STUDY ON CROP-WEED COMPETITION AND WEED MANAGEMENT IN LUCERNE (Medicago sativa L.) FOR SEED PRODUCTION
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Date
1991
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AAU, Anand
Abstract
The field experiment was conducted at the College Agronomy Farm, Gujarat Agricultural University, Anand Campus, Anand, with a view to study the effect of crop-weed competition and herbicides in lucerne seed crop during rabi season of 1989-90. In the present experiment, treatment for crop-weed competition study were lucerne + unweeded control, lucerne + population of only dodder, lucerne + population of only Chenopodium album and lucerne + population of only monocot weeds. In addition to these, weed management treatments viz., one hand weeding (21 DAS), two hand weedings (21 + 42 DAS), pre-emergence application of pendimethalin, fluchloralin, oxyfluorfen, alachlor (each at 0.5 kg/ha), dimethazone (at 0.8 and 1.2 kg/ha), post emergence application of fluazifop-butyl (at 0.3 kg/ha) and glyphosate (at 0.1 and 0.2 kg/ha), were assigned at random in randomized block design with four replications. Periodical weed counts of total, monocot and dicot weeds at 30 DAS, 45 DAS, 75 DAS, 120 DAS, 150 DAS and at the timeof harvest were taken. To know the competiton 11 between crop and dodder, Cj^ album and monocot weeds their count were taken separately. Dry weight of monocot, dicot and total weeds along with weed control efficiency were recorded at harvest. The effect of treatments on yield, yield attributing characters and quality characters were also recorded. The economics of treatments was evaluated on the basis of lucerne forage and seed yield considering the then prevailed market prices. The crop-weed competition was critical upto first three weeks and subsequently the crop was able to compete with weeds. The parasitic weed dodder started, competition with lucerne 30 DAS. Gradually infestation of this weed became serious, so much so that crop reduced seed yield to the tune of 88 per cent as compared to two hand weedings. The competition between Cj_ album and lucerne was highest upto 75 DAS and gradually it was decreased. The lucerne seed yield was not reduced significantly by C^ album and was found at par with two hand weedings. Initially (upto 75 DAS) monocot weed intensity was low, however, when environment become conducive their density increased. Inspite of the higher density, monocot weeds were unable to compete with crop due to vigourous crop growth and deep root system. In respect of suppression of total, monocot and dicot weed count pre-emergence application of alachlor at 0.5 kg/ha and post-emergence application of fluazifop-butyl Ill at 0.3 kg/ha were found superior over rest of the treatments by recording lowest count of total, monocot and dicot weeds at all stages of crop growth. Herbicide dimethazone and oxyfluorfen were observed very effective and consistent in controlling C. album, however, performance of both these herbicides was not encouraging in terms of green forage yield. Single application of glyphosate significantly controlled dodder established on lucerne crop but when crop left for seed production haustoria embedded in host plants and tendrils on host stems recovered growth to varying degree and seriously damaged the seed crop. The dry biomass of total, monocot and dicot weeds at harvest was lowest in pre-emergence application of alachlor @ 0.5 kg/ha followed by pre-emergence application of fluchloralin @ 0.5 kg/ha and post-emergence application of fluazifop-butyl 0.3 kg/ha. Weed control efficiency was significantly increased by all the weed management treatments except glyphosate at lower dose. Plant height and plant population at different stages were significantly higher in post-emergence application of fluazifop-butyl (a 0.3 kg/ha and pre-emergence application of alachlor l? 0.5 kg/ha. IV Green forage yield was significantly increased by different weed management treatments. Pre-emergence application of alachlor @ 0.5 kg/ha recorded highest yield followed by post-emergence application of fluazifop-butyl 0.3 kg/ha. One hand weeding (21 DAS) and two hand weedings (21 + 42 DAS) did not differ significantly for green forage yield. Leafiness and crude protein content of lucerne forage were significantly increased by different weed management treatments. Lucerne seed yield differed significantly with different weed management treatments. Post-emergence application of fluazifop-butyl at 0.3 kg/ha gave the highest lucerne seed yield followed by pre-emergence application of alachlor at 0.5 kg/ha. As regard to economics, alachlor at 0.5 kg/ha ranked first in respect of ICBR value, followed by fluazifop-butyl at 0.3 kg/ha.
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AGRONOMY, AGRICULTURE, A STUDY