Influence Soil Water Research Articles

Predicting USCS soil texture classes utilizing soil spectra and deep learning

Abstract Purpose Soil texture identification is vital for various agricultural and engineering applications but generally involves rigorous laboratory work, especially for estimating USCS (Unified Soil Classification System) soil texture classes. Soil texture influences soil water storage capacity, soil fertility, compaction characteristics, and soil strength. Soil spectroscopy offers a reliable approach that is non-destructive, rapid, and cost-effective to estimate several soil properties including texture. For engineering applications, the USCS soil texture classes are preferred, but very few studies have focussed on estimating USCS soil texture using soil spectroscopy or remote sensing data in general. Methods Two large soil spectral libraries (SSLs), viz., Kellog Soil Spectral Library (KSSL) and Open-source Soil Spectral Library (OSSL), as well as three deep learning algorithms (VGG-16, ResNet-16, and Swin transformers), were used in this study to predict six USCS soil texture classes and three USCS soil texture groups. The USCS soil texture classes and groups were derived by grouping clay, sand, and silt fractions that are closely associated with the corresponding USCS soil texture classes. Results The results indicate that the Swin transformer model performed the best with an accuracy of 67% for six USCS soil texture class predictions and 81% for three USCS soil texture group predictions. Cohen’s kappa value implies a moderate agreement (0.55) for soil texture class predictions and a substantial agreement (0.64) for soil texture group predictions. Conclusion The proposed methodology offers a novel approach for USCS soil texture class predictions utilizing SSLs and deep learning techniques.

Effect of cogongrass biochar enriched with nitrogen fertilizer dissolved in seaweed liquid extract on soil water content of Ultisol

Ultisol dry land is characterized by significantly low organic carbon content, an important factor influencing soil water content and physico-chemical dynamics. The addition of N fertilizer dissolved in seaweed liquid extract as an enrichment solution can change the character of biochar. Therefore, this study aimed to analyze the characteristics of cogongrass biochar enriched with dissolved N fertilizer in seaweed extract of different species and assess its impact on soil water content in Ultisol. Urea was used as a nitrogen source, and biochar enriched with N fertilizer dissolved in seaweed liquid extract from Kappapychus alvarezii, Sargassum sp., and Ulva lactuca was tested. Biochar dose used was 20% of soil weight with a 10% extract concentration for each type. Furthermore, five-level treatments were tested in a pot experiment, namely (i) without biochar, (ii) biochar unenriched, (iii) enriched with N fertilizer dissolved in K. alvarezii extract, (iv) enriched with N fertilizer dissolved in Sargassum sp. extract, and (v) biochar enriched with N fertilizer dissolved in U. lactuca extract. Each treatment was repeated three times, following a randomized block design. The results showed that cogongrass biochar enriched with N fertilizer dissolved in seaweed extract had a more amorphous surface morphology structure. The proportion of elements and functional groups in cogongrass biochar changed. Enriched biochar increased Ultisol moisture levels, but water holding capacity and retention were lower than the unenriched sample.

Vietnamese farmers’ perception of climate change effects on water resources and determinants of climate change

ABSTRACT This study investigates crop farmers’ perception on climate change effects on water resources and factors that influence their perceptions of it in Vietnam. A sample of 253 was randomly selected from a total population of 685 crop farmers and a structured questionnaire was created to gather data. Descriptive and inferential statistics were used. The research results showed that climate change effects on water resources varied by landform. A majority of farmers perceived that: shifts in rainfall amount and variability affect the operation of runoff water and groundwater recharge; shifts in temperature level and variability considerably influence evapotranspiration; and changes in runoff amount and runoff variability greatly influence soil water storage and groundwater. Mixed cropping systems, use of soil conservation, extension contacts, farming practices, non-agricultural activities, credit programme participation, information and communication technology (ICT) owned, and education level are the important determinants of farmers’ perceptions on climate change.

Tillage effects on soil physical properties and maize phenology

ABSTRACT Field and laboratory studies on the effect of different systems of tillage on soil agrophysical properties, seed germination and productivity of maize (corn) demonstrate that tillage influences soil water content, penetration resistance and bulk density throughout the growing season. Faster soil warming and seed germination under the mouldboard plough influenced all stages of maize growth and development; minimal tillage was associated with lesser plant height, leaf area, number of cobs per 100 plants and 1000-grain weight, leading to an average yield shortfall of 0.37–0.88t/ha compared to the mouldboard plough.

