Time of application of pre-emergence herbicides on phytotoxicity and weed control in semi-dry rice

Abstract

A field experiment entitled 'Time of application of pre-emergence herbicides on phytotoxicity and weed control in semi-dry rice' was conducted during first crop season (Virippu) of 1933 i.e., from May to September at Agricultural Research Station, Mannuthy under the Kerala Agricultural University, Vellanikkara, Thrissur. The objective of the trail was to find out the best time of application of pre-emergence herbicided on phytotoxicity and weed control in semi-dry rice. The experiment was laid out in split plot design with three replications. Treatments included in the trail were pre-emergence application of herbicides such as pendimethalin, thiobencarb, butachlor and oxyfluorfen at 0, 3, 6 and 9 days after sowing with handweeded and unweeded plots as the controls. The dominant weeds found in the experiment field were Digitaria sanguinalis and Cynodon dactylon among grasses, Cyperus rotundus and Cyperus iria among sedges and Cleome viscosa and Ageratum conyzoides among broadleaved weeds. The population of grasses was reduced by the application of oxyfluorfen at 6 DAS and pendimethalin upto 6 DAS. Hanweeding was significantly superior than the herbicides in lowering the number of sedges and broadleaved weeds. At 30 DAS the highest weed control efficiency was recorded by oxyfluorfen. Though phytotoxic symptoms were developed in rice seedling where oxyfluorfen was applied at 6 and 9 DAS, it later recovered by about two weeks. Pendimethalin and oxyfluorfen treated plots gave the highest number of tiller/m2. Chlorophyll content of leaves and dry matter production of rice were more in pendimethalin treated plots. Yield attributing characters and yield were higher in plots treated with pendimethalin at 3 DAS. Total returns and return per rupee invested were higher in the case of pendimethalin at 3 DAS and oxyfluorfen at 9 DAS.