Simulated Rainfall Conditions Research Articles

Determining the depth of mixing layer in which soil solute releasing from soil to surface runoff on the unsaturated loess slope under artificial rainfall condition

The mixing zone depth is a critical parameter in many popular agricultural non-point source pollution (NPS) models. Its variation for some special soil conditions and easily erosive region was limitedly studied. This study dealt with the extent of Br− releasing from soil to surface runoff, the actual mixing depth and the calculated one on the unsaturated loess slope, and the influences of soil initial moistures. Br− was placed as a tracer at different soil depths in the loess slope with three soil initial moistures. Br− concentration in surface runoff and soil profiles was monitored under simulated rainfall condition. The actual mixing layer depth was determined by whether Br− in that layer could be detected in surface runoff during the whole rainfall process. The average effective depth of interaction (EDI) was calculated by the confirmation method reported before. The shallower the application depth, the higher the Br− concentration and loss risk in surface runoff. The net loss rate had an exponential decreasing correlation with the solute-applied depth. The depth of Br− peak content in soil profile after the rainfall ended increased with the application depth. Br− concentration in the surface soil was more than that in the runoff at the end of rainfall, which indicated an incomplete mixing between runoff water and soil water in the mixing layer. Under this experimental condition, the actual mixing layer depth for 3.5% soil moisture slope was about 3 cm, that for 10% soil moisture was 6 cm or so, and that for 20% soil moisture was more than 7 cm. The average EDI calculated for 3.5, 10, and 20% soil moisture was 2.31, 3.76 and 4.95 cm, respectively, which were less than the actual mixing layer depth and more than some former studies. The traditional 1.0-cm mixing depth in many agricultural NPS models might not be so exact for some special region.

Effects of rainfall intensity, slope angle, and vegetation coverage on the erosion characteristics of Pisha sandstone slopes under simulated rainfall conditions.

The water loss and soil erosion in the Pisha sandstone region in the middle reaches of the Yellow River are extremely severe, leading to extremely harmful effects on the ecological environment and safety of the lower reaches. In this paper, the effects of the slope angle (20, 30, and 40°), rainfall intensity (20, 50, and 80mm/h), and vegetation coverage (10, 30, and 50%) on the erosion characteristics of the Pisha sandstone slopes are studied using indoor-simulated rainfall tests. The results show that the infiltration into the Pisha sandstone is only 10~15%. It is found that rainfall intensity has the most significant effect on runoff, which gradually increases with increasing rainfall intensity. Vegetation significantly affects runoff reduction when the rainfall intensity is low (approximately 20mm/h), but this effect decreases with increasing rainfall intensity. Rainfall intensity has an extremely significant effect (P < 0.01) on the sediment yield, followed by vegetation coverage, and slope angle. When the vegetation coverage is approximately 50%, the reduction in sediment yield reaches approximately 70%. Additionally, the sediment reduction benefit is more significant than the runoff reduction benefit. The presence of the eroded gullies on slopes with vegetation is less compared to that on the bare slopes. Therefore, relatively high vegetation coverage (≥ 50%) is required for soil and water conservation in Pisha sandstone area. The findings will provide some reference for Pisha sandstone conservation.

Differences in interception storage capacities of undecomposed broad-leaf and needle-leaf litter under simulated rainfall conditions

Leaf litter is an important component of agroforestry ecosystems that plays a key role in soil and water conservation. This study assessed the effect of leaf shape on water interception under controlled laboratory conditions. Two contrasting leaf shapes (needle-leaf, represented by Pinus massoniana; and broad-leaf, represented by Magnolia grandiflora) were placed in a steel box (2 m long and 1 m wide) for separate experiments with different leaf masses per ground area (0.5, 1.0 and 1.5 kg/m2); the steel box was positioned on two different slopes (5° and 20°) corresponding to gentle and steep slopes; the rainfall intensity was 90 mm/h. The results indicated that leaf shapes had specific effects on the interception storage capacity of the leaf litter on a slope. The needle-leaf litter intercepted 2.08 times more rainwater than the broad-leaf litter on average. As the leaf mass increased, the interception storage capacity of the leaf litter successively increased for the needle-leaf litter, while there were no obvious patterns for the broad-leaf litter. This difference occurred because the initially erect broad leaves were easily flattened by raindrop impacts due to their large surface areas and hence formed a horizontal leaf cover (or leaf overlap). This leaf accumulation structure restricted the infiltration of rainwater into the lower leaf litter while providing a short path for rainwater to leave the leaf litter, hence promoting litter flow and leading to less rainwater intercepted by the broad-leaf litter than the needle-leaf litter. Our results provide a better understanding of the effects of leaf shape on leaf litter interception on inclined slopes, which is lacking in the current literature.

