Study to evolve technology for controlling binding weeds in grown-up sugarcane crop

Sugarcane is one of the important cash crops of India and is cultivated in different Agro-Climatic zones. In Tamil Nadu, sugarcane is cultivated in an area of 2.0 lakh hectares with average productivity of 100 tonnes per hectare. The increased productivity in India is only due to favorable climatic conditions of tropical and management practices that India adopted by the growers, guided by the well-structured cane department of the sugar industry. Still, there is a hope to increase productivity by eliminating the yield-reducing factors. Sugarcane yield is severely affected by the presence of weeds.  The wider row spacing between cane rows, initial slow growth, heavy application of fertilizers, and frequent irrigation encourage the growth of weeds.  The weeds compete for land, moisture, sun light and other nutrients and reduce the cane yield Weeds limit the cane and sugar yield, relative to its species and intensity. Due to weed infestation, the yield loss in cane crops was estimated from 40 to 60 per cent.

The annual grasses and broad-leaved weeds can be effectively managed by spraying pre-emergence herbicide viz., atrazine. Due to the selectivity of herbicide, sedges viz., Cyperus sp. was dominant over other species and spread to other areas of the field. Though manual weeding is being practiced for the control of sedges, it is not as effective as that of herbicide; spotted spray of total weed killer is advocated for effective sedges control. Nowadays, a new problem has been noticed in the cane field that the dominance of twining weeds, particularly in the ratoon crop. These weeds are grown after 120 days of the crop age. Though the critical period of weed competition in cane crops is 90 days. Weeds compete with crops for all the inputs and the total actual economic loss, due to weeds in 10 major crops in India, was estimated at US$ 11 billion (Gharde et al. 2018). Hence managing weeds is critical in attaining higher productivity of crops with improved resource use efficiency, to meet the food and nutritional demands of the increasing Indian population as well as increasing income of the farmers (Rao and Chauhan 2015). Weed management involves integrated efforts to manage weeds in crops to selectively minimize the weed competition so as to enable crops to optimally use resources such as soil fertility, water, and sunlight, for attaining the optimal harvestable crop yield (Quimby and Birdsall, 1995).

Materials and Methods:

Field experiments were conducted at Sugarcane Research Station, Cuddalore Tamil Nadu Agricultural University, to evolve technology for controlling binding weeds in grown-up sugarcane crops during 2015-18. The experiments were laid out in Randomized Block Design with three replications and the sugarcane variety tested wasCoC(SC)24.The planting of sugarcane was done at 120 cm row spacing on ridges and furrows.  The treatments constituted of T₁ – PE. atrazine @ 1.0 kg/ha and Po.Emetribuzin 0.75 kg/ha @ 60 DAP, T₂ – PE atrazine 1.0 kg/ha and Po.E 2,4D Na salt 1.25kg/ha @ 60 DAP, T₃ – P.E atrazine 1.0 kg/ha followed by weeding and earthingup on 75 DAP, T₄ – Mechanical weeding by power tiller (45, 90 and 120 DAP), T₅ – Intercropping of sun hemp and its incorporation as insitu  on 60 DAP, T₆ – Detrashing and mulching at 150^th&210^th DAP, and T₇ – hand weeding and manual removal of weeds on 45, 90 and 120^th days and T₈ –Control. All the recommended management practices were followed. Among broad-leaved weeds Euphorbia geniculate, Parthenium hysterophorus, Digeraarvensis, Mereimiaemergianta, Alternanthera sessile, lactularuncianata, chenopodium album were found dominate. While, among grassy weeds Cynodondactylone, Brachiariaeruciformis, cyperusrotundus were found as dominant

Result and Discussion:

Table 1. Effect of weed control treatments on weed flora /m^{2 (}120 DAP)

Among the weed control treatments the pre-emergence application of atrazine @ 1.0 kg a.i/ha followed by post-emergence application of metribuzin @ 0.75 kg/ha 60 days after planting(Table.1 ) recorded the lowest weed flora of the sedges(32), monocots (21), dicots (10) and creeper (3) / m² 120 days after planting compared to other weed control. The treatments control registered more no of weed flora.                

