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基于碎石屏障的土壤盐渍化改良技术及机理研究
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Purpose
Serious soil salinization, including excessive exchangeable sodium and high pH, significantly decreases land productivity. Reducing salinity and preventing alkalization in saline-sodic soils by comprehensive improvement practices are urgently required. The combinations of aluminum sulfate with different types of fertilizer at different rates were applied on rice paddy with saline-sodic soils of the Songnen Plain in Northeast China to improve soil quality and its future utilization.
Materials and methods
Experiments were carried out in a completely randomized block design. Twelve treatments with aluminum sulfate at the rates of 0, 250, 500, and 750 kg hm⁻² with inorganic, bio-organic, and organic-inorganic compound fertilizers were performed. Soil pH, electronic conductivity (EC), cation exchangeable capacity (CEC), exchangeable sodium percentage (ESP), total alkalinity, sodium adsorption ratio (SAR), soil organic carbon (SOC), available nutrients, soluble ions, rice growth, and yield in the saline-sodic soils were measured across all treatments. The relationships among the measured soil attributes were determined using one-way analysis of variance, correlation analysis, and systematic cluster analysis.
Results and discussion
The pH, EC, ESP, total alkalinity, SAR, Na⁺, CO3²⁻, and HCO3⁻ in saline-sodic soil were significantly decreased, while CEC, SOC, available nitrogen (AN), available phosphorus (AP), available potassium (AK), K⁺, and SO4²⁻ were significantly increased due to the combined application of aluminum sulfate with fertilizer compared with the fertilizer alone. The most effective treatment in reducing salinity and preventing alkalization was aluminum sulfate at a rate of 500 kg hm⁻² with organic-inorganic compound fertilizer. This treatment significantly decreased the soil pH, EC, ESP, total alkalinity, SAR, Na⁺, and HCO3⁻ by 5.3%, 28.9%, 41.1%, 39.3%, 22.4%, 23.5%, and 35.9%, but increased CEC, SOC, AN, AP, AK, K⁺, SO4²⁻, rice height, seed setting rate, 1000-grain weight, and yield by 77.5%, 115.5%, 106.3%, 47.1%, 43.3%, 200%, 40%, 6.2%, 43.9%, 20.3%, and 42.2%, respectively, compared with CK treatment in the leaching layer.
Conclusions
The combined application by aluminum sulfate at a rate of 500 kg hm⁻² with organic-inorganic compound fertilizer is an effective amendment of saline-sodic soils in Songnen Plain, Northeast China. These results are likely related to the leaching of Na⁺ from the soil leaching layer to the salt accumulation layer and desalination in the surface soil, and the increase of SOC improved the colloidal properties and increased fertilizer retention in soil. In addition, the environmental impact of aluminum sulfate applied to soil needs to be further studied.
Soil Pore Size Distribution (SPSD) is one of the most important soil physical properties. This research investigated the relationship of SPSD curves location and shape parameters with Plant Available Water (PAW) and Least Limiting Water Range (LLWR) of the Torogh agricultural research station light-textured soils in north-eastern of Iran. Soil Moisture Release Curve (SMRC), PAW and LLWR (measured in matric heads of 100 and 330 hPa for the field capacity) and SPSD curves location and shape parameters of 30 soils with different textures and organic carbon contents were determined and the variables relationships were statistically analyzed. The results showed that the median and mean equivalent pore diameters, Standard Deviation (SD), and skewness of SPSD curves were significantly correlated with PAW330 and LLWR330. Reducing the equivalent pore diameter and increasing the diversity of soil pore sizes, resulted in an increased values of PAW330 and LLWR330. The SD parameters of all soil samples were lower than the optimal ranges which were suggested in the literatures. Comparing the PAW and LLWR values between the soils with the optimal and non-optimal parameters of SPSD curves showed that neither PAW nor LLWR values were significantly different in the soils with the optimal and non-optimal modal equivalent pore diameters. Optimal values of median and mean equivalent pore diameters and kurtosis of SPSD curves led to a significant improvement of PAW330 and LLWR330 as soil physical quality indicators. It was recommended to revise the optimal ranges for SD parameter and modal equivalent pore diameter for future studies.
