Soil Water-holding Capacity Research Articles

Drought-protective effects of nutrient seed treatments during early growth of oilseed rape

Crop production is increasingly affected by water limitation even in temperate climates due to a rising frequency of drought periods, related with global change. The stress-protective nutrients, discussed as a mitigation strategy, were investigated for their potential drought-protective effects of nutrient seed treatments, based on Ca, K, Fe, Zn, Mn on early growth of oilseed rape (OSR). Responses were observed in five OSR hybrids under greenhouse conditions on two soils with contrasting properties (sandy-loam pH 5.6 vs. silty-loam pH 6.9) in two independent pot experiments. A 7-days drought period with reduced soil moisture level (40% soil water-holding capacity. WHC) inhibited shoot and root growth and caused irreversible wilting and leaf necrosis (27-46% of total leaf area) particularly on the sandy-loam with lower WHC, depending on the investigated genotype. Nutrient seed treatment increased shoot (10-15%) and particularly root growth (14-23%) as well as nutrient accumulation, but also reduced the proportion of irreversibly damaged leaves to 17-21%, with the largest effect in strongly drought-affected genotypes under the challenging conditions on the sandy-loam soil. Analysis of physiological stress indicators revealed increased accumulation of phenolics (23-28%), antioxidants (14-47%) and higher activities of ascorbate peroxidase (APX) (23-87%) in the leaf tissue, counteracting drought-induced oxidative stress. Moreover, APX activity was positively related with root length (R20.8953), suggesting a protective effect on drought-induced oxidative IAA degradation with inhibitory effects on root growth. Increased levels of absisic, jasmonic and salicylic acids during drought stress recovery point to stress priming effects, strengthening the natural adaptive responses to water limitation.

Comparative study of pyrochar and hydrochar on peanut seedling growth in a coastal salt-affected soil of Yellow River Delta, China

Biochar (i.e., pyrochar and hydrochar) application is a promising strategy to improve soil quality and productivity. However, the comparison of biochars with different carbonization methods and feedstocks for the plant growth in the coastal salt-affected soil remains limited. In this study, a 30-day microcosmic experiment was conducted to compare the effects of pyrochars and hydrochars derived from reed straw (RPC and RHC) and cow manure (CPC and CHC) on the peanut (Arachis hypogaea L.) seedling growth in a coastal salt-affected soil of Yellow River Delta, China. The results showed that RPC, CHC and CPC significantly elevated fresh shoot weight by 67.77%–89.37%, whereas the RHC amendment showed little effect. The malondialdehyde contents in peanut seedling leaves were significantly declined by 25.28%–35.51% with pyrochar and hydrochar amendments, which might be associated with the enhanced proline contents and K/Na ratios. The stimulation of certain phytohormones (i.e., indole-3-acetic acid, zeatin riboside, gibberellic acid 3) in peanut seedlings with pyrochar and hydrochar amendments might be attributed to the growth enhancement. RPC, CPC and CHC improved the soil properties and fertility such as cation-exchange capacity (CEC), total nitrogen, and available potassium and water holding capacity (WHC) of the coastal salt-affected soil. However, RHC not only significantly decreased soil CEC and WHC, but also increased soil exchangeable sodium percentage. The abundances of soil beneficial bacteria, such as f_Gemmatimonadacea, Sphingomonas, Blastococcus and Lysobacter were enhanced by RPC, CHC and CPC amendments, which were mainly associated with the increased WHC and CEC. Fungal community was less sensitive to pyrochar and hydrochar amendments than bacterial community according to the relative abundance and diversity, and beneficial fungi, such as Oidiodendron and Sarocladium were enriched in the CHC soil. Overall, the application of RPC, CHC and CPC showed greater potentials for the enhancement of peanut growth in a coastal salt-affected soil.

