Effect of integrated weed-management practices in direct-seeded autumn rice (Oryza sativa) on growth, yield and soil microflora

A study was carried out during the rainy (kharif) season of 2015 and 2016 at Assam Agricultural University, Jorhat, to evaluate the effect of 6 weed-management practices on growth, yield and soil microflora with 3 different direct-seeded upland rice (Oryza sativa L.) varieties. The percentage of grasses was higher, followed by broad leaf weeds in variety ‘Maizubiron’ followed by ‘Guni’ during the critical crop growth period. The lowest weed density as well as dry weight at 20, 40 and 60 days after sowing (DAS) was recorded in rice variety ‘Inglongkiri’ under integrated weed management of pretilachlor 1.5 kg/ha and mechanical weeding which resulted in higher weed-control efficiency (36.29 and 37.62%, respectively) at 20 DAS. The light transmission ratio was the lowest in ‘Inglongkiri’ followed by ‘Guni’. The fungal and bacterial populations were reduced at 25 days after herbicide application which gradually increased up to 50 days. Higher grain yield and harvest index among rice varieties were recorded in ‘Inglongkiri’ (1.98 t/ha and 43.09, respectively.) and application of pretilachlor 0.75 or 1.5 kg/ha combined with mechanical weeding 30 DAS resulted in the higher grain yield (1.95 t/ha) and harvest index (39.33%) over 2 years.