Optimization and degradation pattern of extreme levels of atrazine in maize zea mays l And their residual effect on the succeeding cowpea vigna unguiculata l Walp

Abstract

Field and pot experiments were conducted to optimize extreme levels of atrazine newlinein maize (Zea mays L.) for broad-spectrum weed control as well as to study their newlinedegradation pattern in soil and residual effect on the succeeding cowpea (Vigna newlineunguiculata (L.) Walp.). Field experiments were carried out at Eastern block farm, Tamil newlineNadu Agricultural University (TNAU), Coimbatore during Kharif and Rabi seasons of newline2019-20 and 2020-21. The field experiment design was a complete randomized block newlinedesign (CRBD) with three replicates. The experiment was comprised of eleven treatments newlineviz. pre-emergence atrazine 50 % WP at 0.50 kg a.i ha-1 (T1), pre-emergence atrazine newline50 % WP at 0.75 kg a.i ha-1 (T2), pre-emergence atrazine 50 % WP at 1.00 kg a.i ha-1 (T3), newlinepre-emergence atrazine 50 % WP at 1.25 kg a.i ha-1 (T4), pre-emergence atrazine 50 % WP at newline1.50 kg a.i ha-1 (T5), pre-emergence atrazine 50 % WP at 1.75 kg a.i ha-1 (T6), newlinepre-emergence atrazine 50 % WP at 2.00 kg a.i ha-1 (T7), pre-emergence atrazine 50 % newlineWP at 0.50 kg a.i ha-1 fb tembotrione at 120g a.i ha-1 as post-emergence at 25 DAS (T8), newlinepre-emergence atrazine 50 % WP at 0.50 kg a.i ha-1 fb hand weeding at 30 DAS (T9), weed- newlinefree check (T10) and weedy check (T11). Maize was raised during the Kharif season of 2019 newlineand 2020 while cowpea as a residual crop was raised after harvesting maize in an newlineundisturbed field during the Rabi season of 2019-20 and 2020-21. Both crops were raised newlineunder irrigated conditions. newlineThe floristic composition of the experimental field was comprised of twelve weed newlinespecies of which six were grasses, five were broad-leaved weeds (BLW) and one was newlinesedge. Dinebra retroflexa, Echinochloa colona L. and Chloris barbata were the dominant newlinegrasses. Trianthema portulacastrum, Parthenium hyspterophorus, and Digera arvensis newlinewere the predominant BLW while Cyperus rotundus was the only sedge observed in the newlineexperimental field. Total weed density, total weed dry weight, and weed control newlineefficiency (WCE) were recorded at 30, 60, and 90 days after sowing (DAS) of