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Soil pH is one of the essential vital features that increases or decreases the nutrient availability in soil. The lower pH lessens the secondary macronutrient availability while higher pH limits the available micronutrient in soil. Furthermore, the pesticides efficiency, use of organic and inorganic fertilizers sources to soil also required proper pH for maximum utilization by plants. Therefore, soil pH is termed as "principal soil indicator" that affect the biogeochemical cycles and has broader effects on the soil microbial community. Mineral approaches used to alter the soil pH had demonstrated drawbacks that it is too difficult to change. That’s why alteration in rhizospheric pH can be a practical approach. Hence, a microbial-breeding technique such as genome replication of microbes may be a suitable approach to alter rhizospheric pH. It might be possible that microbes genetic product releases too much acidic or basic compounds that increase or decrease the pH of rhizosphere. Greater exploitation of microbes in this respect would be essential to pursue, as they have the ability to resolve several stresses in a more sustainable manner. In order to breed the microbes selectively for optimal nutritional interactions with plants, the genetic components of different traits must first be practiced.
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International Journal of Agriculture and Biological Sciences- ISSN (2522-6584) Jan & Feb 2021
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Influence of Soil Ph and Microbes on Mineral Solubility and Plant Nutrition: A Review
Author’s Details:
Aqarab Husnain Gondal1,*, Irfan Hussain1, Abu Bakar Ijaz1, Asma Zafar1, Bisma Imran Ch1, Hooria
Zafar1, Muhammad Danish Sohail1, Humaira Niazi2, M Touseef1, Asim Ali Khan2, Maryam Tariq1,
Hamza Yousuf1, Muhammad Usama1
1Institute of Soil and Environmental Sciences, University of Agriculture, 38000, Faisalabad, Punjab, Pakistan
2College of Agriculture, University of Sargodha, 40100, Sargodha Punjab, Pakistan
Corresponding Author* Email:
Received Date: 09-Feb-2021 Accepted Date: 27-Feb-2021 Published Date: 28-Feb-2021
Soil pH is one of the essential vital features that increases or decreases the nutrient availability in soil. The
lower pH lessens the secondary macronutrient availability while higher pH limits the available micronutrient in
soil. Furthermore, the pesticides efficiency, use of organic and inorganic fertilizers sources to soil also required
proper pH for maximum utilization by plants. Therefore, soil pH is termed as "principal soil indicator" that
affect the biogeochemical cycles and has broader effects on the soil microbial community. Mineral approaches
used to alter the soil pH had demonstrated drawbacks that it is too difficult to change. That’s why alteration in
rhizospheric pH can be a practical approach. Hence, a microbial-breeding technique such as genome
replication of microbes may be a suitable approach to alter rhizospheric pH. It might be possible that microbes
genetic product releases too much acidic or basic compounds that increase or decrease the pH of rhizosphere.
Greater exploitation of microbes in this respect would be essential to pursue, as they have the ability to resolve
several stresses in a more sustainable manner. In order to breed the microbes selectively for optimal nutritional
interactions with plants, the genetic components of different traits must first be practiced.
Keywords: Soil pH, Rhizosphere, Organic acids, Basic compounds, Nutrient availability, Growth promotion,
Soil health, Genes transfer
Soil is the essential component of life support systems since it supplies several goods and services that have
positive or negative impacts on human well-being such as water regulation, carbon preservation, food
production, and soil fertility including pH (FAO, 2015; FAO and ITPS, 2015; Jones et al., 2013). The pH is a
negative logarithm of hydrogen ion activity in the soil-water continuum (Hong et al., 2018) and is a critical
component of nutrient availability. Hydrogen ion activity in soil is considered as the dominant phenomenon; at
elevated pH value, the hydrogen ion concentration is low and vice versa (Cushman, 2015). A logarithmic pH
scale is used when hydrogen ion concentration ranges over a broad range; with a pH decrease of 1, the acidity
increases by a factor of 10 (Gethin, 2007). The pH scale varies between 0-14 (Schneider et al., 2007) and
differentiates the soil types with different ranges of pH worldwide. For instance, the pH value of ordinary soil
ranges from 3.5 to 9 and in precipitated areas ranges from 5 to 7 and in dry regions varies between 6.5 to 9
(Queensland Government, 2016).
Upper and lower level of pH in soil solution significantly affect the nutrient uptake and all other
phenomenon’s that occurred in soil. Soil pH directly influences the cation exchange capacity (CEC) (Sparks,
2003). The presence of negative charges on soil colloids tends to develop the CEC of the soil, and the CEC of
soil fluctuate significantly due to change in negative charge (Weil and Brady, 2017). Negative charges on soil
particles (allophones, organic colloids, sequiooxides, and 1:1 types silicates) are increased due to an increase in
pH that also tends to increase the CEC of soil and vice versa (Sollins et al., 1988). Commonly, variable and
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permanent charges are the two types of soil charges (Cunha et al., 2014). Variable charges are completely pH-
dependent (vary with variation in pH), while permanent charges are independent (constant) (Cunha et al., 2014).
