Vivekananda Parvatiya Krishi, Anusandhan Sansthan (ICAR) Almora-263 601 (U. P.), India.
A field experiment aimed to study the direct and residual effect of different weed control measures in maize and wheat under sequential cropping was conducted on fixed plots during kharif 1993 to rabi 1995–96. A set of 16 weed control treatments comprising the combination of four treatments each in maize (atrazine, pendimethalin each at 1.25 kg/ha, repeated weeding and weedy check) and wheat (isoproturon and pendimethalin each at 1.0 kg/ha, repeated weeding and weedy check) was evaluated under maize-wheat crop sequence. Uninterrupted weed growth increased the composition of grassy weeds to total weed population from 54.5 to 75.2 and 82.1% in maize and from 29.5 to 32.4 and 39.3% in wheat during 1994 and 1995, respectively. In maize, repeated weeding for entire crop season during first year caused no infestation. of C. benghalensis and B. ramosa in subsequent years, while repeated weeding during first two years brought the population of E. colonum to nil third year. In wheat, repeated weeding during first two years did not allow the infestation of A. ludoviciana on third year. In maize, atrazine was more effective against A. conyzoides and C. benghalensis than pendimethalin, while pendimethalin was more effective than atrazine against E. colonum and B. ramosa. In wheat, pendimethalin proved more effective than isoproturon in controlling P. plebejum, while isoproturon was better than pendimethalin against A. ludoviciana. Weed control measures adopted directly in both the crops reduced the density and dry weight of weeds significantly and improved the yield attributes and yield of both the crops compared to weedy treatment. The highest yield and enhancement in yield attributes of both the crops were observed under repeated weeding. No residual effect of weed control measures applied in previous crop was observed on weeds, yield attributes and yields of either succeeding maize or wheat crop grown in sequence.
