Soil Water-holding Capacity Research Articles

Maize-Straw Biochar Enhances Soil Properties and Grain Yield of Foxtail Millet in a Newly Reclaimed Land

Large-scale land reclamation has become common in northwestern China; however, low soil fertility and poor soil water-holding capacity limit agricultural production on these reclaimed lands, requiring increased fertilizer and irrigation inputs. Biochar, produced from agricultural waste, has shown potential in improving soil quality and water-holding capacity. In this two-year field study (2021 and 2022), we investigated the effects of biochar produced from maize straw on soil properties and grain yield of foxtail millet grown on newly reclaimed land. Three biochar treatments (3000, 4500, and 6000 kg ha−1) were compared to a control (CK) with no biochar application. Biochar application resulted in increased soil organic matter, total phosphorus, total nitrogen, soil enzyme activity, and soil organic acid content. It also significantly decreased soil pH and bulk density. Compared with the CK, biochar increased available nitrogen from 29.7% to 108% in 2021 and 37.0% to 88.4% in 2022. Similarly, biochar increased available phosphorus from 64.7% to 143% in 2021 and 41.9% to 96.5% in 2022. Grain yields ranged from 3092 to 4753 kg ha−1. Biochar treatments increased grain yield compared to the CK, ranging from 12.2% to 24.6% in 2021 and 27.1% to 53.7% in 2022. Correlation analysis revealed that soil pH was negatively related to soil oxalic acid content, phosphorus content, and sucrase activity. Available nitrogen and phosphorus contents were negatively related to soil bulk density and positively related to catalase activity. Soil water content was negatively correlated with soil bulk density and positively correlated with organic matter. In conclusion, biochar improved the rhizosphere soil pH and the effectiveness of soil fertility in the newly reclaimed soil, resulting in an enhanced grain yield of foxtail millet.

Geo-statistical assessment of spatial variability of soil water-holding capacity for optimal irrigation under semi-arid vertisols in South India

Based on a field survey conducted in Lalgudi block, Tiruchirapalli district, Tamil Nadu, India, details about the crops grown, cropping pattern, land utilization and soil samples were collected from 20 locations under seven different soil textures of semi-arid vertisols. Using the data, efficient geostatistical models have been explored to study the spatial variation of irrigation water requirement of paddy, sugarcane and banana grown in the study area. Geostatistics was applied to identify the best interpolation method to acquire the spatial map of the available water holding capacity. Ordinary kriging and Disjunctive kriging were explored with six models viz., Circular, Spherical, Exponential, Gaussian, Penta-spherical and Sine-Hole effect models and were used for spatial prediction. The cross-validation statistics indicated that the Sine-Hole effect model with disjunctive kriging of available water holding capacity was superior for interpolation with a minimum value of RMSE and moderate spatial dependency. With the available water holding capacity map of Lalgudi block, total available water, readily available water and irrigation interval of paddy, sugarcane and banana were estimated. The irrigation interval of paddy, sugarcane and banana were found to vary between 1-2, 3-5 and 2-4 days respectively within Lalgudi block. The adoption of spatial algorithms for estimating crop water requirements would greatly help irrigation planners and water policymakers create efficient regional plans for precision irrigation under semi-arid vertisols.

Influence of Environmental Conditions on Bacterial Remediation of Oil-Contaminated Soil: A Case Study at Baiji Refinery

