Meta-analysis of no-tillage effect on wheat and maize water use efficiency in China

Abstract No-tillage (NT) is a popular agricultural technique worldwide, but it remains unclear how NT affects the yield, evapotranspiration (ET), and water use efficiency (WUE) of maize and wheat. We performed a meta-analysis of the NT effects on the yield, ET and WUE for wheat and maize based on the literatures published during 1950–2018. Yield, ET, and WUE varied by species, region, and agronomic and environmental factors. Averaged across all the geographic locations NT had no effect on the yield, ET, or WUE of wheat in northwestern and northern China, and no effect on the yield or ET of maize, but significantly increased the maize WUE by 5.9%. NT increased the WUE and yield of wheat in regions with ≤400 mm of mean annual precipitation, increased the yield in regions with 400–600 mm of precipitation, and decreased the yield and ET in regions with ≥600 mm, but had no effects on maize. In the first 1–3 years of NT implementation, the wheat ET was reduced. However, a significant decrease in maize yield and ET occurred in 3–6 years of NT implementation. Meanwhile, yield and WUE in both wheat and maize were improved after >6 years. In general, NT effect on yield, ET, or WUE was not related to soil texture. However, NT increased maize WUE in a medium soil texture. Without crop rotation, NT increased wheat yield and ET but decreased maize yield. No NT effects were observed when crop residues retained and under crop rotation. Consequently, optimizing NT effects on yield, ET and WUE for wheat and maize in China was largely dependent on environmental conditions and management practices.