Soil loss: Effect of plant litter incorporation rate under simulated rainfall conditions

AbstractPlant litter can control land degradation by increasing soil organic matter and decreasing soil erosion by covering the soil surface or being incorporated into topsoil. However, the effect of litter incorporation on soil erosion is not clear. This study aimed to investigate the effect of litter incorporation into topsoil on interrill erosion. The poorly decomposed litter was collected from the field and incorporated into topsoil (5 cm) at six rates (ranging from 0 to 0.5 kg m−2). Laboratory rainfall (80 mm hr−1) experiments were conducted under five slope gradients (ranging from 9% to 47%). The results showed that the soil loss rates declined exponentially with increase in litter incorporation rate on slope gradients between 9% and 36%. However, on slope gradient of 47%, litter incorporation caused an increase in the soil loss rate. The efficiency of litter incorporation in controlling soil loss varied from −21.7% to 40.5% with a mean of 10.8%. It decreased linearly with the slope gradient (R2 = 0.34). The decrease can be explained by two simultaneous but opposite effects: the effect of preventing erosion and that of promoting erosion. The former was induced by decreases in the effective erosive force of raindrop and overland flow exerted on soil, and soil erodibility, along with increases in sediment interception. The latter was caused by rapid saturation of the surface soil and concentrated overland flow. The results demonstrate the complexity of the effect of litter incorporation on soil erosion and can improve our understanding of litter in soil loss control.

Impact of Land Management Practices on Runoff, Soil Loss and Infiltration Under Simulated Rainfall

A laboratory study was conducted to quantify the effects of various land management practices on runoff, soil loss and infiltration under simulated rainfall conditions. A prototype rainfall simulator was designed and tested in the laboratory to simulate rainfall at 100 mm.h-1 intensity over different land management practices. The effect of five land management practices on runoff, infiltration and soil loss were evaluated for a set of rainfall intensity (100 mm.h-1), rainfall duration (15 min) and raindrop size/ pore size of the nozzle (3.5 mm). The considered management practices were intense tillage land cover, zero or no-tillage land cover, minimum tillage land cover, perennial grass system and urban environment. Perennial grasses were found to be the best management practices to minimize the surface runoff and soil loss with increase in infiltration rate. Experimental results showed that perennial vegetation produced minimum runoff (0.2 l), very small soil loss (4.99 kg.ha-1) and maximum infiltration rate (117.67 mm.h-1), whereas urban environment (concrete surface) produced maximum runoff (3.7 l), minimum infiltration rate (0.1 mm.h-1) and minimum sediment loss (0.08 kg.ha-1).

Impact of Land Management Practices on Runoff, Soil Loss and Infiltration Under Simulated Rainfall

A laboratory study was conducted to quantify the effects of various land management practices on runoff, soil loss and infiltration under simulated rainfall conditions. A prototype rainfall simulator was designed and tested in the laboratory to simulate rainfall at 100 mm.h-1 intensity over different land management practices. The effect of five land management practices on runoff, infiltration and soil loss were evaluated for a set of rainfall intensity (100 mm.h-1), rainfall duration (15 min) and raindrop size/ pore size of the nozzle (3.5 mm). The considered management practices were intense tillage land cover, zero or no-tillage land cover, minimum tillage land cover, perennial grass system and urban environment. Perennial grasses were found to be the best management practices to minimize the surface runoff and soil loss with increase in infiltration rate. Experimental results showed that perennial vegetation produced minimum runoff (0.2 l), very small soil loss (4.99 kg.ha-1) and maximum infiltration rate (117.67 mm.h-1), whereas urban environment (concrete surface) produced maximum runoff (3.7 l), minimum infiltration rate (0.1 mm.h-1) and minimum sediment loss (0.08 kg.ha-1).

