Impact of Weed Management Practices on the Weed Dynamics, Nutrient Uptake Pattern of Weeds and Direct Seeded Rice

Abstract

Herbicide based weed management is the emerging and effective method for controlling the weed flora of direct seeded rice. Weed growth often has an impact on crop development by interfering with plant nutrients. A two-year weed experiment with twelve treatments was set up at the University of Agricultural Sciences in Bangalore, Karnataka, India to know the effect of weed management practices on weed and nutrient dynamics in direct seeded rice. Significantly lower total weed density and biomass was observed with bispyribac sodium 10 SC 40 g a.i. ha-1 as post emergence which recorded statistically at par values with bensulfuron methyl + pretilachlor 6.6 GR 660 g a.i. ha-1 as pre-emergence during both the years of study. The allelochemicals used in the study performed well over unweeded control but it was far less when compared with chemical herbicides. Nutrient uptake by the direct seeded rice (82.17, 31.76 and 68.83 kg ha-1 NPK in 2020 and 89.38, 38.84 and 75.62 ha-1 NPK in 2021, respectively) and grain yield (4.98 t ha-1 in 2020 and 4.99 t ha-1 in 2021, respectively) was also reported to be higher with bispyribac sodium 10 SC 40 g a.i. ha-1 as post emergence which was on par with bensulfuron methyl + pretilachlor 6.6 GR 660 g a.i. ha-1 as pre-emergence. As the nutrient uptake by the crop and weeds are negatively correlated, the same treatments have recorded lower nutrient removal by the weeds. Higher weed biomass and rapid nutrient removal by weeds had resulted in poor soil nutritional status in unweeded control compared to all other treatments. Application of bispyribac sodium 10 SC 40 g a.i. ha-1 as post emergence or bensulfuron methyl + pretilachlor 6.6 GR 660 g a.i. ha-1 as pre-emergence  were considered to be best management practices for weed management under direct seeded  rice.