RESUMO
Low cost zero till in situ green manuring using plant species like dhaincha (Sesbania aculeata) and sunnhemp (Crotalaria juncea) will eliminate the age old problems of large scale adoption of green manuring across the farming community. These two species germinated and grown well when sown before (as paira crop during last irrigation) or after rice harvest under zero till condition, with assured nor western rain/monsoon rain or with one post sowing irrigation (7.5 cm). The zero till paira dhaincha green manuring process opened up the scope of producing green manuring at lower cost and saves up to Rs.15000/ha over conventional rain fed green manuring system. Green manuring by dhaincha produced 50-60 tonnes of biomass at 35-40 DAS in alluvial (North 24 PGS), lateritic (Purulia) and clay soils (Paschim Medinipur), produced 30-50 q raw rice /ha and saved 20-27 kg (30 per cent) chemical nitrogen/ha. This green manure will help in quicker decomposition of rice straw left after combined harvest (3.5- 6,0 t/ha), minimise its field burning, sequester enough carbon to the soil. Fifty tonnes green biomass of dhaincha/sunnhemp, has the potential to absorb 15 tonnes CO2 from the atmosphere, sequesters 2 tonnes of carbon in soil, minimise environmental pollution, improve soil health, its structure and water holding capacity. This technique can be adopted in rice growing countries across the globe without difficulty. Seed production dhaincha and sunnhemp is possible by growing it as paira crop (40 kg/ha) within kharif rice which grows up to 45 cm height, produces healthy pods and matures by 70 days which otherwise takes 5-8 months in normal season. If the seed crop is not harvested in rice fallows, from shattered seeds, self-seeded zero till and rain fed dhaincha manure can be obtained in rice fallows.
RESUMO
Manual weed control in mustard is very expensive because of its high labour requirement i.e., 150-250 labourers/ha. Chemical weed control again imposes environmental hazards. Mechanical weed control in mustard is not still that popular till date. Due to severe weed competition, the yield reduction in Indian mustard may go as high as 70 per cent. Thus weed control in zero till mustard using its high-density sowing (HDS) was studied in different farmers’ field, at ICAR-CRIJAF, in North 24 PGS and Purulia, from 2018-2022. Fast growing and high- density uniform mustard canopy (100-200 m2) developed at early stages hinders sunlight penetration (up to 99.98 per cent) below its canopy (at 35- 40 days), leading to scanty and under developed growth of different composite weed species at harvest, those germinate or grow below mustard canopy. Weed population below mustard canopy was reduced by 92 to 97 per cent at mustard harvest. It was only 10-80/m2 at harvest over 350-1000/m2 in weedy situation at initial germination. The reduction of dicot weed biomass below matured mustard at harvest was 81-99 percent (5-150g/ m2) percent over weedy plots (500-800/ m2). Reduction of effective flowers/pods of different weeds under matured mustard canopy were up to 99.5 percent. Proper agronomic management practices of HDS mustard e.g., seed rate, date of sowing, uniformity of sowing, irrigation and fertiliser application will eliminate the herbicide application or manual weeding in mustard. Nearly 80 percent mustard plants remain active at harvest. It saves 150-250 labours /ha depending on weed species and its density of germination. Mustard grain yield ranged from 15-30 q/ha depending on management and varieties used. This weed smothering merit of mustard can be used for eco friendly weed control in other wide spaced field/horticultural crops using its dwarf variety (Toria).