Effects of Biochar and Residual Plastic Film on Soil Properties and Root of Flue-Cured Tobacco

Plastic film mulching in the field changes the soil structure and the normal distribution of soil water. Residual plastic film (RPF) in the soil causes serious environmental problems to the agricultural ecosystem. In order to determine the role of biochar in mitigating the negative effects of RPF pollution in the soil on agricultural production, in this work, we conducted a pot experiment without biochar and RPF as the control treatment. Four levels were set for biochar: no biochar (0 t/hm2), low biochar (2.5 t/hm2), medium biochar (7.5 t/hm2), and high biochar (15 t/hm2). Besides, four levels were set for the RPF: 0, 80, 320, and 720 kg/hm2. The results showed that medium biochar could improve the soil environment of the RPF, the saturation water content in the soil was increased by 4.5%–11.4%, and the root activity was increased by 6.3%–13.4%. In addition, the root density of flue-cured tobacco was also significantly increased. Medium and high biochar had a significant effect on higher residual plastic film (320 and 720 kg/hm2). It can alleviate soil tillage obstacles caused by plastic film residue, improve soil water-holding and water-releasing capacity, and optimize tobacco plant growth environment. This study provides evidence for the application of biochar as a soil ameliorant in residual film soil. This suggests that we should do more research on the environmental impact of RPF pollution on agroecosystems.

Oat catch crop efficacy on nitrogen leaching varies after forage crop grazing

This study tested the effect of oat catch crops on mineral nitrogen (N) leaching losses from cool season fodder beet grazing. Undisturbed soil monolith lysimeters were collected from two grassland sites with soils featuring contrasting texture and water holding capacity (WHC) characteristics. After simulated fodder beet grazing in late autumn or winter, synthetic dairy cow urine was applied. Nitrogen leaching losses were measured from lysimeters sown with oats after urine application and compared with those under fallow conditions until spring. Oat dry matter (DM) production and N uptake measurements were obtained. Sowing oats reduced total mineral N leaching losses by up to 59%. Reductions in mineral N leaching were inconsistently affected by soil type but were strongly influenced by urine application timing. Nitrogen uptake by oats (52–143 kg N ha−1) drove reductions in N leaching losses compared with fallow soil. Oats yielded 4–17 t DM ha−1, and both yield and N uptake were strongly affected by urine application timing (winter > autumn) and soil type (high WHC > low WHC). Sowing oats after fodder beet grazing instead of leaving the ground fallow can reduce the environmental impacts of these systems, while simultaneously increasing annual feed supply. Catch crop gains can be maximised by avoiding or delaying autumn grazing of fodder beet, particularly on low WHC soils.

The Use of Soil Conditioners to Ensure a Sustainable Wheat Yield under Water Deficit Conditions by Enhancing the Physiological and Antioxidant Potentials

Traditional mulch material (farmyard manure) has long been used in agriculture. However, recent developments have also introduced the scientific community and farmers to advanced chemicals such as potassium polyacrylamide (KPAM), which has revolutionised the concept of the soil water-holding capacity to many compared with other materials being used. To compare the effect of different organic and inorganic soil amendment materials under water stress conditions, a two-year (2018 and 2019) field study was conducted. The main plots consisted of irrigation treatments, i.e., I0 (control irrigation), I1 (drought-induced by skipping irrigation at the 4th leaf stage), and I2 (drought-induced by skipping irrigation at the anthesis stage). The subplots included a control treatment and soil amended with different conditioners such as potassium polyacrylamide (KPAM, 30 kg/ha), farmyard manure (FYM, 4 tons/ha), and biochar (10 tons/ha); these were mixed thoroughly with the soil before sowing. The results showed a significant reduction in the water relation parameters (water potential up to 35.77% and relative water content up to 21%), gas exchange parameters (net CO2 assimilation rate up to 28.85%, stomatal conductance up to 43.18%, and transpiration rate up to 49.07%), and yield attributes (biological yield up to 8.45% and grain yield up to 32.22%) under drought stress conditions. In addition, water stress also induced an increase in the synthesis of osmoprotectants (proline up to 77.74%, total soluble sugars up to 27.43%, and total free amino acids up to 11.73%). Among all the soil conditioners used, KPAM significantly reduced the negative effects of drought stress on the wheat plants. Thus, it could be concluded that the use of soil conditioners is a promising method for dealing with the negative consequences of drought stress for achieving sustainable crop yields.