Total Petroleum Hydrocarbons (TPH) are a major environmental pollutant, posing serious risks to soil health and ecosystems. TPH contamination, often resulting from crude oil spills and industrial activities, significantly disrupts soil structure, reduces fertility, and hinders the growth of plants and soil-dwelling organisms. In the environment, TPH compounds persist due to their hydrophobic nature, leading to long-term ecological damage. They can infiltrate groundwater, compromising its purity and presenting health hazards to humans and wildlife. The existence of TPH in soil modifies the population of bacteria, reduces biodiversity, and impedes natural processes such as nutrient cycling. Effective bioremediation techniques, such as microbial degradation, are essential for mitigating the harmful impacts of TPH on soil and the broader environment. This study emphasizes the urgent need for sustainable remediation strategies to restore contaminated soils and protect ecological and human health. This study investigates the influence of environmental circumstances on bacteria employed for the remediation of soil polluted with crude oil, focusing on bacterial strains sourced from the Baiji refinery in Iraq. Microbial rehabilitation is an economical and environmentally sustainable method for decomposing hydrocarbons into simpler molecules, making it an effective method for soil bioremediation. The study monitored biodegradation over seven months, assessing the degradation efficiency of total petroleum hydrocarbons (TPH) using gas chromatography-mass spectrometry (GC-MS). Environmental factors, including temperature, moisture levels, and nutrient availability, were closely monitored to assess their impact on bacterial activity. Ideal moisture range for bacterial growth and hydrocarbon degradation is often cited as 40% to 60% of the soil's WHC. Too much water can reduce oxygen availability in the soil, inhibiting aerobic bacterial growth, while too little water can limit microbial metabolism. Temperature affects bacterial metabolism and the rate of hydrocarbon degradation. Most hydrocarbon-degrading bacteria thrive in mesophilic conditions. The ideal temperature range for TPH degradation by bacteria is generally between 25°C and 35°C. At temperatures below 15°C, microbial activity and degradation rates slow significantly, while temperatures above 40°C can inhibit bacterial growth or even kill the microbes. The results revealed that the moisture: 40%–60% of soil's water-holding capacity and temperature 25°C–35°C maintaining these conditions promotes the optimal breakdown of hydrocarbons in bioremediation efforts. The results revealed significant degradation of crude oil, with a reduction of 40 initial compounds in untreated samples to 25-35 compounds in treated samples. The biodegradation rates increased steadily over time, with a removal efficiency reaching 72.38% by the end of the experiment. Additionally, the study demonstrated that environmental conditions, particularly temperature and moisture, play a pivotal role in optimizing bacterial degradation activity. These findings underscore the potential of bacteria in bioremediation efforts and the necessity of optimal environmental conditions, such as controlled temperature, moisture content, and nutrient levels, are essential for maximizing the efficiency of crude oil degradation in contaminated soils.

Old-growth Ficus trees provide soil water and carbon storage to urban greenspaces in a Brazilian metropolis

Urban flooding has been considered one of the most severe natural disasters around the world, and urban greenspaces can provide important flood regulation ecosystem services. In Belo Horizonte (Brazil), the woody vegetation, especially the old-growth Ficus trees, appears to protect an urban park against the flooding of the Arrudas river. Thus, we compared the soil water content, soil water-holding capacity, soil aggregation and porosity among a highly permeable urban park planted with herbaceous and woody species, including Ficus, a semi-permeable parking lot with only Ficus and an impermeable site without trees (Disturbed Site-DS). The soil water content and water holding capacity of the urban park did not differ from that of the Ficus site, but it was lower than DS. These results were correlated with soil organic matter (SOM) content, soil aggregation and porosity, suggesting that Ficus trees play an important role in the hydrological cycle. To understand how the Fiscus species provide such soil permeability, we compared the aboveground plant biomass, soil fertility and soil carbon sequestration (total soil carbon, soil organic matter, humic and fulvic acids and soil isotopic δ13 C) in plots with Ficus and without this species within the park as well as in a preserved urban forest and a disturbed square. The outstanding plant biomass produced by Ficus species explained the high soil carbon sequestration, particularly in humic organic matter, favouring soil aggregation, porosity and water retention. Therefore, Ficus species may be considered an exceptional C-sequestering species, contributing for soil stabilization and the hydrological cycle in urban greenspaces.

Effects of Sugarcane Bagasse Biochar on Ammonium and Nitrate Adsorption and Leaching in a Japanese Tropical Soil Cropped with Japanese Mustard Spinach (Brassica rapa)