A mosaic pattern of apple orchards and farmland affects the distribution of soil water and nutrients in their adjacent areas on the Chinese Loess Plateau

With the vigorous promotion of apple tree planting on the Chinese Loess Plateau (CLP), a mosaic pattern of apple orchards and traditional farmland has emerged in the region. However, the interaction between adjacent farmland and apple orchards in terms of soil water and nutrient migration remains unclear. This study aimed to investigate the spatial distribution of the soil water content (SWC) and soil nutrients, as well as their interactions, in 0–10 m soil layers of apple orchards of different stand ages and adjacent farmland under the orchard-farmland land use pattern. The results revealed a significant decrease in average-depth SWC in the orchards in the 0–10 m soil profile (R2 = 0.90) with increasing orchard age, accompanied by a significant increase in soil water deficit (SWD, R2 = 0.94). The annual growth rate of SWD was found to be as high as 5.94 mm·m−1·y−1. Deep soil and surrounding farmland were identified as important sources of soil water for apple tree growth, particularly in older orchards; a 25-year-old orchard absorbed approximately 10.8 % of soil water towards farmland with a horizontal distance of 7 m. The distribution of soil organic carbon (SOC) and total nitrogen (TN) in the 0–10 m soil profile exhibited a similar pattern, decreasing and then stabilizing with increasing depth. However, the peak depth and accumulation of soil nitrate (NO3–-N) significantly increased with orchard age. The migration and accumulation of NO3–-N in the soil provided a scientific basis for the transport of soil water, with NO3–-N accumulation (405.32 mg kg−1) observed in the deep soil (3–6 m) of farmland located 5 m away from a 30-year-old orchard, confirming the exchange of soil water and nutrients between the orchard and the farmland. The stand age of the orchards was identified as the main environmental factor influencing soil water transport under the orchard-farmland land use pattern. Overall, our findings provide valuable insights into the interaction between apple orchards and farmland under the mosaic pattern, which can contribute to a more rational layout of apple orchards and farmland in the future, promoting the efficient utilization of soil water and nutrients on the CLP.

Alternative Furrow Irrigation Combined with Topdressing Nitrogen at Jointing Help Yield Formation and Water Use of Winter Wheat under No-Till Ridge Furrow Planting System in Semi-Humid Drought-Prone Areas of China

Benefiting from the high–farmland construction program in China, one–off irrigation can be guaranteed in most fields in semi–humid drought–prone areas in China. However, little information is available on water and nitrogen (N) management in wheat production under this condition. This study aimed to explore the effects of alternative furrow irrigation (AFI) and topdressing N fertilizer (TN) on wheat productivity under a no–till ridge–furrow planting system in semi–humid drought–prone areas. The experimental design was as follows: two furrow irrigation (FI) methods, namely, EFI (every furrow irrigation) and AFI (alternative furrow irrigation) with 75 mm at the jointing stage were set as the main treatments. Two topdressing N (TN) patterns, namely, NTN (0 kg ha−1 of N) and TN (60 kg ha−1 of N) along with irrigation were set as the secondary treatments. Moreover, a traditional planting practice with no irrigation and no topdressing N (NINTN) was set as control. In 2018–2020, a field experiment was carried out to investigate the effects on soil water, leaf chlorophyll relative content (SPAD) and net photosynthetic rate (Pn), aboveground dry matter assimilates, grain yield, water use efficiency (WUE) and economic benefit. We found that both FI methods and TN patterns significantly influenced soil water content. Compared with NINTN, the soil water content in each combination of the FI method and TN pattern was effectively improved at the booting and anthesis stages, leading to the significant increase in SPAD and Pn in leaves, post–anthesis dry matter accumulation (POA), grain yield, WUE and economic benefit of winter wheat. Compared with the EFI, averaged across years and TN patterns, the AFI technique increased the soil water storage at booting and anthesis stages and significantly improved the Pn at early milk (4.9%) and early dough (7.5%) stages, POA (40.6%) and its contribution to grain (CRPOA, 27.6%), the grain yield (10.2%), WUE (9.1%) and economic benefit (9.1%). In addition, compared with the NTN, the TN pattern significantly increased the water computation by wheat from booting to maturity, enhanced leaf Pn after anthesis and POA, and finally resulted in the increase in grain yield (14.7–21.9%) and WUE (9.6–21.1%). Thus, the greatest improvement in the leaf photosynthetic characteristics, aboveground dry matter assimilates, grain yield, WUE and economic benefit was achieved under AFITN treatment. Above all, it can be concluded that the AFITN with AFI of 75 mm and TN of 60 kg ha−1 at jointing was an alternative management strategy for optimizing yield formation and water use of winter wheat. This study provided new insights into improving wheat productivity in drought–prone areas where one–off irrigation can be guaranteed.