Furthermore, the pH explains the chemical behaviour of protons, the main player in redox reactions, and
precipitation, surface complexion, crystal degradation, and other geochemical processes (Bethke et al., 2011).
These processes determine the factors such as salinity, nutrients avaibility, pH, and micronutrients association
in soil solution. It also affect the enzymatic activities, and organic matter (Lauber et al., 2009). However,
increase or decrease in pH significantly influence the crop growth, quality and yield in terms minimum nutrient
Furthermore, each pesticide has its prerequisite for proper functioning. Simultaneously, the soil pH
reaches the inappropriate standard; it may either become ineffective and may not degrade as expected (Nicholls,
1988), resulting in difficulties for the subsequent crop growth period. The intensive cultivation and climatic
changes significantly modify the soil characteristics including pH (Guo et al., 2010; Yang et al., 2012). Hence,
plant growth, pesticide efficacy, soil productivity, microbial activity, and nutrient availability are adversely
affected by soil pH; plant growth problems are common in too alkaline or too basic soils. Besides, many heavy
metals become more water-soluble under acidic conditions and can move down to the soil with water and, in
some instances, move to aquifers, surface streams or reservoirs and soils with a pH of 5.5 or less are likely to be
incredibly corrosive to concrete (USDA Natural Resources Conservation Service, 1998).
Various mineral soil conditioners such as limestone, dolomite, and potassium feldspar etc. are generally
used to overcome the problem of soil acidity and these conditioners are rich source of calcium (Ca+2), silicon
(Si), magnesium (Mg+2), and potassium (K) (Yang et al., 2020). Addition of sulfur (S) may acidify the alkaline
soil to the desirable pH range (McCauley et al., 2009). In addition, natural community disrupt the pH
significantly because of their metabolism (Ye et al., 2012). Microbial population change their metabolism in
several ways. Various microbes such as acidophilic (Thiobacillus acidophilus (a type of bacteria), Vorticella (a
type of eukaryote), and Crenarchaeota (a type of archaea)) maintain the pH towards neutral by secreting basic
compounds in the soil solution (Gemmell and Knowles, 2000) and are resistant to salinity and other abiotic
stresses as prescribed in Table 1. Similarly, Alkaliphilic (Thiohalospira alkaliphila) microbes released acidic
compounds to adjust the pH towards neutral and are also resistant to stresses by adopting various mechanisms
(Kulshreshtha et al., 2012). For instance, the applied S is converted into hydrogen sulfate or sulfuric acid by
particular kind of microbes that helps the soils to bring the pH down a bit (Kopecky, 2014).
Table 1. Tolerance of microbes in acidic and basic environment;
Acidity Tolerant
Alkalinity Tolerant
(Watkin et al., 2003).
Rhizobium tropici
(Muglia et al., 2007;
Wang et al., 2018)
Arbuscular mycorrhiza (AM) Fungi
(Clark, 1997; Bloom et al., 2006)
Alkaliphilic Bacteria
(Torbaghan et al., 2017)
(Shin et al., 2017)
(Shin et al., 2017)
(Shin et al., 2017)
Burkholderia bannensis sp.
(Aizawa et al., 2011)
Sulphur oxidizing bacteria
(Bao et al., 2016)
sign show that data is not available.
Fragile effects of the acidic soil environment
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The soil acidity influence plant development in several ways. Hydrogen (H+), iron (Fe+2 or Fe+3), and aluminum
(Al+3) are common acid-forming cations, while sodium (Na+), K+, Ca+2, and magnesium Mg+2 are base-forming
cations (Diriba, 2018). The solubility of manganese (Mn), Al, and Fe become maximum at lower pH. The
excessive soluble Al in soil solution restricts root growth, reduces the supply of macronutrients, which also
affects microbial development (Cornell University, 2010). These nutrients, however, become too poisonous for
plants when their volume reaches the cap. On the other hand, the availability of macronutrients increases as
certain micronutrients and phosphorus decrease. The lower level of these primary and secondary nutrients
negatively affects plant growth, especially by disrupting the many plant characteristics such as biomass, flower
size and number, lateral spread, and pH-induced pollen production (Jiang et al., 2017). Higher amounts of H+
ions dissolve basic cations at a lower pH level, remove them from exchange sites, release them into the soil
solution, and very small concentration of these nutrients is utilized by plant and remaining is lost by leaching
(University of Hawai'i, 2021). In acidic conditions, microbes and their counts are responsible for transforming
nitrogen (N), phosphorus (P), and sulfur (S) into the usable type of plants (Jacoby et al., 2017), thus reducing
the concentration of minerals. In acidic soils, Mg+2, Ca+2, nitrate ions of nitrogen (N), boron (B), P, and
molybdenum (Mo) availability is reduced (Extension Service of Mississippi State University, 1914; Maathuis,
2009; McCauley et al., 2009). The Ca+2 and Mg+2 ions become inaccessible to the plants by reacting with soil
matrix or adsorption by clay particles and leached to some extent (Maathuis, 2009; McCauley et al, 2009). The
symbiotic nitrogen fixation may be impaired in legume crops after alteration in soil pH. Rhizobium is mainly
responsible for N fixation in legumes, which demands more N (Mabrouk et al., 2018), and its activities have
decreased under acidic conditions.
