Decomposition Characteristics, Nutrient Release, and Structural Changes of Maize Straw in Dryland Farming under Combined Application of Animal Manure

Straw and animal manure are major organic waste materials from agricultural ecosystems. Different kinds of animal manure combined with straw (AM-S) may have varying effects on the decomposition, nutrient release, and structural changes of maize straw. Using the Humic Cambisols soil as the experimental area, the straw decomposition characteristics under the co-application of animal manure were studied following the nylon net bag landfill method. The experiment involved four treatments: maize straw only (S), maize straw plus ox manure (SO), maize straw plus chicken manure (SC), and maize straw plus pig manure (SP). The treatments with AM-S accelerated the decomposition of straw and increased the release rate of nutrients and organic components (cellulose, hemicellulose, and lignin). During the 240 days of the study, straw decomposition showed a trend of increasing rapidly in the first stages and then increasing slowly in the latter stages in all the treatments. At 240 d, the straw decomposition rates and carbon release rates of the AM-S treatments were 65.25–71.87% and 64.04–69.35%, respectively. At the end of the experiment, the order for the final release rates of nitrogen (N), phosphorus (P), and potassium (K) was K (93.25–96.56%) > P (42.25–55.08%) > N (40.01–52.23%). Moreover, scanning electron microscopy showed that SP treatment had the highest degree of structural changes of the maize straw compared with the other treatments. The purpose of this study was to screen the effective animal manure that can promote straw decomposition and provide a reference for the rational use of straw and animal manure management. In conclusion, the study suggested that the co-application of animal manure and straw should be adopted in agricultural systems, especially SP treatment, as it was more conducive to promoting the decomposition of maize straw and the release of nutrients.