Soil water dynamics and deep soil recharge in a record wet year in the southern Loess Plateau of China

Terrestrial water cycles are influenced by hydrologic and textural properties of the deep loess layer in the Loess Plateau. Analyses of soil water profile distributions are needed to understand the regional water cycle processes and to guide agricultural production and sustainability. The objective of this study was to quantify the extent of deep soil water recharge and soil water profile dynamics during 1987-2003, especially in a record wet year of 2003, in common cropping systems in a semiarid-subhumid region of the southern Loess Plateau. The Chinese Ecological Research Network (CERN) site and a long-term rotation experiment site in a flat tableland were selected for this study. Soil moisture profiles were measured by a neutron probe to a depth of 6 m in 2003. The precipitation of 954 mm at the Changwu County Meteorological Station in 2003 was 63.4% higher than the long-term average (584 mm), and was a record high since 1957. Although cropping systems affected deep soil water recharge, the persistent dry soil layer formed between 2- and 3-m depths in croplands, resulting from many years of intensive cropping, was fully replenished in all cropping systems in 2003. Further frequency analysis indicated that the desiccated layer between 2- and 3-m depths would be fully recharged at least once in about 10 years for all existing cropping systems excluding continuous alfalfa. This finding should alleviate concerns about the formation of a permanent deep-soil desiccation layer as well as its potential impact on the long-term sustainability of the existing intensive cropping systems in the region.     

Soil water in relation to irrigation, water uptake and potato yield in a humid climate

Efficiently controlling soil water content with irrigation is essential for water conservation and often improves potato yield. Volumetric soil water content (θ_v) in relation to irrigation, plant uptake, and yield in potato hills and replicated plots was studied to evaluate four water management options. Measurements of θ_v using a hammer driven probe were used to derive a θ_v index representing the relative θ_v status of replicated plots positioned along a hill slope. Time series for θ_v were determined using time domain reflectometry (TDR) probes at 5 and 15 cm depths at the center, shoulder, and furrow locations in potato hills. Sap flow was determined using flow collars in replicated field plots for four treatments: un-irrigated, sprinkler, surface drip, and sub-surface drip irrigation (40 cm depth). Irrigated yields were high/low as the θ_v index was low/high suggesting θ_v excess was a production problem in the wetter portions of the study area. The diurnal pattern of sap flow was reflected in the θ_v fluctuation it induces at hill locations with appreciable uptake. Hill locations with higher plant uptake were drier as was the case for the 5 cm (dry) depth relative to the 15 cm (wet) depth and for locations in the hill (dry) relative to the furrow (wet). The surface drip system had the lowest water use requirement because it delivers water directly to the hill locations where uptake is greatest. The sub-surface drip system wetted the hill gradually (1-2 days). Measurement of the θ_v index prior to experimental establishment could improve future experimental design for treatment comparisons.     

Field water supply:yield relationships of grain sorghum grown in three USA Southern Great Plains soils

Field water supply (FWS) combines the three sources of water used by a crop for evapotranspiration (ET), and consists of available soil water at planting (ASWP), rainfall, and irrigation. Examining the grain yield and FWS relationship (Y_g:FWS) may provide insight into the reported variability in crop water production functions such as water productivity (WP) and irrigation water productivity (IWP). Since water is most productive when entirely consumed in ET, diversion of FWS into non-ET losses such as drainage and excessive soil water evaporation results in declines in WP and IWP. The objective of this experiment was to examine the Y_g:FWS and Y_g:ET relationships of grain sorghum grown under a range of irrigation treatments (0, 25, 50, and 100% replacement of ET), beginning soil water contents, evaporative demands, in the Amarillo, Pullman, and Ulysses soils of the Great Plains. The purpose was to determine the amount of FWS beyond which declines in WP and IWP began to occur due to non-ET losses as indicated by a change in the slope and intercept of the Y_g:FWS and Y_g:ET relationships. Large amounts of non-ET irrigation application losses occurred in the finer-textured soils in the T-100 irrigation treatment. In both years, the T-100 irrigation application amounts and ASWP resulted in a FWS ranging from 750 to 870 mm which exceeded the maximum ET requirement of 530-630 mm and which reduced WP and IWP. Piecewise regression analysis of the Y_g:FWS and Y_g:ET relationships for the crops in the Pullman and Ulysses soils identified the knot point, or change in slope and intercept, in the FWS where both WP and IWP tended to be optimized. This was about 500 mm in both soils, and involved the utilization of about 250 mm in ASWP, irrigation applications averaging about 250 mm, and about 60-130 mm remaining in the soil at harvest. For the coarser-textured Amarillo soil, the yield response to increasing FWS was linear, because non-ET application losses such as drainage gradually increased with the irrigation application amount. The linear Y_g response in the sandy Amarillo soil and the piecewise Y_g responses in the clay and silt loams of the Pullman and Ulysses soils to FWS also reflected the difference in water-holding capacities of the soils that affected the amount of available water as irrigation increased. Irrigating without considering FWS resulted in non-ET irrigation application losses and declines in WP and IWP.     