Soil–vegetation–water interactions controlling solute flow and chemical weathering in volcanic ash soils of the high Andes

Abstract. Vegetation plays a key role in the hydrological and biogeochemical cycles. It can influence soil water fluxes and transport, which are critical for chemical weathering and soil development. In this study, we investigated soil water balance and solute fluxes in two soil profiles with different vegetation types (cushion-forming plants vs. tussock grasses) in the high Ecuadorian Andes by measuring soil water content, flux, and solute concentrations and by modeling soil hydrology. We also analyzed the role of soil water balance in soil chemical weathering. The influence of vegetation on soil water balance and solute fluxes is restricted to the A horizon. Evapotranspiration is 1.7 times higher and deep drainage 3 times lower under cushion-forming plants than under tussock grass. Likewise, cushions transmit about 2-fold less water from the A to lower horizons. This is attributed to the higher soil water retention and saturated hydraulic conductivity associated with a shallower and coarser root system. Under cushion-forming plants, dissolved organic carbon (DOC) and metals (Al, Fe) are mobilized in the A horizon. Solute fluxes that can be related to plant nutrient uptake (Mg, Ca, K) decline with depth, as expected from biocycling of plant nutrients. Dissolved silica and bicarbonate are minimally influenced by vegetation and represent the largest contributions of solute fluxes. Soil chemical weathering is higher and constant with depth below tussock grasses but lower and declining with depth under cushion-forming plants. This difference in soil weathering is attributed mainly to the water fluxes. Our findings reveal that vegetation can modify soil properties in the uppermost horizon, altering the water balance, solute fluxes, and chemical weathering throughout the soil profile.

Spatiotemporal Evolution of Soil Erosion and Its Driving Mechanism in the Mongolian Section of the Yellow River Basin

Soil erosion is a popular environmental issue that threatens sustainability. Influenced by multiple factors, such as climate, soil, and terrain, Baotou City, which is in the Bohai Sea Economic Circle and the Economic Belt along the Yellow River, has a severe ecological environment. In this study, revised soil and soil wind erosion equations were used to evaluate the soil erosion dynamics in Baotou City, and the potential driving factors of soil erosion were further investigated. Results showed that from 1990 to 2020, the water erosion modulus in Baotou City increased first, decreased, and then increased, with great fluctuations in annual changes. The wind erosion modulus decreased continuously, with a small fluctuation in annual changes. Water erosion in 2020 was more severe, with 4840.5 km2 added to the desert steppe and 1300.5 km2 reduced in the Yellow River Basin. The extent of wind erosion was significantly reduced, and the phenomenon of wind erosion improved. Meteorological factors are the primary factors that influence soil water erosion and soil wind erosion. Meanwhile, adverse climate changes can alter physical and chemical soil properties and vegetation coverage, thereby indirectly influencing soil erosion. With the implementation of the Beijing–Tianjin sandstorm source control, the farmland return to forest project, the ecological restoration and protection project at the southern and northern foothills of Daqingshan Mountains, grazing prohibition, and rotation grazing—including grassland awards, subsidies, and other policies and systems during this period—the overall deteriorating trend of the grassland ecological environment in Baotou was contained, grassland ecological system functions were improved, wind and sand erosion was prevented, biodiversity was maintained, and the ecological service functions of soil and water conservation were guaranteed.

