Study On The Effect Of Nitrogen Application And Exogenous Regulating Substance On Summmer Soybean

With the variety of Nannong 88-31 (S1) and Caidou-5 (S2) as the material, experiment was carried out to study the effect of nitrogen application (N1, N2, N3) and exogenous regulating substance (C1, C2) on yield and quality of summer soybean in field of Jiangpu Experiment Station of Nanjing Agriculture University in 2002, an attempt was mad to evaluate and recommend the optimum nitrogen application and exogenous regulating substance, at the same time, the physiological basis of yield and quality was first evaluated. The pot experiment was carried out to further clear the physiological and biochemical basis of yield and quality under treatments of different nitrogen application and exogenous regulating substance, at greenhouse of Nanjing Agricultural University in 2003. The results were as follows:At the cooperative application of N2 and C2, the seed yield of soybean was highest, N3 and C2 was secondly, then N1 and C1 was the lowest, and treatments of N2S1C2, N2S2C2, N3S1C2 and N2S1C1, seed yield were all high than 3000 kghm-2. In yield of main stem seed, branch seed and the total, the treatment of N2C2 was the highest than all the others. In three nitrogen applications, the main stem seed yield percentage of S1 showed as N1>N2>N3, however, the S2 showed as N2>N1>N3. In all cooperative applications of nitrogen application and exogenous regulating substance, the treatment of N2C2 was the most suitable to promote number of pods per plant, number of seeds per pod and 100-seed weight, mean while the analysis of variance showed that the differences were very significant, not only between the nitrogen applications but also between the exogenous regulating substances, and the result showed as N2>N3>N1, C2>C1. In the same nitrogen application, the exogenous regulating substance C2 can promote the 100-seed weight of the upper stem, number of pods, number of seeds per pod and 100-seed weight of the middle stem, 100-seed weight of the middle branch seed, number of pods, number of seeds per pod and 100-seed weight of the lower branch.In the same nitrogen application, the protein content of seed under the treatment of C2 was higher than C1, but oil content was lower than C1, and in the same exogenous regulating substance application, the protein content under the tretment of N2 was the highest, hower,the oil content showed as different between the variety of S1 and S2, the conten under treatment of N2C1 and N1C2 to the variety of S1 or under the treatment of N1 to the variety of S2 was high than all the other treatments. The content of mineral elements in seed was apparently higher than all the other treatments, at the same time the raise extent of the content of P and K in branch seed were larger than that in main stem seed.It was under the treatment of N2C2 that was most helpful to accumulate the dry matter from source to sink. In all treatments of exogenous regulating substance, intensity of dry matter accumulation in reproductive organ under the C2 was larger than C|, and in all nitrogen applications, N2 was the largest. Under the cooperative application of N2C2, not only with the largest net photosynthesis rate (Pn), net assimilation rate (NAR) and leaf area index (LAI) during reproductive growth peiod, but maintaining the longest leaf area duration(LAl=4). At the same time, the photosynthetic pigment (Chla, Chlb, Chl(a+b), Car) content in functional leaves increasing rapidly in early growth stage, showing stability in middle period and declinging slowly in later stage. Compared with all the other cooperative application, the treatment of N2C2 was more useful to adjust not only root main characters: inrease the activity and bleeding intensity of root, but the weight and number of root nodules. The activities of nitrate reductase (NRA) and Superoxide dismutase(SOD) were the highest after flowering under the treatment of N2C2, so the utilization efficiency of nitrogen element was increased and the plant senescence was retarded.