Abstract:

Field experiments were used to study the effects of green manure rape returning stages and different nitrogen application rates on yield of spring maize and soil nutrients,in order to provide a theoretical basis for higher using efficiency on less application of nitrogen on spring maize in Northern China Plains. The experiment adopted a split plot design. The stages of returning in the main plots were winter fallow field without returning (G0),initial flowering (G1),full blooming (G2),and pod (G3). The nitrogen application rates of split plots were as follows: 0(N0),135(N135),270(N270),405(N405) and 540 kg/ha (N540).During the maize harvest stage,the five-point sampling method was used to measure soil samples to determine the soil nutrients' contents of each plot,and the maize yields with constituent factors.The results showed that compared with G0 treatment,G2 treatment significantly increased the yield by 5.89%,while the G1 treatment significantly increased the yield by 6.37% in 2020,of which the increases of grain number per ear were 5.59% and 8.37%,respectively,but there were no significant effect on hundred-grain weight;the yield of G3 treatment reduced 8.43% due to decreases of the average 2.62% of grain number per ear and 6.40% of the average hundred-grain weight in 2020. The yield increased significantly with the increase of nitrogen application rates. Under the G1,G2 and G3 treatments, the yields of spring maize reached the hightest when nitrogen application rates were N405,N270 and N405 which were 10 961.21,11 253.34 and 10 331.12 kg/ha, respectively.The yields were higher than others with nitrogen application rates of N405 and N270 for 10 961.21,11 253.35 kg/a,respectively. Model analysis showed that the G1 and G2 treatments could ensure the yield was stable above 10 000 kg/ha,while the nitrogen fertilizer application could be reduced by 7.89%—41.45%. In 2020,the G3 treatment could reduce the nitrogen by 10.53% and the yield by 6.27%. Compared with G0 treatment,G1 and G2 treatments significantly increased the average of soil organic matter and alkaline nitrogen content by 8.28%,4.12%,11.17%,and 12.77%,respectively. Soil total nitrogen contents in G1,G2 and G3 treatments increased significantly by 6.01%,5.86% and 8.00% in 2019. Rape returning significantly decreased the soil total phosphorus and available phosphorus contents. There were no significant differences of total potassium content among treatments,while soil available potassium contents of G1 and G2 treatments were higher than G0 treatment,and G3 treatment significantly decreased for 3.41% than G0 treatment in 2020. Each soil nutrients' contents increased firstly and then decreased with the increase nitrogen application rates,the value with N270 was the highest. In summary,returning green manure rape to the field from the initial flowering to the full flowering period can increase the soil organic matter,total nitrogen,alkali-hydrolyzable nitrogen and available potassium content. With the nitrogen fertilizer application reduced by 7.89%—41.45%,the yield can also stable above 10 000 kg/ha,which achieve the goal of stabilizing the production of spring maize and reducing nitrogen and increasing efficiency in the North China Plain.

Key words: Green manure, Returning stages, Nitrogen fertilizer application, Spring maize, Yield, Soil nutrient