Meta-analysis of the effects of different tillage methods on wheat yields under various conditions in China

Tillage is a useful practice for increasing crop yield, however, its effectiveness is readily influenced by different agro-ecological conditions and cultivation measures. The effects of different tillage methods on wheat yield remain unclear. Therefore, we identified 197 studies and conducted a meta-analysis to determine the effects of three representative tillage methods (no-tillage, subsoiling, and deep ploughing) on wheat yield and soil physicochemical properties according to variations in the mean annual precipitation and temperature, soil texture, soil pH, years of continuous tillage, basic soil fertility, and fertilization level. The average yield increased by 3.5 % under deep ploughing because of the marked decrease in soil bulk density under different production conditions, whereas soil organic carbon and total nitrogen increased significantly, with an average yield increase of 7.0 % under subsoiling tillage. No-tillage overcame the adverse effects of increased soil bulk density on yield by promoting soil carbon and nitrogen accumulation, and had no marked effects on wheat grain yield. The yields increased significantly by 4.5 % after no-tillage for more than seven years. In contrast, deep ploughing tillage initially increased yields, but yields decreased with the number of years under continuous tillage. Overall, subsoiling was the most effective method increasing wheat grain yield and soil physicochemical properties. No-tillage was an effective method under conditions of mean annual precipitation < 400 mm; mean annual temperature < 12°C; loam, neutral or alkaline soil; and medium fertility farmland. Deep ploughing was the most effective in farmlands with low fertilizer levels. The results provide a scientific basis for help agricultural producers to formulate suitable farming practices for appropriate management of production factors.