Modeling of Sandy Soil Compaction and Water Holding Capacity Due to Biogas Slurry Ameliorant

Model could be used to study the behavior of real systems such as hydrosphere (soil system) for improving their performance as basis of decision-making that promote the sustainability. Here, the study focused on SDGs point 15, how the agriculture particularly soil management should keep the life on land. Biogas slurry (BS) is a liquid-solid mix waste from livestock that useful for soil improving soil quality. Sandy soil has some limitations when used as media of plant cultivation, mainly poor in water holding capacity and less of organic content. This study aimed to measure and explore the sandy soil quality (soil compaction, SC and water holding capacity, WHC) due to BS application. A completely randomized design (CRD) in laboratory was adopted in this study where soil and BS put in a pot of diameter and height of 8.2 cm and 12 cm, respectively. The experiment was carried out with treatment of sandy soil as control (K), sandy soil and BS dose15 ton/ha (D1), 30 ton/ha (D2), and 45 ton/ha (D3). The soil was incubated 84 days that every 14 days (incubation time, IT) the SC and WHC were measured. Mathematical model and Two Ways ANOVA Test were applied to analyze the data. Logistic equation was acceptable (R2 > 80%) to describe soil compaction behavior in sandy soil with BS ameliorant. The SC rate of K, D1, D2, and D3 treatments were - 0.0251, -0.0524, -0.0280, and -0.0360, respectively. This study revealed BS and IT significantly affect SC and WHC of sandy soil with BS ameliorant.

Soil physico-chemical properties and water productivity of maize as affected by biochar application under different irrigation regimes in northwest India

ABSTRACT Application of biochar as an amendment not only improves water retention in soil but also improves overall soil physical environment. To test this hypothesis, a field study was conducted for 2 years, i.e., 2019 and 2020, in an ongoing experiment on maize-based system at the Research Farm, Department of Soil Science, Punjab Agricultural University, Ludhiana, in a sandy loam soil. The parameters tested include soil water-holding capacity, moisture retention, water transmission characteristics, aggregate stability, bulk density, and penetration resistance of soil. Six biochar (B), farmyard manure (fym), and nitrogen (N) combinations were tested, which includes BN1 (biochar @ 7.5 t ha−1 + N @ 75 kg ha−1), BN2 (biochar @ 7.5 t ha−1 + N @ 150 kg ha−1), FN1 (fym @ 20 t ha−1 + N @ 75 kg ha−1), FN2 (fym @ 20 t ha−1 + N @ 150 kg ha−1), N1 (N @ 75 kg ha−1), and N2 (N @ 150 kg ha−1) in main plots and two irrigation regimes IW/CPE ratio 0.6 (I0.6) and 0.9 (I0.9) (irrigation water over cumulative open pan evaporation), i.e., deficit and full irrigation were in subplots. Moisture retention at 0.3 bar was significantly higher under biochar treatment BN1, i.e., 30.0%, while the lowest was recorded under N2, i.e., 25.5% at the end of spring 2020. Biochar and fym-amended soils decreased penetration resistance of soil by 22.57% and 20.85% at 10 cm soil depth as compared to unamended soil. BN1 showed increased mean weight diameter by 43.90% over N1 (control). Deficit irrigation, i.e., I0.6, resulted in 6.11% and 18.78% higher water productivity of both kharif and spring maize, respectively, over I0.9. It is also concluded that biochar as soil amendment may retain more water due to its porous nature and more surface area and also reduce the frequency of irrigation, hence sustaining and optimizing the limited water available for crop production in northwest India.

Analysis of leaf-architecture characteristics and ecological adaptability of tree species in the upper reaches of the Chishui River