An arbuscular mycorrhizal fungus alters soil water retention and hydraulic conductivity in a soil texture specific way

Arbuscular mycorrhizal fungi (AMF) alter plant water relations and contribute to soil structure. Although soil hydraulic properties depend on soil structure and may limit plant water uptake, little is known about how AMF influence soil water retention (the relation between the soil water content and soil water potential) and hydraulic conductivity in different soils. Instead, these soil hydraulic properties often are considered to be independent of AMF presence in experiments. We asked if this assumption holds true for both sand and loam. We grew maize plants either inoculated with Rhizophagus irregularis or with autoclaved inoculum in pots filled with quartz sand or loam soil until extraradical spread of the fungus throughout the pots was achieved. Each pot contained a hyphal compartment made of a soil sampling core (250 cm3) covered with a 20-µm nylon mesh to encourage fungus ingrowth but to exclude root ingrowth. We measured soil water retention and unsaturated hydraulic conductivity in these undisturbed root-free soil volumes. We observed that in loam harboring the mycorrhizal fungus, the soil water retention decreased, while in sand, it increased without detectable changes in the soil bulk density. The effects of the fungus on the soil water potential were strongest at low soil water contents in both soils. As a consequence of the altered water potentials in soils with the mycorrhizal fungus, soil hydraulic conductivity increased in loam but decreased in sand after fungus ingrowth. We conclude that in our study, the mycorrhizal fungus acted as a soil conditioner even distant from roots, which encouraged drainage in loams prone to sogginess but enhanced water storage in sands prone to quick desiccation. We recommend considering soil hydraulic properties as being dynamic in future studies on water relations of mycorrhizal plants.

Natural soils in OECD 222 testing — influence of soil water and soil properties on earthworm reproduction toxicity of carbendazim

Soil sorption properties can influence the bioavailability of substances and consequently the toxicity for soil organisms. Current standardised laboratory testing for the exposure assessment of pesticides to soil organisms uses OECD artificial soil that does not reflect the high variation in chemical-physical soil properties found in natural agroecosystems. According to guideline OECD 222, earthworm reproduction tests with Eisenia fetida and the pesticide carbendazim were performed in four natural soils and OECD artificial soil. By using pF 1.6, which ensures a uniformity in actual soil water availability, the control reproduction performance of E. fetida in all natural soils was at the same level as OECD artificial soil. In a principle component analysis, the variation in toxicity between the tested soils was attributable to a combination of two soil properties, namely total organic carbon content (TOC) and pH. The largest difference of 4.9-fold was found between the typical agricultural Luvisol with 1.03% TOC and pH 6.2 (EC10: 0.17 (0.12–0.21) mg a.i. kg−1 sdw, EC50: 0.36 (0.31–0.40) mg a.i. kg−1 sdw) and OECD artificial soil with 4.11% TOC and pH 5.6 (EC10: 0.84 (0.72–0.92) mg a.i. kg−1 sdw, EC50: 1.07 (0.99–1.15) mg a.i. kg−1 sdw). The use of typical agricultural soils in standardised laboratory earthworm testing was successfully established with using the measure pF for soil moisture adjustment. It provides a more application-oriented approach and could serve as a new tool to refine the environmental risk assessment at lower tier testing or in an intermediate tier based approach.

Interseeded cover crop mixtures influence soil water storage during the corn phase of corn-soybean-wheat no-till cropping systems

Interseeded cover crop mixtures influence soil water storage during the corn phase of corn-soybean-wheat no-till cropping systems

Automated sensor-based quantification of soil water retention and microbial respiration across drying conditions

