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A land fallow system (LFS) designed to adjust the winter-wheat summer-maize cropping system to fallow summer-maize was introduced in Hebei Province to alleviate groundwater depletion in the region. However, some of the water saved was lost through evaporation from bare soil and transpiration by weeds. So far, no measurement has been done in the region to address this non-productive water loss, thereby limiting the water-saving potential of the introduced LFS. Furthermore, the reduction in crop production under the summer-maize – fallow system threatens food security. The objective of this study was to determine which practice is effective to keep soil water during fallow and the exact water-saving potential of different cropping system in the region. Firstly, field experiments were conducted under various soil surface management systems — including plastic mulching (PM), straw mulching (SM), shallow tillage (ST) and weed control (WC). The effects of saving water, controlling weeds and managing nutrients were analyzed under the various surface soil management methods. The results showed that compared with the control (no soil surface management, CK), 177, 64.7, 71.0 and 25.0 mm of water was saved respectively under PM, SM, WC and ST surface soil management methods in 2019–2020. The effect of weed control decreased in the order of PM > WC > SM > ST. While PM significantly increased soil nutrient in all the treatments, the others showed slight but insignificant increases. Secondly, the precise water-use of each of the cropping systems was determined using large lysimeters. The analysis showed that compared with the wheat-maize system, 60–100 mm of water was saved under alternating wheat-soybean, wheat-millet, mung bean – fresh edible maize, spring sweet potato cropping systems. The results were key for technical guide in developing future cultivation adjustment policies. • The maize-fallow system saved water 246 mm determined by large lysimeters. • Water-saving potential under various soil surface practice was analyzed during fallow. • Black film mulching proved to be the most effective practice during fallow. • Daily ET variation of different cropping systems was measured by large lysimeters. [ABSTRACT FROM AUTHOR]

Summary: North China Plain (NCP) is one of the most important agricultural production regions in China. A severe water shortage, due to intensive irrigation, exists in the plain. In NCP, crop water-use accounts for 70% of total groundwater use in the floodplains and over 87% in the piedmont regions. Surface water in the plain is limited and restricted for urban water supply. Agricultural production therefore heavily relies on groundwater irrigation; the main driver of groundwater depletion in the region. To address the water shortage issue, a flexible and sustainable water management method is proposed. The method integrates crop-growth and groundwater model, and ensures groundwater recovery via agricultural water-saving. The method is successfully tested for the 4763km2 Shijiazhuang Irrigation District in the piedmont region of Mount Taihang. The model results show that 29.2% or 135.7mm reduction in irrigation could stop groundwater drawdown in the plain. An additional 10% reduction in irrigation pumping (i.e., a total of 39.2% or 182.1mm) would induce groundwater recovery and restoration to the pre-development hydrologic conditions of 1956 in about 74years. The farmers’ current irrigation practices are inefficient and wasteful of the limited water resources. Under appropriate irrigation schemes therefore, grain yield loss as a result of the 39.2% agricultural water-saving is less than 10%. This minimal agronomic loss is economically acceptable, giving the ecological and environmental benefits of groundwater recovery in the study area. However, successful agricultural water-saving requires not only practical feasibility of models, but also sufficient political commitment, promotion of water-saving incentives and efficient water-saving technologies, and enforcement of sustainable water management policies. [ABSTRACT FROM AUTHOR]