Residual effect of pre and post emergence herbicides and fertility levels on succeeding crops after soybean

Abstract

Herbicides proved important tool in modern farming systems. With the intense farming practice and multiple cropping, the paucity of agricultural labour is seen. Their peak demand for a short period, inaccessible field conditions during crop seasons also encourages using herbicides in modern farming. But continuous application of herbicides in intense cropping systems may leads to it’s residue accumulation in the soil. This persistence of a herbicide may limit the choice of succeeding crops. Therefore, residual studies are essential to determine the feasibility of any herbicide. Rabi sorghum, bajra, barley and ragi are the important succeeding crops grown after soybean in South Saurashtra region. Therefore, the present study about residual effect of pre and post emergence herbicides and fertility levels in succeeding crops after soybean was undertaken at Instructional Farm of Junagadh Agricultural University, Junagadh during Kharif season of 2006. Eighteen treatment combinations comprising six levels of weed management practices as main plot treatments viz., W 1 Pre-emergence pendimethalin @ 0.5 kg ha + HW and IC at 30 DAS, W 2 – Postemergence quizalofop-ethyl @ 40 g ha at 25 DAS + HW and IC at 45 DAS, W 3 Post-emergence imazethapyr @ 75 g ha at 25 DAS + HW and IC at 45 DAS , W 4 2 HW + 2 IC at 20 and 40 DAS, W 5 Weed free upto 60 DAS through hand weeding and W 6 Unweeded control and three levels of fertilizers as sub plot treatments viz., F 1 20:40:20 kg N:P 2 O 5 :K 2 O ha F 2 30:60:30 kg N:P 2 O 5 :K 2 O ha F 3 40:80:40 kg N:P 2 O 5 :K 2 O ha were tried in Split Plot Design with three replications. The soil of the experimental plot was low in available nitrogen, medium in available phosphorus and high in available potash. Pre-emergence application of pendimethalin herbicide was done after 24 hours of sowing of soybean and post pre-emergence application of herbicide quizalofop-ethyl and imazethapyr was done after 25 days after sowing. The succeeding crops Rabi sorghum, bajra, barley and ragi were sown after harvesting of soybean within a week. The biometric observation about germination percentage of succeeding crops was done after 10 days of sowing. Plant height