Effects of substituting chemical fertilizers with manure on rice yield and soil labile nitrogen in paddy fields of China: A meta-analysis

Abstract

Substituting chemical fertilizers with manure is an important method for efficient nutrient management in rice cropping systems of China. Labile nitrogen (N) is the most active component of the soil N pool and plays an essential role in soil fertility. However, the effects of manure substitution on soil labile N in rice cropping systems and their relationships with soil properties, fertilization practices, and climatic conditions remain unclear and should be systematically quantified. Here, we investigated rice grain yield and four types of soil labile N that have been widely reported, including available nitrogen (AN), ammonium nitrogen (NH+4-N), nitrate nitrogen (NO-3-N), and microbial biomass nitrogen (MBN). We reviewed 187 published articles and performed a meta-analysis to quantify the effects of manure substitution on yield and soil labile N. The results showed that manure substitution increased AN, MBN, NH+4-N, and NO-3-N by 11.3%, 38.5%, 5.9%, and 8.1%, respectively. Partial substitution significantly increased the yield by 1.4%–5.9%, but full substitution significantly decreased the yield by 2.9%. The positive effects of manure substitution on yield and AN were stronger with long-term fertilization. The differences in responses varied across specific manure types, N application rates, soil properties, and climatic factors. In conclusion, manure substitution can increase soil labile N and is regarded as an efficient strategy for improving soil N fertility and a recommended measure for applying both chemical and organic fertilizers in rice systems. This study provides evidence of the effects of manure substitution on yield enhancement by increasing soil labile N.