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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.

Water use efficiency (WUE) is one of the most widely used indicators in agricultural water management. Although this indicator has obvious advantages, it is limited to measuring the relationship between crop yield and corresponding water use. In recent years, many researchers have noted that understanding the economic efficiency of water use (EEWU) could have great water-saving potential, while it has been poorly investigated with respect to China’s agricultural water management. This paper assesses EEWU through a household farmer-level survey in the piedmont region of North China. First, EEWU of crops are estimated based on agricultural water consumption (including irrigation water and effective precipitation) and profit (including gross profit and net profit); Second, the impact of monthly price changes in 2019 and annual price changes in 2014–2019 on EEWU is analysed. Main conclusions are as follows: (1) EEWU values of cash crops such as apple and cauliflower are much higher than those of grain crops such as wheat and maize; (2) For different crops, the median economic efficiency of irrigation water (EEWiU) and total water (EEWtU) range from 31.71 to 99.54 ¥/m3 and 11.31 to 44.05 ¥/m3, respectively; (3) The multi-year average EEWiU and EEWtU ranged from 4.75 to 63.99 ¥/m3 and from 2.67 to 31.71 ¥/m3, respectively. Economic efficiency of water use shows a slightly downward trend in the period of study, which would contradict the trend towards the use of more water-efficient technologies and shows an even larger margin of improvement in the domain of agricultural water efficiency. The results provide a powerful reference for the management of agricultural water use through economic leverage.