Frequency of cultivation and pendimethalin application as weed control on soybean monoculture and intercropped with corn (Zea mays L.).

Two separate field experiments were conducted simultaneously using PSB-SY-2 soybean variety and IPB Var 2 corn, one on monoculture and the other intercropped with corn which employed the interrow cultivation and pendimethalin herbicide as weed control. The general objective of the study was to develop a good weed control approach in soybean monoculture and intercropped with corn. Results of the study revealed that in both cropping practices, three times cultivation at 14, 21 and 28 DAE exhibited the highest grain yield of 1,441.83 kg/ha for monoculture and 920.24 kg/ha for intercropped with corn, respectively. Application of pendimethalin-herbicide, at the rate of 1.3 kg ai/ha gave the highest yield followed by 1.0 kg ai/ha for soybean monoculture with an average grain yield of 1,669.43 and 1,538.43 kg/ha, respectively. The control plots significantly showed the lowest grain yield of 922.85 kg/ha. For soybean culture intercropped with corn, pendimethalin application at the rate of 1.3 kg ai/ha had the highest grain yield of 1,085.15 kg/ha which was significantly higher compared to 0.7 kg ai/ha and the control. The study failed to show any significant difference in the yields of corn used as soybean intercrop. However, statistical analysis revealed a significant difference in the weight of 100 kernels and shelling percentage. Cost and return analysis on soybean monoculture under various methods of weed control showed that the highest net return of P9,489.2 per ha was obtained from treatment combination of three-time cultivation and pendimethalin herbicide application at the rate of 1.3 kg ai/ha. For soybean intercropped with corn the highest net return per hectare was P10,606.81 as obtained from the two-time cultivation treatment applied with pendimethalin herbicide at the rate of 1.3 kg ai/ha. More return on investment per peso was observed on soybean intercropped with corn when compared to the monoculture soybean. Comparing soybean monoculture and soybean intercropped with corn, the latter gave a higher return per peso invested of one peso and forty-five centavos (P1.45).