm) in southern Alberta was examined in an irrigated barley silage cropping system. Manure type (CM versus SM) had a significant effect on certain soil salinity parameters. Calcium, Mg, Na, K, and SO4-S were significantly (p ≤ 0.05) greater for SM- than CM-amended soils for certain bedding materials and rates. Electrical conductivity, concentration of soluble cations and anions (Na, K, SO4-S, Cl), SAR, PAR, and pH in the surface soil were greater for ST than WD bedding. Two exceptions were Ca and Mg, where soil concentrations were generally greater for WD than ST. Salinity parameters were greater with increased application rate, and greater for amended than unamended soils. Overall, bedding had considerably more significant effects on soil salinity parameters compared to manure type. Wood-chip bedding may be a management tool for feedlots to lower EC, soluble cations and anions, and pH of surface soils.
Despite a contemporary interest in biochar application to agricultural fields to improve soil quality and long-term carbon sequestration, a number of potential side effects of biochar incorporation in field soils remain poorly understood, e.g., in relation to interactions with agrochemicals such as pesticides. In a field-based study at two experimental sites in Denmark (sandy loam soils at Risoe and Kalundborg), we investigated the influence of birch wood biochar with respect to application rate, aging (7–19 months), and physicochemical soil properties on the sorption coefficient, K
d (L kg−1), of the herbicide glyphosate. We measured K
d in equilibrium batch sorption experiments with triplicate soil samples from 20 field plots that received biochar at different application rates (0 to 100 Mg ha−1). The results showed that pure biochar had a lower glyphosate K
d value as compared to soils. Yet, at the Kalundborg soils, the application of biochar enhanced the sorption of glyphosate when tested after 7–19 months of soil–biochar interaction. The relative enhancement effect on glyphosate sorption diminished with increasing biochar application rate, presumably due to increased mineral–biochar interactions. In the Risoe soils, potential biochar effects on glyphosate sorption were affected by a distinct gradient in soil pH (7.4 to 8.3) and electrical conductivity (0.40–0.90 mS cm−1) resulting from a natural CaCO3 gradient. Thus, glyphosate K
d showed strong linear correlation with pH and EC. In conclusion, the results show that biochar, despite initially being a poor sorbent for glyphosate, can increase glyphosate sorption in soil. However, the effect of biochar on glyphosate sorption is depends on prevailing soil physicochemical properties.
Pot experiments were conducted to study the effects of biochar application rates (5, 10, 20 g/kg) and types of wheat straw biochar (WS), corn stalk biochar (CS) and peanut shell biochar (PS) on Suaeda salsa (S. salsa) growth and properties of saline soil in Yellow River Delta. It was found that S. salsa yield increased from 11.7 to 115 % under WS application at a range of 5–10 g/kg compared with control. As biochar rate increased to 20 g/kg, the increment decreased to 102 %. The underground biomass of S. salsa only increased at 20 g/kg rate. The S. salsa growth respond to biochar followed the order of PS > WS > CS. Biochar application generally reduced saline soil pH and the effect was more obvious for WS. The content of total organic matter increased significantly at biochar rate of 10–20 g/kg. WS at higher application rate (20 g/kg) significantly increased available phosphorus content. At the same time, CS increased more available phosphorus content while PS decreased more of exchange sodium percentage. In generally, biochar application improved saline soil quality and enhanced plant growth although these effects should be tested in long-term period.
