Field experiment was conducted during the summer of 1999 and 2000 at Kukumseri (2872 m above msl) on sandy loam soil to find out viable fertility level in relation to weed control in rajmash. All the herbicide treatments being statistically at par among themselves produced significantly lower weed number and dry matter, thus resulting in significantly higher seed yield of rajmash over weedy check. The minimum weed number and dry matter accumulation were recorded following the application of pendimethalin 0.9 kg+alachlor 0.75 kg ha−1 and resulted in weed control efficiency of 71.7% as compared to weedy check. This was followed by alachlor 1.5 kg ha−1 and pendimethalin 1.2 kg ha−1. The highest benefit: cost ratio was resulted following the application of alachlor at 1.50 kg ha−1. Weed population was not influenced by increase in fertility levels. Significantly highest weed biomass was recorded when crop was fertilized with 150% of recommended fertility level (40 kg N, 60 kg P2O5 and 30 kg K2O ha−1). Increase in fertility level did not bring significant increase in the yield attributes and grain yield. The benefit: cost ratio was highest (5.14) following 100% recommended dose.
