Wheat Straw Decomposition Patterns and Control Factors Under Nitrogen Fertilization

Understanding farmland ecosystem processes such as straw decomposition under nitrogen fertilization is critical for predicting carbon and nitrogen cycles. Nitrogen fertilization significantly affects soil and straw quality, which may significantly affect straw decomposition; however, comprehensive studies considering both factors are lacking. To evaluate the decomposability of crop residues under nitrogen fertilization, we conducted three subexperiments involving straw decomposition in situ, decomposition of the same straw in soils with different nitrogen fertilization regimes and decomposition of different straw types in the same soil with nitrogen fertilization and investigated the changes in soil respiration and wheat straw physicochemical properties. Nitrogen fertilization promoted straw decomposition: 180 and 360 kg N ha−1 year−1 increased the weight loss rate by 9.95% and 11.15%, respectively, but the difference between the two was not significant. The carbon emissions under 360 kg N ha−1 year−1 were significantly higher than those under 180 kg N ha−1 year−1. Straw chemical characteristics exhibited different sensitivities to nitrogen fertilization; hemicellulose responded positively to 180 kg N ha−1 year−1, while carbon and cellulose had obvious responses to only 360 kg N ha−1 year−1. The soil temperature, soil moisture, straw nitrogen content, and straw C/N ratio were the main factors affecting decomposition. Excessive nitrogen fails to promote nutrient return during straw decomposition and may also increase carbon emissions from farmland soil and aggravate the greenhouse effect. This study provides a theoretical basis for understanding nutrient cycling in farmland ecosystems under reasonable fertilization regimes and for improving farmland soil quality and nitrogen fertilization.