This study investigated the dynamics of ammonium-nitrogen (NH4+-N) and nitrate-nitrogen (NO3–-N) adsorption and leaching in a Japanese tropical soil amended with sugarcane bagasse biochars (SBBs) in the presence of plant. Adsorption and column leaching studies were conducted in a laboratory in Japan, and the column study was performed for 21 days. Biochar was produced from sugarcane bagasse at the maximum pyrolysis temperatures of 400°C (SBB400) and 800°C (SBB800) for use in the experiments. Adsorption isotherms for NH4+-N and NO3–-N were developed for soil only, SBB400-amended soil, and SBB800-amended soil. Column leaching study included 6 treatments: fertilizer only, fertilizer and plant, fertilizer and SBB400, fertilizer and SBB400 and plant, fertilizer and SBB800, fertilizer and SBB800 and plant. This study showed that soil and SBBs-amended soils fitted well into the Langmuir adsorption model for NH4+-N and NO3–-N (r2= 0.983–0.994 and 0.956–0.970, respectively). Application of SBBs to soil significantly decreased cumulative NH4+-N leached from the soil (P < 0.05) because of increased adsorption capacity due to high acid functional groups and increased soil water holding capacity (WHC) due to high specific surface areas and pore volumes, regardless of the presence of plant. However, the SBBs application did not affect the adsorption capacity for NO3–-N because of negatively charged surfaces. However, cumulative NO3–-N leached was significantly reduced (P< 0.05) due to increased soil WHC, regardless of the presence of plant. Therefore, more soil water contents retained and less NO3–-N leached from the soil may have contributed to greater plant growth with the SBBs application. This study showed that the SBBs application to soil could enhance adsorption capacity for NH4+-N but not for NO3–-N, nevertheless increase soil WHC and reduce leaching of both NH4+-N and NO3–-N, thus contributed to increased plant growth.

Impacts of Compost Amendment Type and Application Frequency on a Fire-Impacted Grassland Ecosystem

Composting organic matter can lower the global warming potential of food and agricultural waste and provide a nutrient-rich soil amendment. Compost applications generally increase net primary production (NPP) and soil water-holding capacity and may stimulate soil carbon (C) sequestration. Questions remain regarding the effects of compost nitrogen (N) concentrations and application rates on soil C and greenhouse gas dynamics. In this study, we explored the effects of compost with different initial N quality (food waste versus green waste compost) on soil greenhouse gas fluxes, aboveground biomass, and soil C and N pools in a fire-impacted annual grassland ecosystem. Composts were applied annually once, twice, or three times prior to the onset of the winter rainy season. A low-intensity fire event after the first growing season also allowed us to explore how compost-amended grasslands respond to burning events, which are expected to increase with climate change. After four growing seasons, all compost treatments significantly increased soil C pools from 9.5 ± 0.9 to 30.2 ± 0.7 Mg C ha−1 (0–40 cm) and 19.5 ± 0.9 to 40.1 ± 0.7 Mg C ha−1 (0–40 cm) relative to burned and unburned controls, respectively. Gains exceeded the compost-C applied, representing newly fixed C. The higher N food waste compost treatments yielded more cumulative soil C (5.2–10.9 Mg C ha−1) and aboveground biomass (0.19–0.66 Mg C ha−1) than the lower N green waste compost treatments, suggesting greater N inputs further increased soil stocks. The three-time green waste application increased soil C and N stocks relative to a single application of either compost. There was minimal impact on net ecosystem greenhouse gas emissions. Aboveground biomass accumulation was higher in all compost treatments relative to controls, likely due to increased water-holding capacity and N availability. Results show that higher N compost resulted in larger C gains with little offset from greenhouse gas emissions and that compost amendments may help mediate effects of low-intensity fire by increasing fertility and water-holding capacity.

Response on root regrowth potential to soil moisture in Sedum species during winter in Særheim, Norway

PurposeThe impact of winter moisture on root metabolism and root integrity has potential consequences for the geographical distribution of drought-adapted succulent species and for their long-term performance on green roofs. The interacting effects of soil characteristics and precipitation frequency on root mortality under winter conditions and the potential to grow new roots in spring were evaluated for six Sedum species under controlled conditions. MethodsTo test for the impact of soil moisture during winter on root regrowth potential in six Sedum species, we used a combination of two substrates with differing water-holding capacity and four contrasting watering regimes. Specially, for the fine and coarse substrates, total pore volume was 42 and 46 %, respectively, and maximum water-holding capacity (i.e. field capacity) was 0.50 and 0.33 kg water per L, respectively. The four watering treatments involved overhead watering to runoff (approx. 10 mm): once every second week, once a week, three times per week and three times per week with 1 cm standing water in trays from January to March 2019. ResultsIt was found that winter soil moisture had no major impact on root mortality or root regrowth potential in spring. Root mortality was not affected by watering frequency and regrowth potential showed no directional response to increased watering frequency, although species-specific responses were involved. Root diameter did not differ between the substrates, but there were some differences between the species. Sedum rupestre had on average the thickest roots (0.17 mm), followed by S. acre, S. anglicum and S. sexangulare (0.15–0.16 mm), while S. album and S. hispanicum had the thinnest roots (0.12–0.13 mm). Moreover, effects of watering frequency on root mortality and regrowth potential were not influenced by soil water-holding capacity across species. We concluded that winter soil moisture had no negative effects on root performance within the range of treatments tested here. ConclusionsRoot response to transient waterlogging or moist but unsaturated soil may not be an important mechanism for determining the survival and distribution of temperate Sedum species during winter.

