Crop establishment methods and weed management on productivity of cowpea [Vigna unguiculata (L.)Walp.]

Abstract

owpea is an important pulse crop grown throughout India and Kerala as a grain and vegetable crop. Weeds possess severe problem in the early growth stages of cowpea due to wider spacing and low initial growth and resulted in yield reduction. Hence the crop requires to be kept weed free particularly during the initial 6-8 weeks, ie the critical period of competition. The present study was carried out with the objective to enhance the productivity of cowpea grown under different crop establishment methods by adopting proper weed management measures. Field experiment was conducted from October to December 2020 at the Department of Agronomy, College of Agriculture, Vellanikkara. The experiment was laid out with factorial RBD with two factors replicated thrice. Factor A with two methods of establishments such as broadcasting and line sowing. Factor B with six weed management practices such as hand weeding @ 20 and 40 DAS , imazethapyr + imazamox, 40 g/ha @ 15-20 DAS , imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS, imazethapyr, 40 g/ha @ 15- 20 DAS, imazethapyr, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS and unweeded control. Cowpea variety PGCP-6 was used as test crop. Results revealed that methods of crop establishment had significant effect on weed density, growth parameters and yield attributes of cowpea. Line sowing resulted in 39% and 31% reduction in weed count and weed dry weight. Weed control efficiency and yield was 14% and 3% higher compared to broadcasting. The lowest weed count, weed dry weight and higher weed control efficiency was recorded in hand weeding at 20 and 40 DAS. The lowest weed index was observed in imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS Application of imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding at 40 DAS resulted in taller plants. At 30 DAS higher LAI was noted in imazethapyr, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS. Imazethapyr, 40 g/ha @15- 20 DAS recorded higher LAI at 40 DAS.The highest dry matter production was recorded in imazethapyr, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS. Application of imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding imazethapyr, 40 g/h registered significantly higher number of pods per plant and pod weight. Number of seeds per pod and 100 grain weight was higher in imazethapyr, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS. The highest yield was recorded from plots where two hand weeding were conducted (937.67 kg/ha), followed by imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding (877.30 kg/ha). Line sown cowpea received two hand weeding recorded higher yield (923.67 kg/ha) compared to other treatment combinations. Adoption of weed management practices resulted in 70 % higher yield in cowpea. Nitrogen uptake by crop was higher in imazethapyr 40 g/ha @ 15- 20 DAS fb hand weeding @ 40 DAS, which was on par with hand weeding twice. Broadcasted plot, where two hand weeding were conducted recorded higher N uptake by crop. Higher P uptake was noticed in hand weeding @ 20 and 40 DAS. Higher soil N availability was observed in imazethapyr + imazamox 40 g/ha @ 15- 20 DAS and P availability was higher in imazethapyr + imazamox, 40 g/ha @ 15- 20 DAS fb hand weeding @ 40 DAS. Among crop establishment methods higher net return and B:C ratio was observed in broadcast sowing compared with line sown cowpea. The highest net return (Rs. 102861) and B:C ratio (2.45) was registered in imazethapyr + imazamox @ 40 g/ha @ 15- 20 DAS fb hand weeding @ 40 DAS. Results of the study indicated that application of imazethapyr + imazamox, 40 g/ha @ 15- 20 DAS fb hand weeding @ 40 DAS can be recommended as a cost effective weed management practice for broadcasted and line sown cowpea.