Effect Of N Management On C And N Metoblisms And Yield Of Soybean

A pot experiment was conducted to study the effects of N management on C and N metabolisms,indexes of population quality and yield of soybean at N 0,N 30 kg/hm2 and N 60 kg/hm2 levels, and topdressing N 30 kg/hm2 at R1, R2, R3, R4 and R5 stages under basic N 30 kg/hm2.The N content,SPAD value,soluble sugar content and starch content in soybean leaves were analized, the uriede content in soybean stems and N content in soybean pods were also measured. The results showed that N content and accumulation in soybean leaves increased from N0 to N60 kg/hm2. Compared with N60, topdressing N treatments at different stages enhanced N content in soybean leaves. Compared with N60, the N content of N30+30R3 increased by 5.62% (P<0.05). The uriede content in soybean stems reduced as N application rate increased. Compared with N60, topdressing N at R3 stage increased the uriede content by 19.12%(P<0.01), the uriede accumulation in stems increased by 20.79% (P<0.05).The soluble sugar content in soybean leaves descreased as N application rate increased from V4 to R3 stages, but incraesed from R4 to R5 stages. Compared with N60, topdressing N at R3 stage significantly increased the soluble sugar content in soybean leaves by 5.57% at R5 stage. The starch content in soybean leaves increased as N application rate increased from R3 to R5 stages. Topdressing N at R2 and R4 stages increased the starch content in soybean leaves, compared with N60, both reached 5% significant level. The effect of N30+30R3 on the starch content in soybean leaves was the heighest among all the treatmentsC/N decreased as N application rate increased from V4 to R2 stages, but increased along with increasing N application rate after R2 stage. Compared with N60, N30+30R3 increased C/N by 7.19% at R4 stage. Topdressing N at different stages increased C/N at R4 and R5 stages. Compared with N60, C/N of N30+30R5 was higher than other treatments. The second was N30+30R3, compared with N60, C/N increased by 7.70%.The dry matter accumulation of soybean leaves and pods increased as N application rate increased. Compared with N60, N30+30R3 increased the dry weight by 13.84% at R4 stage. The dry weights of pods of topdressing N at different stages were higher than that of N60 at R8 stage. Compared with N60, topdressing N at R3 stage increased dry weight of pods by 7.78% (P<0.05).The LAI increased as N application rate increased from R2 to R5 stages. Topdressing N treatments at different stages improved LAI. N30 and N60 treatments had little effect on pod/ leaf ratio, and more pods fell at R8 stage. N30+30R3 had significant effect on pod/ leaf ratio, and fewer pods fell at R8 stage.The yield difference for different N application treatments was not significant.The yield of N30+30R3 was higherst among all treaments. Compared with N0, the yield increased by 10.4%( P<0.05) . The second was N30+30R5, compared with N0, the yield increased by 8. 7%( P<0.05) .