Fragile effects of the alkaline soil environment
At very alkaline pH levels, mineralization of organic matter is delayed or halted due to weak microbial behavior
(Diriba, 2018) associated with nitrification and nitrogen fixation that is also hindered. The pH of soil influence
the degradation and mobility of insectides and hercides and also influence the heavy metals solubility (Smith
and Doran, 1996). The pH affects cation exchange reactions that modify soil aggregation (Sumner and Miller,
1996), e.g. Ca+2 ions serve as a barrier between clay particles and organic colloids in alkaline or acidic
environments. In addition, the Gaeumannomyces graminis fungus grows well at alkaline pH and thus affects
barley, rye, wheat and various other grasses (Smith and Doran. 1996). At higher pH, denitrification process
become limited due to inhibition in microbial community and accumulation of nitrite (NO2-) occur (Albina et
al., 2019). Mineralization of organic matter is slowed down at alkaline pH and organic matter is pH dependent
(McCauley et al., 2009).
Correlation of soil nutrients and pH
Soil nutrients are essential for vigorous plant growth. Macronutrients (potassium (K), P, and N) are needed by
crop pants in greater quantity and can be handled and applied by fertilizers on crop-based requirements (Rosse
et al., 2011). Fertilizers (organic and inorganic) are a more incredible nutrient source and are pH-dependent
(Neina, 2019). Furthermore, pesticides stability is adversely affected by pH (Schilder, 2008). Soil pH can
change the available type of nutrients in soil solution (Jensen and Thomas, 2010). Changing pH to the indicated
value greatly influences the essential plant nutrient, and plants typically grow well above 5.5 pH. As a rule, 6.5
is the most appropriate pH level for optimum nutrient absorption (Cornell University, 2010). The supply of
nutrients, solubility, microbial population, and various other processes depend on pH. For instance, a higher pH
value promotes micronutrient availability than neutral or alkaline soils that favour plant growth (Lončarić et al.,
2008). Similarly, soil chemical, biological, physical, and other processes are closely interlinked with
biogeochemical cycles and positively affected by soil pH, which eventually influences plant growth, yield, and
biomass (Neina, 2019; Minasny et al., 2016).
pH specification of macro and micronutrients
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A pH range of either 7 or nearly 7 is most suitable for plant growth, since all plant nutrients are readily
available (Hayman and Tavares, 1985) and at pH 5.5 poor solubility of phosphorus, molybdenum, calcium, and
magnesium while solubility of Fe, Al, and B is high. Furthermore, calcium and magnesium become more
abundant at pH 7.8 and pH of 6.6 to 7.3 is optimal for microbial activities that contributes towards plant
available nutrients (N, S, and P) (USDA Natural Resources Conservation Service, 1998). The availability of B
to the plants decreases with an increase in soil pH (Marx et al., 1996), particularly above pH 6.5. However,
highly acidic soils (pH less than 5.0) often appear to be poor in usable soil B due to boron sorption of iron and
aluminium oxide on the soil mineral surfaces (Goldberg, 1997). The K fixation between clay layers tends to be
lower under acidic conditions and is believed to be attributed to the presence of soluble Al occupying the
binding sites, while the accessible type of S had no effect on soil pH (Stanford, 1947). The pH had a crucial
impact on the solubility of Fe (Lindsay and Schwab, 1982). Less than 50% of Fe is available to the plants at pH
7 and due to the precipitation of iron hydroxide at pH 8; none of the Fe is to be found in the soil solution. More
than 90% of Fe become accessible to plant as pH tends toward acidic (< 6.5) (Fageria et al., 2014). With each
unit rise in pH lessens the solubility of Fe approximately by 1000-fold (Lindsay, 1979; Fageria et al., 2014).
The activity of Mn, Cu, and Zn is decreased by 100-fold approximately with increase in each unit of pH in the
range of 4-9 (Lindsay, 1979). Hydrated copper (Cu) exhibit the process of hydrolysis as the pH of soil increases
(pH >6.0), that tends to increase the adsorption of Cu to the organic matter (OM) and clay minerals (Fageria and
Nascente, 2014).