Enhancing Corn Yield and Soil Quality in Irrigated Semiarid Region with Coal Char and Biochar Amendments

Sustainable use of croplands is facing a challenge to maintain organic carbon (C) in soil. Pyrolyzed coal or coal char (CC) is a porous C material produced from the pyrolysis of coal containing high organic C, large surface area, and low bulk density like biochar (BC). This study evaluates corn (Zea mays L.) grain yield and selected soil properties in soil amended with CC and BC at two rates (22 and 44 Mg ha−1) with farmyard manure (FM) (66 Mg ha−1) and without FM addition. This field experiment was performed in sandy loam soil at the University of Wyoming’s Sustainable Agricultural Research and Extension Center (SAREC), Lingle, WY, USA. Two years of field study results indicated CC and BC applied at 22 Mg ha−1 with FM resulted in significantly greater average corn grain yields (13.04–13.57 Mg ha−1) compared to the no char’s treatment (11.42 Mg ha−1). Soil organic matter (SOM) content was significantly greater in the higher application rates of CC and BC than in treatments without chars. Overall, soil nitrate nitrogen (NO3-N), phosphorous (P), and potassium (K) were found significantly greater in CC and BC co-applied with FM treatments. Soil water-holding capacity (WHC) significantly improved in sandy loam soil (up to 27.6% more than the no-char treatment) at a greater concentration of char materials. This study suggests that char materials applied at a moderate rate (22 Mg ha−1) with FM can improve soil properties and crop yield.

Drought stimulus enhanced stress tolerance in winter wheat (Triticum aestivum L.) by improving physiological characteristics, growth, and water productivity

The impact of drought events on the growth and yield of wheat plants has been extensively reported; however, limited information is available on the changes in physiological characteristics and their effects on the growth and water productivity of wheat after repeated drought stimuli. Moreover, whether appropriate drought stimulus can improve stress resistance in plants by improving physiological traits remains to be explored. Thus, in this study, a pot experiment was conducted to investigate the effects of intermittent and persistent mild [65%–75% soil water-holding capacity (SWHC)], moderate (55%–65% SWHC), and severe drought (45%–55% SWHC) stress on the growth, physiological characteristics, yield, and water-use efficiency (WUE) of winter wheat. After the second stress stimulus, persistent severe drought stress resulted in 30.98%, 234.62%, 53.80%, and 31.00% reduction in leaf relative water content, leaf water potential, photosynthetic rate (Pn), and indole-3-acetic acid content (IAA), respectively, compared to the control plants. However, abscisic acid content, antioxidant enzyme activities, and osmoregulatory substance contents increased significantly under drought stress, especially under persistent drought stress. After the second rehydration stimulus (ASRR), the actual and maximum efficiency of PSII and leaf water status in the plants exposed to intermittent moderate drought (IS2) stress were restored to the control levels, resulting in Pn being 102.56% of the control values; instantaneous WUE of the plants exposed to persistent severe drought stress was 1.79 times that of the control plants. In addition, the activities of superoxide dismutase, peroxidase, catalase, and glutathione reductase, as well as the content of proline, under persistent mild drought stress increased by 52.98%, 33.47%, 51.95%, 52.35%, and 17.07% at ASRR, respectively, compared to the control plants, which provided continuous antioxidant protection to wheat plants. This was also demonstrated by the lower H2O2 and MDA contents after rehydration. At ASRR, the IAA content in the IS2 and persistent moderate drought treatments increased by 36.23% and 19.61%, respectively, compared to the control plants, which favored increased aboveground dry mass and plant height. Compared to the control plants, IS2 significantly increased wheat yield, WUE for grain yield, and WUE for biomass, by 10.15%, 32.94%, and 33.16%, respectively. Collectively, IS2 increased grain growth, yield, and WUE, which could be mainly attributed to improved physiological characteristics after drought-stimulated rehydration.

