Animal manure application promotes nitrogen and organic carbon accumulation in soil organic matter fractions: A...

The United Nations identified nitrogen (N) management in agriculture as one of the most important environmental challenges of the 21st century. Animal manure applications provide nutrients to crops and enhance soil organic matter (SOM) content and fertility. However, few comprehensive studies have assessed the effect of animal manure applications on N and OC in physical SOM fractions, thus limiting our ability to provide a global perspective of manure-derived N management. A meta-analysis of 57 experimental sites was performed to evaluate how animal manure applications modify the concentrations of N and OC in physical SOM fractions. Overall, N and OC concentrations are greater following animal manure applications than mineral N fertilization, and the difference is even greater when compared to an unfertilized control. The relative response is particularly pronounced for particulate organic matter (POM), light particulate organic matter (L-POM), and heavy particulate organic matter (H-POM) compared to mineral-associated organic matter (MAOM) and the whole soil. A positive linear relationship is observed between manure application rate and the response of N and OC in whole soil and all fractions. Moreover, the response of POM N and OC is greater with solid than liquid manures, in alkaline than in acidic soils, and in dry than in moist climates. This study highlights the significance of POM, and more specifically the H-POM fraction, in the retention of animal manure-induced C in agricultural soils, and possibly as pools involved in the N supply capacity of manured soils, thereby providing insights for improving N management.