Role of pH in microbial growth
In natural environments, microbes are widespread biota; from hot springs to deep aquifers, in the natural
habitats and also commonly support the microbes in ocean floor (Edwards et al., 2012). They modify a number
of biogeochemical cycles ranging from global carbon cycling and redox reaction to weathering (Maguffin et al.,
2015). A wide variety of environmental factors such as temperature, supply of nutrients, salinity and pH
regulate their metabolism (Amend et al., 2013). Among these factors, pH has greater influence (Chen et al.,
2004). The pH is the indication of managing the microbial community, their activities, and composition (Lauber
et al., 2009). On maximum basis, microbes are classified into three groups namely, alkaliphiles grow fastest
above pH 9, acidophiles grow best at pH <5, neutrophils grow optimally at pH between 5 to 7 (Baker-Austin
and Dopson, 2007). One unit increase or decrease the pH reduce the microbial growth 50% (O'Flaherty et al.,
1998; Kotsyurbenko et al., 2004).
Management of soil pH
Various approaches, methods, and strategies are being used to mitigate the problem of soil pH. Generally for the
management of acidic soils, calcitic limestone is used to maintain the pH towards neutral and is more effective
than the dolomitic limestone (Pennisi and Thomas, 2015) and for high pH elemental sulfur is recommended in
certain cases. Gypsum is more effective to enhance electrical conductivity (EC) of soil than S but S is effective
to reduce the pH of soil than that of gypsum (Turan et al., 2013). Both application pulls the pH towards neutral
as shown in Figure 1. Unfortunately, to change the soil pH is a complicated phenomenon because of all the
artificially applied nutrients sources are pH dependent. Therefore, management of soil pH is necessary to
achieve successful production of horticultural and agronomic crops (Shober et al., 2019). The microbial
breeding approaches can be suitable alternative.
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Figure 1. The mineral application drag the pH towards neutral.
Mechanism of innovative microbial approach
The fluctuation of pH in rhizosphere could be a suitable phenomenon that increase or decrease the pH by
several folds in rhizosphere. The microbial approach can be beneficial if manage properly. In this technique, the
collected microbes (that release organic acids or essential compounds) may be multiplied through genome
transferring until their characteristics become too acidic or basic in rhizosphere to help to alter soil pH where
nutrients are readily available to the plants. The microbial community collected from different sites, alkaline
and acidic medium can be helpful for this purpose because every bacteria has its own characteristics collected
from various locations. The Figure 2 clearly explains the innovative mechanism. Furthermore, in recent years,
this view has helped to begin to answer some common evolutionary concerns regarding how bacteria, along
with their host species, have evolved from their early ancestors. Furthermore, it is of vital significance to
consider how plant tolerance has been affected by their encounters with microbes, although much remains
Acidic soil
Calcitic limestone
Sulfur, gypsum
pH maintenance (neutral
Basic soil
Mineral compounds
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Figure 2. Innovative microbial approach towards neutral soil pH.
In addition, the next challenge is to identify the primary genetic elements that support how different plant
genotypes interact with rhizospheric bacteria. Decades of study have shown that the vulnerability to pathogenic
microorganisms is heavily dependent on the genome of plants, between various species as well as on accessions
of the same species (Zhang et al., 2013). Similarly, Arabidopsis accessions have demonstrated considerable
variance in support for the development of the rhizospheric bacterium Pseudomonas fluorescens in the
hydroponic system (Haney et al., 2015).
Microbial efficiency towards soil pH
Plants do not live on their own; they still have dynamic relationships with microbes (Knack et al., 2015).
Plants allow the microbes (fungi, archaea and bacteria) in all over their tissue and the subsequent accumulation
of microbes is called as phytomicrobiome (Knack et al., 2015; Smith et al., 2017). Various organic acids such as
malic acid, gluconic acid, citric acid, oxalic acid, tartaric acid, lactic acid, and succinic acid are produced by
microbial biota in which both anions and cations serve as chelating agents and anions trap positively charged
ions (Ca+2, Al+3, and Fe+3) present in the soil (Mardad et al., 2013). Plant roots, decay of organic matter, and
bacteria may be the cause of acids in the soil. Previous studies agreed that microbes are the primary cause of
soil organic acid production and therefore the problems associated with the formation of organic acids are
becoming important (Adeleke et al., 2017). From wider variety of ecosystem, the organic acids concentration
Microbial genes
Variation in heredity
material of basic
Variation in heredity
material of acidic
New microbial
Basic compounds
Acidic compounds
New compounds
pH maintenance
Plant growth promotion
Soil productivity
Crop yield
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varies between 0 to 50 μM for tri or dicarboxylic acids such as tartaric acid, citric acid oxalic acid, malic, and
succinic acid while these concentrations varies greatly ranging from 0 to 1 mM in monocarboxylic acids
including formic, valeric, lactic acid, acetic acid, propionic acid, and butyric acids. (Strobel, 2001). However, it
should be focused that these concentrations are extremely variable based on the soil composition, organic matter
degradation, root exudates, and microbes. Microorganisms including bacteria, fungi, and lichen species contain
large quantities of soil organic acids (Ryan et al., 2001, Lian et al., 2008, Aoki et al., 2012).
Increasing or decreasing pH significantly influence the nutrients in soil and ultimately affect the growth and
yield of plants. Various methods are used to solve these problems but it is very complex phenomenon.
