Effects Of Optimized Fertilization On NPK Uptake And Distribution Of Soybean

A field experiment with the densities of 28×104 and 33×104 plants·hm-2 using two varieties (Kejiao and Kefu)was conducted to study the effects of optimized fertilization based on slow-released urea on NPK accumulation and distribution as well as the yield of soybean.Optimized fertilization improved N supply during late growth stages and increased N content in all organs of soybean. It also promoted N accumulation in soybean plants after R4, especially during the period of R4 to R6. Similar tendencies were observed between two varieties. N accumulation of optimized fertilization during R4 to R6 was higher than that of FFP( Farmer's Fertilization Practice )by 41% (p<0.01). Optimized fertilization could put off the senility of soybean leaves, maintaining N contents in leaves up to 3.70%-4.49% at pod filling stage. N content in leaves of optimized fertilization was 10.52% higher than that of FFP under high density in Kejiao, but there's no significant difference among the treatments of Kefu.Optimized fertilization increased P content in leaves and seeds of soybean during late stages, and promoted P accumulation in leaves and pods after R4. P accumulation in soybean plants was also increased during the period of R4 to R6. P accumulation of optimized fertilization during R4 to R6 was higher than that of FFP by 26%-31% (p<0.05) under high density. P accumulation of optimized fertilization was 9.97% higher (p<0.05) than that of FFP in Kefu at R6. There's no significant difference among the treatments of Kejiao.Optimized fertilization increased K content in all organs of soybean at different stages and promoted K accumulation in soybean plants after R2, especially during the period of R2 to R4. K accumulation of optimized fertilization during R2 to R4 was higher than that of FFP by 13.74% (p<0.05) under high density in Kejiao. There's no significant difference among treatments of Kefu. K accumulation in stems was increased in optimized fertilization, the value was 33%-46% higher (p<0.01) compared to FFP under high density at R6. K accumulation of soybean plant in optimized fertilization was 22% higher (p<0.01) than that in FFP at R6.Optimized fertilization increased soybean yield by 1.23%-15.46% under low density and 5.29%-10.54% under high density, respectively. Yield of Kefu was higher than that of Kejiao by 6.10% on average. A positive correlation was observed between NPK accumulation during the period of R2 to R6 and soybean yield. Optimized fertilization increased N supply at later stages and extended functional period of leaves, resulted in a high photosynthetic capacity at R6, and ensured soybean plants a high capacity of NPK absorption and accumulation. Optimized fertilization could promote redistribution of nutrients and assign nutrients to soybean seeds effectively, leading to the increase of soybean yield.