Competition for nutrients between weeds and black rice as influenced by date of rice transplanting and weed management treatments in system of rice intensification (SRI)

Heavy weed infestation is a major problem in System of Rice Intensification cultivation method of rice (SRI) due to wider spacing and lack of flooding in the field. Yield losses due to weed infestation amounts to 25-47%. Thus, a field experiment was conducted to study the competition for nutrients between weeds and black rice (Oryza sativa L.) as influenced by the date of transplanting and integrated weed management in SRI. The experiment was conducted in the experimental farm of SAS, Nagaland University during Kharif season 2019 and 2020. A split plot design was used with three dates of rice transplanting in main plots and five methods of weed management in sub plots. The transplanted black rice with pre-emergence application (PE) of pretilachlor 0.75 kg/ha at 3 days after transplanting (DAT) followed by (fb) handweeding at 40 DAT recorded maximum decrease in weeds biomass and nutrient depletion by weeds with significant increase in the weed control efficiency, nutrient uptake and yield of black rice.