Numerical assessment of effective evapotranspiration from maize plots to estimate groundwater recharge in lowlands

To maximize the irrigation efficiency and to protect groundwater from agrochemical pollution, two variables must be known with good accuracy: effective evapotranspiration and infiltration, especially in lowland areas were the run-off is minimal. Three different experimental plots cultivated with maize were equipped with tensiometers and soil moisture probes to monitor every day the water movement in the unsaturated zone. Other relevant parameters of the various soil layers, as hydraulic conductivity and water retention curve, were obtained in laboratory experiments, while boundary conditions, as precipitations, temperature and root growth, were obtained on site. Inverse modeling was performed using HYDRUS-1D to assess the degree of uncertainty on model parameters. Results showed a good model fit of water content and head pressure at various depths, in each site, using Penman-Monteith formula for daily potential evapotranspiration calculation, but poor fit applying the Hargreves and Turk formulas. Best performance of model fit was observed for S-shaped equation employed to simulate the root water-uptake reduction with respect to Feddes equation. The soil parameters uncertainty was limited and remained within analytical errors, thus a robust estimation of cumulative infiltration and evapotranspiration has been derived. This study points out that evapotranspiration is the most important variable in defining groundwater recharge for maize crops in lowlands.     

Soil water dynamics and water use efficiency in spring maize (Zea mays L.) fields subjected to different water management practices on the Loess Plateau, China

Soil water supply is the main limiting factor to crop production across the Loess Plateau, China. A 2-year field experiment was conducted at the Changwu agro-ecosystem research station to evaluate various water management practices for achieving favorable grain yield (GY) with high water use efficiency (WUE) of spring maize (Zea mays L.). Four practices were examined: a rain-fed (RF) system as the control; supplementary irrigation (SI); film mulching (FM); and straw mulching (SM) (in 2008 only). The soil profile water storage (W) and the crop evapotranspiration (ET) levels were studied during the maize growing season, and the GY as well as the WUE were also compared. The results showed that mean soil water storage in the top 200 cm of the profile was significantly (P < 0.05) increased in the SI (380 mm in 2007, 411 mm in 2008) and SM (414 mm in 2008) compared to the FM (361 mm in 2007, 381 mm in 2008) and RF (360 mm in 2007, 384 mm in 2008) treatments. The soil water content was lower at the end of growing season than before planting in the 60-140 cm part of the profile in both the RF and FM treatments. Cumulative ET and average crop coefficiency (K_c) throughout the whole maize growing season were significantly (P < 0.05) higher in the SI (ET, 501 mm in 2007, 431 mm in 2008; K_c, 1.0 in 2007, 0.9 in 2008) treatment than in the other treatments. Both FM and SI significantly improved the GY. The WUE were increased significantly (23-25%; P < 0.05) under the FM treatment. It was concluded that both SI and FM are beneficial for improving the yield of spring maize on the Loess Plateau. However, FM is preferable because of the shortage of available water in the area.     

Managing natural resources of watersheds in the semi-arid tropics for improved soil and water quality: A review

Soil, water and production systems constitute the most important natural resources of a watershed in the rainfed agro-ecosystem; and for sustainability of the production systems they need to be in harmony with the environment. To learn from the past research, a review is made of literature on the impact of natural resource management practices on soil and water quality in the semi-arid tropical regions of India. The results from long-term on station field experiments show that an integrated use of soil and water conservation practices with balanced plant nutrition can not only sustain increased productivity but also maintain soil quality at the watershed or catchment level. Natural resource management practices that conserve soil and water also help to maintain surface and groundwater quality. The changes in soil and water quality, as impacted by natural resource management practices, need to be monitored and assessed on a continuing basis as the outcome of such research offers valuable opportunity for the implementation of corrective management practices, as and when needed.     

