One−off irrigation enhances wheat yield and water productivity: Evidence from meta−analysis and a three−year and three−site field experiment

Currently, one−off irrigation (irrigation once time during the growth period) is increasingly applied in wheat production system where agricultural water is insufficient. The impacts of one−off irrigation on wheat yield and water productivity (WP) varied significantly depending on many factors such as irrigation strategies, climate factors, soil properties, fertilizer additions, and so on. However, few study has systematically investigated the effects of one−off irrigation concerning all these factors up to now. Therefore, we analyzed 122 global published studies and conducted a three−year and three−sites field experiment to reveal the improvement laws of one−off irrigation on wheat yield and WP under these factors. The meta−analysis revealed that, compared to zero−irrigation, one−off irrigation increased wheat grain yield by 22.8 % and WP by 4.1 %. The yield improvement was mainly ascribed to the increase in spike numbers per unit area (9.9 %) and grains per spike (9.4 %). The suggested strategy for one−off irrigation was 70–90 mm at jointing stage for most wheat production system. In detail, the one−off irrigation strategies recommended for maximizing yield in Shandong, Henan, Shanxi, Hebei and Shaanxi province in China should be irrigated at anthesis, booting, overwintering, overwintering, and jointing stage, with irrigation amounts of < 60, > 90, > 90, 70–90 and < 60 mm, respectively. Our field experiment also demonstrated that one−off irrigation significantly increased the grain yield, WP, and economic benefit by 41.0 %, 26.4 %, and 59.9 %, respectively, while decreased nitrate−N residue in 0–200 cm soil depth at harvest by 19.8 %. These findings can serve valuable guidelines into optimizing irrigation practice for wheat high−yield and high−efficiency in dryland where one−off irrigation is assured.