The leaf-architecture characteristics of 15 ligneous plants of the karst region of the upper reaches of the Chishui River were assessed using spatial syntax. Furthermore, the relationship between leaf-architecture characteristics, plant functional traits, and soil water-holding capacity as well as the adaptation of plant architecture to this habitat were explored. The following results were obtained: (1) The integration, connectivity, and control of primary veins are significantly better than those of secondary veins, indicating strong interveinal ranking. The integration, connectivity, and control of evergreen tree species are superior to those of deciduous tree species, suggesting a more complex spatial morphological structure of evergreen leaves. In evergreen trees, the spatial morphological structure of tree leaves is more complex than that of shrubs, while the spatial morphological structure of tree leaves of deciduous trees is simpler than that of shrubs. (2) The dry matter content of the leaves of the investigated 15 ligneous plants ranged from 10.79 to 31.83 mg·g−1. The leaf relative water deficit, maximum net photosynthetic rate, transpiration rate, and the specific leaf area content ranged from 35.15 to 66.53%, 0.4–32 μmol·m−2·s−1, 0.07–0.71 g·cm−2·h−1, and 230.15–585.39 cm2·g−1, respectively. (3) The spatial syntax index is significantly correlated with transpiration rate, leaf relative water deficit, as well as soil maximum and available water-holding capacity. (4) Based on the spatial morphological structure of leaves, four basic modes of the leaf architecture can be classified: evergreen mode with complex morphological leaf-structure, evergreen mode with lower complex morphological leaf-structure, mixed evergreen and deciduous modes with lower complex leaf-morphological structure, and deciduous mode with simple morphological leaf-structure. (5) The spatial morphological structure of leaves in karst areas effectively exposes differences of architecture among different plants. Space syntax effectively represents leaf-architecture characteristics and is important for the study of plant architecture. Understanding plant architecture characteristics and their adaptation to the environment provides a scientific basis for the selection of tree species and planting patterns in the vegetation restoration area.

Importance of soil amendments with biochar and/or Arbuscular Mycorrhizal fungi to mitigate aluminum toxicity in tamarind (Tamarindus indica L.) on an acidic soil: A greenhouse study

Tamarindus indica L. is a forest plant species widely used in semi-arid regions and has an important socio-economic role. A 90 d greenhouse pot experiment was conducted to evaluate the efficiency of soil amendments with biochar and/or three Arbuscular Mycorrhizal Fungi (AMF) strains; Rhizophagus fasciculatus (Rf), Rhizophagus aggregatus (Ra), and Rhizophagus irregularis (Ri) on T. indica grown under aluminum stress. The amendments consisted of 5% biochar and 20 g kg−1 AMF as (i) control; (ii) biochar; (iii) biochar + Rf; (iv) biochar + Ra; (v) biochar + Ri; (vi) Rf; (vii) Ra; (viii) Ri. The treatments with biochar significantly (P < 0.05) increased soil pH and reduced the content of soil exchangeable Al3+ relative to the control and exclusive AMF treatments. All the treatments improved total nitrogen and phosphorus uptake by roots and shoot of T. indica and resulted in improved plant growth and root/shoot dry weight. The ability of biochar to enhance the soil's water-holding capacity played a key role in improving the intensity of mycorrhization. Overall, biochar amendments significantly improved the photosynthetic potential of T. indica and the activities of antioxidant enzymes compared to other treatments. Thus, the combined effects of enhanced (a) soil physicochemical parameters, (b) mycorrhization, (c) nutrient uptake, (d) photosynthetic potential, and (e) antioxidant activities played an important role in mitigating Al-related stress to improve the growth of T. indica. Therefore, the application of biochar in combination with AMFs can serve as a strategy for ensuring plant biodiversity in acid and Al-toxic soils in arid and semi-arid regions in Africa.

Chemical Response of Soils to Traditional and Industrial Byproduct Wood Biochars

ABSTRACT Soil degradation and a global focus on carbon (C) sequestration in soils have resulted in growing societal interest in soil health practices. Biochar has a high C content, porosity, pH, and cation exchange capacity that benefit soil properties. Here we described an incubation study that aims to evaluate the influences of biochar additions on representative forest organic, forest mineral, blueberry, potato, and mixed vegetable soils from Maine, USA. The experiment consisted of amendments of either a lime stabilized industrial byproduct softwood pulp biochar (SPB) or pine wood biochar (PB) at application rates equivalent to 0, 5, 10, 25, 50, and 100 t ha−1. Here we report influences of biochar addition on soil pH, loss-on-ignition (LOI), water-holding capacity (WHC), and exchangeable cations. In general, both SPB and PB increased the value of these soil properties in all mineral soils, with significant increases often being found at a rate of 100 t ha−1. Forest organic soils, however, were more variable attributable to the high organic C concentration of this substrate. Soil response to SPB amendments was strongly influenced by the lime component, although few significant differences were found between SPB and PB amended soils. Analysis of carbon dioxide (CO2) emissions from SPB amendments due to lime dissolution and acid neutralization represented less than 3% of the total carbon added in SPB treated soils, leaving SPB and PB both important potential soil amendments. This suggests that both traditional and industrial byproduct biochars have potential for soil health and C sequestration management goals.