A modified climate diagram displaying net water requirements of wetlands in arid and semi-arid regions

Flooding regimes in arid and semi-arid regions are heavily influenced by climate change and water shortage, water regulations, and increased water demands. Wetlands managed as part of regulated water systems in agricultural landscapes often require external water supplies to sustain or support desired properties or services. Therefore, water resource managers must weigh water requirements necessary to support wetland functions alongside other water demands. This paper presents a simple method of using a modified climate diagram to display net water requirements for a managed wetland in Xi’an, China. The net water requirements were estimated using the DRAINMOD simulation model by assuming that evaporation is the only path for water loss. For this case study, the ratio of water supply to air temperature was adjusted to 1:1. Three water supply estimates were generated to support a desired water table depth of 30 cm for 5%, 12.5%, and 25% of the growing season in Xi’an. When water supply reaches or exceeds a curve, it creates a wetter condition than that represented by the curve. The results also indicate that timing of recharge is very important in preserving wetland hydrology in dry regions. This modified climate diagram prompts an intuitive understanding of the relationship between recharge and consequent wetness of a wetland. It may be used as a standard tool for determining adequate water demand in arid regional water resources management that considers wetland protection or restoration.     

地面水—土壤水—地下水连续系统田间水有效性评价

本文将灌溉管理质量评价体系中的田间水有效性,区分为存贮效率和利用效率,对两种指标评价的物理意义、实验方法及具体数值,结合气候干旱、浅地下水埋深型灌区求得初步研究成果。评价田间水利用的有效性应以作物需水量为目标,考虑地面水—土壤水—地下水连续系统(SSGC)中的水量交换,对单元体总水量进行动态评估,较传统方法合理,符合浅地下水埋深型灌区实际,有助于节水灌溉的分析与管理决策。     

Operational aspects of satellite-based energy balance models for irrigated crops in the semi-arid U.S.

SEBAL and METRIC remote sensing energy-balance based evapotranspiration (ET) models have been applied in the western United States. ET predicted by the models was compared to lysimeter-measured ET in agricultural settings. The ET comparison studies showed that the ET estimated by the remote sensing models corresponded well with lysimeter-measured ET for agricultural crops in the semi-arid climates. Sensitivity analyses on impacts of atmospheric correction for surface temperature and albedo showed that the internal calibration procedures incorporated in the models helped compensate for errors in temperature and albedo estimation. A repeatability test by two totally independent model applications using different images, operators and weather datasets showed that seasonal estimations by the models have high repeatability (i.e. stable results over ranges in satellite image timing, operator preferences and weather datasets). These results imply that the SEBAL/METRIC remote sensing models have a high potential for successful ET estimation in the semi-arid United States.     

蓄水坑灌下矮砧苹果园水分监测点位置研究

以蓄水坑灌(坑深40 cm)下的5 a生矮砧富士苹果树为研究对象,通过田间测定直径小于等于2 mm的吸水根分布和不同位置的土壤含水率情况,采用数据拟合和聚类分析的方法,探讨蓄水坑灌下矮砧苹果树土壤水分监测点的合理布置。结果表明:1蓄水坑灌下,苹果树吸水根在水平方向上主要分布于距树干0~90 cm范围内,其根长密度占总根系的90%以上;垂直深度上主要分布于距地表0~120 cm深度范围内,其根长密度占总根系的80%以上,并在40~60 cm深度达到生长峰值,其根长密度占总根系的40%以上。2以Dr90(距离树干90 cm,深度0~120 cm)监测点为含水率分析区域,通过水分分布曲线拟合和聚类分析得出,Dr90监测点60 cm深度处的含水率可代表整个0~120 cm深度剖面的含水率情况,并利用2013年的实测数据进行验证,含水率相对误差在±5%范围内。     

东北垄作蓄水保墒耕作体系与配套机具

针对我国北方地区(特别是东北垄作地区)旱作农业现状,通过组合多项先进农艺技术,得到适合东北垄作地区特点的蓄水保墒耕作技术体系及联合作业工艺方案,设计适合该地区主要农作物的多功能蓄水保墒秸秆-根茬粉碎还田联合、耕整联合、耕整种植联合的作业机具。试验证明,系列机具各项作业指标均满足现代农艺要求,达到蓄水保墒、高效节能、增产增收的目的,已在农业生产中应用。     

Effects of precipitation patterns and temperature trends on soil water available for vineyards in a Mediterranean climate area