A laboratory study was conducted to test the effects of biochars made from different feedstocks on soil quality indicators of arid soils. Biochars were produced from four locally-available agricultural residues: pecan shells, pecan orchard prunings, cotton gin trash, and yard waste, using a lab-scale pyrolyzer operated at 450 °C under a nitrogen environment and slow pyrolysis conditions. Two local arid soils used for crop production, a sandy loam and a clay loam, were amended with these biochars at a rate of 45 Mg·ha−1 and incubated for three weeks in a growth chamber. The soils were analyzed for multiple soil quality indicators including soil organic matter content, pH, electrical conductivity (EC), and available nutrients. Results showed that amendment with cotton gin trash biochar has the greatest impact on both soils, significantly increasing SOM and plant nutrient (P, K, Ca, Mn) contents, as well as increasing the electrical conductivity, which creates concerns about soil salinity. Other biochar treatments significantly elevated soil salinity in clay loam soil, except for pecan shell biochar amended soil, which was not statistically different in EC from the control treatment. Generally, the effects of the biochar amendments were minimal for many soil measurements and varied with soil texture. Effects of biochars on soil salinity and pH/nutrient availability will be important considerations for research on biochar application to arid soils.
The development of irrigated agriculture is necessary for fulfilling the rising food requirements of the burgeoning global population. However, the intensification of irrigated agriculture causes the twin menace of waterlogging and soil salinization in arid and semiarid regions where more than 75% of the world's population lives. Waterlogging and salinization have direct and indirect effects on plant growth and yield. The damage to plant growth and yield is much serious when these processes occur simultaneously and generally yield reduction is linearly correlated with the salinity level. The control of shallow water table with irrigation management and installation of drainage systems are suggestible to control the waterlogging and salinization problems of irrigated agriculture. This paper presents an overview of the different aspects of waterlogging and soil salinization and its impact on the food production and sustainability of irrigated agriculture. Conclusions are provided which could be useful for all the stakeholders
Soil health is essential and irreplaceable for plant growth and global food production, which has been threatened by climate change and soil degradation. Degraded coastal soils are urgently required to reclaim using new sustainable technologies. Interest in applying biochar to improve soil health and promote crop yield has rapidly increased because of its multiple benefits. However, effects of biochar addition on the saline-sodic coastal soil health and halophyte growth were poorly understood. Response of two halophytes, Sesbania (Sesbania cannabina) and Seashore mallow (Kosteletzkya virginica), to the individual or co-application of biochar and inorganic fertilizer into a coastal soil was investigated using a 52 d pot experiment. The biochar alone or co-application stimulated the plant growth (germination, root development, and biomass), primarily attributed to the enhanced nutrient availability from the biochar-improved soil health. Additionally, the promoted microbial activities and bacterial community shift towards the beneficial taxa (e.g. Pseudomonas and Bacillus) in the rhizosphere also contributed to the enhanced plant growth and biomass. Our findings showed the promising significance because biochar added at an optimal level (</=5%) could be a feasible option to reclaim the degraded coastal soil, enhance plant growth and production, and increase soil health and food security.
Soil cadmium (Cd) contamination and drought stress are among the main issues hindering global food security. Biochar has been used to reduce metal uptake by plants and water stress mitigation, but long-term residual effects of biochar under Cd stress at different moisture levels needs to be investigated. A following rice (Oryza sativa L.) was grown after wheat on Cd-contaminated soil amended with different levels of biochar (0, 3.0, and 5.0%, w/w). Thirty five days old plants were irrigated with three moisture levels including zero drought as a control (1-2 cm water layer on soil), mild drought (MD, 50% of soil water holding capacity, WHC), and severe drought (SD, 35% of soil WHC) for an accompanying 35 days. Plant height, biomass and photosynthesis were reduced whereas oxidative stress increased under MD and SD than control in un-amended soil while opposite trends were observed in plants grown in biochar amended soil. At the same biochar addition, Cd concentrations in seedlings were lower in continuous flooding than MD and SD treatments. The biochar supply reduced the bioavailable Cd in the soil whereas increased the soil EC and pH than the control treatment. In conclusion, continuous flooding plus residual biochar can be strategized in mitigating Cd-contamination in paddy soils and decreased Cd concentrations in rice which may reduce the potential risks to humans.
