Effect of freeze–thaw cycles on carbon stocks of saline–alkali paddy soil

This study aims to provide basic data to support accurate estimation of carbon stocks and reveal the physicochemical factors that influence the carbon cycle in saline–alkali soils. Soil samples were collected during initial freezing, complete freezing, initial thawing and complete thawing stages. Levels of soil organic carbon (SOC), soil inorganic carbon (SIC), moisture, salinity, pH and available nitrogen were determined, and variations were observed during the freezing and thawing periods. Correlation analysis and regression analysis of carbon contents and physicochemical properties were performed. The results showed that freeze–thaw cycles have significant effects on carbon contents. The SOC content initially decreased in the freezing stage and then increased in the thawing stage. However, the SIC content initially increased in the freezing stage, decreased in the initial thawing stage and finally increased in the complete thawing stage. The migration and transformation of SOC and SIC were observed both temporally and spatially. SOC was positively correlated with available nitrogen, moisture and salinity and negatively correlated with pH; while SIC was negatively correlated with available nitrogen, moisture and salinity and positively correlated with pH. Among the factors evaluated, available nitrogen and salinity exerted the greatest effects on SOC and SIC contents, respectively.     

Soil nitrogen leaching losses in response to freeze–thaw cycles and pulsed warming in a temperate old field

Climate warming and increased climate variability are both predicted to increase the frequency of soil freeze–thaw cycles in temperate regions. We exposed intact soil-plant mesocosms to freeze–thaw cycles and examined the effects on nitrogen leaching losses. Freezing treatments were performed by incubating the mesocosms in the soil with their tops exposed to air to impose freezing from the top down, such that realistic freezing rates and cycle amplitudes were experienced across the soil profile. Leaching events were then initiated by water addition the following day for both the freezing treatment and control mesocosms. While water addition alone explained the major part of soluble organic nitrogen leaching, nitrate leaching approximately doubled in response to freeze–thaw cycles, and nitrogen leaching remained high after 11 freeze–thaw cycles. In a second experiment, pulses of warming were applied in situ to mesocosms over fall, winter or spring, in order to melt snow, and thereby increase freeze–thaw cycling by exposing soils to diurnal fluctuations in air temperature. Warming pulses had little effect on sub-surface soil temperatures and no effect on soil nitrogen leaching. However, warming pulses over spring severely reduced the abundance of the legume Coronilla varia in the following growing season. Overall, the results of these experiments indicate that while increased soil freeze–thaw cycles combined with leaching events are capable of increasing soil nitrogen losses, warming pulses will only promote increased freeze–thaw cycles if they are followed by cold, snow-free weather. The strong effect of warming on the N-fixer C. varia highlights that changes in plant species composition in response to warming may have stronger implications for soil nitrogen dynamics than the direct effects of freeze–thaw cycles on soil nitrogen leaching losses.     

Effects of freeze–thaw cycles and the soil water content on carbon and nitrogen changes in different soil types of Heilongjiang Province,China

To reveal the influence of freeze–thaw cycles (FTCs) on soil carbon and nitrogen changes, six typical soils in Northeast China were selected as the research objects to conduct a FTC simulation test in an artificial climate chamber. Three soil volumetric water contents (10%, 20%, 30%) and eight FTCs (0, 2, 4, 6, 8, 10, 15, 20) were set. The results showed that the soil organic carbon (SOC) and microbial biomass carbon (MBC) contents of different soil types under the FTCs initially exhibited a downward and then an upward trend, while the dissolved organic carbon (DOC) content exhibited an upward and then a downward trend. Otherwise, the fourth and sixth FTCs were the key points of change. The SOC, MBC and DOC contents in paddy fields were higher than those in dry fields, showing upward and then downward trends spatially from northeast to southwest. The SOC and MBC contents in each soil type were the highest at the 20% water content, and the DOC content gradually increased with increasing water content. The ammonium nitrogen (NH₄⁺-N) content in different soil types at different water contents under the FTCs showed an upward trend first, then a downward trend and finally an upward trend. The NH₄⁺-N content in paddy fields was higher than that in dry fields. The nitrate nitrogen (NO₃^‒-N) content showed a downward trend first, then an upward trend and finally a downward trend. The NO₃^‒-N content in dry fields was higher than that in paddy fields. The NH₄⁺-N contents in the three soil types on the Sanjiang Plain were significantly higher than those on the Songnen Plain. The NH₄⁺-N and NO₃^‒-N contents showed upward trends with increasing water content, but the differences were not significant. The results have implications for the study of different types of soils and provide references for research on the mechanism of soil carbon and nitrogen transformation in typical farming areas in Northeast China.     