The objective of this paper is to analyse the impact of temperature increases and irregular rainfall distribution, associated with climate change, on water availability for rainfed vineyards cultivated in a Mediterranean climate area. The study includes the analysis of the interrelations between precipitation distribution, temperature, evapotranspiration and runoff rates, and the resulting water storage in vineyards soils of the Penedès region (NE Spain). A hierarchical cluster analysis was applied to classify the years according to water availability. The influence of water stored into the soil on yield for some one of the main vine varieties cultivated in the area is analysed. A vineyard, representative of the land management practices in this area, was selected for soil moisture monitoring and runoff evaluations, as well as for grape yield, which was compared with yields recorded in other plots.According to rainfall distribution and water availability, the 12 analysed years represent five different situations: wet years with positive and negative water balance; dry years; years with average annual rainfall but irregularly distributed throughout the year leading to a negative water balance; and extreme situations. Significant water deficits were observed in years in which total rainfall amount was above the annual average in the area, being similar to those observed in dry years: in 8 of the 12 analysed years deficits higher than 100 mm (up to 309 mm) during the growing period (budbreak-harvest) were recorded. At annual scale, 42% of the analysed years recorded deficits ranging between 27.7 and 191.4 mm. In the driest years, and those with more irregular rainfall distribution, soil moisture contents below the wilting point were reached. The high intensity rainfalls, producing important runoff losses (in many cases out of the periods in which crop water needs are higher), together with the increasing temperature trends, which give rise to significant evapotranspiration increases (values up to 32% higher than the average were recorded during the study period), are the main responsible factors for the water deficits recorded during grape development. Winegrape yield was influenced by the water stored into the soil, bloom-veraison or during budbreak-bloom depending on the variety.     

Combined effect of technical, meteorological and agronomical factors on solid-set sprinkler irrigation: I. Irrigation performance and soil water recharge in alfalfa and maize

In this work, maize (Zea mays L.) and alfalfa (Medicago sativa L.) were irrigated in two adjoining plots with the same sprinkler solid-set system. Irrigation was evaluated between four sprinklers in the central position within each plot, above the canopy with pluviometers and in the soil with a FDR probe. Maize and alfalfa were simultaneously irrigated under the same operational and technical conditions during two seasons: in 2005, the solid-set irrigation system layout was rectangular, 15 m between sprinklers along the irrigation line and 15 m among lines (R15 × 15), and the seasonal irrigation applied according to the crop evapotranspiration (ET_c); in 2006, the solid-set layout was R18 × 15 and the seasonal irrigation was around 30% lower than the ET_c. The irrigation depth above the canopies (ID_C) and the soil water recharge after irrigation (RW) were monitored using a 3 m × 3 m grid (25 points in 2005 and in 30 points in 2006). For maize, RW was assessed both in the lines of plants (CL) and between the lines (BCL).The average values of ID_C were similar between crops during both seasons but the uniformity (CUC) of the ID_C noticeably depended on the crop: the differences were greater between crops than between sprinklers spacings (R15 × 15 and R18 × 15). The CUC of ID_C, the RW and the CUC of RW were greater for alfalfa than for maize. The CUC of ID_C was greater than the CUC of RW for both crops. The RW was significantly related with the ID_C throughout the irrigation season for alfalfa. The correlation was weaker for maize, with important differences between positions and between growth stages. At the beginning of the season, the RW significantly correlated with the ID_C, both in the CL and BCL positions. However, the correlation weakened when the maize grew, especially in the CL, because the maize plants redistributed the water.The results show that the height and canopy architecture of the crop must be considered in the analysis of the sprinkler water distribution as factors influencing the irrigation performance.     

Effect of mulching on soil and plant water status, and the growth and yield of wheat (Triticum aestivum L.) in a semi-arid environment

Mulching is one of the important agronomic practices in conserving the soil moisture and modifying the soil physical environment. Wheat, the second most important cereal crop in India, is sensitive to soil moisture stress. Field experiments were conducted during winter seasons of 2004-2005 and 2005-2006 in a sandy loam soil to evaluate the soil and plant water status in wheat under synthetic (transparent and black polyethylene) and organic (rice husk) mulches with limited irrigation and compared with adequate irrigation with no mulch (conventional practices by the farmers). Though all the mulch treatments improved the soil moisture status, rice husk was found to be superior in maintaining optimum soil moisture condition for crop use. The residual soil moisture was also minimum, indicating effective utilization of moisture by the crop under RH. The plant water status, as evaluated by relative water content and leaf water potential were favourable under RH. Specific leaf weight, root length density and dry biomass were also greater in this treatment. Optimum soil and canopy thermal environment of wheat with limited fluctuations were observed under RH, even during dry periods. This produced comparable yield with less water use, enhancing the water use efficiency. Therefore, it may be concluded that under limited irrigation condition, RH mulching will be beneficial for wheat as it is able to maintain better soil and plant water status, leading to higher grain yield and enhanced water use efficiency.     