Infiltration-excess runoff properties of dryland floodplain soil types under simulated rainfall conditions

The study estimated infiltration-excess runoff properties of three floodplain soil-types under aquifer water management at Anglo American Kolomela Iron Ore mine in Postmasburg, Northern Cape Province of South Africa. Rainstorm regimes of amounts 60 (high), 30 (medium), and 15 (low) mm with respective intensities of 1.61, 0.52, and 0.27 mm min−1 were simulated on 1 m2 plot with 1% slope. Infiltration-excess runoff properties were affected by a rainstorm, but not soil-type. When combined with rainstorm, soil-type affected accumulative run-off rates. High rainstorm had different (p ≤ 0.05) accumulative runoff rates (0.1–0.61 mm min−1) and increased with clay content. Different response times of 4, 10, and 17 min for respective high, medium, and low rainstorms were quickest on higher clay plus silt content and bulk-density under high and lower rainstorms, respectively. Lower rainstorms had similar effects on accumulative runoff rates (0.01–0.05 mm min−1), total runoff yield (0.59–18 mm), and runoff coefficients (4.29–18%). Under the high rainstorm, total runoff yields (11.4–25.8 mm) and runoff coefficients (19–42.9%) were different and increased with clay plus fine-silt content. Although simulated rainstorms had constant intensities, results showed high rainstorms to be of primal influence on infiltration-excess runoff. Clay plus silt content and bulk-density influenced infiltration-runoff properties for respective high and lower rainstorms. Apart from rainstorm characteristics, surface clay plus silt content and bulk-density are important for harnessing surface runoff in floodplains for aquifer recharge.

Parameterization for EROSION-3D Model under Simulated Rainfall Conditions in Lower Shivaliks of India

The Shivalik foothills of northwestern India are very prone to soil erosion by water due to undulating slopes, highly erodible soils and high intensity rainstorm events during monsoon season. Physically based soil erosion modeling is seen as viable method for planning of measurements to reduce damages done by soil erosion. Nevertheless, parametrization of such models is a major challenge for large inaccessible areas. Several methods do exist for the estimation of the input parameters skin factor, surface roughness and resistance to erosion for the physically based soil erosion model EROSION-3D. Four rainfall experiments, each including dry and wet run, were conducted on different land use conditions on a research farm of the Regional Research Station Ballowal Saunkhri to test estimation methods. Modeling parameters were determined from these experiments. Parameter estimation by two methods for experimental conditions produced values in close range to experimentally determined values for resistance to erosion and surface roughness. Therefore, existing estimation methods are considered to be applicable for the conditions of the Shivalik mountains, except for skin factor. A first modeling with EROSION-3D using preliminary data of a small example catchment shows uncertainties resulting from range of determined and estimated soil parameters.

Variation in leaf area density drives the rainfall storage capacity of individual urban tree species

AbstractA rapid rise of urban population is making cities denser. Consequently, the proportion of impervious surface cover has enlarged, increasing the amount and speed of run‐off reaching urban catchment areas, which may cause flash flooding. Trees play a key role to reduce run‐off in the city, as they intercept rainfall and store part of it on their leaves and branches, reducing the amount and speed of water running onto impervious surfaces. Storage capacity will depend on the rainfall event, the climate conditions and tree characteristics and canopy density. These canopy characteristics vary greatly among different species and their phenology. Furthermore, these canopy characteristics can vary greatly among individual trees of the same age, size, and species. This study tested how canopy density and leaf characteristics of three different tree species affect storage capacity under simulated rainfall conditions. Three species were selected (Ulmus procera, Platanus × acerifolia, and Corymbia maculata), each being of the same height and similar canopy dimensions. Storage capacity was measured using a mass balance approach during a 15‐min indoor, simulated rainfall event (2.5 mm/hr). Canopy metrics were estimated using a terrestrial laser scanner. Canopy surface area was measured through destructive harvest and leaf/twig/branch scanning. To investigate variations in the canopy leaf density, leaves were systematically removed to create four treatments: full, half, quarter, and woody. Canopy storage capacity was well correlated to plant surface area (m2), plant area index (m2/m2), and plant area density (m2/m3). All analyses indicated U. procera as the most efficient species for storing rainfall water within a canopy of equal volume or area index. Results reveal the complexity of evaluating interception of rainfall by tree canopies. This study contributes to the discipline and practice by distinguishing how variation in the leaf density is important to consider when selecting urban tree species to be planted.

