Assessing the contribution of China's grain production during 2005-2020 from the perspective of the crop-water-land nexus

Water shortages and diversion of arable lands to other uses represent systemic risks to global agricultural production. However, few studies have comprehensively assessed blue-green water and land resources performance in crop cultivation and grain production. This study establishes a crop-water-land nexus accounting framework that distinguishes between blue and green water. Contributions of water and land resources to increases in grain production in China in the years 2005, 2010, 2015 and 2020 were evaluated based on provincial-scale cropwater-land nexus accounting. China produced 580.4 Tg of grain using 805.1 x 103 km2 yr- 1 of arable land per year, 76.1 % of which was accounted for by 13 major grain-producing provinces. Annual water consumption in grain production was estimated to be 614.3 x 109 m3, including 183.0 x 109 m3 blue and 431.3 x 109 m3 green water. Albeit with significant spatial variation, land and water resource inputs increased over time. Excluding agronomic improvements, blue water, green water and arable land jointly contributed 65.4 % of the national increase in grain production (185.5 Tg) from 2005 to 2020. Irrigated cropland in major grain-producing provinces dominated grain production increases and national level shifts in water resources over the period studied. The marginal efficiency of blue water (0.784 kg m-3) in grain production was greater than that of green water (0.071 kg m-3). Reclaiming reserve land, upgrading irrigation technology and improving rainwater use efficiency in the provinces along a southwest to northeast axis (e.g., from Heilongjiang to Yunnan), are effective approaches for the country to continue to increase food production in the future.