Weed dynamics and yield of direct seeded upland autumn rice (Oryza sativa L.) varieties as influenced by integrated weed and nutrient management practices

A field experiment was conducted during autumn, 2014 at ICR Farm, Assam Agricultural University, Jorhat, Assam to compare three different direct seeded upland rice varieties along with different integrated weed and nutrient management practices. The experiment was carried out in factorial randomized block design replicated thrice with 15 treatments involving 3 varieties: Inglongkiri, Maizubiron and Rasi along with 5 treatments of weed and nutrient management, i.e. 20-10-10 kg/ha N-P₂ O₅-K₂ O + pretilachlor @ 750 g/ha followed by grubber 30 DAS (W1), 30-15-15 kg/ha N-P₂O₅-K₂ O + pretilachlor @ 750 g/ha followed by grubber 30 DAS (W2), 10-5-5 kg/ha N-P₂O₅-K₂ O + pretilachlor @ 750 g/ha followed by grubber 30 DAS + Vermicompost @ 1 t/ha (split equally at sowing & 30 DAS) + Sesbania (Sesbania aculeata) green mulch (up to 30 days) (W3), 10-5-5 kg/ha N-P₂O₅-K₂ O + pretilachlor @ 750 g/ha followed by grubber 30 DAS with intra-row spacing 15cm (W4), and 20-10-10 kg/ha N-P₂O₅-K₂ O + Weedy check (W5). The predominant weed floras observed in the experimental field were Ageratum conyzoides, Cynodon dactylon, Cyperus rotundus and Cyperus iria. Treatment W3 resulted significantly lowest weed population at all growth stages. Weed dry weight was significantly lowest with application of 30-15-15 kg/ha N-P₂O₅-K₂ O along with pretilachlor @ 750 g a.i./ha and grubber 30 DAS at 20, 60 DAS and at harvest of rice crop. The results revealed an increase in yields as evident by higher grain and straw yield for all the three varieties with pre-emergence application of pretilachlor (750g a.i./ha) + grubber 30 days after sowing + 30-15-15 kg/ha of N-P₂O₅-K₂ O.