Pyrogenic carbon (PyC), including soil native PyC and engineered PyC (biochars), is increasingly being recognized for its potential role as a low-cost immobilizer of contaminants in soils. Published reviews on the role of soil native PyC as a sorbent in soils have so far focused mainly on organic contaminants and paid little or no attention to inorganic contaminants. Further, a comprehensive review on the production of both natural PyC and engineered PyC (biochars), mechanisms involved and factors influencing their role as soil contaminant immobilizer is so far not available. The objective of this review is thus to systematically summarize the sources, formation and properties of PyC, including its quantification in soils, followed by their roles in the immobilization of both organic and inorganic contaminants in soils. Effectiveness of PyC on bioavailability, leaching, and degradation of soil contaminants were summarized. Notably, mechanisms and factors (for the first time) influencing the immobilization processes for soil contaminants were also extensively elucidated. This review helps better understand and design PyC for soil contaminant immobilization.
Experiments were conducted on two wheat (Triticum aestivum L) cultivars exposed to NaCl stress with and without potassium (K) supplementation. Salt stress induced using NaCl caused oxidative stress resulting into enhancement in lipid peroxidation and altered growth as well as yield. Added potassium led to significant improvement in growth having positive effects on the attributes including nitrogen and antioxidant metabolism. NaCl-induced stress triggered the antioxidant defence system nevertheless, the activity of antioxidant enzymes and the content of non-enzymatic antioxidants increased in K fed plants. Enhancement in the accumulation of osmolytes comprising free proline, sugars and amino acids was observed at both the developmental stages with K supplementation associated with improvement of the relative water content and ultimately yield. Potassium significantly increased uptake and assimilation of nitrogen with concomitant reduction in the Na ions and consequently Na/K ratio. Optimal K can be used as a potential tool for alleviating NaCl stress in wheat to some extent.
Salinity is an important environmental constraint to crop productivity in arid and semi-arid regions of the world. Most crop plants, including tomato (Lycopersicon esculentum Mill), are sensitive to salinity throughout the ontogeny of the plant. Biochar was used in the present study to improve the available water content (AWC), growth, yield and irrigation water use efficiency of tomato plant under saline soil condition. The biochar was applied at the rates of, 0%, 2% and 4% w/w and expressed as Ck (control), T1 and T2, respectively. The experiment was conducted in the pots inside the greenhouse. The results showed that soil bulk density, field capacity, permanent wilting point, AWC, and soil organic matter were improved significantly as biochar application rate increased. Biochar application also enhanced plant height, stem diameter, plant fresh and dry weights and yield components of tomato plant. It was found that biochar application at T2 treatment in the whole growing period was best to improve tomato plant growth and yield, providing a biochar amendment recommendation for tomato production in field. Moreover, biochar application improved the irrigation water use efficiency. Therefore, biochar amendment could be an effective option to improve saline soil which affected croplands.
To assess the effects of rice husk biochar (400 °C, 0.5 h) on the conversion of soil phosphorus in different soil types in China, a nine week microcosm incubation experiment was performed using acid red soil, organic brown soil, and saline soil, which were amended with 0, 10, 20 and 40 t/hm² biochar. Soil physico-chemical properties, microbial biomass, phosphatase activities, phosphate solubilizing bacteria, and bacterial community characteristics were investigated. The results showed that rice husk biochar significantly modulated the pH of the three studied soils by 0.1–0.2 units and increased the soil gravimetric water content by 0.3–1.4% over that of the controls. The addition of biochar significantly enhanced the Olsen-P and microbial biomass carbon in all studied soils, and this was partly dependent on the rate of biochar application. The levels of soil microbial biomass phosphorus and phosphatase activities were most significantly increased with 20 t/hm² biochar treatment. These results showed that treatment with rice husk biochar could provide more suitable growth conditions for soil bacteria and significantly enhance soil phosphorus availability and related enzymes. Furthermore, bacterial communities were investigated in all three soils using Illumina MiSeq pyrosequencing to generate tentative taxonomic assignments, which differed statistically over time. The results of a heat map with principal component analyses suggested that the biochar tended to shape the structure of bacterial communities in degraded soils such as acid red soil and saline soil. The most significant variation could be observed in the acid red soil. Biochar increased the relative abundance and distribution of Thiobacillus, Pseudomonas, and Flavobacterium in soils by varying degrees; all three are reported to be genera of phosphate solubilizing bacteria. In conclusion, biochar had a positive effect on phosphate solubilizing bacteria and contributed to increasing phosphorous availability.
