Organic materials incorporation and nitrogen utilization are both important measures to enhance soil fertility and crop productivity. To evaluate the effect of different organic materials on soil N utilization and crop yield, three kinds of organic materials, including straw (ST), pig manure (PM), and biogas residue (BR), were incorporated into the soil with equal N in the wheat (Triticum aestivum L.)-maize (Zea mays L.) cropping system with chemical fertilizers (CFs) as a control in Wuqiao County in the North China Plain. The contents of soil N, nitrate N, ammonium N, N use efficiency, N partial productivity (NPFP), N uptake efficiency (NUPE), and N harvest index (NHI) were measured and calculated. The results of 2-yr field trials suggested that, compared with CF, soil total N (TN) content of ST, PM, and BR treatment increased by 3.04, 8.99, and 9.10%, respectively. An even larger increase was found in nitrate N, which was 25.87, 44.67, and 44.93% in ST, PM, and BR, respectively. For N utilization, PM significantly increased NPFP, NUPE, and NHI by 4.01, 5.86, and 3.04%, respectively, meanwhile decreasing soil N dependency rate by 4.64%; BR improved NUPE by 5.15%, while ST showed little improvement in the utilization of soil N. Overall, organic materials promoted soil N maintenance and increased N utilization.Among the kinds of organic material amendment in the study, PM had a better performance in improving soil N utilization and crop yield than BR and crop ST return in field experiments.
INTRODUCTIONIn crop and soil systems, N has been suggested to be a factor in crop growth and yielding ability by participating in plant genetic metabolism (material synthesis and signal transduc-