Changes in Soil Hydrological Retention Properties and Controlling Factors on Shaded and Sunny Slopes in Semi-Arid Alpine Woodlands

Slope orientation significantly influences soil’s physicochemical properties and the soil hydrological environment. However, the regulatory mechanisms and effects, particularly in semi-arid highlands, remain poorly understood. This study investigated soil physicochemical and hydrological properties on shaded and sunny slopes. Results indicated that in the 0–20 cm soil layer, the water-holding capacity was higher on sunny slopes, while water retention in the 10–20 cm layer was significantly higher on shaded slopes. This suggests that vegetation on shaded slopes experiences less soil erosion due to higher topsoil water retention. Additionally, slope orientation altered soil properties: the electrical conductivity (EC) of the 0–20 cm soil layer was significantly higher on shaded slopes. Nutrient elements such as Ca, Cu, and Zn were also relatively higher on shaded slopes, whereas soil organic matter was significantly lower compared to sunny slopes. Overall, soil water-holding capacity and supply were primarily controlled by EC, followed by capillary porosity and nutrient elements like Ca, Mn, and Fe. Therefore, slope orientation has a significant effect on soil hydrological properties, with stronger topsoil water retention on shaded slopes. These findings offer valuable insights for vegetation restoration in semi-arid highland ecosystems.

Sensitivity of joint atmospheric-terrestrial water balance simulations to soil representation: Convection-permitting coupled WRF-Hydro simulations for southern Africa

Regional weather and climate models play a crucial role in understanding and representing the regional water cycle, yet the accuracy of soil data significantly affects their reliability. In this study, we employ the fully coupled Weather Research and Forecasting Hydrological Modeling system (WRF-Hydro) to assess how soil hydrophysical properties influence regional land-atmosphere coupling and the water cycle over the southern Africa region. We utilize four widely-used global soil datasets, including default soil data for model from the Food and Agriculture Organization, and alternative datasets from the Harmonized World Soil Database, Global Soil Dataset for Earth System Model, and global gridded soil information system SoilGrids. By conducting convection-permitting coupled WRF-Hydro simulations with the Noah-MP land surface model using each of the aforementioned soil datasets, our benchmark analysis reveals substantial differences in soil hydrophysical properties and their significant impact on the simulated regional water cycle during the austral summer. Alterations in soil datasets lead to both spatial and temporal variations in surface water and energy fluxes, which in turn profoundly influence the atmospheric thermodynamic structure. Reduced soil water-holding capacity leads to subsequent reduction in soil moisture and latent heat, resulting in significant decreases in convective available potential energy and convective inhibition, signaling potential effects on precipitation distributions. In arid interior regions of southern Africa, shifts towards drier and warmer surface conditions due to soil data discrepancies are found to enhance atmospheric moisture convergence, suggesting a possible localized negative feedback of soil moisture on precipitation. Overall, the results for southern Africa indicate that soil data discrepancies exert more pronounced impact on terrestrial fields in dry subregions and on atmospheric fields in temperate subregions, highlighting the broad uncertainties in the regional water cycle reproduced within the model.

Leafina: Potency of Kakawate leaves, fishbone meal and saba banana peel compost soil amendment to the water holding capacity of loam soil

In tropical regions like the Philippines, drought susceptibility is caused by high evaporation rates and poor soil water retention. To deal with this, soil amendments are crucial, enhancing soil properties to aid plant growth. In this study, LeaFiNa, a compost soil amendment composed of Kakawate leaves (KL), fishbone meal (FB), and Saba banana peels (BP) was introduced, aiming to boost soil water holding capacity (SWHC) of loam. Different LeaFiNa ratios were tested, including 3KL:1FB:2BP, 6KL:4FB:1BP, and 3KL:8FB:1BP, alongside vermicast and commercial soil amendment (neem cake) as positive controls, and plain loam soil as the negative control. Percolation method and pressure plate extraction was performed. One-way ANOVA showed a significant difference among the experimental treatments (α=0.05) in which 6KL:4FB:1BP ratio emerged with the highest SWHC of 49.60%. Meanwhile, Tukey’s HSD test revealed no significant difference between 6KL:4FB:1BP and vermicast, yet a significant difference with the negative control. Moreover, the experimental treatments, particulalry the 6KL:4FB:1BP, also exhibited ideal results on other SWHC parameters such as the soil moisture content at saturation and wilting points, and in terms of gravitational water and plant available water. These findings suggest the LeaFiNa’s potential in alleviating drought stress in tropical soils by enhancing water retention, offering promising outcomes for sustaining agricultural productivity in water-scarce regions.