Therefore, breeding of microbes may be suitable option. Microbes release organic acids that take part in much
of the physico-chemical processes that make the soil ecological system working. Future crop production may
entail more breeding for pH stress resistance and the introduction of microbial technologies that have improved
tolerance to pH stress. However, the underlining theory that organic acids synthesis in the soil setting is one
process involved in the mineralization and solublization of poorly available and complex minerals, and that it
leads to the carbon cycle, the detoxification of soil metals, among other functions, is possible, although it also
needs further study. Comparing of current and previous genes characteristics by these microbes should be
checked through experiments. In order to selectively breed the microbes for optimal nutritional interactions for
plants, the genetic components of this trait must first be established.
Conflict of interest
The authors do not have any conflict of interest with each other.
All the authors are highly thankfull to Institute of Soil and Environmental Sciences, University of Agriculture,
Faisalabad, Punjab, Pakistan and College of Agriculture, University of Sargodha, Sargodha Punjab, Pakistan.
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... Reduced pH from soil acidification has a negative impact on soil microbes and plants [52]. The nitrogen absorption, nutrient activity, and all other phenomena that occur in soil are substantially impacted by the upper lower pH levels in the soil solution [53]. Beside this, leaching removed considerable quantities of NO3¯ and NH4⁺ − NH from the soil. ...
... Reduced pH from soil acidification has a negative impact on soil microbes and plants [52]. The nitrogen absorption, nutrient activity, and all other phenomena that occur in soil are substantially impacted by the upper lower pH levels in the soil solution [53]. Beside this, leaching removed considerable quantities of NO 3 − and NH 4 + − NH from the soil. ...
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Proper greenhouse fertilization is crucial for establishing high-quality yields, particularly as food demand grows. In this review, the effect of fertilizers, specifically nitrogen, on greenhouses and degradation caused by nitrogen interactions are critically evaluated based on a literature analysis. Nitrogen (N) fertilizers, which represent reactive or biologically accessible nitrogen in soil, are currently used in agricultural systems. Soil, water, and air are endangered by reactive nitrogen pollution. Increasing food demand causes a rise in N fertilizer use, which harms the environment and living organisms. In developing countries, more N is used per capita than in underdeveloped countries. Greenhouse agriculture accounts for 3.6% of total agricultural production. It was revealed that greenhouses in China often get 13–17 times as much nitrogen fertilizer as traditional farming. N was overused abundantly throughout the year, which led to soil acidity, nutritional imbalance, and secondary salinization. Studies on soil salinization and secondary salinization in China date back 70 years. This review attempts to draw attention to the soil damage in greenhouses caused by excessive nitrogen. Nitrate leaching and soil acidity received special attention in this review. Numerous eco-friendly techniques for avoiding soil degradation brought on by the execessive use of fertilizer are also discussed.
... Moreover, the allelopathic interactions between crop residues and aqueous extracts can enhance or affect nutrient availability and yield crop [71]. The most suitable soil pH to enhance nutrient absorption by plants is usually close to 6.5 [72]; PN has a pH closest to that value ( Table 2). In any case, PP, OP and AP have lower pHs than PN. ...
... Therefore, AP, CP, OP, PN, PP and VP could be incorporated mainly in alkaline soils to control the pH. The proper choice of waste is key for crops since variations in soil pH can modify the availability of secondary macronutrients, micronutrients and trace elements that could be presented in the organic wastes and adsorbed in soil surfaces [12,16,28,72]. ...
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Member States of the European Union must ban burning arable stubble by 2023 and improve the recycling of organic waste into fertilizers and organic farming practices by 2030. The current lack of nutrients from soils and crops leads to food insecurity, human malnutrition and diseases. Consequently, innovative solutions are required, as technosols are constructed by waste. The objective of this paper is to educate on the nutrients that some pruning residues can provide. This work characterizes elemental composition, nutrients soluble fraction and physical and chemical properties of the following organic wastes: almond tree pruning, commercial peat substrate, olive tree pruning, pine needle, date palm leaf pruning, sewage sludge compost and vine pruning. The results show significant differences between macro (Na, K, Ca, Mg) and micronutrient (Fe, Mn, Cu, Zn) content and their solubility. Sewage sludge compost, olive pruning and pine needle are the three residues with the highest presence of nutrients in their elemental composition. Nevertheless, if a farmer applies pruning residues as a nutritional supplement for crops, it will be key to finding the short-term soluble nutrient rate and synchronizing the nutritional requirement curve of a plant’s life cycle with its nutrient release. Consequently, organic waste (without composting treatment) obtains higher solubility rates, being date palm leaf residue the one with the greatest value. The solubility index of organic wastes can be significant in providing short-term nutrients to crops. Hence, our results can help in choosing the proper waste to enhance plant nutrient supply, mainly K, Ca, Mg and Na for crop nutrition, to ensure efficient biofertilization.
