The Effects Of Optimized Fertilization On Population Quality And Yield Of Soybean

A field experiment with 8 treatments was set to study the effects of optimized fertilization on population quality and yield of soybean. The rates of N, P and K in optimized fertilization treatments (OF) were determined based on nutrient contents in soil, and slow-released urea was used as N fertilizer. FFP treatments were carried out with the same rate of N ,using common urea as N fertilizer, a higher amount of P and no K was applied. Leaf area, dry matter of leaves, stem and pods of soybean were determined, and LAI, SLW and NAR were caculated as well.LAI in FFP was higher than that in OF at R2. LAI of middle and whole canopy reaches its peak at R4 while the upper canopy LAI reaches its peak at R6. LAI of different parts and whole canopy shows no significant difference in all treatments at R4. At R6, whole canopy and upper LAI in OF of Kejiao under two densities was significantly higher than that of FFP (p<0.05) as well as Kefu under high density (p<0.05). LAI of middle canopy of Kefu in OF under low density was significantly higher than that of FFP (p<0.05) at R6. LAI of upper and middle canopy in OF and FFP of Kefu showed no significant difference at R6.SLW of whole canopy at R4 and that of upper canopy at R4 and R6 of Kejiao was increased in OF, and there's a significant positive relation between upper canopy SLW of R6 and soybean yield, which indicates the importance of a higher upper canopy SLW at R6 in the increasing of yield. NAR of whole canopy during R2-R4 and R4-R6 was higher in OF compared to FFP (p<0.05).Dry matter accumulation during R2-R4 was higher in OF, as well as dry mass of upper and whole canopy at R6 and whole canopy at R8. There's a significant positive relation between whole canopy dry matter accumulation at R6 and R8 and soybean yield. Dry matter accumulation in leaves at R4 and R6 were also increased in OF, which ensured a better photosynthetic capacity for leaves at pod filling stage and extended the functional period of leaves. OF increased dry matter accumulation of soybean stems in podding and pod filling stages as well, which is important in improve the lodging resistance of soybean. Dry matter accumulation of pods of upper and whole canopy at R6 was increased as well.Soybean yield under high density was significantly improved in OF compared to FFP (p<0.05). Yield difference was significant (p<0.05) under low density in Kefu, meanwhile the yield difference was not significant in Kejiao. The results also showed that upper canopy plays a more important role than middle canopy in their contribution to soybean yield.