Synthesis of a superabsorbent hydrogel from Artocarpus heterophyllus Lam seed polysaccharides and its application in relieving drought stress in plants

AbstractSustainability in agriculture can only be achieved by protecting important resources, one of them being water. Availability of water in the soil greatly influences agricultural productivity. Hydrogels play a key role in ensuring water availability and achieving agricultural sustainability. A novel superabsorbent hydrogel was synthesized from Artocarpus heterophyllus Lam seed polysaccharides. The synthesized hydrogel was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy. Swelling capacity of the hydrogel in different solutions, water retention duration, its influence on the soil water holding capacity (SWHC), and degradation in soil were assessed. The hydrogel absorbs up to 326 g/g and degrades naturally at around 1.4 wt% daily. The hydrogel improved the SWHC by 34% at a concentration of 0.3% w/w. Further pot experiments with black gram (Vigna mungo (L.) Hepper) plants showed that the superabsorbent hydrogel ensured water availability for 35 days and relieved the plants from drought‐induced stress. The data presented here indicates that the synthesized hydrogel can potentially be used as a soil conditioner for the sustained release of water and fertilizer.

Reduction of nitrogen loss in runoff from sloping farmland by a ridged biochar permeable reactive barrier with vegetated filter strips

IntroductionEutrophication due to nitrogen (N) loss from sloping farmland has a high risk in the Three Gorges Reservoir. Biochar and vegetated filter strips (VFS) are used to control nutrient runoff and increase soil water-holding capacity, soil nutrient retention, and crop yield. However, surface biochar application has limited ability to control N loss, especially from sloping farmland.MethodsIn this study, different widths of ridged biochar permeable reactive barrier (RB-PRB) with VFS were employed to intercept N loss in runoff from sloping farmland. Adsorption characteristics of biochar for nitrate and ammonium N were evaluated using isothermal and kinetic adsorption models before field experiments. N index values for ammonium (NH4+), nitrate (NO3−), dissolved N (DTN), particulate N (PN), and total N (TN) lost through runoff were monitored from April 2019 to January 2020.ResultsNO3− and NH4+ sorption on biochar was predominantly physical adsorption with a maximum capacity of 4.51 and 4.12 mg g-1, respectively. During the research period, the dominant transportation pathway of N loss involved dissolved total N movement through subsurface flow, which accounted for 65.55% of the total loss. TN loss for CK was 1954 g·hm-2, while RB-PRB and VFS decreased N loss from sloping farmland by 36.7%. The interception efficiency of RB-PRB was highest at 0.3 m width. VFS successfully intercepted particulate N and reduced it by 32.75%. In terms of soil nutrients, the RB-PRB and VFS interventions led to a substantial 41.69% increase in the TN content of the soil at a 0.4 m width.DiscussionThe findings suggest that biochar has a favorable adsorption effect on NH4+ and NO3−, an appropriate width of RB-PRB with VFS could effectively reduce nitrogen loss from sloping farmland. Simultaneously, it enhances the water and fertilizer retention capacity of sloping cropland soil; however, the long-term implications necessitate further validation.

Replacing nitrogen in mineral fertilizers with nitrogen in maize straw increases soil water-holding capacity

Soil water-holding capacity decreases due to long-term mineral fertilizer application. The objective of this study was to determine how replacing mineral fertilizer with maize straw affected the soil water retention curve, soil water content, soil water availability, and soil equivalent pore size. Replacement treatments in which 25% (S25), 50% (S50), 75% (S75), and 100% (S100) of 225 kg ha−1 nitrogen from mineral fertilizer (CK) was replaced with equivalent nitrogen from maize straw were conducted for five years in the Loess Plateau of China. The Gardner model was used to fit the soil water retention curve and calculate the soil water constant and equivalent pore size distribution. The results indicated that the Gardner model fitted well. Replacing nitrogen from mineral fertilizer with nitrogen from straw increased soil specific water capacity, soil readily available water, soil delayed available water, soil available water, soil capillary porosity, and soil available water porosity over time. S25 increased field capacity and wilting point from the fourth fertilization year. S50 enhanced soil readily available water, soil delayed available water, soil available water, and soil available water porosity from the fifth fertilization year, whereas S25 and S75 increased these from the third fertilization year or earlier. Soil specific water capacity, soil readily available water, soil delayed available water, soil available water, soil capillary porosity, and soil available water porosity could better reflect soil water-holding capacity and soil water supply capacity compared with field capacity and wilting point.

