| A pot experiment, a plot experiment and a field experiment were conducted to study the effects of N management on population quality of soybean. The pot experiment at N 0, N 30 kg/hm2, N 60 kg/hm2 levels, and topdressing N 30 kg/hm2 at R1, R2, R3 and R4 stages under basic N 30 kg/hm2. The plot experiment at N 60 kg/hm2 level, at slow-release urea 0%, slow-release urea 25%, slow-release urea 50% and slow-release urea 75%. The field experiment at N 50 kg/hm2, N 60 kg/hm2, N 75 kg/hm2 levels, at half of slow-release in every level. LAI, light transmittance, dry weight of leaves, dry weight of stems, dry weight of pods were investigated, grain-leaf ratio, SLW, seed-stem ratio, exfoliated ratio of soybean pods, EPMS and TPMS of soybean stems were also measured.1. The result showed that LAI increased from N 0 to N 60 kg/hm2. Compared with topdressing N 0, topdressing N treatments at different stages enhanced LAI, at R6, compared with N 60 kg/hm2, the LAI of N30+R2 increased by 33.9% (P<0.01), compared with N30+R1, the LAI of N30+R2 increased by 11.6% (P<0.05), compared with N30+R3, the LAI of N30+R2 increased by 7.3%. The import effect on reducing fading of soybean leaves from increasing slow-release urea. The results showed that the significantly positive correlations between LAI and yield at R5 and R6. The light transmittance increased from increasing slow-release urea under R5, The light transmittance reduced from increasing slow-release urea behind R5.2. Compared with topdressing N 0, topdressing N treatments at different stages enhanced dry weight of soybean plant leaves and pods, topdressing N treatments at R2 and R4 had important effect. Increasing slow-release urea could enhance dry weight of soybean plant leaves and pods. EPMS and TPMS of soybean stems were enhanced by topdressing N 30 kg/hm2 and increasing slow-release urea.3. Grain-leaf ratio was an important index on the coordination of source-sink of soybean population quality. At R4 and R5, the grain-leaf ratio showed that N30+R2>N30+R4>N30+R3> N30+R1>N60>N30>N0, the grain-leaf ratio showed the opposite correlation at R6. At R4 and R5, the result of field experiment showed that optimize3> optimize 2> optimize 1, the grain-leaf ratio showed the opposite correlation at R6. The results showed that the significantly positive correlations between the grain-leaf ratio and yield at R4 and R5, the significantly negative correlations between the grain-leaf ratio and yield at R6.4. SLW increased from N 0 to N 60 kg/hm2. The leaves of topdressing N treatments and increasing slow-release urea were bigger and thicker than others, the SLW of topdressing N treatments and increasing slow-release urea were increased. The results showed that the positive correlations between the seed-stem ratio and yield at R4 and R5, but there were no correlations between the seed-stem ratio and LAI. Compared with topdressing N 60 kg/hm2, topdressing N treatments at R2 and R4 could reduced the exfoliated ratio of soybean pods by 54.23% (P<0.01) and 53.92% (P<0.01). The exfoliated ratio of field soybean pods showed that ptimize1> optimize 2> optimize 3, Compared with ptimize1, the optimize 3 reduced by 33.91% (P<0.01), Compared with ptimize2, the optimize 3 reduced by 13.06% (P<0.01).5. The yield increased as N application rate increased, the result showed that N60>N30>N0, but there was no significantly correlation on the yield increasing. Topdressing N treatments at different stages enhanced yield of soybean, compared with topdressing N 60 kg/hm2, topdressing N at R2 enhanced the yield by 11.84% (P<0.05). The yield of field experiment showed that ptimize3> optimize 2> optimize 1, compared with optimize 1, ptimize2 and optimize3 enhanced yield by 5.02% (P<0.05) and 7.68% (P<0.05). The yield of plot experiment showed that slow-release urea 75%>slow-release urea 50%>slow-release urea 25%>slow-release urea 0%. The yield increased as the slow-release urea increased. The results showed that the positive correlations between the dry weight of soybean leaves and yield at R4 and R5, the positive correlations between the dry weight of soybean pods and yield too.The results of pot and field experiments showed that the negative correlations between the oil and protein. Topdressing N at R2 and R4 enhanced significantly on protein. Compared with N 60 kg/hm2, topdressing N at R2 and R4 enhanced protein by 2.71% and 2.12%. The protein increased as the slow-release urea increased, compared with optimize 2 and optimize 1, the optimize 3 enhanced protein by 2.75% and 2.16%. |
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