Branch Formation And Its Relationship With Yield Of Relay Strip Intercropping Soybean

Maize and soybean relay strip intercropping pattern makes full use of land resources, plays a prominent role in increasing the supply of soybean and farmers’ income and ensuring the food security, which show broad development prospects. However, low soybean yield become the key issues constraining the further development of this cropping pattern in large area production. In maize-soybean relay strip intercropping, the total yield gets down, while the branch yield proportion get rise and become the main part of the total yield. There is lack of research on the reason of the branch yield advantage above. Therefore, this research studied the branch formation, branch morphology, branch canopy physiology, branch biomass and the relationship between branch and yield of relay strip intercropping soybean. In depth understanding of branch and branch yield formation, confirming the reason of branch yield advantage and laying the foundation for high-yield of relay strip intercropping soybean with full use of branch yield advantage. The results are as follows:1. Photosynthetic active radiation of relay strip intercropping and sole cropping is significantly different. At reproductive stage, the transmittance of relay strip intercropping soybean is higher than the sole cropping soybean significantly with advantageous lighting. As the density increases, the transmittance decreased significantly. Transmittance within the soybean line between the middle and lower part show the same trend, but the middle part is higher than lower part significantly.2. Shading at seedling stage of relay strip intercropping soybean inhibits the branch formation, the emergence day is delayed for 9-12d. With the advancement of growth period, the lowest branch position of sole cropping soybean increased gradually, while the relay strip intercropping soybean keeps lower and relatively stable. The mutual shading of leaf canopy of sole cropping soybean is pretty severe, resulting in the withering and shedding of branch in the middle and lower part of main stem, which shows the phenomenon that the lowest branch position rising. While the branch of relay strip intercropping soybean grows normally because of its better light environment. With the advancement of growth period, the highest branch position increased gradually. The branch number of sole cropping soybean shows the tendency of increased firstly, and the decreased, while the relay strip intercropping soybean show the tendency of increased gradually and slowly. The branch number of sole cropping and relay strip intercropping soybean eventually converged. The branch formation process of relay strip intercropping soybean is more reasonable and effective.3. Seeding shading of relay strip intercropping affected the branch morphology adversely, but it can be compensated after the shade is lifted. At the R1 stage, the branch length, node number, stem diameter and leaf area of the relay strip intercropping soybean are significantly lower than the sole cropping soybean. But at the R1-R5 stage, due to the significant improvement of light environment, branch length, node number, stem diameter and leaf area achieved substantial growth, the branch length, node number, stem diameter and leaf area reached or exceeded the branch level of sole cropping soybean at R5 stage, making up for the adverse effects of the seedling shading and laying the foundation for the branch yield formation at later stages. The branch morphology is significantly different at various densities, the branch length, node number, stem diameter and leaf area decreased with the increasing of density.4. After the shade is lifted, the soybean branch leaf population of relay strip intercropping grows rapidly, which can reach or even exceed the level of sole cropping. With the advancement of growth period, the SPAD value of sole cropping soybean branch keeps relatively stable, while the SPAD value of relay strip intercropping soybean branch increased substantially. The branch SPAD value of relay strip intercropping soybean is significantly higher than that of the sole cropping soybean. The leaf area duration of sole cropping soybean is larger at the early stage, while the relay strip intercropping soybean increased substantially and it is higher than that of the sole cropping soybean at the late stages. The leaf area index of relay strip intercropping is significantly lower than that of the sole cropping soybean at the early stages, but it increased largely compared to the sole cropping. At R5 stage, the leaf area index of relay strip intercropping may reach or exceed the level of sole cropping. With the increasing of density, the branch SPAD value did not change significantly, while the branch leaf area duration decreased gradually and the leaf area index increased gradually of relay strip intercropping soybean.5. Shading at seedling stage of relay strip intercropping significantly decreased the biomass of stem, leaf and the total biomass at R1 stage. But after the shade is lifted, the branch biomass of relay strip intercropping soybean grows much stronger than that of sole cropping soybean. At reproductive stages, the soybean branch net assimilation rate and crop growth rate of relay strip intercropping are significantly higher than sole cropping. The branch biomass of A3 cultivar with strong branching ability can reach or exceed the level of sole cropping soybean at R5 stage. With the increasing of density, the biomass of branch decreased gradually, while the crop growth rata showed an increasing trend.6. Under relay strip intercropping conditions, the main stem yield decreased significantly, the branch yield ratio showed an increasing tendency, the branch yield affect the plant yield significantly. Soybean cultivar with strong branching ability produced much higher yield. The pod number, seed number and seeds weight of main stem were significantly decreased, the larger the density, the greater the decline; the pod number, seed number and seeds weight of branch were increased significantly under lower density, the larger the density, the greater the decline; the total number of pod, seed, yield per plant showed no significantly decline or rise under lower density, while they decreased under higher density; branch pod ratio, seed ratio, seed weight ratio showed an upward trend. The branch yield and plant yield is better under lower density, but the total yield is rather lower, indicating that high yield per plant under lower density is unable to make up the yield loss of smaller group number; under high density, the yield perform better, while yield per plant perform poor; medium density (100000plant/hm2) can take the plant yield and total yield into account at the same time and it is conductive to realize the high yield of relay strip intercropping soybean.In summary, maize-soybean relay strip intercropping inhibits the branch formation and affects the branch adversely, but the predominant light environment after maize is harvested is conducive to the growth of branch traits. Selecting soybean variety with strong branching ability is conducive to exert the yield improvement potential of branch, making up for the adverse effects of seedling shading. Meanwhile, it is better to construct a reasonable population density, making it not only be able to ensure adequate growth of branch traits and yield formation, but also to maintain a reasonable population of group, in order to achieve high yield of relay strip intercropping soybean.