Evaluation of methods of sowing and post emergence herbicides for efficient weed control in zero till sown rice fallow black gram Vigna mungo L

A field experiment was conducted at Agricultural College and Research Institute, Madurai to evaluate different methods of sowing and post-emergence herbicides for efficient weed control in zero till sown rice fallow black gram during Rabi season of two consecutive years 2004 and 2005. The experiment was laid out in split plot design replicated thrice. The main plot consisted of different methods of sowing viz broadcasting of seeds in the standing crop of rice with and without sand mix application of pendimethalin @ 1 kg ha⁻¹, dibbling the seeds immediately after harvest of rice with and without sand mix application of pendimethalin @ 1 kg ha⁻¹ and dibbling the seeds three days after pre-sowing application of paraquat @ 0.5 kg ha⁻¹. Different weed management practices like post-emergence application (PoE) of fenoxapropp-ethyl @ 75 g ha⁻¹, imazethapyr @ 100 g ha⁻¹ and cyhalofop butyl @ 100 g ha⁻¹, one manual weeding at 20 days after sowing (DAS) and unweeded check were assigned to sub-plots. All post-emergence herbicides were applied at 15 DAS. The dominant weed flora observed on sandy clay loam soils of rice fallow blackgram were Echinochloa colonum, E crusgalli, Panicum repens, Cyperus rotundus, Sphaeranthus indicus and Eclipta alba. Grasses were found to be dominant followed by broad leaved weeds and sedges. Among different methods of sowing, pre-sowing application of paraquat @ 0.5 kg ha⁻¹ followed by dibbling the seeds three days after application registered significantly lower values of weed density, weed dry matter production and higher values of weed control efficiency, crop growth parameters and yield of rice fallow blackgram. Among different weed management practices, post-emergence application of fenoxaprop-p-ethyl @ 75 g ha⁻¹ or cyhalofop butyl @ 100 g ha⁻¹ on 15 DAS significantly reduced the dominant grassy weed population and increased the growth and yield of rice fallow black gram. The interaction effect was also found to be significant. The best combination to manage the weeds effectively and efficiently and to exploit higher seed yield potential in zero till sown rice fallow black gram was dibbling the seeds three days after pre-sowing application of paraquat @ 0.5 kgha⁻¹ with post-emergence application of either fenoxaprop-p-ethyl @ 75 g ha⁻¹ or cyhalofop butyl @ 100 g ha⁻¹ on 15 DAS. However higher monetary returns were obtained in dibbling the seeds three days after pre-sowing application of paraquat followed by PoE application of fenaxoprop-p-ethyl @ 75 g ha⁻¹.