... In addition, Ca and Mg become more available and optimal for microbial growth, which further helps plants obtain available nutrients (N, S, and P). At more acidic pH, the activities of Mn, Cu, and Zn decrease (Gondal et al. 2021). Chlorophyll content did not vary significantly among the treatments, and it was observed that the substrate did not affect the pigment concentration. ...
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Malus niedzwetzkyana is an endemic, endangered, and valuable plant species. To conservation Malus niedzwetzkyana in nature, it is necessary to obtain planting material with a high survival rate. Selection of optimal pH, light intensity, and fertilizers is necessary to obtain high survival rate during the adaptation period of microshoots after micropropagation and in vitro culture. For optimization of adaptation condition of in vitro rooted microshoots of M. niedzwetzkyana were used. This work investigated the effect of pH level, light intensity, and fertilizers on the growth parameters of micropropogated microshoots of M. niedzwetzkyana. To select the optimal pH and substrate four types of substrates were studied: neutral peat, acid peat, neutral soil, and acidic soil. In addition, as the artificial light source two lighting conditions were studied: LED phyto tapes (4680 lx) and fluorescent phytolamps (7410 lx). In result, highest survival rate was obtained in treatments using peat or soil at neutral pH and 7410 lx light intensity. Additionally, to acclimatize the plantlets in a greenhouse the fertilizers effects were studied: potassium nitrate, monoammonium phosphate, Special crystallon, ammonium nitrate. Thus, irrigation with the Special Crystallon was an effective treatment for seedlings and substantial growth was observed in the aboveground and underground parts of the plants post transfer to greenhouse conditions. After 4 months the average height of seedlings, the number of shoots, and the crown diameter were 114.42 cm, 25.67, and 61.83 cm, respectively with 90% survival rate of planting material after three years under natural conditions.
... Eventually, the unconsumed Ca(OH) 2 absorbs CO 2 from the ambient air, forming CaCO 3 [19]. At the same time, a high pH is not suitable for plants; most of them are conformed to pH values of approximately 7 (for some species up to 8) [31]. A very complicated chain of chemical reactions was determined to assure fast and reliable hardening and, at the same time, fast lowering of the composite pH ( Figure 4) to guarantee the best growing environment for most plant species. ...
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A modern, environmentally friendly urban lifestyle requires paying attention to landscaping and green areas. The scarcity of free land in cities and the high price of land require the combination of greenery with buildings—both vertically and horizontally. The developed green technology for construction brings together computer numerical control (CNC) processing of supporting structures and prefabricated solid planting blocks made of concrete composite. The timber structures are fixed together using traditional carpentry joints. The details, which will be manufactured in the factory using CNC processing at a controlled temperature and humidity corresponding to indoor conditions, can be easily assembled on the construction site. The high bending strength but good elasticity and connections of carpentry joints endow the structure with good properties in a non-controllable environment. By combining CNC-processed wooden structures with concrete technology as substrate composites, labor-intensive manual work in landscaping and gardening will be reduced in the future. The novel material-hardening substrate composite material uses only the residues as the raw materials.
... The micronutrient contents were negatively correlated with pH and electrical conductivity (EC) of soils, whereas organic carbon showed non-significant correlation. Also, the concentration of micronutrients was highly affected by pH as higher concentrations of available micronutrients were generally associated with a neutral to slightly acidic range of pH (Gondal et al. 2021). The heavy texture soils with higher organic matter and lower pH could usually provide a greater reserve of these elements than coarse textured soils such as, the sand having lesser reserves which tend to run out quickly (Yadav and Meena 2009). ...
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Different types of agricultural cropping systems involving wheat coupled with rice, maize and cotton are adapted by most of the farmers around the world. In order to increase the production of food grains with the adaptation of these cropping systems, intensive cultivation is required which eventually needs more quantity of macro as well as micronutrients. The availability of micronutrients to plants is majorly affected by cropping patterns and their profile distribution and the chemical pools. For instance, rice–wheat (R-W) cropping system depletes the available micronutrients status in soil. Many crops have a deep root system that allows them to fulfill their micronutrients requirement from deeper soil layers. In pedon, the surface layer of soil is richer in micronutrients than sub-surface soils. Thus, the knowledge of all the forms or fractions of micronutrient in soil and conditions that help in converting them to their available forms is essential. Excessive use of macronutrient fertilizers in soil with alkaline pH, results in an upsurge accumulation of micronutrients under R-W system. Consequently, it is essential to understand the relationship between accumulation of micronutrients by plants and different chemical pools of micronutrients and their distribution in the pedon. Also, the incorporation of different crops in various cropping systems has a marked influence on microbial communities in soil which play a crucial role in nutrient cycling, gaseous exchanges, aggregation and soil biochemical processes that ultimately influences crop productivity and soil health. Thus, imaging the extent of micronutrient availability to plants, various fractions of micronutrients and microbial community in soil under different cropping systems is necessary.