Freeze–thaw cycle amplitude and freezing rate effects on extractable nitrogen in a temperate old field soil

Freeze–thaw cycles can promote soil N losses as a result of microbial and root cell lysis; however, minimal freeze–thaw effects have typically been observed in studies that have imposed moderate temperature cycles. We conducted laboratory incubations on surface soil (top 3 cm) collected in a temperate old field from late fall through mid-winter to examine how variation in freeze–thaw amplitude, number, timing of collection, and freezing rate altered soil extractable N. We varied freeze–thaw amplitude by imposing minimum cycle temperatures of 0, −1, −2, −5, and −10°C for a series of either one or two cycles and held control samples constant at 3°C. We also examined the effects of freezing rates of 1, 3, and 30°C h⁻¹. We hypothesized that extractable N would be highest for both the maximum freezing amplitudes and rates. While multiple freeze–thaw cycles at −10°C and freeze–thaw cycles associated with artificially high freezing rates increased extractable N, freeze–thaw cycles representative of field conditions at our site had no effect on extractable N in late fall and early winter. By mid-winter there was a significant freeze–thaw cycle effect but, contrary to our prediction, less N was extracted from freeze–thaw treated samples than from the control samples, which remained thawed over the treatment period. Increased extractable N in control samples was driven by increased organic N rather than increased inorganic N. Our results suggest that freeze–thaw damage to soil organisms does not contribute substantially to N release in our system. Instead, soil extractable N may increase during mid-winter thaws as a result of increased soil proteolytic activity above freezing temperatures.     

Is sewage sludge a valuable fertilizer? A soil microbiome and resistome study under field conditions

Journal of Soils and Sediments - Sewage sludge land application is strongly recommended to improve soil quality and fertility despite the presence of pollutants, pathogens and antibiotic resistance...     

Legume–barley intercropping stimulates soil N supply and crop yield in the succeeding durum wheat in a rotation under rainfed conditions

Legume–cereal intercropping is increasingly being appreciated in dryland areas, where severe climatic conditions and intensive agricultural practices, generally dominated by continuous cereal cultivation, determine depletion of soil nutrient resources and decline of soil fertility. This research aimed to assess whether and to what extent a newly introduced legume-based intercropping system is able to ameliorate the biological fertility status of an arable soil in a way that is still noticeable during the succeeding durum wheat cropping season in terms of changes in bacterial community structure, soil C and N pools, and crop yield. A field experiment was carried out under rainfed conditions in Southern Italy on a sandy clay loam soil cultivated with durum wheat following in the rotation a recently established grain legume (pea, faba bean)–barley intercropping. Soil chemical, biochemical and eco-physiological variables together with compositional shifts in the bacterial community structure by LH-PCR fingerprinting were determined at four sampling times during the durum wheat cropping season. Soil fertility was estimated by using a revised version of the biological fertility index. Results showed that even though the microbial biomass was significantly altered, the preceding legume intercrops stimulated C-related functional variables thus leading to an increased release of mineral N, which was larger in crop treatments succeeding pea-based than faba bean-based intercropping. The increased N made available in soil enabled the succeeding durum wheat to achieve an adequate grain yield with a reduced N-fertilizer use. Soil type and environmental conditions rather than crop treatments were major determinants of bacterial community structure. The biological fertility status was not varied, suggesting that in intensively managed rainfed areas long-term crop rotations with intercropped legumes are needed to consistently ameliorate it.     

Forage qualities,forage yields and seed yields of some legume–triticale mixtures under rainfed conditions

