Water resource shortages restrict the economic and societal development of China’s arid northwest. Drawing on groundwater resources for irrigation, field experiments growing seed maize (Zea mays L.) were conducted in 2013 and 2014 in the region’s Shiyang River Basin. The Soil–Water–Atmosphere–Plant (SWAP) model simulated soil water content, salinity, and water–salt transport, along with seed maize yield, in close agreement with measured values after calibration and validation. The model could accordingly serve to simulate different saline water irrigation scenarios for maize production in the study area. Waters with a salinity exceeding 6.0 mg/cm³ were not suitable for irrigation, whereas those between 3.0 and 5.0 mg/cm³ could be acceptable over a short period of time. Brackish water (0.71–2.0 mg/cm³) could be used with few restrictions. Long-term (five years) simulation of irrigation with saline water (3.0–5.0 mg/cm³) showed soil salinity to increase by over 9.5 mg/cm³ compared to initial levels, while seed maize yield declined by 25.0% compared with irrigation with brackish water (0.71 mg/cm³). An irrigation water salinity of 3.0–5.0 mg/cm³ was, therefore, not suitable for long-term irrigation in the study area. This study addressed significance issues related to saline water irrigation and serves as a guide for future agricultural production practices.

In order to explore the relationship between crop yield and water salt stress, field experiments were conducted under deficit irrigation with saline water in Shiyang Rive Basin. It introduced into the crop-water-salt production function. The crop-water-salt production function parameters were calibrated and validated based on the field experiments measured data. The results showed that the simulated evapotranspiration and yield agreed well with the measured values of seed maize at different growth stages. The crop-water-salt production function parameters after calibration and validation were b=6.72, k_y1 =0.43, k_y2 =0.82, k_y3 =1.41, k_y4 =0.65, k_y5 =0.24, respectively. The yield response factor (k_y ) reflected sensitivity to the seed maize at different growth stages under water salt combination stress. The crop-water-salt production function can well simulate the seed maize evapotranspiration and yield under water salt combination stress after calibration and validation.

Background and aims To investigate the effects of different water-saving irrigation quota on soil water and salt flux under the growth conditions of crop, providing a theoretical basis for the prevention of soil salinization and the efficient utilization of water resources in arid area. Methods The SWAP (Soil-Water-Atmosphere-Plant) model parameters were calibrated and validated based on field experiments data to simulate soil water-salt flux and soil water-salt cumulative flux under different scenarios in the Northwest China. Results Soil water flux, soil water cumulative flux, soil salt flux and soil salt cumulative flux decreased with the decrease on irrigation quota at the lower interface of crop root zone and storage zone under different scenarios. The soil water cumulative flux and soil salt cumulative flux changed small, when the irrigation quota was reduced to 70%IQ (Irrigation Quota) and 60% IQ. Soil water could be stably stored in 0-100 cm soil layer to meet the growth requirements of summer maize, which brought in by irrigation and rainfall. When the irrigation quota of summer maize was 70% IQ (3500 m ³ ·ha ^− 1 ), soil water-salt flux and soil water-salt cumulative flux were minimal at the lower interface of crop root zone and storage zone. The yield reduction of summer maize was only 10%. Conclusions 3500 m ³ ·ha ^− 1 was the optimal irrigation quota for summer maize from the perspective of soil water-salt balance and crop growth. It was to provide technical support for the efficient utilization of water resources and also guided agricultural production practice in the Northwest China.

As an effective measure for retaining paddy drainage and control agricultural non-point source pollution, the paddy field-ditch-pond system can buffer nitrogen and phosphorus pollutants in field drainage. Few studies have investigated the spatiotemporal dynamics of nitrogen and phosphorus across an integrated paddy field-ditch-pond system in polder landscapes. So in this paper, water quality monitoring through a paddy field-ditch-pond system were conducted in a typical polder area of southern China. Total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N) and orthophosphate (PO₄³⁻) of the paddy field-ditch-pond system were measured during the growth periods of paddy rice. The temporal and spatial distribution characteristics of nitrogen and phosphorus were analyzed. The results showed that the concentrations of TN and TP ranged from 1.31 to 3.54 mg·L^− 1 and 0.038 to 0.14 mg·L^− 1, respectively, in the drainage ditches during the paddy rice growth period. The concentrations of TN and TP varied between 0.11 ~ 4.90 mg·L^− 1 and 0.02 ~ 0.22 mg·L^− 1 in the ponds, respectively. The concentrations of TN, NH₄⁺-N, NO₃⁻-N, TP and PO₄³⁻ in paddy fields, drainage ditches and ponds showed a decreasing trend from paddy fields to drainage ditches and ponds. The ditch-pond subsystem had a certain interception and purification effect on nitrogen and phosphorus of paddy field drainage water. In the study area, setting up ecological drainage ditches, adopting controlled drainage and growing aquatic plants in drainage ditches can be taken to improve water quality. Findings from this research may provide scientific basis for precise prevention and control of agricultural non-point source pollution in the polder area.

In order to explore the rule of groundwater salt dynamic in Hetao Irrigation District, a typical monitoring area was selected as the research area in Yongji Irrigation Area of Hetao Irrigation District. The groundwater level and groundwater salinity were analyzed during the year and inter-annual variation in 2008-2013. The groundwater level showed an obvious seasonal change trend during the year variation. The groundwater level was at the peak value after spring irrigation and autumn irrigation. The groundwater level was at the low value before melting and autumn irrigation. The groundwater level had an obvious periodicity during the inter-annual variation. The groundwater level could keep a relatively stable for many years. The groundwater salinity showed an obvious seasonal change trend during the year variation. The groundwater salinity was greatly affected by irrigation and had a decreased trend after irrigation. The groundwater salinity had an obvious periodicity during the inter-annual variation and could keep a relatively stable for many years in cultivated land. The groundwater salinity had an increased trend during the inter-annual variation in wasteland. The wasteland was the drainage area for cultivated land. The wasteland had an obvious role in adjusting salt dynamic balance in Hetao Irrigation District.