Contrasting patterns of water use efficiency and annual radial growth among European beech forests along the Italian peninsula

Tree mortality and forest dieback episodes are increasing due to drought and heat stress. Nevertheless, a comprehensive understanding of mechanisms enabling trees to withstand and survive droughts remains lacking. Our study investigated basal area increment (BAI), and δ13C-derived intrinsic water-use-efficiency (iWUE), to elucidate beech resilience across four healthy stands in Italy with varying climates and soil water availability. Additionally, fist-order autocorrelation (AR1) analysis was performed to detect early warning signals for potential tree dieback risks during extreme drought events. Results reveal a negative link between BAI and vapour pressure deficit (VPD), especially in southern latitudes. After the 2003 drought, BAI decreased at the northern site, with an increase in δ13C and iWUE, indicating conservative water-use. Conversely, the southern sites showed increased BAI and iWUE, likely influenced by rising CO2 and improved water availability. In contrast, the central site sustained higher transpiration rates due to higher soil water holding capacity (SWHC). Despite varied responses, most sites exhibited reduced resilience to future extreme events, indicated by increased AR1. Temperature significantly affected beech iWUE and BAI in northern Italy, while VPD strongly influenced the southern latitudes. The observed increase in BAI and iWUE in southern regions might be attributed to an acclimation response.

Optimizing Biochar Application Rates to Improve Soil Properties and Crop Growth in Saline–Alkali Soil

There is great demand for the amelioration of saline–alkali soils, which requires efficient and economical amendments. Biochar addition could alleviate the adverse impacts of saline–alkali stress in crops. However, their efficiency and optimal amounts in saline–alkali soil restoration remain contradictory and inconclusive. The objective of this study was to investigate the effects of biochar application on the properties of saline–alkali soil and crop growth, as well as to determine the optimal application rate of biochar. We conducted pot experiments with biochar (B) application rates, including 0 (CK), 1% (B-1%), 2.5% (B-2.5%), 5% (B-5%), and 10% (B-10%), studying the impact of biochar on soil water content (SWC), soil salinity, soil electrical conductivity (EC), soil ion content, soil nutrients, soil enzyme activity, and crop growth. A four-parameter Gaussian function was established for the curves depicting the relationship between soil salinity characteristics and the biochar application rates to determine the most optimal application rate. The results indicated that: (1) Compared to the CK, all biochar treatments improved soil water-holding capacity and reduced soil Na+ content and sodium adsorption ratio (SAR). (2) B-1%, B-2.5%, and B-5% treatments reduced soil content, EC, Cl−, and SO42− content over CK, while the results were reversed for the B-10% treatment. (3) Compared to the CK, all biochar treatments significantly increased soil fertility, enhanced soil enzyme activity (alkaline phosphatase, catalase, and urease activity), and significantly promoted the growth of maize. (4) The results of the Gaussian model suggested that a biochar application rate of 3.16% is the optimal rate for alleviating soil salinity in saline–alkali soils. This research demonstrated the potential of biochar to improve soil properties and promote crop growth and provided useful information on biochar application rates for ameliorating saline–alkali soils.

Influence and Mechanism Study of Soil Moisture on the Stability of Arsenic-Bearing Ferrihydrite in Surface Soil Vertical Profiles

Ferrihydrite is usually used as a remedy for arsenic (As)-contaminated soil due to its strong affinity and large specific surface area. However, its noncrystalline phase makes it unstable in long-term applications in the soil. In this study, a soil incubation experiment was designed using the diffusive gradient in thin film (DGT) technique and spectral techniques to investigate the fate of As-bearing ferrihydrite [As(V)-Fh] after long-term incubation at different soil water holding capacities (SWHCs). After As(V)-Fh (0.05 and 0.005 As/Fe molar ratio) was incubated in soil for 360 days, both DGT-derived labile As and Fe were released at 70% SWHC and 120% SWHC into the soil (at a vertical depth of 12 cm). The concentrations of DGT-As and DGT-Fe increased with incubation time and were greater at 120% SWHC. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that As(V)-Fh gradually transformed into hematite and goethite after 360 days of incubation. Goethite was mainly found in the 120% SWHC treatment after 180 days. Hematite and goethite formation rates were greater in the 120% SWHC treatment and in the bottom soil layer. Mechanistic analysis based on X-ray photoelectron spectroscopy (XPS) revealed that the variation in soil pH and the formation of Fe(II) (under flooded water conditions) are the two key factors promoting the formation of hematite (dehydrogenation and dehydration) and goethite (As(V)-Fh dissociation and reorganization). The As release mainly occurred due to the loss of adsorption sites. Thus, it is recommended that ferrihydrite be applied in paddy–dry rotations or dry-field patterns to effectively avoid the loss of As(V)-Fh in long-term-saturated soil.