In spite of well-known mechanisms of iron consumption by plants from the soil and action patterns of iron ions in the soils, the work to eliminate the deficiency of this trace element in plants is still relevant. The article presents an assessment of the effect of iron (III) chelate complexes with diethylenetriaminepentaacetic acid (DTPА Fe) and ethylenediaminetetraacetic acid (EDTA Fe) on the mobility and availability of iron for plants in soil with a pH close to neutral. In a model experiment with using of drainage columns, there were established the patterns of iron distribution in the soil and its removal with irrigation water from the root zone of plants (10 cm). Against the background of similar distribution of iron in the soil, a higher content of its mobile forms in the lower layers was noted when using EDTA Fe. The leaching of iron from the soil was confirmed using both DTPA Fe and EDTA Fe. The vegetation experiment revealed the effect of chelate forms on the accumulation of iron in barley plants (Hordeum vulgare L.) during their early growth period (11 days). The iron content in the shoots varied from 120 to 140 µg/g, in the roots – from 233 to 244 µg/g, with a content of 200 µg/g in the control sample. A significant contribution to the accumulation of iron in barley seedlings was observed at the level of the root system in the experiment with EDTA Fe. Data on the accumulation of iron in barley roots were correlated (r = 0.99) with data on their ash content.
The ever-increasing population, degradation of agricultural lands, use of synthetic chemicals, abrupt change in climate, and crop diseases are posing a threat to agriculture and food security, globally. Modern sustainable agricultural approaches such as nanotechnology could ensure enhanced yield and improve the quality of products without damaging the environment. The rhizospheric bacteria have been shown to improve plant nutrient supply and soil health. Similarly, the input of nanoparticles (NPs) has a positive impact on rhizospheric microbes as well as plant growth with improved soil properties. Thus, the integration of nanotechnology and rhizospheric bacteria will not only boost crop production but also soil health, allowing a sustainable supply of food for a fast population explosion. It is also explored that the addition of NPs as fertilizers could alleviate stress faced by plants. Therefore , the chapter covers the most recent scientific developments in nanotechnology and rhizosphere microbiome manipulation for sustainable agriculture, especially in saline conditions.
Bu araştırmada asit yapılı toprağa kireç ile organik ve inorganik (atık çamuru-AÇ; zeolit- ZEO; polyacrylamide-PAM) kökenli toprak düzenleyici uygulamalarının mısır bitkisinin fosfor beslenmesine etkileri incelenmiştir. Sera koşullarında yürütülen araştırmada kireç 3, düzenleyiciler 4 farklı dozda uygulanmışlardır. Araştırma toprağı killi tekstüre, başlangıçta kuvvetli asit reaksiyona (pH, 5.2) ve orta seviyede organik madde kapsamına sahiptir. Faktöriyel düzende yapılan çalışmada topraklar 56 gün süre ile inkübasyona tabi tutulmuştur. İnkübasyon sonrasında saksılarda mısır bitkisi yetiştirilmiştir. Yapılan uygulamaların çeşit, uygulama düzeyi ile toprağın pH değerine bağlı olarak yetiştirilen mısır bitkisinin P beslenmesinde değişime neden olduğu belirlenmiştir. Düzenleyicilerin mısır bitkisinin P beslenmesi üzerindeki etkileri bakımından AÇ>ZEO> PAM şeklinde sıralandıkları saptanmıştır. AÇ'nun farklı pH seviyelerinde, PAM ve Zeolitin ise sadece nötr pH düzeylerinde etkil oldukları görülmüştür. AÇ'nun %6.0 dozu hafif asit yapılı toprakta P beslenmesinde en etkili uygulama olarak belirlenmiştir.
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Bacterial respiration of nitrate is a natural process of nitrate reduction, which has been industrialized to treat anthropic nitrate pollution. This process, also known as "microbial denitrification", is widely documented from the fundamental and engineering points of view for the enhancement of the removal of nitrate in wastewater. For this purpose, experiments are generally conducted with heterotrophic microbial metabolism, neutral pH and moderate nitrate concentrations (<50 mM). The present review focuses on a different approach as it aims to understand the effects of hydrogenotrophy, alkaline pH and high nitrate concentration on microbial denitrification. Hydrogen has a high energy content but its low solubility, 0.74 mM (1 atm, 30 • C), in aqueous medium limits its bioavailability, putting it at a kinetic disadvantage compared to more soluble organic compounds. For most bacteria, the optimal pH varies between 7.5 and 9.5. Outside this range, denitrification is slowed down and nitrite (NO 2 −) accumulates. Some alkaliphilic bacteria are able to express denitrifying activity at pH levels close to 12 thanks to specific adaptation and resistance mechanisms detailed in this manuscript, and some bacterial populations support nitrate concentrations in the range of several hundred mM to 1 M. A high concentration of nitrate generally leads to an accumulation of nitrite. Nitrite accumulation can inhibit bacterial activity and may be a cause of cell death.