The ridge-furrow system combined with supplemental irrigation strategies to improves radiation use efficiency and winter wheat productivity in semi-arid regions of China

Agricultural productivity in semi-arid regions of China relies on the ridge furrow (RF) micro rainfall harvesting system, and supplemental irrigation reduces damage caused by drought stress. However, the extent to which the interactive effects of supplemental irrigation and simulated rainfall conditions can further improve winter wheat production and radiation use efficiency (RUE) remains unknown. Therefore, a mobile rainproof shelter was used to explore the potential benefit of the RF system under four supplemental irrigation (150, 75, 37, 0 mm) levels and three simulated rainfall (275, 200, 125 mm) levels. Data collected over two years indicated that the interactive effects of supplemental irrigation (150 mm) with simulated rainfall concentration (200 mm) could significantly improve the LAI (88.8%), Pn value (21.3%), PAR interception efficiency (In; 34.1%), interception of PAR accumulation (IPAR) (58.9%), RUE (11.2%), and PAR capture ratio (97.1%), due to reduction in the PAR reflection ratio (45.2%), canopy light transmittance (LT) (78.5%), and PAR penetration ratio (83.8%), and significantly increase the grain yield (60.0%) as compared to that of the RF3150 treatment. Consequently, this RF system significantly improved the grain yield, with earlier development and rapid plant growth during each growth stage of winter wheat, at each supplemental irrigation and simulated rainfall level. The results suggest that in semi-arid regions of China, where water shortage is a serious problem, the RF2150 treatment should be adopted as standard farming practice for improving crop growth, LAI, photosynthesis, efficient conversion of intercepted solar radiation by apical dominance, IPAR, RUE, total DMA, and winter wheat production.

The nutrient and carbon losses of soils from different land cover systems under simulated rainfall conditions

Nutrient losses constitute an important issue for the protection of both soil and water resources. Organic carbon transport is also important for the global carbon cycle. In this study, it was aimed to determine the amount of nutrients and the total organic carbon which was transported by surface runoff water formed under simulated rainfall conditions from areas with different land cover systems.Accordingly, 3 cultivated areas having various product patterns under similar conditions (potato field (P), bean-cultivated area (B), abandoned farmland covered with Noaea sp. (AB)), 2 plantation areas (cedar (C) and almond (AL)) and 2 rangelands covered with Thymus sp. (T) and Stipa sp. (S) were chosen for performing applications. The applications were performed in two repetitions on 0.28 m2 circular experimental plots established in the above-mentioned areas. The collection of surface runoff was performed during land applications. The pH, electrical conductivity, nitrate (NO3−), ammonium (NH4+), total phosphorus, orthophosphate (PO43−), total organic carbon (TOC), and total nitrogen (TN) parameters of surface runoff water were measured. The land cover change affects total nitrogen, nitrate, ammonium, pH, electrical conductivity, total phosphorus, orthophosphate and TOC parameters. Nitrate transport was found to be B > P > T > AB > C > AL > S from highest to lowest. Ammonium transport was B > T > AL > C > AB > P > S. The total nitrogen transport was B > P > T > AB > C > AL. The total phosphorus transport was found to be P > B = T > AB > AL > C > S. Ortho-phosphate transport was P > B > T > AB > C > AL > S. In terms of the TOC transport, the order was found to be T > B > P > AB > AL > C from highest to lowest.

Loss characteristics of Cd in soil aggregates under simulated rainfall conditions

Soil particles exert a significant influence on the migration of heavy metals in soil and water environments. In this study, a simulated rainfall experiment was conducted to investigate the loss characteristics of cadmium (Cd) from a red soil surface. Two rainfall intensities (50 and 100 mm h−1) were considered and the distribution of Cd in different fractions (>1, 1–0.25, 0.25–0.05 and <0.05 mm) of aggregates lost from the soil was examined. The result showed that in the artificially polluted soil, the Cd content in different aggregates decreased with particle size, with the lowest Cd content in the <0.05 mm fraction aggregates. In the rainfall experiment, the runoff rate generally increased with the rainfall duration, while the sediment yield rate first increased and then remained stable. The loss rates of various fractions of aggregates in the sediment generally followed the order of (<0.05) mm > 1–0.25 mm > 0.25–0.05 mm > (>1) mm. The proportions of the <0.05 mm-fraction aggregates were the highest in the loss sediment throughout the entire rainfall process. The lost Cd was transported mainly in the sediment-bound form, while only a very small portion of Cd was lost in the water phase of runoff. High rainfall intensity led to greater Cd loss in runoff. In the lost sediment, the concentration of Cd was higher in the macroaggregates. The phenomenon of Cd enrichment in the fine particles was not observed. Although the concentration of Cd in the <0.05 mm fraction was the lowest, the contribution of this fraction to the total Cd content in the sediments was the highest.

