The effects of the different sowing methods and planting density on the yield components of soybean (Glycine max) under intercropping condition with rhodes grass (Chloris gayana Kunth.)

Abstract

In Japan, grass-legume intercropping systems are being developed to increase quality and yield of grain and forage. Hence, this study evaluated the effects of sowing methods and planting density on yield traits of forage soybean under intercropping condition with rhodes grass. The field experiment was laid on in a completely randomized block design with four treatments and four replications. Rhodes grass seeds were sown at 2.8 kg/10a in a field containing mono- and intercropping-plots. For soybeans, two levels of sowing densities (about 15 or 30 seeds/m2: named “L” and “H”) and two sowing methods (row or spray: named “R” and “S”) were applied for a total of four different intercropping combinations. Rhodes grass DMY obtained the highest in low level of sowing density with rowing methods (LR) (338 kg/10a) while soybean DMY obtained the highest in high level of sowing density with rowing methods (HR) (251 kg/10a) and in high level of sowing density with spray methods (HS) (177 kg/10a). Intercropping at low density increased CP (12%) and CPY (40.4 kg DM/10a) in Rhodes grass, and CP (18.9%) in soybeans, whereas high sowing density increased soybean CPY in HR (41.5 kg DM/10a) and contributed to higher soybean CPY in DM percentage at 66% (HS) and 56% (HR). Overall, high density sowing increased the 1st total DMY while row sowing increased the 1st total CPY in both crops at the first cutting, while monocropping increased Rhodes grass yield and plant length at the second-cutting. Also, sowing soybean by a broadcast spreader could obtain sufficient crude protein yield as a forage soybean in southern Kyushu, Japan. Further studies are needed for soybean overseeding method and use of early-maturity soybean lines