Optimizing the Application Time of Pre-emergence Herbicide Pendimethalin and Oxyfluorfen Application for Effective Weed Management in Irrigated Blackgram (Vigna mungo L.) and Its Residue Persistence

Time of pre-emergence herbicide application is an important factor that decides the efficiency of herbicide. If the pre-emergence herbicide is not applied at appropriate time, it may cause ineffective weed control or toxicity to crops. With this background, a field experiment was conducted at TNAU, Madurai to optimize the time of pre-emergence herbicides namely pendimethalin and oxyfluorfen application for effective weed management in irrigated blackgram.

The experiment was laid out in randomized block design with three replication. Treatments were application of pendimethalin at 0.75 kg ha^-1 and oxyfluorfen at 0.2 kg ha^-1 on 1, 2, 3, 4 days after sowing, weed free check and unweeded check.

Results of the study revealed that oxyfluorfen gave maximum weed control efficiency as compared to pendimethalin, but toxicity to the crop was observed when oxyfluorfen was sprayed after 2 days of sowing. Yield and economics were achieved higher with application of 0.75 kg ha^-1 of pendimethalin at 2 DAS, which was on par with application of 0.2 kg ha^-1 of oxyfluorfen at 1 DAS due to lesser toxicity. Application of 0.75 kg ha^-1 of pendimethalin and 0.2 kg ha^-1 of oxyfluorfen didn’t leave any herbicide residue after harvest. Hence, application of 0.75 kg ha^-1 of pendimethalin at 2 DAS and 0.2 kg ha^-1 of oxyfluorfen at 1 DAS can be recommended for effective weed management in irrigated balckgram.