The Effects of Plant and Soil Characteristics on Partitioning Different Rainfalls to Soil in a Subtropical Chinese Fir Forest Ecosystem

The climate-induced changes in soil water patterns pose a serious threat to subtropical plantations. Mixed species stands have been advocated as an efficient way to enhance ecosystem stability. However, little is known about their possible impact on the soil water-holding capacity in the subtropics. In this study, we employed a stable hydrogen isotope to assess the contribution of rainfall to soil water (CRSW) in a pure Chinese fir (Cunninghamia lanceolata) plantation and in two mixtures of Chinese fir with Cinnamomum camphora or with Alnus cremastogyne after three different magnitudes of rainfall events in subtropical China. Furthermore, we used structure equation modeling (SEM) to quantify the relative importance of vegetation and soil properties on the CRSW. The results indicated that the CRSW did not differ among these three Chinese fir plantations after light rainfall, whereas the CRSW of moderate and heavy rainfall to soil water were 15.95% and 26.06% higher in Chinese fir plantation with Cinnamomum camphora, and 22.67% and 22.93% higher in Chinese fir plantation with Alnus cremastogyne than that in the pure Chinese fir plantation, respectively. SEM analysis showed that the vegetation biomass and soil properties significantly affected the CRSW following light rainfall, but the soil properties were the most important factors influencing the CRSW under moderate and heavy rainfall. Our findings demonstrate that the mixed conifer–broad-leaved plantation is a more effective strategy for improving the soil water-holding capacity than the pure conifer plantation in subtropical regions, which is conducive to coping with the frequent seasonal droughts and extreme precipitation events.

Expected effects of climate change on the production and water use of crop rotation management reproduced by crop model ensemble for Czech Republic sites

Crop rotation, fertilization and residue management affect the water balance and crop production and can lead to different sensitivities to climate change. To assess the impacts of climate change on crop rotations (CRs), the crop model ensemble (APSIM,AQUACROP, CROPSYST, DAISY, DSSAT, HERMES, MONICA) was used. The yields and water balance of two CRs with the same set of crops (winter wheat, silage maize, spring barley and winter rape) in a continuous transient run from 1961 to 2080 were simulated. CR1 was without cover crops and without manure application. Straw after the harvest was exported from the fields. CR2 included cover crops, manure application and crop residue retention left on field. Simulations were performed using two soil types (Chernozem, Cambisol) within three sites in the Czech Republic, which represent temperature and precipitation gradients for crops in Central Europe. For the description of future climatic conditions, seven climate scenarios were used. Six of them had increasing CO2 concentrations according RCP 8.5, one had no CO2 increase in the future. The output of an ensemble expected higher productivity by 0.82 t/ha/year and 2.04 t/ha/year for yields and aboveground biomass in the future (2051–2080). However, if the direct effect of a CO2 increase is not considered, the average yields for lowlands will be lower. Compared to CR1, CR2 showed higher average yields of 1.26 t/ha/year for current climatic conditions and 1.41 t/ha/year for future climatic conditions. For the majority of climate change scenarios, the crop model ensemble agrees on the projected yield increase in C3 crops in the future for CR2 but not for CR1. Higher agreement for future yield increases was found for Chernozem,while for Cambisol, lower yields under dry climate scenarios are expected. For silage maize, changes in simulated yields depend on locality. If the same hybrid will be used in the future, then yield reductions should be expected within lower altitudes. The results indicate the potential for higher biomass production from cover crops, but CR2 is associated with almost 120 mm higher evapotranspiration compared to that of CR1 over a 5-year cycle for lowland stations in the future, which in the case of the rainfed agriculture could affect the long-term soil water balance. This could affect groundwater replenishment, especially for locations with fine textured soils, although the findings of this study highlight the potential for the soil water-holding capacity to buffer against the adverse weather conditions.