Triticale (Triticosecale Wittmack) grown with legume has a better forage quality and greater yield potential than triticale grown alone. The objective of the study was to determine the suitable mixture rate of legume and triticale grown under the rainfed conditions in the northeast of Turkey. Field experiments, designed in a factorial randomized complete block with three replications, were carried out during 1998–1999 and 1999–2000 starting in the first week of November, 1998 and 1999. The highest dry matter yield (10.96 t ha^?1) was obtained from the mixture including 50% Hungarian vetch (Vicia pannonica Crantz.) and 50% triticale (Triticosecale Wittmack). Decreasing the seed rate of triticale in mixtures decreased dry matter yield while it increased the crude protein concentration of the hay mixture. The mixtures of 50% grasspea line 38 (Lathyrus sativus L.) and 50% triticale (Triticosecale Wittmack) and 50% hairy vetch and 50% triticale produced the highest seed and crude protein yield. Similarly, 50% Hungarian vetch (Vicia pannonica Crantz.) and 50% triticale (Triticosecale Wittmack) mixture produced the highest crude fiber and ash yield. Pure hairy vetch (Vicia villosa Roth.) and grasspea line 38 (Lathyrus sativus L.) yielded the maximum amount of NO₃ ^? -N to soil, and the highest plant concentration of crude protein, respectively. The mixtures outyielded the pure sowings with respect to dry matter (RYT=1.58) and grain yield (RYT=1.76).     

Effect of different safflower (Carthamus tinctorius L.)–bean (Phaseolus vulgaris L.) intercropping patterns on growth and yield under weedy and weed-free conditions

Two field experiments were carried out over two consecutive years (2010–2011) in the research field of the College of Agriculture, Shiraz University, Fars Province, southern Iran. The study was a factorial experiment based on a randomized complete block design with three replications: the first factor was the ratio of safflower (Carthamus tinctorius L. Pi cv.) to bean (Phaseolus vulgaris L. Saiad cv.) at five levels (safflower and bean sole cropping, and intercropping of safflower and bean at ratios of 1:3, 2:2 and 3:1); and the second factor was weed management at two levels: weed-free (complete weed control) and weedy (no weed control). The results showed that an intercropping system was the most appropriate method for decreasing the adverse effect of weeds on the performance of both crops. Intercropping was more suitable for weedy than weed-free conditions. According to the land equivalent ratio (LER) value, if the main crop was bean, the best intercropping treatment was one row of safflower and six rows of bean (S₁B₃) under both weedy and weed-free conditions. By contrast, if the main crop was safflower, the best treatment under weedy conditions was S₁B₃, whereas under weed-free conditions the best treatment was two rows of safflower and four rows of bean (S₂B₂). Overall, S₁B₃ can be introduced as the best intercropping method.     

Effects of Different Organic Materials on Crop Production under a Rice–Corn Cropping Sequence

Soil organic matter (SOM) is an important index of soil quality because of its relationship with crop yield. The application of organic matter to soil is a significant method for increasing SOM. Different organic materials have varying effects in increasing SOM. This study investigates the effects of combining different sources of organic matter (i.e., compost, leguminous green manure, and peat) with a chemical nitrogen (N) fertilizer on the growth and N accumulation in corn and rice plants. This study examines seven treatments, including a no-fertilization check and a conventional chemical fertilizer treatment. Shoots of corn and rice were sampled at the tasseling (panicle initiation for rice) and maturity stages. The biomass yield was measured and the total N was analyzed. At the maturity stage, the soil samples were collected to determine the chemical properties. The results showed that a small percentage of the N in the compost and peat, after their application, was available to the crop during the growth season; the production of biomass and N absorption among rice and corn plants was minimal compared to that treated with chemical N fertilizer. The application of compost and peat resulted in SOM accumulation, particularly with peat. However, the application of compost combined with chemical fertilizer not only produced sufficient nutrients for crop growth but also resulted in an accumulation of SOM, which is vital for enhancing the soil quality. Most of the N in green manure (GM) was mineralized shortly after application, causing excessive growth of rice and corn plants during the early stage, but reducing their reproductive growth and grain yield.     

Tillage and Forage System Effects on Forage Yields and Nutrient Uptake under Broiler Litter–Amended Soils

Abstract

Planting and harvesting high‐yielding forage grasses may remove phosphorus (P), copper (Cu), and zinc (Zn) from surface soils with a long history of broiler litter application. A study was conducted in Alabama's Sand Mountain region from 1998 to 2000 to determine tillage and forage systems best suited for removing nutrients from such overloaded soils. Tillage treatments included no‐till, moldboard plowing, chisel plowing, and each combined with paraplowing. Forage treatments included bermudagrass (Cynodon dactylon (L.) Pers.) cv. Russell, tall fescue (Festuca arundinacea Schreb.) cv. Kentucky‐31, and an annual rotation of ryegrass (Lolium multiflorum Lam.) and sorghum sudangrass (Sorghum bicolor L. Moench×Sorghum vulgare sudanense). The annual rotation produced highest yields and P uptake. Moldboard plowing the annual rotation further increased yields. It appears the annual rotation best removes P, Cu, and Zn via plant uptake. Tillage reduced P concentrations in the soil surface in the following order: moldboard>chisel>no‐till.     

