Weed management in organic soybean (Glycine max (L.) Merr.)
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
The present investigation, “Weed management in organic soybean (Glycine max (L.) Merr.)” was carried out at Students’ Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana during Kharif 2015. The soil of the experimental field was sandy loam having normal pH, medium organic carbon, available N and available K and high available P. The experiment comprised of twelve treatments viz straw mulch @ 4 t ha-1, straw mulch @ 4 t ha-1 followed by hand weeding at 6 weeks after sowing (WAS), straw mulch @ 6 t ha-1, straw mulch @ 6 t ha-1 followed by hand weeding at 6 WAS, cowpea intercropping (1:1) and harvesting at 6 WAS, cowpea intercropping (1:2) and harvesting at 6 WAS, cowpea intercropping (1:1) and its in-situ mulching at 6 WAS, cowpea intercropping (1:2) and its in-situ mulching at 6 WAS, hand weedings at 2, 5 and 8 WAS with weed biomass retained, hand weedings at 2, 5 and 8 WAS with weed biomass removed, weed free and unweeded control. The treatments were quadruplicated in a randomized complete block design. The crop was raised organically with green manuring of sunnhemp and 8 t ha-1 of FYM. The straw mulch was applied immediately after flat sowing of soybean cultivar SL 958. One or two rows of cowpea cultivar CL 367 were sown between the soybean rows as per the treatments. Trianthema portulacastrum was the predominant weed in the crop. The straw mulch and hand weeding treatments were superior in weed control and resulted in reduced weed population, weed dry matter accumulation and N, P and K uptake by weeds. The cowpea intercropping treatments were ineffective to control weeds during the initial period and cowpea harvesting at 6 weeks after sowing resulted in damage to soybean plants leading to its decreased plant population. However, cowpea (1:1) intercropping treatments were better in weed control than cowpea (1:2) treatments during the later crop growth stages. The crop growth parameters like plant height, dry matter accumulation, number and dry weight of root nodules, N, P and K uptake and yield attributes were higher with straw mulch and hand weeding treatments than cowpea intercropping. The microbial populations were higher with rice straw mulching except phosphorous solubilizing bacteria (PSB) which did not vary with weed control treatments. Straw mulch, hand weeding and cowpea (1:1) treatments gave significantly higher seed yield of soybean than unweeded control. Cowpea (1:1) treatments compensated damaged plant populations of soybean with more number of pods plant-1 and resulted in statistically similar seed yield to that with straw mulch and hand weedings. Both straw mulch treatments, SM 4 t ha-1 and SM 6 t ha-1 resulted in highest B:C (1.89, each). Thus, the application of straw mulch 4 to 6 t ha-1 was found to be more efficient for weed control, obtaining higher seed yield and more economic returns.
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