Effect of nitrogen levels and weed management practices on pigeonpea (Cajanus cajan) and rice (Oryza sativa) intercropping system under ridge-furrow planting system.

A field experiment was conducted during 2004-05 and 2005-06 at Varanasi to find out the effect of nitrogen levels (0 and 25 kg N/ha for pigeonpea and 50,75 and 100 kg N/ha for rice) and weed management practices(weedy check, pendimethalin @ 1.0 kg/ha, pendimethalin @ 1.0 kg/ha+1 hand weeding at 45 days after sowing and 2 hand weedings at 15 and 45 days after sowing) on growth, yield attributes and yield of pigeonpea [Cajanus cajan (L.) Millsp.] and rice (Oryza sativa L.), pigeonpea grain equivalent yield, nitrogen uptake by cropping system, weed numbers, weed dry matter and nitrogen removal by weeds and net returns. Application of 25 kg N/ha to pigeonpea gave significantly higher value of growth and yield attributes and yields of both crops, pigeonpea grain equivalent yield, nitrogen uptake by cropping system, weed numbers, weed dry matter, weed control efficiency, nitrogen removal by weeds and net returns. Application of increasing levels of nitrogen from 50 to 100 kg/ha to rice did not show any significant effect on growth, yield attributes and yields of pigeonpea as well as pigeonpea grain equivalent yield, whereas growth, yield attributes and yields of rice significantly increased up to 75 kg N/ha. Weed numbers, weed dry matter, nitrogen removal by weeds increased with increasing N levels up to 100 N/ha in rice. Among weed management practices, 2 hand weedings at 15 and 45 days after sowing found at par with pendimethalin @ 1.0 kg/ha+1 hand weeding at 45 days after sowing in respect of growth, yield attributes and yield of pigeonpea. Significantly higher values of growth, yield attributes and yields of rice and pigeonpea grain equivalent yield were recorded with 2 hand weedings than other weed management practices. In respect to growth, yield attributes and yields of rice and pigeonpea grain equivalent yield; next weed management practice in order of superiority was pendimethalin @1.0 kg/ha+1 hand weeding at 45 days after sowing which gave significantly higher net returns among all weed management practices.