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Two strains of acid-neutralizing bacteria, E25(T) and E21, were isolated from torpedo grass (Panicum repens) growing in highly acidic swamps (pH 2-4) in actual acid sulfate soil areas of Thailand. Cells of the strains were gram-negative, aerobic, non-spore-forming rods, 0.6-0.8 µm wide and 1.6-2.1 µm long. The strains showed good growth at pH 4.0-8.0 and 17-37 °C. The organisms contained ubiquinone Q-8 as the predominant isoprenoid quinone and C(16 : 0), C(17 : 0) cyclo and C(18 : 1)ω7c as the major fatty acids. Their fatty acid profiles were similar to those reported for other Burkholderia species. The DNA G+C content of the strains was 65 mol%. On the basis of 16S rRNA gene sequence similarity, the strains were shown to belong to the genus Burkholderia. Although the calculated 16S rRNA gene sequence similarity of E25(T) to strain E21 and the type strains of Burkholderia unamae, B. tropica, B. sacchari, B. nodosa and B. mimosarum was 100, 98.7, 98.6, 97.6, 97.4 and 97.3 %, respectively, strains E25(T) and E21 formed a group that was distinct in the phylogenetic tree; the DNA-DNA relatedness of E25(T) to E21 and B. unamae CIP 107921(T), B. tropica LMG 22274(T), B. sacchari LMG 19450(T), B. nodosa LMG 23741(T) and B. mimosarum LMG 23256(T) was 90, 42, 42, 42, 45 and 35 %, respectively. The results of physiological and biochemical tests including whole-cell protein pattern analysis allowed phenotypic differentiation of these strains from previously described Burkholderia species. Therefore, strains E25(T) and E21 represent a novel species, for which the name Burkholderia bannensis sp. nov. is proposed. The type strain is E25(T) ( = NBRC 103871(T)  = BCC 36998(T)).
There is increasing evidence that the origins of organic acids (OAs) are as important as their roles and pathways of production. This review focuses on information about challenges associated with various aspects of OA production and release in the soil with the primary intention of harmonising different views to enable better understanding of this topic.A considerable body of work devoted to the understanding of origins, roles and dynamics of OAs in soil has been critically scrutinised for their various positions in this review. Organic acids in the soil originate from a variety of sources that may include plant roots, microorganisms and organic decomposition. Although OA synthesis in the soil environment may reflect a natural response of biological systems to biotic and abiotic stresses, they also play crucial roles in physiochemical processes such as mineralisation and solubilisation of poorly available and complex minerals as well as contribution to the carbon cycle and detoxification of metals. However, these roles are conceivably a pooled effect of soil OAs interacting with other factors (soil type, soil pH, microbes and other metabolites). The key challenge to elucidate and unravel the dynamics of OAs in the soil lies with the ability to explain and understand how OAs are released in the rhizosphere alongside other important metabolites, which perhaps influence the dynamics.
The western area of the Jilin province, a typical seasonal frost region, is located in the southern Songnen plain of China. Significantly salinized soils are widely distributed on the Songnen plain in western Jilin. Soil salinization can cause degradation of cultivated land and grass, which threatens the human environment. To investigate the treatment of saline-alkali soil, a laboratory test was conducted to evaluate the ability of sulfur-oxidizing bacteria to improve the performance of saline-alkali soil in western Jilin. The results showed that sulfur-oxidizing bacteria treatment was suitable for the soil from pH 7.5 to 8, and 50 ml thiobacillusthiooxidans showed the best improvement to the saline- alkali soil.
The availability of phosphorus (P) can limit net primary production (NPP) in tropical rainforests growing on highly weathered soils. Although it is well known that plant roots release organic acids to acquire P from P-deficient soils, the importance of organic acid exudation in P-limited tropical rainforests has rarely been verified. Study sites were located in two tropical montane rainforests (a P-deficient older soil and a P-rich younger soil) and a tropical lowland rainforest on Mt. Kinabalu, Borneo to analyze environmental control of organic acid exudation with respect to soil P availability, tree genus, and NPP. We quantified root exudation of oxalic, citric, and malic acids using in situ methods in which live fine roots were placed in syringes containing nutrient solution. Exudation rates of organic acids were greatest in the P-deficient soil in the tropical montane rainforest. The carbon (C) fluxes of organic acid exudation in the P-deficient soil (0.7 mol C m−2 month−1) represented 16.6% of the aboveground NPP, which was greater than those in the P-rich soil (3.1%) and in the lowland rainforest (4.7%), which exhibited higher NPP. The exudation rates of organic acids increased with increasing root surface area and tip number. A shift in vegetation composition toward dominance by tree species exhibiting a larger root surface area might contribute to the higher organic acid exudation observed in P-deficient soil. Our results quantitatively showed that tree roots can release greater quantities of organic acids in response to P deficiency in tropical rainforests.
Denitrification potential of marsh soils in two natural saline-alkaline wetlands
  • J Bai
  • Q Zhao
  • J Wang
  • Q Lu
  • X Ye
  • Z Gao
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