The mass water content of paddy soil after harvest is strongly associated with the accumulation of organic matter as the source of available nitrogen

ABSTRACT Paddy soils are the dominant source of nitrogen for rice via mineralization, and knowledge about the available nitrogen (AN) in paddy soil is important for rice cultivation. Although the relationship between AN and soil physicochemical parameters has been studied, no systematic studies of the relationships between AN and the soil moisture content of various soil types in Japan have been studied. Therefore, we examined the impacts of soil types and treatment of organic matter application or paddy–upland rotation on these relationships. We sampled topsoils from 30 paddy fields throughout Japan. We compared the relationships between AN and soil physicochemical properties, such as total nitrogen (TN), cation exchange capacity, soil water-holding capacity (WHC), mass water content after harvest (MWH), and water content after harvest (WCH). The scatter diagram revealed that AN and either MWH or WCH (p < 0.01) had the highest positive linear correlation coefficient; the pattern became clearer after separating Andosols and non-Andosols. We analyzed the relationship between AN and either TN or MWH in 100 topsoils, including soils from treatment plots with successive organic matter application or paddy-upland rotation. A significantly positive correlation between AN and TN was observed, although the regression slopes for volcanic or non-volcanic soils differed. The decrease in AN due to frequent paddy–upland rotation was greater than that for TN. On the other hand, a highly positive correlation between AN and MWH was observed, and the coefficient of determination was higher than that for AN and TN. TN and the WHC increased when the accumulation of organic matter in paddy soil was greater. As there was a positive correlation between WHC and MWH, a positive correlation was also observed between AN and MWH. Additionally, we investigated year-to-year variation in MWH using topsoil samples collected before autumn tillage, for 3–5 consecutive years in 24 plots, for various soil types throughout Japan. In order to eliminate the effects of precipitation and to minimize the fluctuation of MWH in paddy topsoil, it was desirable to collect topsoil samples within 24–96 hours of the last precipitation of 1 mm h−1 or more, for the measurement of moisture content.

Variability and correlation of selected soil attributes and maize yield influenced by tillage systems in mountainous agroecosystem

Soil and topographic variability severely influence agricultural productivity and food security in a mountainous agroecosystem. Understanding these soil spatial disparities are important to optimize suitable land use planning and adoption of appropriate conservation practices to ensure sustainable agricultural productivity in mountainous regions. A field survey and sampling of 108 elevation sites were conducted to assess spatial dynamics and influence of prevalent tillage systems on selected soil attributes and on reported maize (<i>Zea mays</i> L.) grain yield (MGY) in mountainous valleys of Pakistan. Measured soil properties were effective soil depth (ESD), soil penetration resistance (SPR), soil bulk density (SBD), fraction of rock fragments (FRF), soil organic matter (SOM), and soil water holding capacity (SWHC). Additionally, the influence of three existing tillage systems—integrated tillage (IT), bullock tillage (BT), and tractor tillage (TT)—on soil properties and MGY were assessed. Research results showed that ESD, SPR, SBD, FRF, SOM, SWHC, and MGY varied from 15.0 to 40.0 cm, 180.0 to 278.0 psi, 0.9 to 1.7 g cm⁻³, 13.2% to 43.5%, 0.6% to 2.9%, 10.5% to 35.6%, and 4.1 to 10.2 t ha⁻¹, respectively. Differences between soil parameters were significant among the sampling sites studied. Soil properties were found to be strongly associated with each other and with the MGY and were grouped through Pearson correlation, principal component analysis, and heatmap. Moreover, significant variation of soil properties was noted due to the tillage systems adopted by the farmers. The ESD (26.8 cm), SOM (1.4%), SWHC (16.9%), and MGY (7.8 t ha⁻¹) were the highest under IT while the SPR (262.8 psi), SBD (1.6 g cm⁻³), and FRF (38.0%) were the greatest with TT compared to the other tillage systems. Findings of this study are imperative for agriculturists, soil managers, land use planners, and policy makers to identify and implement suitable interventions for sustainable use of agricultural lands to bring economic produce while conserving the mountainous agroecosystem and its resources on sustainable basis.