Long-term fertilization effects on crop yields,soil fertility and sustainability in the Static Fertilization Experiment Bad Lauchstädt under climatic conditions 2001–2010

The Static Fertilization Experiment Bad Lauchstädt (1902) consists of a crop rotation of sugar beets, spring barley, potatoes and winter wheat. Three farmyard manure (FYM) treatments and six mineral fertilizer treatments are combined orthogonally. Comparing the first and last decades, crop yields nearly doubled. In unfertilized plots, yields and N uptake by crops also increased when comparing first and last decades. On average for the decade 2001–2010, N uptake in unfertilized plots amounted 51.6 kg ha^?1. Although soil organic carbon (SOC) levels for unfertilized plots remain almost unchanged, SOC increases slowly in the most highly fertilized treatment, resulting in a gradual widening of differences in SOC between the most extreme treatments to 0.952%. Climate change and increased harvesting and root residues due to rising yields are suggested as an explanation. Except for the plot with the highest application of mineral and organic fertilizer, in all treatments more N was taken up by crops than was applied by fertilizers. Higher FYM input leads to more unfavourable N balances because N release from FYM cannot be controlled. Considering atmospheric N input, only in the exclusively mineral fertilized treatment is N balanced out. Similar results are found for C balances: the exclusively mineral fertilized treatment shows the most favourable C balance.     

Predicted trends of soil erosion and sediment yield from future land use and climate change scenarios in the Lancang–Mekong River by using the modified RUSLE model

Soil erosion and sediments in the Lancang-Mekong River Basin as a result of climate change and changes in land use pose a threat to the existence of the riparian people, biodiversity and ecosystems. This study seeks to assess the annual soil erosion in terms of spatial distribution and the trends of sediment yield with the climate and land changes in future scenarios in 2030 and 2040 through the modified RUSLE model. Future lands were simulated by using the MLP artificial neural network and the Markov chain analysis. The future climate was examined by using the Max Planck Institute model, which showed a corrected bias and downscaled grid size under the Representative Concentration Pathways (RCPs). The simulated land use indicated that the forest areas were converted mostly to agricultural lands and urban areas. In the future, the average rainfall under all RCP scenarios is higher than that from the historical period. The R and C factors changed constantly, thereby affecting the soil erosion rate and sediment yield. The maximum erosion was estimated at approximately 21,000 and 21,725 t/km²/y under RCP8.5 in both years. Meanwhile, the results of sediment yield in 2030 and 2040 under RCP scenarios were much higher when compared to historical sediment data around 66.3% and 71.2%, respectively. Thailand's plateau, some parts of Cambodia and Laos PDR and the Mekong Delta are vulnerable to increase soil erosion and sediment yield. Measures to address these issues need to be planned to prepare and mitigate the possible effects, especially the loss of storage capacity in dams.     

The effect of lime and fertilizers on four lignite overburdens under non‐drained conditions: II. Weathering.

Abstract

Four lignite overburdens from a potential lignite mining area of Louisiana were used to evaluate the effect of rates of fertilizer, lime, plant growth and simulated poor drainage conditions on the weathering of these materials. Common bermudagrass (Cynodon dactylon) grown on each overburden material in pots lined with polyethylene bags received 0, 1/2>x, 1x, 2x and 4x the recommended rate of fertilizer which was a combination of N, P and K. Lime was applied to the overburdens based on soil test lime requirement to increase the pH to 6.5.

Enrichment (fertilizers, non‐drained conditions and lime) had a significant effect on the weathering of the overburdens. The pH, EC, organic C, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, Na and Al were significantly affected by one or more of these parameters. Visual observations indicated that fertilizers stimulated root production, which effectively increased the weathering of the overburdens. Lime, applied as CaO, did not increase the pH of the Cow Bayou material substantially, suggesting the presence of pyrite, which was confirmed by X‐ray diffraction analysis. As pyrite oxidized in the Cow Bayou material, soluble salts accumulated on the surface of the material and on the lower parts of the plant. Gypsum and jarosite precipitated as the solution ionic strength of this material increased due to the weathering of the pyrite.

