Herbigation in Okra (Abelmoschus esculentus (L.) Moench)

Abstract

Herbigation is the method of application of herbicides through irrigation water. Conventional method of herbicide application takes considerable time and expensive due to the increasing cost of manual labour. Also, heavy wind at the time of spraying and improper application causes more herbicide loss, environmental pollution and drift injury to the nearby fields especially on sensitive crops. Herbigation ensures no additional costs of application. Okra is one of the important vegetable crop of Kerala. Weed competition during early stage of crop growth significantly lowers crop yields. Heavy weed infestation in okra is mainly due to wider spacing, slower crop growth during early stages, high fertilizer use and frequent irrigation. Therefore, the present study was undertaken with a view to study the effect of herbigation through drip irrigation system in okra and also to evaluate the economic feasibility of the system. The experiment was conducted at Water Management Research Unit, Vellanikkara from December 2019 to April 2020. The experiment was laid out in RBD with ten treatments and three replications. Treatments comprised of herbigation and conventional spraying of oxyfluorfen applied in two doses (0.15 kg ha-1 & 0.20 kg ha-1) at two different time of application , a hand weeded control and an unweeded control. The okra variety used was Arka Anamika. Predominant grasses seen in the plots were Panicum maximum, Digitaria sanguinalis, Brachiaria miliformis, Digitaria bicornis and Axonopus compressus. Predominant broad leaved weeds were Ageratum conyzoides, Euphorbia hirta, Mollugo disticha, Cleome burmanii, Trianthema portulacastrum, Alternanthera bettzickiana, and Synedrella nodiflora. The sedges present were Cyperus spp., and Bulbostylis barbata in the experimental field. Observations on weed count showed that application of oxyfluorfen was effective in controlling both grass and broad leaved weeds. Maximum weed control efficiency was observed in conventional spraying with oxyfluorfen @ 0.20 kg ha-1 two days before sowing followed by hand weeding at 30 DAS with 91.31 per cent at 20 DAS; conventional spraying with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS with 90.08 per cent at 50 DAS and hand weeded control recorded 90.59 per cent at 80 DAS. Lowest weed index was recorded from herbigation with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS followed by the treatment conventional spraying with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS. Even though, conventional spraying recorded lesser weed count and weed dry weight, the yield was less due to the scorching of crop foliage. During herbigation, herbicide is applied through drip to the crop root zone, due to which weeds in the interspaces that can germinate in water stress conditions will grow. While in conventional spraying, the entire cropped area come in contact with herbicide and results in complete control of weeds. The nutrient removal by weeds was maximum in unweeded control. Herbigation with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS was on par with hand weeded control in terms of plant height, number of leaves and leaf area. It also recorded highest number of fruits per plant (17.8), average fruit weight (13.73 g), fruit yield per plant (243.90 g) and fruit yield (13.02 t ha-1). It was on par with hand weeded control (13.04 t ha-1), conventional spraying with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS and herbigation @ 0.20 kg ha-1 two days before sowing followed by hand weeding at 30 DAS. Weed competition resulted in 58.97 per cent yield reduction in okra. Unweeded control recorded significantly lower fruit yield (5.35 t ha-1). Both conventional spraying and herbigation with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS were equally effective in controlling weeds. Herbigation with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS resulted in higher gross return, net return and B: C ratio (1.97) which was closely followed by conventional spraying with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS (1.89). The result of the study revealed that the farmers can adopt either herbigation or conventional spraying of oxyfluorfen according to their convenience because both treatments performed equally well. Herbigation can be implemented in fields in which already fertigation is carried out because it doesn’t involve any additional costs.