THE SHORT TERM EFFECT OF TILLAGE SYSTEM ON SOIL MOISTURE RETENTION IN BAYELSA STATE, NIGERIA

The objective of the study was to determine the short time effect of tillage system on the water retention capacity of soils in the Niger Delta University Teaching and Research Farm, Bayelsa State. Five treatments (No-till, Digging, Hoeing, Hoeing+Digging once, and Hoeing+Digging twice) were considered. Plant Available Water Content (PAWC) and the Soil Water Holding Capacity (SWHC) were used to determine the soil water retention capacity. The results revealed that the crude tillage methods had a significant (P&lt;0.05) impact on some soil properties. The highest bulk density (1.18g/cm3) was found in the No-till zone, while the lowest (0.89g/cm3) was in the Hoe+Digging twice method. The tillage methods also affected the hydraulic conductivity as the highest value (4.67cm/hr) was found in the hoe+digging zone and the lowest (2.61cm/hr) in the no-till area. Furthermore, the PAWC and SWHC were highest (0.14cm3cm-3 and 2.03cm) at the No-till zone and lowest (0.06 cm3cm-3 and 0.95cm) at the Hoe+Digging twice zone. It is therefore recommended that, for unrestricted flow of water through the soils, compacted soils should be pulverized using tillage implements. Also, for optimal plant water availability, there should be less tillage on coarse-textured soils, as the disturbance promotes rapid leaching.

Impacts of Soil Properties, Topography, and Environmental Features on Soil Water Holding Capacities (SWHCs) and Their Interrelationships

Soil water holding capacities (SWHCs) are among the most important factors for understanding the water cycle in forested catchments because they control available plant water that supports evapotranspiration. The direct determination of SWHCs, however, is time consuming and expensive, so many pedotransfer functions (PTFs) and digital soil mapping (DSM) models have been developed for predicting SWHCs. Thus, it is important to select the correct soil properties, topographies, and environmental features when developing a prediction model, as well as to understand the interrelationships among variables. In this study, we collected soil samples at 971 forest sites and developed PTF and DSM models for predicting three kinds of SWHCs: saturated water content (θS) and water content at pF1.8 and pF2.7 (θ1.8 and θ2.7). Important explanatory variables for SWHC prediction were selected from two variable importance analyses. Correlation matrix and sensitivity analysis based on the developed models showed that, as the matric suction changed, the soil physical and chemical properties that influence the SWHCs changed, i.e., soil structure rather than soil particle distribution at θS, coarse soil particles at θ1.8, and finer soil particle at θ2.7. In addition, organic matter had a considerable influence on all SWHCs. Among the topographic features, elevation was the most influential, and it was closely related to the geological variability of bedrock and soil properties. Aspect was highly related to vegetation, confirming that it was an important variable for DSM modeling. Information about important variables and their interrelationship can be used to strengthen PTFs and DSM models for future research.

Thermal infrared imaging study of water status and growth of arbuscular mycorrhizal soybean (Glycine max) under drought stress

The influence of arbuscular mycorrhizal fungi (AMF) on plant water status and growth under drought stress were investigated using soybean subjected to drought stress (40% of soil water-holding capacity (WHC)) and control conditions (60% WHC) either inoculated with AMF or uninoculated controls. Leaf temperature (Tleaf) and stomatal conductance (gs) were determined at 10:00, 12:00 and 18:00 on the harvest day. The effects of AMF on the water physiological status and growth of soybeans under drought stress were examined using thermal infrared imaging technology (TIIT). AMF inoculation under drought stress increased plant above- and below-ground biomass, nutritional status, and nitrogen, phosphorus and potassium uptake rates, and reduced plant root/shoot ratio. Monitoring Tleaf reflected the effect of AMF on plant water physiological status under drought stress. AMF inoculation resulted in a decline in Tleaf of 0.1–0.4 °C as water uptake proceeded compared with an increase of 0.2–1.4 °C in uninoculated controls. Thus, the effects of AMF on soybean drought resistance changed from positive to negative. AMF reduced plant Tleaf, promoted the accumulation of photosynthetic products, reduced malondialdehyde accumulation, and increased stomatal regulation and Tleaf. These preliminary results provide a basis for further studies on the effects of AMF on the water and growth status of plants under drought stress in arid areas.