Understanding soil responses to climate-induced precipitation variability is important for improving global carbon models and the development of climate-resilient agriculture. However, our knowledge remains limited regarding factors that influence soil water dynamics and microbial respiration across drying conditions, partially hindered by the lack of easily accessible methodologies. We developed a low-cost, automated, and integrated system to simultaneously quantify microbial respiration and soil water retention in response to drought conditions. This system integrates a CO2 sensor and a digital scale, enabling continuous measurement of CO2 concentration and soil water loss by evaporation when soils are incubated with desiccants inside air-tight chambers. Here we show that the sensor platform provides accurate and repeatable CO2 measurements when compared to a spectroscopy gas analyzer and the alkali trap method. Using the sensor platform, we further demonstrated that averaged microbial respiration of rewetted soil over 4-day incubation declined as management intensity increased following the order of Till ≤ NoTill ≤ Till_fallow ≤ NoTill_fallow = Hay field < Forest. These soils were air-dried for two years before use in incubation experiments, and microbial respiration upon rewetting showed a unimodal response, which rapidly increased and peaked within 12 h except for in forest soils that exhibited a delayed response with respiration peaking at 30 h. Under drying conditions, rewetted soil from the Hay field showed lower water loss than other soils. Volumetric water content at the end of the drying period increased in the order of Till ≤ NoTill < Till_fallow ≤ NoTill_fallow = Hay field < Forest. We posit that this sensor platform provides a powerful tool for functional soil health assessments and fundamental understanding of soil water dynamics and microbial activities in responses to climate-induced water stress.

Steroidal saponin concentrations in switchgrass cultivars Liberty and Independence in North America

Core Ideas Switchgrass has various ecosystem benefits. Switchgrass cultivars Liberty and Independence were evaluated for steroidal saponins. Steroidal saponins were detected in all leaf and stem tissues of both Liberty and Independence cultivars. Steroidal saponins may reduce aboveground pests and influence soil nutrient and water dynamics.

Spatial variation in soil water on a hillslope with ephemeral gullies restored by different vegetation restoration modes on the Loess Plateau

Vegetation restoration in an ephemeral gully (EG) can alter the traits of soil, vegetation, and microtopography, and therefore likely influences soil water. Nevertheless, few results have been reported regarding the response of soil water regime to vegetation restoration modes in EGs in semiarid region. This research was designed to clarify the spatial variation in soil water in an EG with different restoration modes on the Loess Plateau of China. For the selected EG, the two banks of ephemeral gully were well restored by natural succession and artificial planting. Soil water content (θg) was quantified on the ephemeral gully floor (F), natural successional restored ephemeral gully top (NT), and artificial planted restored ephemeral gully top (AT) in both the vertical and longitudinal directions. A sloping farmland was selected as the control. The results revealed that θg increased significantly with soil depth (i.e., 0–1 m) and the distance from the ephemeral gully head (i.e., 0–60 m). In the vertical direction, the mean θg of the six test points of the ephemeral gully floor was 1.1 to 1.2 times greater than that of the control in each soil layer, while the mean θg of the six test points of NT and AT decreased by 12.3 % to 15.6 % and 29.2 % to 29.9 % compared to the control in each soil layer. Along the longitudinal direction, the θg (i.e., 0–1 m soil layer) abided by the pattern of F > NT > AT. The difference in θg between the three ephemeral gully units and their variations in the vertical and longitudinal directions were mainly driven by the variations in soil clay content, bulk density, organic matter content, plant root density, plant litter density, and the distance from the ephemeral gully head. The findings are useful to clarify the spatial variation in soil water and to select a reasonable vegetation restoration mode on hillslopes in semiarid regions.

Water-table response to extreme precipitation events

Extreme precipitation events (EPEs) will play a significant role in influencing soil–water and groundwater storage worldwide. We examined water-table depth (WTD) response to EPEs for 17 cases representative of soils and climate settings across the United States. Precipitation data from NOAA’s Precipitation Frequency Data Server were used for each case to characterize 1-day extreme precipitation events (EPEs) with annual exceedance probabilities of 0.1 % over an average baseline date range of 1981–2011. The inverse solution in the HYDRUS-1D modeling software was used to obtain the soil–water retention curve for each case. Non-EPE and EPE scenarios were modeled and compared to examine water-table displacement (ΔWTD) and recession time (trec). The ΔWTD ranged from 0.6 to 2.4 m across cases and were not directly controlled by EPE amount; instead, ΔWTD was inversely related to available porosity. Soils with low available porosity experienced large ΔWTD compared to soils with higher available porosity. In cases with larger diffusivity values, the modeled water table receded faster than in cases with smaller diffusivity values. This was because water-table recession times, trec, were inversely related to hydraulic diffusivity. For all cases, recession back to pre-EPE levels ranged from months to years suggesting an increased role by the unsaturated zone in buffering EPEs that should be considered in future EPE-groundwater modeling studies.