Purpose
Nutrient deficiency and salt stress (sodium, Na+) strongly limited the productivity of the degraded coastal soils in the Yellow River Delta. Biochar-based functional materials have been considered as a promising amendment to solving the problem of global soil security (e.g., erosion, fertility loss, acidification, and salinization). Therefore, this study aimed to explore the potential of using a biochar-compost amendment (BCA) to improve the coastal soil properties and productivity.
Materials and methods
The BCA was produced from composting of biochar and additives including seafood shell powder, peanut shell, commercial humate, and inorganic nutrients. Two halophytes, sesbania (Sesbania canabina (Retz.) Pers) and seashore mallow (Kosteletzkya virginica), were chosen as the tested plants in a 52-day pot experiment. BCA was added as the rates of 0, 1.5, 5, and 10 % (w/w). At the end of the incubation, the shoot height, biomass, and root morphological parameters including length, tips, and surface area were measured, as well as the properties (e.g., soil organic matter (SOM) content and cation exchange capacity (CEC)) of the rhizosphere and non-rhizosphere soils.
Results and discussion
The BCA application at 1.5 % enhanced the growth of sesbania and seashore mallow and increased their total biomass by 309 and 70.8 %, respectively, while significantly inhibited both the halophyte growths at 10 %. Similarly, both the halophyte root morphologies (e.g., length and tips) significantly increased by BCA addition at 1.5 %. The promoting growth of the both halophytes could be resulted from the improvement of soil properties such as the increased SOM and CEC, the decreased amount of the exchangeable sodium (Ex-Na) and exchangeable sodium percentage (ESP), and the rhizosphere effect (e.g., decreased soil pH). The higher rate of BCA addition (e.g., 10 %) sharply increased soil salinity, responsible for the inhibition of both the halophyte growths. Although BCA addition may directly supply much nitrogen (N) for the soils, N bioavailability for both halophytes was not largely improved.
Conclusions
The short-term laboratory pot experiments revealed that producing the biochar-compost with desired properties (e.g., BCA) could be a feasible alternative to remediate the degraded coastal soil in the Yellow River Delta. Moreover, the addition of BCA should be kept at an optimal level, which may produce expected positive results. Our results will be helpful for supporting the strategy of designing right biochar-compost for the right soil.
Soda saline-alkali soils are characterized by high concentration of sodium cations on the exchange complex or in soil-water resulting in soils which are physically as well as nutritionally challenging for crop production. Biochar application has received growing interest as a sustainable technology to improve physicochemical properties in non-saline and non-alkali soils. However, information is inadequate regarding potential of using corn straw derived biochar as an organic material to reduce soda saline-alkali stress. Based on the established model of corn straw biochar-soda saline alkali soil-corn system, soil and plant samples were collected from long-term field experiment in soda saline-alkali land with different addition rates of corn straw biochar (CK: control, T5: 5 ton ha-1, T10: 10 ton ha-1, T15: 15 ton ha-1, T20: 20 ton ha-1, T25: 25 ton ha-1, T30: 30 ton ha-1). In the seedling and harvest period, addition of corn straw biochar enhanced the contents of cation exchange capacity (CEC), organic matter, and nutrients of 0-20 cm and 20-40 cm saline-alkali soil layers and the above ground and underground parts of corn. However, the results were contrary as far as pH, salt, and Na+ were concerned, and the effect of T20 was the most significant. Principal component analysis showed that CEC, pH, salinity, and organic matter could be used as indicators to evaluate the improvement effect of biochar on soda saline-alkali soil. Irrespective of the application of biochar, pH, salt content, Na+, and nutrients concentrations at seedling stage were higher than those at harvest stage, indicating that planting corn could improve soda saline-alkali soil. It may be concluded that corn straw biochar can be used as an organic amendment for reducing adverse effects of salinity and alkalinity on soil functions governed by their rates of addition.
