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Optimum management of irrigated crops in regions with shallow saline groundwater requires a careful balance between application of irrigation water and upward movement of salinity from the groundwater. Few field-validated surrogate models are available to aid in the management of irrigation water under shallow groundwater conditions. The objective of this research is to develop a model that can aid in the management using a minimum of input data that are field validated. In this paper a 2-year field experiment was carried out in the Hetao irrigation district in Inner Mongolia, China, and a physically based integrated surrogate model for arid irrigated areas with shallow groundwater was developed and validated with the collected field data. The integrated model that links crop growth with available water and salinity in the vadose zone is called Evaluation of the Performance of Irrigated Crops and Soils (EPICS). EPICS recognizes that field capacity is reached when the matric potential is equal to the height above the groundwater table and thus not by a limiting hydraulic conductivity. In the field experiment, soil moisture contents and soil salt conductivity at five depths in the top 100 cm, groundwater depth, crop height, and leaf area index were measured in 2017 and 2018. The field results were used for calibration and validation of EPICS. Simulated and observed data fitted generally well during both calibration and validation. The EPICS model that can predict crop growth, soil water, groundwater depth, and soil salinity can aid in optimizing water management in irrigation districts with shallow aquifers. [ABSTRACT FROM AUTHOR]

Biochar is proposed as a soil amendment to improve soil physical-chemical properties and crop productivity. However, the effect of biochar on crop yield is not consistent and the mechanisms affecting plant growth are still not well-understood. In this paper, field experiments were carried out to investigate the impact of biochar addition on soil properties, water and fertilizer productivity of tomato in semi-arid area of Inner Mongolia, China. The tested biochar was made from maize straw by slow pyrolysis. Four biochar treatments were conducted including addition of 10, 20, 40 and 60 t ha −1 and no biochar as a control. Addition of biochar reduced the bulk density and increased the porosity of soil. Electrical conductivity of soil increased with increasing biochar application rate. Soil pH was not affected by addition of biochar in one growing season. Yield, crop water productivity and partial factor productivity for fertilizer were nonlinearly (quadratic) proportional to application rate of biochar. Highest water and fertilizer productivity obtained from the 40 t ha −1 biochar treatment. Comprehensive analysis of biochar impact on yield, water and nutrient productivity, and cost-benefit for the grower indicate that addition of approximate 30 t ha −1 is an appropriate rate for tomato production in the study area. This suggestion is based on the relatively short term effect and local market conditions. A prolonged experiment is desirable to understand the long term response of soil and crop to biochar addition. [ABSTRACT FROM AUTHOR]

• The combined algorithm can extract crop planted structure in the YRB. • Spring wheat planted area decreased over 2001–2020, other food crops were opposite. • Water-saving measures and other factors jointly affect the crop planted structure. Accurate extraction of crop planting structure is the fundamental for estimating regional crop yield and crop water consumption in the Yellow River Basin (YRB). However, the planted area of the main food crops in the YRB in recent 20 years is still unclear. Therefore, the MODIS image data was used to extract the growing area of the main food crops (winter wheat, summer maize, spring wheat and spring maize) in the YRB over 2001–2020 by the combination of the differential algorithm, spectral mutation algorithm and threshold method. The results revealed that the combined method could be used to track the planted area of the main food crop in the YRB, with R 2 and RMSE values ranged from 0.51 to 0.82 and 11.01 to 68.92 × 103 hm2, respectively. The planted area of winter wheat and summer maize in the down-stream irrigation district accounted for 74.7% and 86.7% of the total in the YRB, respectively. Inner Mongolia and Ningxia autonomous regions are the main producing areas for spring wheat and spring maize, accounting for 73.8% and 83.5% of the total in the YRB, respectively. The planted area of winter wheat, summer maize and spring maize had an increasing trend with the rate of 1.440 × 104 hm2 per year, 2.375 × 104 hm2 per year and 2.257 × 104 hm2 per year over 2001–2020. Whereas, the planted area of spring wheat had a decreasing trend with the rate of −2.019 × 104 hm2 per year. Implementation of water-saving irrigation measures, variations of diverted water from the Yellow River, local policies improvement and agricultural market might be the main driving forces for the changes of the planted area for food crops. The results can provide a fundamental agricultural information dataset for further study of regional crop water consumption in the YRB. [ABSTRACT FROM AUTHOR]