Table 2.Total weed numbers (m²) and weed control efficiency (%)

The pre-emergence application of atrazine @ 1.0 kg a.i/ha followed by post-emergence application of metribuzin @ 0.75 kg/ha on 60 days after planting  table.2 (T₁) significantly registered the minimum weed numbers 78.0 (m²) and weed control efficiency of 85.0 (%) and it was on par with the treatment (T₃ ) Pre-emergence application of atrazine 1.0 kg/ha followed by weeding and earthing up on 75 days after planting the weed numbers of 86.43  /m² and weed control efficiency  83.52 (%). The same result was recorded during the second season of the crop study.

Table.3 Germination (%), Tillers (000/ha), and Economic shoots (000/ha)

The pre-emergence application of atrazine @ 1.0 kg a.i/ha followed by post-emergence application of metribuzin @ 0.75 kg/ha 60 days after planting significantly registered the maximum germination per cent (93.7), tiller population of 1, 83,230 on 90 days after planting and 2,11,520 on 120 days after planting. Regarding the economic shoot population the same treatment recorded the maximum economic shoots of 1, 66,220/ha on 210 days after planting, the same trend was followed during the second season crop study and the lower growth attributing characters were observed in the control.

Table.4 Effect of weed control treatments on sugarcane yield parameters

Among the treatments thepre emergence application of atrazine @ 1.0 kg a.i/ha followed by post-emergence application of metribuzin @ 0.75 kg/ha on 60 days after planting (T₁) significantly registered the maximum values of millable canes 1,33,500  and 1,32,400 ha¹, cane length of  270 and 271 cm, cane girth of 2.54 and 2.49 cm and the individual cane weight of 1.25 kg and it was comparable with the (T₃ ) Pre-emergence application of  atrazine 1.0 kg/ha followed by weeding and earthing up on 75 days after planting during both the years of the study 2015-16 and 2017-18. The lowest yield parameters were recorded in the treatment control.

Table.5 Effect of treatments on cane yield

The pre-emergence application of atrazine @ 1.0 kg a.i/ha followed by post-emergence application of metribuzin @ 0.75 kg/ha on 60 days after planting (T₁) significantly registered the maximum cane yield of 131.40 and 132.98 t/ha, the CCS per cent of 10.73 and 10.74 and the sugar yield of 12.37 and 12.52 t/ha in both the years of study and it was on par with the treatment (T₃ ) Pre-emergence application of  atrazine 1.0 kg/ha followed by weeding and earthing up on 75 days after planting. The treatment control registered the lowest yield attributing characters.

Table.6Effect of Treatments on Economics

            Among the weed control treatment, the pre-emergence application of atrazine @ 1.0 kg a.i/ha followed by post-emergence application of metribuzin @ 0.75 kg/ha on 60 days after planting (T₁) registered the maximum net income of Rs.1,81,675/ha and the highest B: C ratio of 2.22. The Pre-emergence application of atrazine 1.0 kg/ha followed by weeding and earthing up on 75 days after planting stands next in order with a net income of 1,75,050 Rs./ha. The treatment control registered the lowest in economic characteristics.

Conclusion

         Based on the performancePre-emergence application of atrazine @ 1.0 kg a.i/ha followed by post-emergence application of metribuzin @ 0.75 kg/ha 60 days after planting was the best treatment for controlling weeds in grown-up sugarcane and yield attributing characters compared to control. The lowest weed flora of  sedges(32), monocots (21), dicots (10), and creeper (3) / m² 120 days after planting, minimum weed numbers 78.0 (m²) and weed control efficiency of 85.0 (%) , maximum germination per cent (93.7), tiller population of 1, 83,230 on 90 days after planting and 2,11,520 on 120 days after planting, the maximum values of millable canes 1,33,500  and 1,32,400 ha¹, cane length of  270 and 271 cm, cane girth of 2.54 and 2.49 cm and the individual cane weight of 1.25 kg, maximum cane yield of 131.40 and 132.98 t/ha, the CCS per cent of 10.73 and 10.74 and the sugar yield of 12.37 and 12.52 t/ha and higher net income of Rs.1,81,675/ha and the highest B: C ratio of 2.22.

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