Effects of manure fertilizer on crop yield and soil properties in China: A meta-analysis

The intensive use of mineral fertilizer may have negative effects on plant growth and the soil environment, but the application of manure could alleviate these problems. However, the effects of manure application on crop yield and soil properties in different climates, soil conditions, and management practices should be investigated before we could conclude that it is universally practical. We performed a meta-analysis of 774 comparisons from 141 published studies and found that manure application increased yield by an average of 7.6% compared to mineral fertilizer. The effects of manure application were more pronounced in acidic soils, warm and/or humid climates, and longer experimental periods. Manure application also increased soil pH (3.3%), water-stable aggregation (28.8%), soil organic carbon (17.7%), total (15.5%) and available nitrogen (16.0%), available phosphorus (66.2%), available potassium (19.1%), the activities of urease (23.5%), sucrase (18.3%), and catalase (16.1%), and the abundances of bacteria (60.0%), fungi (27.7%), and actinomyces (38.0%). Manure application decreased soil bulk density (−3.9%). Increases in the nutrient pool and decompositional capacity of the soil may explain the positive effects of manure application on yield. Our results indicate that long-term manure application may improve sustainable soil productivity and crop yield in China.