Soybean Yield and Quality Relative to Mollisols Fertility with 7‐year Consecutive Cattle Manure Application under Maize‐soybean Rotation

Improving soil productivity is the best way to increase grain production by 1% annually for feeding the rising population within the next 20 years in China. Nevertheless, how soybean yield and seed quality are affected by improving soil quality via consecutive manure addition are still unclear. A 7-year consecutive cattle manure addition experiment was conducted under a soybean [Glycine max (Merrill.) L.] and maize (Zea mays L.) rotation in Mollisols. Treatments were as follows: CK: the non-fertilizer control; CF: chemical fertilizer (NPK); CFM1: CF + 15 Mg ha(-1) cattle manure; CFM2: CF + 30 Mg ha(-1) cattle manure. The results showed CFM1 significantly increased soybean yield by 22%-105% and 21%-86% compared to CK and CF during 2014-2018. The consecutive cattle manure addition significantly increased the proportion of macro-aggregates (1-0.25 mm) but decreased the proportion of micro-aggregates (0.25-0.053 mm) and slit (<0.053 mm). The SOC storage in the large (>1 mm) and small macro-aggregates (1-0.25 mm) was higher (by 24%-156%) under cattle manure addition than that under CK and CF. The soil productivity was enhanced by cattle manure addition because of the increase in soil available nutrients, that is, NH4+-N and NO3--N, and Olsen-P, all of which had positive correlations with the yield increase. At least 36% of soybean yield variation under CFM1 could be attributed to the indirect effect of pH value on increasing soil available nutrients concentrations. The cattle manure addition increased soybean seed oil concentration but decreased protein concentration. However, there were no differences in yield and quality between CFM1 and CFM2 after 7-year of the treatment. It suggests that cattle manure addition at 15 Mg ha(-1) is a practical approach to improve Mollisols' productivity and SOC stability.