Abstract:

To investigate the effects of different application rates of nitrogen fertilizer on soil characteristics of spring wheat and pea intercropping,spring wheat monoculture and pea monoculture.Three planting methods including intercropping of wheat and pea(SI),sole cropping of spring wheat(SS)and sole cropping of pea(PS)were set,and four nitrogen application levels 0(N0),90(N1),180(N2),270 kg/ha(N3)were set.At 85 days after sowing,the activities of five soil enzymes,including sucrase, β-glucosidase,urease,glutaminase and phosphatase,and the contents of five soil nutrients,including total nitrogen,alkali-hydrolyzed nitrogen,total phosphorus,available phosphorus and organic carbon were measured.The results showed soil sucrase activity was increased(65.51%,57.88%)by N application(N2,N3)in PS soil,and N2 level reached the maximum value.Under four nitrogen levels,the sucrase activity of SI planting pattern was significantly increased by 31.25%-94.07% compared with PS.N3 treatment significantly increased SS β-glucosidase activity(17.81%);soil urease activities in SS and SI were increased by N application,and reached the highest at N2 level,SI>SS>PS under the same fertilization;N2 significantly increased the glutaminase activities in SS,SI and PS soils(26.95%,67.05%,55.03%,respectively).Soil phosphatase of SS,SI and PS all reached the highest level in N2,and SI was significantly higher than SS and PS(increased by 128.35%,337.21%,respectively).Nitrogen application could increase soil alkali-hydrolyzed nitrogen,total phosphorus and available phosphorus contents,among which alkali-hydrolyzed nitrogen and available phosphorus reached the highest at N2 level;soil sucrase activity was very significantly correlated with the urease, phosphatase, and significantly correlated with the available phosphorus content. Soil urease activity was very significantly correlated with phosphatase activity and alkaline hydrolyzable nitrogen content, and was significantly correlated with total nitrogen and available phosphorus content. Soil phosphatase activity was very significantly correlated with total nitrogen, available phosphorus content, and significantly correlated with alkaline hydrolyzable nitrogen. The total nitrogen content of soil was very significantly correlated with alkaline hydrolyzable nitrogen.There was a significant interaction between nitrogen treatment and planting mode pattern on soil urease,glutaminase,phosphatase activities,soil total phosphorus,available phosphorus contents.In conclusion,180 kg/ha was the best nitrogen application rate,and intercropping was better than monoculture under the same nitrogen application rate.

Key words: Wheat, Peas, N application, Intercropping, Soil enzyme activity, Soil nutrients