Tillage and deficit irrigation strategies to improve winter wheat production through regulating root development under simulated rainfall conditions

Knowledge of rooting systems and soil water status across rooting zones is important for stabilizing agricultural productivity in the semi-arid regions of China. In the present study, a mobile rainproof shelter trial was performed to find out the effects of cultivation mode on the temporal and spatial root growth distribution, soil water content, root respiration rate, and grain yield during 2015–2016 and 2016–2017 growing seasons. The two cultivation modes were: (1) the ridge furrow (RF) rainfall harvesting technique; and (2) traditional flat planting (TF). In addition, three simulated rainfall (1: 275, 2: 200, 3: 125 mm) and two deficit irrigation (150, 75 mm) levels were used. Our results showed that different cultivation modes with simulated precipitation levels significantly improved moisture content for wheat growth, improved root growth, and provided favourable conditions for higher wheat production. The RF150 treatment with 200 mm rainfall significantly increased morphology of the wheat rooting system, especially in the top 40 cm soil layer compared with TF cultivation. The RF150 treatment significantly increased root dry weight (47%), root tissue density (6.7%), root fineness (4.8%), root length ratio (20.3%), root mass ratio (27.3%), and grain yield (18.9%) of wheat at 200 mm rainfall than that of TF2150 treatment. Root weight density, root length density, root surface area density, and root diameter were significantly higher under RF150 treatment with 200 mm and 275 mm precipitation in the 40 cm soil layer and reached maximum values at the flowering stage. The root dry weight, root respiration rate, and grain yield were significantly improved under RF2150 treatment, but there were no significant differences when the rainwater increased from 200 to 275 mm under both cultivation modes. Therefore, we suggested that the RF2150 treatment is a suitable water saving strategy to improve temporal and spatial root growth distribution, resulting in higher grain yield in a dry-land farming system.

Ridge-furrow mulched with plastic film improves the anti-oxidative defence system and photosynthesis in leaves of winter wheat under deficit irrigation.

In semi-arid areas of China, the ridge-furrow mulched with plastic film (RF) cultivation system is a common water-saving agricultural technique where the shortage of water resources has become a serious problem. Therefore, we aimed to explore whether this cultivation is actually an improvement over the traditional flat planting (TF) method while testing two deficit irrigation (150, 75 mm) levels to grow winter wheat. Furthermore, we examined the responses of the anti-oxidative defence system and photosynthetic capacity of winter wheat flag leaves under three simulated rainfall (275, 200 and 125 mm) conditions. The results showed that the RF system with 150 mm deficit irrigation and 200 mm simulated rainfall condition (RF2150) treatment raised soil water content (%) at the jointing and flowering stages and achieved higher net photosynthesis rates (Pn) in flag leaves. Furthermore, such improvements were due to the reduction of malondialdehyde (MDA) content and oxidative damage during different growth stages of winter wheat. The RF2150 treatment significantly increased the activities of superoxide dismutase (SOD); peroxidise (POD), catalase (CAT) and ascorbate peroxidase (APX) and the content of soluble protein (SP) during different growth stages of winter wheat. Furthermore, RF2150 treatment attained the highest value at the flowering stage, while also exhibiting significant declines in contents of proline, MDA, H2O2 and O2 in flag leaves. The higher free H2O2 and O2 scavenging capacity and better anti-oxidative enzyme activities under the RF2150 treatment were due to the lower level of lipid peroxidation, which effectively protected the photosynthetic machinery. The net photosynthetic rate of flag leaves was positively correlated with SOD, POD, CAT, APX and SP activities, and negatively correlated with proline, MDA, H2O2 and O2 contents. We concluded that the RF2150 treatment was the better water-saving management strategy because it significantly delayed flag leaf senescence and caused the increases in SWC, WUE, Pn, antioxidant enzyme activities and grain yield of winter wheat grown in semi-arid regions of China.