Difference in soil water holding capacity and the influencing factors under different land use types in the alpine region of Tibet, China

To investigate the variation of soil water holding capacity under different land use types can provide scientific basis for evaluating the change characteristics and regulation mechanism of water conservation capacity in alpine ecosystems. We collected soil samples at different depth intervals (0-10, 10-20 and 20-30 cm) under three land use types (farmland, forest, and grassland) in Tibet alpine region to measure the maximum water holding capacity, capillary water holding capacity, field capacity, and basic soil physicochemical properties. The associated environmental factors (mean annual precipitation, normalized difference vegetation index, altitude, slope gradient and surface roughness) were extracted to analyze the change characteristics and influencing factors of soil water holding capacity under different land use types. The results showed that soil water holding capacity (the maximum water holding capacity, capillary water holding capacity, and field capacity) of farmland, forest, and grassland all decreased with increasing soil depth. The mean values of the maximum water holding capacity, capillary water holding capacity, and field capacity in the 0-30 cm soil layer of grassland were 379.79, 329.57 and 194.39 g·kg-1, respectively, which were significantly higher than that of farmland (301.15, 259.67, and 154.91 g·kg-1) and forest (293.09, 251.49, and 117.01 g·kg-1). Results of the redundancy analysis showed that soil properties significantly influenced soil water holding capacity, with explanation rate of 44.6%, 42.7%, 37.6% and 35.8% for total porosity, soil organic matter, capillary porosity and soil bulk density, respectively. Results of the principal component analysis showed that mean annual precipitation, normalized difference vegetation index, altitude, slope gradient, and surface roughness were the main environmental factors affecting the spatial variation of soil water holding capacity, with a cumulative contribution of 72.4%. The grassland in the alpine region of Tibet had the highest water holding capacity and could effectively prevent soil erosion. Therefore, the implementation of returning farmland to grassland and the enclosure management of degraded grassland would be conducive to improve soil water conservation capacity in the alpine regions.

Effects of microplastics on evaporation dynamics in porous media

Microplastics (MPs) pollution is an emerging threat to soil ecosystems. The present study aims to investigate the impacts of MPs on soil water evaporation dynamics and patterns. Two series of laboratory experiments were conducted using sand particles and clay mixed with different MPs to investigate how evaporation dynamics and patterns are influenced by the presence of MPs. Quartz sand including 0, 0.75, 1.5, and 4.5% of Polyethylene (PE) and Polyvinylchloride (PVC) were used to evaluate MPs effects on evaporation rates while bentonite mixed with sand and 0, 0.75, 1.5, 4.5, 6, 8, and 10% of PE and PVC were used to investigate evaporation-induced cracking patterns. The experiments were conducted under controlled laboratory conditions in a climate chamber at constant ambient temperature. Our results suggest that the addition of MPs led to more water evaporation compared to the samples without MPs. Microscopic imaging and analysis enabled us to evaluate the possible MPs effects on the modification of soil characteristics and pore structure affecting the evaporation behavior. Moreover, although increasing MPs concentrations appeared to induce only minor effects on the crack morphology formed as a result of evaporation from the mixture of sand and bentonite, the type of MPs (PE vs PVC) had more notable effects on the drying-induced cracking patterns. The reported experimental data and analysis extend our physical understanding of the parameters influencing soil water evaporation in the presence of MPs.

Effects of low-till parabolic subsoiling frequency and furrow irrigation frequency on maize in the Yazoo-Mississippi Delta

