The Effects Of N Application On Plant Morphology, Flower And Pod Abscission And Yield Of Soybean In Monoculture And The Strip Intercropping System

Previous research and field observations indicate that the southwest region had less light and abundant rainfall, after soybean intercropping nitrogen fertilizer, resulting in vigorous leaf growth, flower and pod shedding serious, higher expulsion rates became prominent production problems,this restricted the improvement of intercropping soybean yield.Therefore, we must recognize the causal relationship between the abscission and yield about intercropping soybean, proved the general rule of intercropping soybean flower and pod abscission, explaining the causes of high abscission,search production technology under intercropping, such as controlling flourishing, reducing abscission and increasing production, to provide technical support for the South soybean production.Therefore, the author had a preliminary study on soybean flower and pod abscission and yield, about zero, reduced and conventional N application under the soybean monoculture and maize-soybean relay strip intercropping.Further study in NanDou 12, GongXuan 1 and NanXiaDou 25 three varieties, the influence of plant morphology and abscission under low N application, medium N application, high N application (N3). The main conclusions were as follows:1.Intercropping and reduced N application significantly reduced soybean flower and pod abscission rate. Compared with the SS, MS, the falling rate of pods,flower and the abscission were decreased respectively by 20.4%,28.1% and 17.3%, the total number of flower and pod abscission showed a trend of central> bottom> top.The falling flower rate of RN treatment, whole plant and top were significantly reduced in MS systems, the flower and pod abscission was lowest, respectively lower 10.8%,10.2% than the NN and CN.Compare with MSNN and MSCN, the pods per plant,biomass and yield of MSRN were significantly increased 33.0%,11.0%,33.0%,14.1% and 34.5%,11.9%.2. In the maize-soybean relay strip intercropping, combined with variety and nitrogen was benefitcal to building a legitimate form of soybean plants. With the increases of N application, height and stem diameter increment, stem bending force showed a decreasing trend, but a significant increasing on the number of branches and the first inter-node stem length.Compared with P2N2and P2N3,height ratio of P2N1 significantly reduced 6.1%, 5.3%, Stem of P3Nlwere 10.7% and 16.5% higher than P3N2 and P3N3. SPAD and LAI increased with N application, when R4 period, the LAI of P1N1and P2N2 were lower 25.5%,23.0%,28.9%,50.3% than other treatment.Before the R4 stage, leaves distribution rate was improvement of P1N1, stem distribution rate was reduced. After the R4 stage, dry matter allocated to a large number of pod, pod distribution rate of all varieties reduced with increasing N, pods allocation rate of P1N1 was the largest. With increased levels of applied N, C,N content in plants increased.In R4 stage,C/N of P1N1 was higher, the nutrient supply was sufficient.3.In the maize-soybean relay strip intercropping,variety and N application changed the number of flowering and abscission rate of soybean. Compared with PlandP3, the flower numbers of P2 was higher, respectively31.1% and 24%.The falling numbers of flower and pod in P1 were lowest, respectively 51.7% and 25.2% reduction compared with P2 and P3.The flower and pod abscission rate showed a trend of P1<P3<P2, three treatments all increased with increased N application amount, the lowest treatment P1N1 reduced 50.5% than the highest treatment P2N3. With increased N application,the number of pods per plant and yield declined in this experiment, compared with N2, N3, pods per plant of N1 was higher 9.6%,19.1%.Under the P1 and P3 treament, yield per plant of N1 were higher than N2, N3 treatments, respectively 20.5%,31.6% and 13.6%,19.1%.4.In the maize-soybean relay strip intercropping, there was a significant correlation between plant morphology and flower and pod abscission rate, also existed between abscission rate and yield and its components.Soybean flower and pod abscission rate and plant height, nodes per plant, number of branches, LAI showed a significant positive correlation, the correlation coefficient was 0.61,0.41,0.63 and 0.51.it was significantly negatively correlated with stem bending force, leaf length width ratio and SPAD, the correlation coefficient was -0.44,-0.52,-0.60.Soybean flower and pod abscission with yield per plant, pods per plant had highly significant negative correlation,The abscission rate was affected by the growth of plants, dry matter accumulation, carbon and nitrogen metabolism.