Crop land degradation is a common phenomenon in most regions of the world, especially in arid and semi-arid regions. To mitigate cropland degradation and further enhance crop productivity, it is crucial to restore soil quality by utilizing efficient soil management practices. Although biochar has been widely used to improve soil conditions, the efficiency of biochar in enhancing crop productivity is often limited by inappropriate agricultural practices (e.g. irrigation and fertilization). Moreover, little information is available regarding the link among availability of water, biochar and productivity. In this study, we measured the effects of biochar addition, daily fertigation and their combination on overall soil quality, crop yield and water-fertilizer productivity in alkaline soils of a semi-arid region, over two years. To comprehensively evaluate soil quality, a wide range of soil physical, chemical, biological and ecological properties were measured and integrated into a soil quality index (SQI). The treatments evaluated were (i) untreated soils managed with traditional irrigation and fertilization (control), (ii) soils treated with biochar and managed with traditional irrigation and fertilization (B), (iii) untreated soils managed with daily fertigation (DF), and (iv) soils treated with biochar and managed with daily fertigation (B + DF). In general, biochar addition enhanced soil quality (expressed by SQI) mainly through increasing soil water content (SWC), available phosphorus (AP), the capacity of soil microbes to utilize miscellaneous (CSM-MI) and microbial biomass carbon (Cmic), and decreasing soil pH and plant-parasitic nematode abundance. Daily fertigation improved soil quality primarily by enhancing SWC, AP, CSM-MI and Cmic. The SQI exhibited strong positive correlations with both plant biomass and fruit yield. In addition, the treatment B + DF showed not only the highest SQI and fruit yield, but also the highest irrigation water-productivity (326.3 and 557.9 kg mm−1 in 2017 and 2018, respectively) and partial factor productivity for fertilizer in both years 2017 and 2018. Our results show that biochar addition combined with daily fertigation can improve overall soil quality, and further enhance cucumber yield and water-fertilizer productivity in alkaline soils.
This paper extends the work of van Duijn et al. (2018) where travelling wave solutions for wetting fronts were considered under the presence of only capillary hysteresis effect and only dynamic capillary effect. In this work, we investigate how the gravity driven wetting fronts behave while moving through long vertical homogeneous porous columns, under the combined effect of capillary hysteresis and dynamic capillarity. It is shown that the developed saturation profiles will exhibit non-monotone behaviour if certain parametric conditions are satisfied. The characteristics of the profiles are explained in detail for all the cases. Moreover, parametric conditions that inhibit the fronts from reaching full saturation are laid out. The analysis agrees well with experimental observations. Finally, numerical results are shown that confirm all the theoretical predictions.
In porous media subject to drying conditions such as arid regions and excavation zones (deep gas injection or nuclear waste disposal), capillarity is involved in weathering processes because it modifies the geochemical and poromechanical balances within the porous network. Heterogeneous porous media like sedimentary rocks can host significant volumes of tensile capillary water in large pore bodies, and the negative pressure within is controlled by capillary forces exerted at nanometric pore throats.
We have developed experiments using synthetic bimodal pore systems conducive to capillary tension. In microtubes, salts precipitated in an evaporating solution to build a dual-porosity system. A large volume (ø200 µm) became trapped behind nanometric pores, where high capillary tension was applied. We investigated the gas-water interactions there, especially how gas nucleated in the trapped liquid and how it subsequently changed size. After gas nucleation, the decreasing of gas volume that we observed has been attributed to two complementary geochemical effects. On the one hand, the water’s tensile state increases gas solubility, as predicted by thermodynamics: capillarity is a “gas-in” process. On the other hand, while the total volume of the gas-water assemblage remains constant, the water’s molar volume increases by capillary forces. Consequently, capillary forces exerted at the nano-throats can (re)induce a superheated monophasic liquid state from a biphasic liquid-gas assemblage even after gas nucleation. Tensions required for gas shrinkage have been estimated at 7 ± 3 MPa and 53 ± 15 MPa. This regeneration process offers opportunities for water to regularly return to a capillary state, making the capillary lifetime less limited than expected.