Microbial decomposition and invertebrate comminution of a particular organic substrate are largely regulated by temperature and water availability. Numerous metrics have been used to model decay processes at large regional-to-global scales. However, their use at smaller landscape scales might not be practical or feasible. Aridity, generally defined as the balance between long term annual precipitation (P) and potential evapotranspiration (PET), is a metric that synthesizes the major climatic drivers regulating ecosystem processes including the activity of microbes and invertebrates on the forest floor. Thus, aridity indices (AIs) can theoretically represent suitable predictors of decomposition and comminution processes at landscape scale.
Biochar and nitrification inhibitors are increasingly being proposed as amendments to improve nitrogen use efficiency (NUE). However, their effects on soil denitrification and the major N loss in rice paddies over an entire rice-growing season are not well understood. In this study, using intact soil core incubation combined with N2/Ar technique, the impacts of biochar and a nitrification inhibitor (Ni), 2-chloro-6-(trichloromethyl)-pyridine, on rice yield and soil denitrification, as well as ammonia (NH3) volatilization, were investigated over two rice-growing seasons in the Taihu Lake region of China. Field experiments were designed with four treatments: N0 (no N applied), N270 (270 kg N ha? 1 applied), N270 + C (25 t ha? 1 biochar applied) and N270 + Ni (2-chloro-6- [trichloromethyl] -pyridine, 1.35 kg ha? 1 N applied). Compared with single application of N fertilizer alone (N270), biochar (N270 + C) and Ni (N270 + Ni) applications increased rice yields by 4.2?5.2% and 6.2?7.3%, respectively. The cumulative N2-N and NH3-N losses in different treatments varied from 11.9 to 21.8% and from 11.5 to 22.0% of the applied N, respectively. Compared with the single application of N fertilizer, the Ni application increased total NH3 emission by 4.0?20.6% and significantly decreased total N2-N emission by 9.7?19.4% (p < 0.05), while the biochar application increased total NH3 and N2-N emissions by 8.6?17.9% and 3.3?9.7%, respectively. Overall, the biochar application resulted in an 11?15% higher net gaseous N than the Ni application. Although the biochar application may increase the rice yield and consequently the plant N uptake, it also promoted N loss more than Ni. Therefore biochar may not be good for maintaining soil fertility over a long period. Instead, applying Ni may be an optimal practice to ensure food security, while decreasing gaseous N loss, for rice production in the Taihu Lake region of China.
Biochars are, amongst other available amendment materials, considered as an attractive tool in agriculture for carbon sequestration and improvement of soil functions. The latter is widely discussed as a consequence of improved physical quality of the amended soil. However, the mechanisms for this improvement are still poorly understood. This study investigated the effect of woodchip biochar amendment on micro-structural development, micro-and macro-structural stability, and resilience of two differently textured soils, fine sand (FS) and sandy loam (SL). Test substrates were prepared by adding 50 or 100 g kg −1 biochar to FS or SL. Total porosity and plant available water were significantly increased in both soils. Moreover, compressive strength of the aggregates was significantly decreased when biochar amount was doubled. Mechanical resilience of the aggregates at both micro-and macro-scale was improved in the biochar-amended soils, impacting the cohesion and compressive behavior. A combination of these effects will result in an improved pore structure and aeration. Consequently, the physicochemical environment for plants and microbes is improved. Furthermore, the improved stability properties will result in better capacity of the biochar-amended soil to recover from the myriad of mechanical stresses imposed under arable systems, including vehicle traffic, to the weight of overburden soil. However, it was noted that doubling the amendment rate did not in any case offer any remarkable additional improvement in these properties, suggesting a further need to investigate the optimal amendment rate.