| A pot experiment including5treatments was conducted to study the effects of N application timing on accumulation and distribution of soluble sugars and phosphorus, potassium in various parts of soybeans at different growth stages. The main results are as follows:Compared with N50treatment, the content of soluble sugar at R5stage with N15+35R3and N15+35R4treatments increased by24.5%and29.5%(P﹤0.01). Compared with N0+50R3and N0+50R4treatments, the differences level reached5%. Soluble sugar in stems rapidly transited into grains during R6-R8stage. Compared with N50treatment, content of soluble sugar in stems in N15+35R3and N15+35R4treatments increased by13.9%and17.6%(P﹤0.01) during R6stage. In R6-R8stages, compared with N50treatment, soluble sugar content in shells in N15+35R3and N15+35R4treatments were4.06%-7.68%higher than that in N15+35R4treatment (P﹤0.01).The output rate of soluble sugar in stems and shells in N15+35R4treatment were4.76and4.07percentage points higher than N50treatment. In R8stage, accumulation of soluble sugar of pods in N15+35R4and N15+35R3treatments were higher (P﹤0.05) than N50, N0+50R3and N0+50R4treatments and the N15+35R4treatment (P<0.01).Accumulation of P in leaves with N15+35R3and N15+35R4treatments was less (P﹤0.05) than the treatment of N50at R4stage. The treatment of N50made P descend quickly and accumulation of P showed14.9%-31.8%lower (p<0.05) than N15+35R3and N15+35R4treatments. Accumulation of P in pods mainly concentrated in R6-R8stages. Compared with other treatments, the treatments of N15+35R3and N15+35R4made it5.7%-21.3%higher. Especially, the treatment of N15+35R4was15.9%and21.3%higher than N50treatment in R6and R8stage, respectively.In later stages of soybean growth, the K contents and accumulation in leaves and pods were higher than those in other treatments. At R4stage, N50treatment K accumulation reached the highest level. Compared with N50, N0+50R3, N15+35R3, N15+35R4and N0+50R4treatments, N50showed significant(P<0.05) differences. At R5stage, N15+35R4treatment K accumulation in leaves reached the highest level. Compared with N0+50R3and N0+50R4treatments, N15+35R4showed significant (P﹤0.05) differences. At R6stage, K accumulation in leaves of N15+35R4was15.2%-25.0%higher (P﹤0.05) than other treatments. At R5stage, the treatments of N15+35R3and N15+35R4was16.9%and7.6%higher (P﹤0.05) than that with N50, respectively. At R6stage, stems K accumulation for N15+35R4treatment was higher (P﹤0.05) than other treatments. In R5stage, pods potassium accumulation with N15+35R3and N15+35R4treatments were13.0%-16.9%higher (P﹤0.05) than N50treatment. During R6-R8stages, the output rate of K in stems was more than74.6%and the rate was1.66-2.30percentagepoints higher (P﹤0.05) than other treatments. At R5stage, pods K accumulation with N15+35R3and N15+35R4treatments were13.0%and16.7%higher (P﹤0.05) than N50treatment. During R6-R8stages, pods K accumulation with N15+35R3and N15+35R4treatments were higher (P﹤0.05) than other treatments. At R8stage, pods K accumulation in N15+35R3and N15+35R4treatments were13.5%and17.1%higher (P﹤0.01) than that of N50treatment.Compared with other3treatments, N15+35R3and N15+35R4treatments improved soybean yield by6.8%-17.0%. During R6-R8, there was a positive relationship between yield and output rate of soluble sugar. In R6period, accumulation of P and K had a positive correlation with yield. The treatments of N15+35R3and N15+35R4could provide sufficient N for later growth, promote absorbtion of P and K, postpone leaf aging.In the period of grain filling, due to strong photosynthetic capacity of leaf, the efficient transportation of P, K and carbohydrate could distribute nutrients to grain of soybean effectively. Therefore, N15+35R3and N15+35R4treatments improved yield significantly, compared with N50treatment, the difference level reached1%. |
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