Weed dynamics, nutrient uptake and yield in Indian mustard (Brassica juncea)-weed ecosystem as influenced by nitrogen levels, planting geometry and herbicides

A field experiment was conducted at Jabalpur, Madhya Pradesh, during the winter seasons of 1996-97 and 1997-98, to find out the effect of nitrogen, planting geometry and herbicides on weed dynamics, yield and nutrient uptake in Indian mustard [Brassica juneea (L.) Czernj. & Cosson]. Treatments comprised combinations of 4 N levels (0,40,80 and 120 kg/ha) and 2 planting geometry (uni-and bi-direction) in main plots, 2 herbicides, viz. Isoproturon 1.0 kg and Oxadiazon 0.75 kg/ha, as pre-emergence were compared with hand-weeding 30 days after sowing and weedy check in subplots. Weed population declined, whereas weed dry matter increased with advancement in age of the crop. Increasing levels of nitrogen and change in planting geometry did not influence the weed population, whereas weed dry matter at harvest declined significantly at 120 kg N/hg compared with no nitrogen application. Seed yield and nutrient uptake also increased significantly at 120 kg N/ha. Both the herbicides significantly increased the nutrient uptake by checking the weed growth compared to weedy check. Isoproturon being at par to oxadiazon resulted in the highest seed yield. Application of 120 kg N/hg and Isoproturon gave the highest net return and benefit : cost ratio.