A Smartphone Application to Compute Soil Erosion based on the Revised Universal Soil Loss Equation (RUSLE)

Erosion negatively affects farming. It leads to a 50% decline in land productivity (Nellemann et al, 2009). In Africa, erosion generates significant yield reduction (Eswaran, Lal &amp; Reich, 2001). The loss of 75 billion tons of soil per year represent a cost of US$400 billion. An acre of U.S. cropland loses 5 tons of soil per year (Briggs, 2020). Moreover, soil carried away is the source of respiratory illnesses and damages that amount to over $14 billion per year (Eswaran, Lal &amp; Reich, 2001). Furthermore, erosion reduces soil water-holding capacity. The Revised Universal Soil Loss Equation (RUSLE) is the major tool to calculate erosion caused by rainfall erosivity; the resistance of the environment (including soil erodibility; topographical factor, plant cover, and farming techniques) and human techniques (erosion control practices in farming) (Roose, 1996). RUSLE is instrumental in keeping erosion within acceptable limits. This paper presents a new, and the first of its type, smartphone application developed to help farmers and stakeholders compute soil erosion at any location in the world using the RUSLE model. Such an application can help land users to have a more accurate perception about soil erosion and its negative impact.

Conservation Agriculture Effects on Soil Water Holding Capacity and Water-Saving Varied with Management Practices and Agroecological Conditions: A Review

Improving soil water holding capacity (WHC) through conservation agriculture (CA)-practices, i.e., minimum mechanical soil disturbance, crop diversification, and soil mulch cover/crop residue retention, could buffer soil resilience against climate change. CA-practices could increase soil organic carbon (SOC) and alter pore size distribution (PSD); thus, they could improve soil WHC. This paper aims to review to what extent CA-practices can influence soil WHC and water-availability through SOC build-up and the change of the PSD. In general, the sequestered SOC due to the adoption of CA does not translate into a significant increase in soil WHC, because the increase in SOC is limited to the top 5–10 cm, which limits the capacity of SOC to increase the WHC of the whole soil profile. The effect of CA-practices on PSD had a slight effect on soil WHC, because long-term adoption of CA-practices increases macro- and bio-porosity at the expense of the water-holding pores. However, a positive effect of CA-practices on water-saving and availability has been widely reported. Researchers attributed this positive effect to the increase in water infiltration and reduction in evaporation from the soil surface (due to mulching crop residue). In conclusion, the benefits of CA in the SOC and soil WHC requires considering the whole soil profile, not only the top soil layer. The positive effect of CA on water-saving is attributed to increasing water infiltration and reducing evaporation from the soil surface. CA-practices’ effects are more evident in arid and semi-arid regions; therefore, arable-lands in Sub-Sahara Africa, Australia, and South-Asia are expected to benefit more. This review enhances our understanding of the role of SOC and its quantitative effect in increasing water availability and soil resilience to climate change.

Immobilization of heavy metal(loid)s in acid paddy soil by soil replacement-biochar amendment technology under normal wet condition.

The remediation of agricultural soil contaminated by acid mine drainages (AMD) with extreme acidity and elevated concentrations of metal(loid)s still remains to be solved. In the present study, the combination of soil replacement-biochar (BC) amendment was adopted in 270-day incubation experiments to evaluate the effect on the metal(loids) (As, Pb, Cu, Cd, and Zn) immobilization and soil properties (pH, dissolved organic carbon (DOC), redox potential (Eh), and soil water holding capacity (SWC)). The incubation study showed that soil replacement-biochar amendment improved soil health by changing soil properties, which in turn exhibited significant effects on CaCl2-extracted metal(loid)s. The combination of soil replacement and biochar amendment exhibited positive effect on the immobilization of Pb, Cu, Cd, and Zn, while, the risk of As and Cd mobility induced by biochar in the ageing process should be paid attention. Further laboratory seed germination study suggested that soil replacement-biochar amendment could effectively alleviate the stress of metal(loid)s, with the treatment of S50BC achieving the best remediation results. The results of this study suggested that soil replacement-biochar amendment was a promising remediation technology for agricultural soil contaminated by AMD. Graphical abstract.