Growth, nutrient uptake and yield ofdirect seeded rice as influenced by weed management practices

A field experiment was conducted during the rainy (Kharif) seasons of 2018 and 2019 at the Kerala Agricultural University, Kerala, to evaluate the effect of herbicides and herbicide combinations on the weed management and growth, nutrient uptake and yield of direct seeded rice (DSR). The experiment was laid out in a randomized block design with three replications. Nine weed control treatments were used, including sole application of three herbicides (cyhalofop butyl @ 80 g/ha, bispyribac sodium @ 25 g/ha, fenoxaprop-p-ethyl@ 60 g/ha), five herbicidal combinations (penoxsulam + cyhalofop butyl commercial formulation @ 150 g/ha, cyhalofop butyl @ 80 g/ha + carfentrazone ethyl @ 200 g/ha, bispyribac sodium @ 25 g/ha + cyhalofop butyl @ 80 g/ha, bispyribac sodium @ 25 g/ha + fenoxaprop-p-ethyl @ 60 g/ha and stale seedbed followed by (fb) glyphosate @ 800 g/ha + oxyfluorfen @ 150 g/ha at 15-20 days after land preparation + cyhalofop butyl @ 80 g/ha + carfentrazone ethyl @ 200 g/ha), and hand weeding twice at 20 and 40 days after sowing. Weeds removed 27.72, 4.61 and 67.95 kg of N, P and K/ha respectively at 45 days after treatment application (DATA) under unweeded conditions in direct seeded rice. Herbicidal treatments enhanced grain yield by 23.89 to 58.84 % and herbicide combinations increased grain yield by 56 to 59 % compared to the unweeded control in direct seeded rice. Tank mix combination of bispyribac sodium @ 25 g/ha + fenoxaprop-p-ethyl @ 60 g/ha and bispyribac sodium @ 25 g/ha + cyhalofop butyl @ 80 g/ha and premix combination of penoxsulam + cyhalofop butyl @ 150 g/ha recorded higher nutrient uptake and grain yields (5.03, 4.76 and 4.79 t/ha, respectively) and were on par to hand weeding twice. Unweeded control recorded the lowest pooled grain yield (2.07 t/ha) and uncontrolled weed competition resulted in 59.95 % reduction in grain yield. Keywords: Crop competition, Herbicide combinations, Herbicide interactions, Nutrient removal, Nutrient uptake, Yield reduction