Effects of N and Mg Application on Population Quality and C and N Metabolisms of Soybean
|School||Northeast Agricultural University|
|Keywords||Soybean Mg Population quality C and N metabolism|
A pot experiment was conducted to study the effects of N and Mg application on population quality, carbon and nitrogen metabolisms, yield and quality of soybean. The treatments were N 30 kg/ha,N 60 kg/ha,N 30 kg/ha+Mg 15 kg/ha,N 30 kg/ha+ Mg3 0 kg/ha,N 60 kg/ha+ Mg 15 kg/ha and N 60 kg/ha+Mg 30 kg/ha. The SPAD value and LAI of soybean leaves, root nodule dry weight, starch and soluble sugar contents in soybean leaves, stems and pods, accumulation of nitrogen in leaves, stems and pods, as well as ureide content were investigated.1. Application of Mg improved soybean population quality, highthened SPAD, LAI, specific leaf weights,raised the grain-leaf ratio, increased unit-leaf-area load. It was good for photosynthesis product transportation and distribution to soybean grain. Compared with the N30 treatment, exfoliated pods of N30+Mg15 and N30+Mg30 reduced by 6 and 9 percentage points. Compared with the N60 treatment, exfoliated pods of N60+Mg15 and N60+Mg30 reduced 20 and 18 percentage points.2. Application of Mg increased N uptake and assimilation of soybean. Compared with N60, the N accumulation of pods in N60 + Mg15 and N60 + Mg30 increased by 22.25% and 24.47% at R5 stage. Root nodule dry weight for N60 was lower than N30 at vegetative growth stages, and both N30 and N60 were higher than other treatments. But application of Mg could increase the root nodule dry weight at R4 and R5 period. Compared with N60, root nodule dry weight of N60 + Mg30 increased by 25.65% and 23.96% reapectively.3. Compared with the N30, soluble sugar and starch contents of N30 + Mg15 and N30 + Mg30 increased and carbon metabolism increased, N60+Mg15 and N60+Mg30 slowed down the inhibition of the high nitrogen to carbon metabolism of soybean. Compared with N60, soluble sugar and starch increased significantly, particularly at R5 stage for the high-yield and high-quality material basis. Soybean starch content increased after application of Mg. It’s good for plant growth in earlier stage, good for flowering and pod development in medium-stage and good for providing more nutrients for grain-filling in later stage. Besides, it’s also provided adequate carbohydrates for roots and delayed the aging of roots.4. Compared with N30, grains per pod, seed weight, 100-seed weight and yield of N30 + Mg15 and N30 + Mg30 increased, but the effect was not significant; grains weight, 100-seed weight and yield of N60 + Mg15 raised by 8.57%, 3.96% and 16.28%, significant at 5% level; pods per plant, grain weight and yield of Mg30 + N60 raised by21.15%, 22.74 and 20.66%, significancant at 5% level. Application of Mg can also increase the fat content of soybean. Compared with the N60, fat contents of N60+Mg15 and N60+Mg30 increased by 1.33% and 1.15 % respectively. Application of Mg has little effect on soybean protein content.