Effect of precipitation change on water balance and WUE of the winter wheat-summer maize rotation in the North China Plain

Limited precipitation restricts crop yield in the North China Plain, where high level of production depends largely on irrigation. Establishing the optimal irrigation scheduling according to the crop water requirement (CWR) and precipitation is the key factor to achieve rational water use. Precipitation data collected for about 40 years were employed to analyze the long-term trend, and weather data from 1984 to 2005 were used to estimate the CWR and irrigation water requirements (IWR). Field experiments were performed at the Luancheng Station from 1997 to 2005 to calculate the soil water consumption and water use efficiency (WUE). The results showed the CWR for winter wheat and summer maize were similar and about 430 mm, while the IWR ranged from 247 to 370 mm and 0 to 336 mm at the 25% and 75% precipitation exceedance probabilities for winter wheat and summer maize, respectively. The irrigation applied varied in the different rainfall years and the optimal irrigation amount was about 186, 161 and 99 mm for winter wheat and 134, 88 and 0 mm for summer maize in the dry, normal and wet seasons, respectively. However, as precipitation reduces over time especially during the maize growing periods, development of water-saving management practices for sustainable agriculture into the future is imperative.     

Soil water dynamics under various agricultural land covers on a subsurface drained field in north-central Iowa, USA

Modification of land cover systems is being studied in subsurface drained Iowa croplands due to their potential benefits in increasing soil water and nitrogen depletion thus reducing drainage and NO₃-N loss in the spring period. The objective of this study was to evaluate the impacts of modified land covers on soil water dynamics. In each individual year, modified land covers including winter rye-corn (rC), winter rye-soybean (rS), kura clover as a living mulch for corn (kC), and perennial forage (PF), as well as conventional corn (C) and soybean (S), were grown in subsurface drained plots in north-central Iowa. Results showed that subsurface drainage was not reduced under modified land covers in comparison to conventional corn and soybean. Soil water storage (SWS) was significantly reduced by PF treatments during the whole growing seasons and by kC during May through July when compared to the cropping system with corn or soybean only (p < 0.05). Treatments of rC and rS typically maintained higher SWS than C and S, respectively, during the 3 years of this study. In the spring during a 10-15-day period when the rainfall was minimal, SWS in plots with rye, kura clover, and forage decreased at a significantly higher rate than the C and S plots which were bare. Estimated evapotranspiration (ET) during this period was significantly higher in rS, kC, and PF treatments than C and S. The results of this study suggested that significantly higher ET and similar drainage for modified land covers may increase water infiltration, which would be expected to reduce surface runoff thus to decrease stream flow. Because subsurface drainage reduction was not seen in this study, impact of modified land covers on NO₃-N loss needs further investigation.     

Particle-size effects on soil temperature, evaporation, water use efficiency and watermelon yield in fields mulched with gravel and sand in semi-arid Loess Plateau of northwest China

Gravel and sand mulch is an effective practice in conserving soil and moisture. However, the proportion of different particle size in this kind of mulch layer is an important factor to be considered in order to obtain optimal results from this practice. From 2005 to 2007, a series of experiments including one with watermelon were conducted in the semi-arid Loess Plateau of northwest China to determine the influence of particle size and its proportion in mulch layer on soil temperature, evapotranspiration, water use efficiency (WUE) and watermelon (Citrullus lanatus L.) yield. The treatments in no-watermelon experiments included particle sizes classified as <0.3, 0.3-1, 1-2, 2-4, 4-6, 6-8 and 8-10 cm mesh size or various rates of 2-6 cm pebble accounting for 0, 10, 20, 30, 40, 50, 60 and 70% with 30% 1-2 cm gravel-sand in mulch layer (as well as correspondingly decreasing sand proportions). The watermelon experiment included three particle sizes, 0.3-1, 1-2 and 2-6 cm. Soil temperature at 8:00 h was highest for the 1-2 cm treatment, and the daily average temperature at 14:00 h was highest for the 0.3-1 cm treatment. Soil temperature decreased with particle size increasing due to porosity enlarging. The relationship between soil temperature and particle size followed a quadratic or cubic curve. Soil temperature was increased by gravel-sand mulch plus plastic film. The increment of soil temperature was larger especially for 1-4 cm particle size. In the gravel-sand mulch layer having different size particles, the greater percentage being of 2-6 cm pebbles, increases porosity, and lowers soil temperature, and causes more evaporation. The results of the watermelon experiment showed that soil moisture before seeding would not affect the yield during the years of using gravel mulch. Watermelon yield and WUE were higher for 1-2 and 0.3-1 cm treatments than 2-6 cm treatments in later experiments during 2006 and 2007. In conclusion, 2-6 cm large size particles would not account for much in gravel-sand mulching layer. It would be better if the percentage of 2-6 cm particles was less than 30%.     

