High density uniform broadcast jute for weed smothering:
A.K. Ghorai, Retired Principal Scientist, ICAR-CRIJAF, Kolkata, WB, India
Jute being a C3 crop, it cannot compete with the C4 weeds at its early stage and about 40 per cent of total cost of cultivation of jute goes in weeding process alone. Upsurge of new weed flora, labour scarcity, herbicidal resistance and its environmental concern and slow mechanization urged us to control weeds in jute field by its smothering effect. Experiments were conducted at ICAR-CRIJAF, Barrackpore, WB in 2018-19, 2019-20 & 2020-21 with jute (cv. NJ-7010) by its high density broadcast sowing (seed rate @ 6.0 to 7.5 kg/ha). Irrigation, fertiliser and pesticides requirements were standardised for this purpose. Only 45 cm wide strip (5% of total area) around the jute fieldwas manually weeded to prevent seed formation of weeds in boarder areas. The dense jute canopy(200-348 /m2) of 29 cm mean height at 25- DAS reduced the incident light at jute base by 90-95 percent and dominated all C4 weeds. In this 1st year it reduced the grass, broadleaf, sedges weedpopulation (max 52 m2) and weed bio mass by 98, 98.5, 64.5 and 91.65 per cent respectively over manual weeding twice. Next year at 25 DAS it reduced the grass sedges weed population by 70, and 62% respectively over initial status. In third year most of the grass (507/m2), broad leaved (504/m2)and sedges (52/m2) were smothered by its cover crop effect at early stage (25 DAS). Remaining weeds were rudimentary, incapable of producing seeds. In consecutive three years out, of 20.7 lakh (40 DAS), 26.8 (25 DAS), 34.8 l lakh jute plants/ha (15 DAS), only 3.3, 6.3 and 7.64 lakhs jute plants/ha i.e., 16, 23.5 and 22 % of total initial population were found effective and harvested (125 to135 DAS). The improved experiment of 2nd and 3rd year produced 3.837 & 3.798 t fibre/ha respectively which were at par with manual weeding, chemical herbicide and mechanical weed control process. It eliminated weeding and thinning processes and consumed only 195 and 276 man days/ha from sowing to fibre extraction over conventional method (340 to 365 man days/ha). It saved 89-145 man days/ha (Rs.22500 to 36250/ha). Mesta (Hibiscus cannabinus) also showed similar response as smother crop (2018-19). Pretilachlor 50 EC @ 0.9 l a.i/ha (POE, 7 days) was found effective for weed control in zero till piara crop. Weed smothering by inter cropping green gramwith jute (1:1)/mixed cropping were also found economic, produced 0.8-1.0 t pulse grain/ha along with 2.7-2.9 t jute fibre and 1.7 to 2 tonnes nitrogen rich (2.35%) pulse waste per ha..This weed smothering merit of jute can be used for reducing weed seeds in seed bank growing in repeated flushes, it can also be used as cover crops for different crops which will sequester a lot of carbon to soil also. Weed smothering by high density broadcast jute sowing will eliminate dependence on herbicides, mechanical and manual weeding and make jute farming more remunerative and sustainable in nature.
Relay sowing of jute within maturing pod harvested green gram will add 2-3 tonnes of nitrogen rich (2.35% Nitrogen) bio mass to the soil for soil sustainability and good fibre yield. (Ghorai et al,, 2016). The above said farmer harvested 11.2 q/ha green gram grains (cv. Virat) before relay high density jute ( seed rate 7 kg per ha, seed viability more than 90 percent) sowing. He maintained the fertiliser dose as recommended for high density jute ( Ghorai et al., 2022) and wee was effectively smothered. No thinning was made here. The ICAR-CRIJAF total N:P:K::80:80:80. Basal dose is N:P:K::20:80:80. Second and third irrigations were given on 7 and 21(with 20 Kg N top dressing) days after sowing.Fourth irrigation was given at 35 days after sowing(with 20 Kg N top dressing). One spray of Tebuconazole 1.5 ml/l is require to avoid fungal attack.
References:
1.A.K. Ghorai and Suman Roy (2022).Weed smothering in jute (corchorus olitorius l.) by its high density broadcast sowing.Journal of Krishi Vigyan:
10 (2) : 329-335
2.A.K. Ghorai and Suman Roy (2022). Weed Smothering (Corchorus olitorius L.) in Jute by its High Density Broadcast Sowing, using Cover Crop Principle.Int.J.Curr.Microbiol.App.Sci. 11(03):108-119
3.A.K. Ghorai, Mukesh Kumar and C.S. Kar (2016).Inter cropping in jute.with green gram for weed smothering.Ind.J. weed sci
48(3): 343-344