Nutrient losses due to water erosion using simulated rainfall in southern Brazil

La erosión es la principal forma de degradación en el mundo, en consecuencia de la pérdida de suelo, agua y nutrientes, provocando daños directos e indirectos. El objetivo de este trabajo es cuantificar las pérdidas de N, P y K por erosión hídrica en condiciones de lluvia simulada mediante la aplicación de seis pruebas de erosión en cultivo continuo de especies de ciclo estacional, incluyendo cultivos aislados y cultivos intercalados. El estudio se llevó a cabo en el campo en la Estación Experimental de Agronomía en Eldorado do Sul (RS), Brasil, en un Argisol Rojo Distrófico típico. Para el análisis de la pérdida de nutrientes, se aplicaron seis ensayos de erosión con lluvia simulada a los tratamientos entre finales de octubre y mediados de diciembre, utilizando el simulador de lluvia con brazos giratorios de Swanson. Las pérdidas de N y P se vieron influenciadas por las condiciones de la superficie, con la eliminación parcial de los residuos del cultivo y la no movilización del suelo. La excepción fue K, debido a su alta solubilidad en el suelo con baja actividad coloidal, que se perdió fácilmente en la escorrentía superficial del agua del suelo, independientemente de la cobertura total de la superficie del suelo por los residuos de los cultivos.

Soil erosion and transport of Imidacloprid and Clothianidin in the upland field under simulated rainfall condition

Surface runoff has been recognized as an important medium of pesticides transport to surface water and groundwater causing critical risk to the aquatic ecosystem. Although total pesticide transport in surface runoff in most cases reported being below 1% of applied mass, much larger losses may occur in extreme cases. In this study, surface runoff potential of Imidacloprid and Clothianidin was investigated in an upland field with 5% slope under two simulated rainfall experiments of 70 mm/h intensity. Additionally, the downward movement of the pesticides was determined in soil (n = 87) taken at several depths on different time scales. The result showed that the second rainfall experiment caused more surface runoff than first rainfall experiment, and accounted 30.0 mm and 21.2 mm of applied rainfall, respectively. The cumulative surface runoff developed during first and second rainfall experiments was equal to 30% and 44% of the applied rainfall, respectively. The sediment transport in runoff was relatively higher in second rainfall than first rainfall, and was mostly stable after 30 min of rainfall. The chemical masses of Imidacloprid and Clothianidin were primarily transported in runoff sediments than runoff water and accounted for 10.8% and 7.93% of the applied mass, respectively. The transport of Imidacloprid both in runoff water and sediment was 1–2 times greater than that of Clothianidin. The concentrations of both pesticides were measured highest in the second fraction of runoff (10 min) collected during the first experiment. In soil, the transport of both pesticides prior to rainfall experiment was 1–2 times greater than post-rainfall experiments. The concentration of these pesticides decreased continuously with the time in the upper layer of soil; while a gradual increase of the pesticides mass was observed in the second soil layer. The cumulative mass transport of both pesticides was directly proportional to the cumulative runoff depth.

Migration and leaching characteristics of base cation: indicating environmental effects on soil alkalinity in a karst area.

In karst areas, rock dissolution often results in the development of underground networks, which act as subterranean pathways for rapid water and nutrient (and possibly soil) loss during precipitation events. Loss of soluble nutrients degrades surface soils and decreases net primary productivity, so it is important to establish flow pathways and quantify nutrient loss during rainfall events of different magnitudes. We conducted a simulated rainfall experiment in karst and nonkarst areas to compare the concentration of nutrients in surface and subsurface flow water and effects on soil alkalinity in three lithologic soil formations under five different rainfall intensity treatments. Compared with the nonkarst area, the runoff in subsurface flows and the proportion of nutrient loss in the subsurface flow are larger in the karst area and less affected by rain intensity. The maximum loss loads of calcium (Ca2+) and magnesium (Mg2+) ions were 32.9 and 19.8kgha-1, respectively. With the estimate of base cation loss loads in the China southern karst area under the rainfall intensity of 45mmh-1, more than 80% of the base cation loss load occurred in the limestone karst area. Although the alkalinity leaching value in nonkarst was similar to that in the karst area under simulated rainfall conditions, its impact on the ecological environment was quite different.