Soil environment, carbon and nitrogen cycle functional genes in response to freeze-thaw cycles and biochar

Freeze-thaw cycles (FTCs) are a common phenomenon in seasonal frozen soil areas, which can significantly affect the changes in the soil environment and functional genes of microorganisms. To explore the effect of biochar application on soil carbon and nitrogen cycling under FTCs, an indoor soil column simulation test was used in this study. The experimental setup included different application rates of biochar (0%, 1%, 2%), with the carbon and nitrogen cycle functional genes serving as indicator genes. Real-time fluorescence quantitative PCR technology was employed for analysis. Based on the correlation heat map and redundancy analysis (RDA), the response mechanism of soil environment changes and carbon and nitrogen cycle functional genes before and after FTCs was analyzed. The results revealed that the application of biochar significantly increased soil's water-holding capacity held available nutrients in soil, and increased the ability of environmental change. Due to the influence of soil moisture and aeration, biochar reduced the variation of soil carbon sequestration gene cbbL, cbbM, and nitrogen fixation gene nifH abundance after FTCs. The application of 2 % biochar significantly increased the abundance of the nitrification gene amoA and denitrification gene nirK and enhanced the respiration of soil microorganisms. Soil moisture (SM) is the main environmental factor that determines the abundance changes of the soil carbon sequestration genes cbbL and cbbM. Soil organic matter (SOM), pH, nitrate nitrogen (NO3−-N), and ammonium nitrogen (NH4+-N) were the main environmental factors determining the abundance of soil nitrogen fixation gene nifH, nitrification gene amoA, and denitrification gene nirK. This study can provide new insights into the internal mechanism of the soil carbon and nitrogen cycle in seasonal frozen soil areas, and provide some reference for the rational application of biochar and the efficient utilization of water and soil resources in seasonal frozen soil areas in the future.

Optimized tillage can enhance crop tolerance to extreme weather events: Evidence from field experiments and meta-analysis

The frequency of droughts and floods has increased due to climate change and human activities, leading to adverse impacts on agricultural production. Conventional tillage exacerbates the vulnerability of crops to extreme weather. Optimized tillage practices can maintain crop yield stability by increasing soil water-holding capacity during dry seasons and improving crop lodging resistance during heavy rainfall events. The effects of tillage practice under different rainfall types on the productivity of summer maize were studied by combining a five-year field experiment and a meta-analysis. The study tested four tillage treatments: conventional tillage (CT), no-tillage (NT), ridge cultivation with no-tillage (RNT), and winter wheat conventional tillage followed by summer maize no-tillage (NC). Normal rainfall years (2018, 2019 and 2021), a wet year (2020), and a drought year (2022) were experienced during the experiment. Compared to CT, NC significantly increased available soil water storage during the dry season by an average of 19.7 % (P < 0.05). NC and RNT had lower lodging rates during the wet year than CT, and over the five years, NC had a higher average maize yield (9.8 t ha−1) than RNT, while RNT had a higher yield during the wet year (10.7 t ha−1). NC also had significantly higher yield stability than CT. Furthermore, NC and RNT had higher rainwater use efficiencies (RUE) (23.9 and 23.0 kg ha−1 mm−1, respectively) than NT and CT (22.9 and 21.6 kg ha−1 mm−1, respectively). A meta-analysis showed that the crop yield under combined tillage (COT) was significantly higher than CT and NT by 6.7 % and 7.1 %, respectively, confirming the reliability and universality of the field experiment results. Overall, NC rotation is recommended as the best tillage system for sustainable crop production under semi-arid conditions, while RNT can be used in areas with abundant rainfall and prone to flooding. Our research findings offer evidence-based insights into management strategies that can enhance agricultural ecosystem resilience and production stability under extreme climate conditions.