WEED MANAGEMENT IN DIRECT SEEDED RICE UNDER SEMI-DRY SYSTEM

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Date
1993
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ANDHRA PRADESH AGRICULTURAL UNIVERSITY HYDERABAD
Abstract
The present investigation entitled "WEED MANAGEMENT IN DIRECT SEEDED RICE UNDER SEMI-DRY SYSTEM" was conducted on sandy clay loam soil at Agriculture College Farm, Rajendranagar, during Kharif 1992. The experiment was laid-out in a randomised block design (Factorial) with 18 treatments, replicated thrice. The treatments consisted of two varieties viz., Praaaooa {V) and Erramallelu (V) and nine weed control pr!ctices Line weeding_fad hoeing at 20 and 40 DAS, Anilofos@ 0.2 kg a.i ha at 10 DAS+ lin~1weeding and hoeing at 30 DAS, AnilofQf@ 0.4 kg a.i ha at 10 DAS, Anilofos@ 0.4 kg a.i ha at 10 DAS+ lin~1weeding and hoeing at 40 DAS, Anilofos_f 0.2 kg a.i ha at 10 DAS + 2,4-DE~l@ 0.5 kg a.i ha at 30 DAS, Anilofo§1@ 0.2 kg a.i ha at 10 DAS+ 2,4-Q!E@ 0.5 kg a.i ha at 40 DAS, 2,(-DEE@ 1.0 kg a.i ha at 20 DAS+ line weeding and hoeing at 40 DAS, line ~Ieding and hoeing at 20 DAS + 2,4-DEE @ 1.0 kg a.i ha at 40 DAS and unweeded check). The weed spp observed during the study were; Cyperus rotundus, C¥perus difformis (sedges); Echinochloa crusgalli, Digitaria sanguinallis, Panicum spp, Cynodon dactylon (grasses); Eclipta alba, Parthenium hysterophorus, Cessulia auxillaFI's, Ph~llanthus maderas atensis, Euphorbia hirta and Trianthema portulacastrum broad leaved weeds). Lower weed density and weed dry matter {except at 20 DAS and harvest) was recorded in Prasanna. Weed control efficiency and weed index was not significant in between varieties. Plant growth characters like, plant height, crop dry matter (except at harvest) and straw yield was higher in Prasanna. While, panicle weight, 1000 grain weight, total grains per panicle, harvest index grain yield (7.3%), gross and net returns and returns per rupee invested were higher in Erramallelu. However, nutrient uptake by crop and weeds were not significant between the ~arieties. Lower weed density, weed dry matter, were obtained at 40 DAS to harvest with line weeding and hoeing at 20 and 40 DAS, whereas at 20 DAS the weed density and_yeed dry matter was lower in anilofos@ 0.4 kg a.i ha (W and W ), mainly due to effective control of monoc~ts, {7~%) such as Cyperus rotundus, Cyperus difforrnis, Echinochloa crusgalli and Panicum spp and_~icots (30%). Anilofos at lower rates {0.2 kg a.i ha ) was effective on grasses_£nly. Application of 2,4-0EE {@ 0.5 and 1.0 kg a.i ha ) was effective in controlling broad leaved weeds (85 to 98%) and to some extent sedges. Phytotoxic effects were not severe due to application of herbicides. Plant growth characters, weed control efficiency (harvest), yield components, grain yield, harvest index and gross returns were higher in line weeding and hoeing at 20 and 40 DAS. However, net returns and returns per rupee invested were higher in line we~1ing .and hoeing at 20 DAS with 2,4-DEE@ 1.0 kg a.i ha at 40 DAS. Integration of physical {line weeding), mechanical (hoeing) and chemical {herbicide) methods favoured higher growth and yield than application of herbicides alone. NPK uptake by crop was maximum at harvest and weeds at 80 DAS, but rate of uptake by crop and weeds was higher at 80 DAS. Line weeding and hoeing at 20 and 40 DAS recorded maximum nutrienb uptake by crop and minimum by weeds. Reduced plant ·growth and luxuriant weed growth was recorded in unweedy check (Wg). Herbicide residue study using cucumber indicated non-residual nature of the herbicides. There was no interaction between varieties and weed control treatments. Line weeding and hoei~i at 20 DAS with application of 2,4-DEE@ 1.0 kg a.i ha at 40 DAS is recommended for both varieties to achieve higher monetary returns.
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