Naturally forming or mechanically induced hardpans limit water infiltration and crop productivity in many agricultural regions including the Mid-South U.S. This research was conducted to determine whether low-till parabolic subsoiling and furrow irrigation interact to influence soil water dynamics and maize production in the Mid-South. The factorial effects of subsoiling frequency (no subsoiling, NS; subsoiling only before cotton, CS; subsoiling only before maize, MS; and subsoiling every year, ES) × irrigation frequency (no irrigation, NI; low-frequency irrigation, LI; and high-frequency irrigation, HI) on infiltration, grain yield, and profit over specified costs were investigated for the maize portion of a maize-cotton rotation experiment in a silty clay loam soil near Tribbett, Mississippi. Subsoiling before maize improved the infiltration of irrigation (p < 0.05) but not the infiltration of in-season rainfall for irrigated treatments. By subsoiling before maize, high-frequency irrigation maximized grain yield in just one—rather than three—out of five years. Subsoiling before maize also increased non-irrigated yield in all five years. Overall, the combination of subsoiling only before maize and low-frequency irrigation achieved the largest average profit and a relatively small risk. These findings support the practice of low-till parabolic subsoiling before maize as a hydrologically effective and economically viable strategy to conserve freshwater resources in the Mid-South.

Influence of Benggang slope cracks on soil water regimes: Comparison of model simulation and time‐domain reflectometry

AbstractCracks greatly influence the saturated hydraulic conductivity (Ks) of soil and are one of the most important factors for increasing Ks. Moreover, both cracks and Ks influence soil water distribution. This study aimed to investigate the consistency of the effects of cracks and Ks on the water distribution along slopes. Ks was measured in three soil layers along two typical Benggang (a severe gully erosion landform) slopes using a double‐ring infiltrometer. The Ks values show a gradual decrease with increasing distance from the gully head in the same soil layer, and this phenomenon is consistent with the distribution of cracks on the slope measured by the staining tracer method. This indicates that the distribution of cracks can be accurately predicted by measuring the spatial variation in Ks. The VADOSE/W model was employed to simulate soil water configurations and yielded inaccurate simulation results, typically in the lower slope. In addition, the simulation results were greatly improved through the inclusion of effective cracks by adjusting the material properties, but not solely by adjusting the Ks. Therefore, the influence of cracks on the water distribution is not well reflected by Ks, and cracks must be incorporated into the relevant models. The soil water content in the topsoil of the lower slope near the headwall with more cracks was than that of the upper slope, implying that cracks likely accelerate the downward movement of water and increase leakage. This process increases the water content and pore water pressure in deeper soil layers, thereby eventually increasing the likelihood of soil erosion. The results of this study can improve our understanding of the triggers of Benggang erosion and provide guidance on the prevention and control of soil erosion risks in areas with granitic soil.Highlights The influence of cracks on water distribution cannot be strongly reflected by Ks. Cracks must be considered when analysing the soil water content in a simulation mode. The distribution of cracks influences the timing and frequency of Benggang erosion. Soil cracks distribution is important in soil risk remediation and control such as Benggang erosion.

Soil tillage and machinery traffic influence soil water availability and air fluxes in sugarcane fields

Intensive soil disturbance by conventional tillage and heavy machinery traffic for planting, cultivation, and harvesting operations are the main causes of soil compaction and degradation of soil physical quality in sugarcane fields. However, the adoption of conservation soil tillage practices, such as no-till and reduced tillage associated with traffic control have been proposed as a key strategy to preserve soil physical quality, enhancing water availability and air fluxes. Nevertheless, the effects of reduced tillage associated with traffic control in sugarcane fields are still not well documented. A study was carried out to quantify soil water availability and air flux indicators in two soils with contrasting textures (named Sandy Loam and Clayey soil) under conventional and reduced tillage practices associated with and without controlled machinery traffic in central-southern Brazil. Soil physical parameters such as bulk density, total porosity, air-filled porosity, air permeability, pore continuity index, and the least limiting water range (LLWR) were measured. In both soils, there was no difference between conventional and reduced tillage in bulk density, air permeability, and LLWR. However, reduced tillage with non-traffic decreased bulk density and increased macroporosity, air-filled porosity, air permeability, pore continuity, and LLWR in Sandy Loam soil. In Clayey soil, the bulk density and LLWR did not change between tillage practices, but air permeability and pore continuity index were larger under reduced tillage with non-traffic. These results highlighted that soil disturbance by conventional tillage does not improve the water availability and air permeability during the crop cycle. However, the traffic control is essential to support the adoption of reduced tillage in sugarcane fields, preserving soil water availability and air fluxes for the subsequent ratoons. Reduced tillage and traffic control are two of the most important pillars for reducing soil compaction and promoting sustainability of sugarcane production in Brazil.