Abstract
A field trial to see the effect of some pre and post-emergence herbicides viz. pendimethalin 330E (N-1-ethylpropyi)-3, 4 dimethyl-2, 6-dinitro benzenamine), trifluralin 23EC (cr., a-trifluoro 2, 6-dinitro-N-N-dipropyl-p-toluidine), paraquat 20 EC(1,11-dimethy1-41-4'-bipyridinium ion), and dalapon 85 WP (2,2-dichloropropionic acid) on the growth and yield of cotton and weed population was carried out during 1986-87 on a sandy clay loam soil. The results revealed that the herbicidal treatfnents such as pendimethalin at 1.15 kg al (ha) pre-ernergence or pre-ernergencelincorporat-ed and trifluralin at 0.175 kg ai (ha)- pre-emer-gence incorporated were not effective against perus rotundus (Purple Nutsedge), however, their effect against Cynodon dactylon (Bermuda grass) was relatively better. Although the total population of Paspalum a palodes (Nam) and Triantherna rnonogyna (!tsit) was low but these three herbicides were effective against these weeds. Directed post-ernetlgence apprication of dalapon ati 6.76 kg ai (ha) and paraquat at 400 g ai (ha) controlled all the four weed species, except dalapon which did not effect Pasa alum pasapalodes (Naru). Directed post-emergence applif cation of dalapon at the rate of 6.76 kg ail (ha)and paraquat at the rate of 400 g ai (ha) gave maximum seed cotton yield. This study indicated that directed post emergence application of herbi-cides is better practice than pre-emergence applica-tion.
