Appropriate dense planting with N fertilisation increased maize grain yield and soil organic carbon

Abstract

Soil organic carbon (SOC) fractions and soil enzyme activities were effective indicators to represent C changes under different plant densities (PD) and nitrogen (N) application levels, which influenced crop yield in turn. The aim of the experiment was to investigate the impact of PD and N application levels on soil productivity. The experiment conducted in the North China Plain included three plant densities: 1) PD1 -60,000 plants ha −1 , 2) PD2 -67,500 plants ha −1 , and 3) PD3 -75,000 plants ha −1 , and three N application levels: 1) N0 -0 kg ha −1 N, 2) N1 -220 kg ha −1 N, and 3) N2 -290 kg ha −1 N. Maize (Zea mays L.) grain yield was higher when N was applied at the N1 and N2 application levels each year. Obviously, the grain yield and its components at the N1 and N2 application levels showed no difference at each PD, and vice versa. Plant densities and N fertilisation rates significantly affected the content of SOC, microbial biomass C (MBC), and dissolved organic C (DOC). Ranged from 1.85 to 1.98 mg d g −1 , the sucrase activity was larger in the treatment with a high PD and N fertilisation rate. Higher PD yielded the increase of grain yield (GY) by 19.38%, while the kernel number per ear (KN) and the 1,000-kernel weight (TKW) were decreased by 7.81% and 9.03%, respectively. In addition, the grain yield and yield components were dramatically increased at the N2 application level. The SOC content and its fractions and the sucrase activity were also increased with the PD and N fertilisation rate. These results indicated that the optimum PD and N fertilisation rates were benefits for increasing the grain yield and soil C storage. Considering both soil parameters and grain yield, the PD of 75,000 plants ha −1 and the N fertilisation rate of 220 kg ha −1 N were benefits for crop production and soil sustainability.