The Prairie Terrace overburden was selected as the best potential topsoil since it had more favorable physical and chemical characteristics which would promote successful reclamation. Reduced materials such as Cow Bayou and Naborton had undesirable physical and chemical properties. Changes in the chemical properties of these materials would be difficult to predict and soil amendments such as lime and gypsum would be needed in significant quantities for successful reclamation. Dolet Hills, a sandy material, had a less desirable texture and would require frequent irrigation and fertilization if it were used as a topsoil substitute.     

Snow cover and soil moisture controls of freeze–thaw-related soil gas fluxes from a typical semi-arid grassland soil: a laboratory experiment

In situ field measurements as well as targeted laboratory studies have shown that freeze–thaw cycles (FTCs) affect soil trace gas fluxes. However, most of past laboratory studies adjusted soil moisture before soil freezing, thereby neglecting that snow cover or water from melting snow may modify effects of FTCs on soil trace gas fluxes. In the present laboratory study with a typical semi-arid grassland soil, three different soil moisture levels (32 %, 41 %, and 50 % WFPS) were established (a) prior to soil freezing or (b) by adding fresh snow to the soil surface after freezing to simulate field conditions and the effect of the melting snow on CO₂, CH₄, and N₂O fluxes during FTCs more realistically. Our results showed that adjusting soil moisture by watering before soil freezing resulted in significantly different cumulative fluxes of CH₄, CO₂, and N₂O throughout three FTCs as compared to the snow cover treatment, especially at a relatively high soil moisture level of 50 % WFPS. An increase of N₂O emissions was observed during thawing for both treatments. However, in the watering treatment, this increase was highest in the first thawing cycle and decreased in successive cycles, while in the snow cover treatment, a repetition of the FTCs resulted in a further increase of N₂O emissions. These differences might be partly due to the different soil water dynamics during FTCs in the two treatments. CO₂ emissions were a function of soil moisture, with emissions being largest at 50 % WFPS and smallest at 32 % WFPS. The largest N₂O emissions were observed at WFPS values around 50 %, whereas there were only small or negligible N₂O emissions from soil with relatively low soil water content, which indicates that a threshold value of soil moisture might exist that triggers N₂O peaks during thawing.     

Quantifying the uncertainties of transpiration calculations with the Penman–Monteith equation under different climate and optimum water supply conditions

The uncertainties of transpiration calculations with the Penman–Monteith equation were quantified under different climate conditions of Brazil, Germany and Israel using maize as a common crop type. All experiments were carried out under non-limiting growing conditions. Canopy resistance was determined by scaling to canopy level specific relations between in situ measurements of incident radiation and stomatal conductance using a light penetration model. The model was tested against heat-pulse measured sap flow in plant stems. The root mean square error (RMSE) of daily calculated transpiration minus measured sap flow was 0.4 mm/day. It was dominated by its variance component (variance = 0.2 {mm/day}²; bias = 0.0 mm/day). Calculated transpiration closely matched the measured trends at the three locations. No significant differences were found between seasons and locations. Uncertainties of canopy conductance parameterizations led to errors of up to 2.1 mm/day. The model responded most sensitively to a 30% change of net radiation (absolute bias error = 1.6 mm/day), followed by corresponding alterations of canopy resistances (0.8 mm/day), vapour pressure deficits (0.5 mm/day) and aerodynamic resistances (0.34 mm/day). Measured and calculated 30-min or hourly averaged transpiration rates are highly correlated (r² = 0.95; n = 10634), and the slope of the regression line is close to unity. The overall RMSE of calculated transpiration minus measured sap flow was 0.08 mm/h and was dominated by its variance component (0.005 {mm/h}²). Measured sap flow consistently lagged behind calculated transpiration, because plant hydraulic capacitance delays the change of leaf water potential that drives water uptake. Calculated transpiration significantly overestimated sap flow during morning hours (mean = 0.068 mm/h, n = 321) and underestimated it during afternoon hours (mean = ?0.065 mm/h; n = 316). The Penman–Monteith approach as implemented in the present study is sufficiently sensitive to detect small differences between transpiration and water uptake and provides a robust tool to manage plant water supply under unstressed conditions.     

Effects of hydrostatic pressure on phosphorus transformation at the water–sediment interface of a deep reservoir: novel insights into bacterial community and functional genes

Journal of Soils and Sediments - The release of endogenous phosphorus from sediments leads to the eutrophication of water bodies. Bacteria in sediments play a vital role in phosphorus cycling. A...     