Interactive effects of planting models with limited irrigation on soil water, temperature, respiration and winter wheat production under simulated rainfall conditions

The development of effective water-saving farming practices have been vitally important for increasing wheat productivity in semi-arid regions of China. Ridge-furrow (RF) rainfall harvesting is a technique for efficient consumption of precipitation that increases water accessibility to crops at critical growth stages. However, this system has not yet been characterized under simulated rainfall conditions with limited irrigation. A two-year field study was carried out from Oct 2015 to May 2017 to investigate the potential role of two planting models: (1) the RF system and (2) traditional flat planting (TF) under three levels of simulated precipitation (1:275 mm, 2: 200 mm, 3:125 mm), with two limited irrigation levels (150 mm or 75 mm). The topsoil (from 5 to 25 cm) temperature and ET were significantly higher under TF planting than in the RF system, which increased both soil moisture between (0–200 cm) and soil respiration rate during different growth stages. The RF system also regulated soil temperature and respiration rate, reduced ET (46%), and prolonged the period of water accessibility which led to exhibited fast and stable seedling establishment. The average grain yield increased by 10.6% and 12.6% for RF1150 and RF175, compared to TF1150 and TF175, and increased by 18.9% and 22.5% for RF2150 and RF275 as compared to TF2150 and TF275, while RF3150 and RF375 treatments significantly increased by 14.3% and 8.9% as compared to TF3150 and TF375, respectively. Average WUE significantly improved by (P < 0.05) in RF1150, RF175, RF2150, RF275, RF3150, and RF375 were 53.3%, 56.4%, 75.8%, 85.1%, 68.2% and 75.3% compared to TF planting, respectively. As precipitation increased from 200 to 275 mm there were no significant increases in moisture contents, soil respiration rate, ET, WUE, and grain yield under both planting models. Therefore, we concluded that the RF2150 treatment is suitable as a water-saving technology to achieve higher wheat production and WUE in semi-arid agro-ecosystems of China.

The ridge furrow cropping technique indirectly improves seed filling endogenous hormonal changes and winter wheat production under simulated rainfall conditions

We sought to study the effects of the ridge furrow (RF) rainwater collecting technique on winter wheat seed filling with limited irrigation under simulated rainfall concentrations and its correlation with hormonal changes. The RF system was compared to traditional flat planting (TF) with two limited irrigation levels (150, 75 mm) under three simulated precipitation concentrations (1: 275, 2: 200, 3: 125 mm) during 2015–2017 experimental years. The results indicated that the RF150 treatment with 125 mm rainfall, a significantly improved seed filling rate was observed in the basal and upper seeds. The RF150 treatment with 200 mm precipitation also significantly improved the single seed weight and seed filling rate in the basal and upper seeds. In contrast, the RF system with 275 mm precipitation showed no significant influence on the seed filling rates and seed weight of basal and upper seeds under either limited irrigation level. The RF system at 125 and 200 mm simulated rainfall level exhibited increased (IAA) indole-3-acetic acid and (Z) zeatin + (ZR) zeatin riboside contents. The RF system under 150 mm limited irrigation showed decreased (ABA) abscisic acid and gibberellic acid (GAs) in the basal and upper seeds. The RF system with 275 mm precipitation had no significant influence on the IAA, Z + ZR, ABA and GA contents in the basal and upper seeds under either limited irrigation levels. The IAA, Z + ZR, ABA and GAs in the seeds s were positively correlated with the maximum and mean seed-filling rate and the maximum seed weight. Our results demonstrate that the RF2150 treatment significantly improved the soil water contents and soil respiration rate, thereby regulating the wheat seed filling rate and creating hormonal changes. These fluctuations significantly affected the agronomic properties of winter wheat production in semi-arid regions.

Spatial heterogeneity of surface roughness on tilled loess slopes in erosion stages

The main soil erosion areas of the Chinese Loess Plateau are tilled slopes. The knowledge of their spatial heterogeneity will contribute to the understanding of erosion mechanisms on a microtopographic scale. In this study, the spatial heterogeneity of four conventionally tilled slopes was examined under simulated rainfall conditions using a semivariogram-based methodological framework. Results show that all tilled slopes have a relatively stable spatial structure and the erosion stages of all tilled slopes have a similar spatial variability. The rainfall in the splash, sheet, and rill erosion stages has a degree of relief effect, strengthening effect, and relief effect on the surface roughness, respectively. However, the effects of tillage practices and slope gradient on the spatial heterogeneity are much larger than those of the rainfall. The spatial heterogeneity decreases with increasing slope gradient. The general autocorrelation scale of the tilled slopes is 3.15 m and their fractal dimension ranges from 1.59 to 1.85. The tilled slopes have certain anisotropy with respect to the slope direction from 10° to 22.5° while they show isotropy or weaker anisotropy in other directions. In this work, a semivariogram-based methodological framework was established for the spatial heterogeneity of microtopographic-scale slopes. The results also provide a theoretical foundation for future tillage measures on sloping fields of the Loess Plateau.