This shows that pore heterogeneity in rocks submitted to drying processes results in tension for water in pores that is long-lived. As a consequence, capillarity may significantly impact the long-term geochemical budget through its effects on gas and solid solubility and/or poromechanics (compaction, tensile stress, fracturing, etc.), so that it may play an important role in the weathering of drying porous materials.
Burying a straw layer and applying flue gas desulfurization (FGD) gypsum are effective practices to ameliorate soil salinization or alkalization and to increase crop yield, but little information exists on the effects of such integration in saline-alkali soils. A soil column experiment was conducted to investigate the effects of a straw layer plus FGD gypsum on the distribution of soil salinity and alkalinity. We placed a straw layer (5 cm thick) at a depth of 30 cm and mixed FGD gypsum in the 0-20 cm soil layer at application rates of 7.5, 15.0, 22.5, and 30.0 t ha⁻¹; the absence of both the straw layer and FGD gypsum served as the control (CK). Compared with that of the CK, the soil water content in the 0-30 cm soil layer significantly increased (>7.8%) in the treated soils after infiltration but decreased after evaporation. However, the electrical conductivity (EC) in the 10-30 cm soil layer was 230.2 and 104.9% higher in the treated soils than in the CK after infiltration and evaporation, respectively. Furthermore, EC increased with increasing rates of FGD gypsum, and Ca²⁺ and SO4²⁻ were dominant in the dissolved salts. Compared to those in the CK, the concentrations of Na⁺, Cl⁻ and HCO3⁻ decreased in the treated soils at depths above 55 cm, but the other soluble ions increased after infiltration. A similar trend occurred in the other ions after evaporation, except for HCO3⁻. Furthermore, the pH and exchangeable sodium percentage (ESP) in the treated soils were significantly lower than those in the CK over the entire profile, and these values decreased with increasing FGD gypsum application rates. The overall results suggest that the incorporation of a straw layer plus FGD gypsum is a suitable practice to reduce salinity and alkalinity, but the quantity of FGD gypsum should also be controlled in saline-alkali soils.
Column experiments were carried out to investigate effects of total dissolved solids (TDS) (30 g/L and 100 g/L), vadose zone lithology (fine sand and silt clay) and depth of groundwater table (0.5 m, 1.0 m and 3.0 m) on distribution of soil salt accumulation under condition of high salinity phreatic water evaporation in arid areas. Samples were taken seven times from different depths of column for soil salt analysis. The results indicate that under condition of high salinity phreatic water evaporation, the less depth the groundwater table is, the larger soil salinity at the same depth will be. Salinity in soil profile with vadose zone lithology of silt clay is higher than that of fine sand when other conditions are fixed. In addition, soil salinity of phreatic water with TDS of 30 g/L is higher than that with TDS of 100 g/L in the upper layer of silt clay column due to the membrane effect of tenacious soil and filling effect of crystal salt in soil pore, and lower in the lower part of the column. Depth of salt accumulation in silt clay profile tends to shift down with the increase of phreatic water TDS due to the change of capillary water gravity and soil structure as a result of higher TDS.
Seal formation on the soil surface during rainstorms reduces rain infiltration and leads to runoff and erosion. The objective of this study is to investigate the soil seal formation in different soils, and to analyze the chemical and physical processes in it. Experiments were conducted with four different soils with different exchangeable sodium percentages (ESP) (2, 5, 10 and 20) and different clay contents (10%, 20%, 40% and 60%) under rainfall simulation. The effects of ESP and clay content of soil on seal formation were discussed by means of shielding chemical and physical seal formation with spreading phosphogypsum (PG) (2000 kg/hm2) and PG plus (polyacrylamide) PAM (PG 2000 kg/hm2 + PAM 20 kg/hm2) on soil surface. In high ESP soils, chemical seal formation is predominated, and in low ESP soils, the physical seal formation take more shares. The physical seal formation is in low degree with low clay content soils, however, developed well in high clay content soils.
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