Interspecies Interactions Dynamics between Soybean and Corn as Affected by Different Soybean Varieties
Competitive pressure dynamics depends on choice of corn plant density and soybean varieties that provide a more realistic result for soybean productivity per unit area. A two – year study was carried out at Giza Agricultural Experiments and Research Station, Agricultural Research Center during the two summer seasons 2016 and 2017 to evaluate competitive pressure between soybean varieties and corn under three intercropping systems. The treatments were three intercropping systems (50% corn: 50% soybean, 33% corn: 67% soybean and 100% corn + 50% soybean) and three soybean varieties (Giza 22, Giza 35 and Crawford) in addition to sole plantings of both crops. Intercropping systems were randomly assigned to the main plots and soybean varieties were allocated to sub-plots. The results indicated that 100% corn + 50% soybean had lower corn grain yield per plant and higher corn grain yield per hectare than 50% corn : 50% soybean or 33% corn : 67% soybean. Corn grain yields per plant and per hectare were not significantly affected by soybean varieties or the interaction between soybean varieties and intercropping systems. Higher soybean seed yields per plant and per hectare were achieved by decreasing number of corn plants from 47600 to 15708 plants per hectare. Soybean variety Giza 22 recorded higher seed yields per plant and per hectare than soybean variety Giza 35 or Crawford. Growing soybean variety Giza 22 with decreasing corn plant density from 100 to 33% of sole corn planting gave the highest seed yields per plant and per hectare compared with the other treatments. Growing soybean variety Giza 22 with increasing corn plant density from 33 to 100% of sole corn planting recorded high land equivalent ratio (LER) and land equivalent coefficient (LEC), meanwhile high system productivity index (SPI) was obtained by growing soybean variety Crawford or Giza 35 with corn in intercropping system 33% corn: 67% soybean. Growing two rows of soybean variety Giza 22 in middle of corn beds (140 cm width) had desirable soybean productivity, LER and LEC through reducing interspecies interactions.