Sensitivity of root pruned ‘Conference’ pear to water deficit in a temperate climate

The present study examines the need for irrigation in pear trees (Pyrus Communis, cv. ‘Conference’) under low evaporative demand conditions, like in Belgium, in order to maintain a consistent fruit yield and high fruit size. To determine the sensitivity of the pear yield under low evaporative demand conditions three different orchards were monitored. The study shows that a Ψ_soil of −60 kPa during shoot growth has no effect on fruit yield but lower Ψ_soil values induced a decline in both fruit size and total yield. Just as for arid environments a Ψ_stem of −1.5 MPa is related to negative yield responses. In dry conditions lower Ψ_soil and Ψ_stem values were observed in root pruned trees compared to not root pruned trees in the same irrigation treatment, however without yield decline. In one orchard a biannual bearing tendency was observed after root pruning. Furthermore intensive Ψ_soil measurements show a high variation in Ψ_soil between orchards, and within an orchard. This underlines the need for irrigation management on a parcel level and the need for new irrigation scheduling techniques which take the spatial variation in the orchard into account.     

Remote sensing for irrigation water management in the semi-arid Northeast of Brazil

Northeast of Brazil is a semi-arid region, where water is a key strategic resource in the development of all sectors of the economy. Irrigation agriculture is the main water consumer in this region. Therefore, policy directives are calling for tools to aid operational monitoring in planning, control and charging of irrigation water. Using Landsat imagery, this study evaluates the utility of a process that measures the level of water use in an irrigated area of the state of Ceará. The experiment, which models evapotranspiration (ET), was carried out within the Jaguaribe-Apodi irrigation scheme (DIJA) during two months of the agricultural season. The ET was estimated with the model Mapping Evapotranspiration at High Resolution and with Internalized Calibration (METRIC). The model uses the residual of the energy balance equation to estimate ET for each pixel in the image. The results of the estimates were validated using measurements of ET from a micrometeorological tower installed within a banana plantation located near the irrigation scheme. After evaluating the ET estimates, the average fraction of depleted water for a set of agricultural parcels combined with the monthly ET mapping estimates by METRIC provided a method for predicting the total water use in DIJA for the study period. The results were then compared against the monthly accumulated flow rates for all the pumping stations provided by the district manager. Finally, this work discusses the potential use of the model as an alternative method to calculate water consumption in irrigated agriculture and the implications for water resource management in irrigated perimeters.     

Combining an ecological model with remote sensing and GIS techniques to monitor soil water content of croplands with a monsoon climate

Soil water is an important factor affecting photosynthesis, transpiration, growth, and yield of crops. Accurate information on soil water content (SWC) is crucial for practical agricultural water management at various scales. In this study, remotely sensed parameters (leaf area index, land cover type, and albedo) and spatial data manipulated using the geographic information system (GIS) technique were assimilated into the boreal ecosystem productivity simulator (BEPS) model to monitor SWC dynamics of croplands in Jiangsu Province, China. The monsoon climate here is characterized by large interannual and seasonal variability of rainfall causing periods of high and low SWC. Model validation was conducted by comparing simulated SWC with measurements by a gravimetric method in the years 2005 and 2006 at nine agro-meteorological stations. The model-to-measurement R² values ranged from 0.40 to 0.82. Nash-Sutcliffe efficiency values were in the range from 0.10 to 0.80. Root mean square error (RMSE) values ranged from 0.028 to 0.056 m³ m⁻³. Simulated evapotranspiration (ET) was consistent with ET estimated from pan evaporation measurements. The BEPS model successfully tracked the dynamics and extent of the serious soil water deficit that occurred during September-November 2006. These results demonstrate the applicability of combining process-based models with remote sensing and GIS techniques in monitoring SWC of croplands and improving agricultural water management at regional scales in a monsoon climate.