Long-term effect of manure and mineral fertilizer application on the distribution of organic nitrogen fractions in soil under a rice–wheat cropping system

A long-term experiment was used to evaluate the effect of integrated nutrient management on the distribution of soil organic N fractions and their contribution to N nutrition of a rice–wheat system. Continuous application of mineral fertilizers, alone or in combination with organic manures for 7 years, led to a marked increase in total N, hydrolysable N (amino acid-N, amino sugar-N, ammonia-N, hydrolysable unknown-N) and non-hydrolysable N compared with their original status in soil. However, continuous rice–wheat cropping without any fertilization resulted in depletion of total N, hydrolysable N and non-hydrolysable N by 21.3, 23.5 and 15.1% over their initial status in surface soil. The effect of press mud (PM) treatment was more pronounced in increasing total and hydrolysable N compared with farmyard manure (FYM) or green manure (GM) treatment. Incorporation of PM, FYM and GM along with mineral fertilizers increased the total N content by 32.8, 18.3 and 5.1% and that of hydrolysable N by 25.7, 19.6 and 9.5%, respectively, over mineral fertilizer treatment. Among the most important fractions, amino sugar-N, amino acid-N and ammonia-N were found to be most the important fractions contributing to grain yield and nitrogen uptake of rice and wheat crops.     

Soil microbial communities and enzyme activities in a reclaimed coastal soil chronosequence under rice–barley cropping

Purpose

A field experiment with a reclamation chronosequence under rice?Cbarley cropping was conducted to investigate soil enzyme activities and microbiology in a coastal saline soil. The aim of this study was to test whether changes in enzyme activity and microbial community structure are directly impacted by changes in soil pH, electrical conductivity (EC), and organic carbon (SOC) due to reclamation.

Materials and methods

The research area is located in south-eastern China. Four experimental sites were reclaimed in 1976, 1984, 1996, and 2006, respectively, and each site was divided into three plots, each of which was 22?m?×?10?m. Each year, the plots were planted with rice (cv Xiushui) in summer and barley (cv Yanmai) in winter. Soil pH and EC were determined in an aqueous suspension with a 1:5 ratio of soil and water. Soil organic carbon content was measured by dichromate oxidation with heating. Measured soil enzyme activities included catalase, urease, and protease. Soil microbial community structures were assessed using denaturing gradient gel electrophoresis.

Results and discussion

Reclamation under rice?Cbarley cropping reduced EC and pH, but increased SOC, the activities of catalase, urease and protease, and the cell numbers of bacteria, actinomycetes, and fungi, resulting in an increase in the bacterial community diversity. The enzyme activities and bacterial community diversity were significantly positively correlated with SOC, and negatively correlated with pH and EC. Five bacterial groups related to Gaetbulibacter, Sporosarcina, Flavobacterium, Aequorivita, and Gillisia, which have been associated with saline waters, did not appear in the soils that had been reclaimed prior to 1996.

Conclusions

Results of this field study suggest that soil properties which affect microbial activity such as EC, pH, and SOC significantly influence the activities of catalase, urease, and protease, and microbial community composition. More than 10?years after reclamation under rice?Cbarley cropping, EC had decreased and bacteria typically found in marine and saline environments had disappeared from the soil.     

Evaluation of Soil Physical Quality under Amendments and Hydrogel Applications in a Soybean–Wheat Cropping System

A field study was conducted in alluvial sandy loam soil to assess the impact of amendments and hydrogel application on soil hydrophysical properties. Soil physical environment was characterized and quantified using soil physical quality index (S). The main treatments include farmyard manure (FYM) and tank soil applied at 5 t ha^?1 and no amendment, and subtreatments included three rates of hydrogel: 5, 2.5, and 0 kg ha^?1. Hydrogel was applied at 5–7 cm deep just below the seed in rows. Results revealed that FYM along with gel application at 5 kg ha^?1 significantly increased mean weight diameter, field capacity moisture content, plant-available water content and relative field capacity, retention pores (Ret P), water-stable structural units, and structural coefficient and reduced transmission pores (TP), penetration resistance, and saturated hydraulic conductivity (K_s). Significantly greater values of S in hydrogel-treated plots and close associations of S with other soil physical parameters were obtained.