Abstract
Synthetic nitrogen fertilizer substitution (NSS) with different types of organic material is a cleaner agricultural practice for reducing the application of synthetic N input in farmlands while also relieving the environmental issues caused by the discharge of organic wastes. However, the effects of the NSS practice on crop yields, being the primary objective of agricultural activity, is still uncertain in China. This study conducted a meta-analysis to assess the impacts of the NSS practices with different types of organic materials on crop yields. Results showed that the average crop yield was increased by 3.4%, with significant differences under NSS, thereby demonstrating that this practice contributed to improving crop yields, especially of rice and maize. According to published reports, the NSS practices involving chicken manure, pig manure, and crop straw increased crop yields by 4.79, 7.68, and 3.28%, respectively, with significant differences, thus demonstrating the superior effects needed for replacing synthetic N fertilizer. Moreover, substitution ratios (SR) between 0% and 60% could be suggested when using the NSS practice, with the high SR recommended when the original soil fertility was adequate for crops. Considering the long-term effects of applied organic materials, improving the grain yield with the NSS practice should be expected in the long-term. By effectively applying the NSS, this study attempted to scientifically decide on the type of organic materials and the appropriate SR based on the conditions of the soil and the crop. The results provide research information for the development of clean agricultural production and food security in China.
Highlights
Nitrogen (N) is the main limiting factor of crop productivity
The results provide the theoretical basis for the rational application of the N fertilizer substitution (NSS) practice in China, and new research information for the development of clean agricultural production in the world
In North China and southwest China, the materials provided a rich source for the growth ofbut soilthe microorganisms, thereby yields were increased by carbon
Summary
Nitrogen (N) is the main limiting factor of crop productivity. During the past fifty years, the grain yield per unit area in the world has increased by 130.34%, which the wide application of synthetic N fertilizer around the world has significantly contributed to [1]. The negative environmental impacts caused by the excessive application of synthetic N fertilizer has exceeded the positive benefits of increasing the crop yield in China. Large amounts of organic wastes, such as crop straw and animal manure, are generated in China each year, but the utilization rate is less than 40% [17] In this context, the NSS practice was paid more attention by researchers for reducing synthetic N fertilizer use and disposing of organic wastes. This study conducted a meta-analysis to quantitatively assess the impacts of the NSS practices with different types of organic materials on grain yields in China, including crop straw, animal manure, biogas residue, and biochar. The results provide the theoretical basis for the rational application of the NSS practice in China, and new research information for the development of clean agricultural production in the world
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