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Aim: The study was conducted to design pectin beads for achieving slow release of agrochemicals in wetlands via ion gelation method. Place and Duration of the Study: The laboratory experiment was carried out at the Department of Nano Science & Technology, Tamil Nadu Agricultural University, Tamil Nadu during March-July 2021. Methodology: Pectin beads were synthesized varying the concentrations of pectin (4, 6, 8, and 10 per cent) and calcium chloride (CaCl2) concentrations (0.5, 1, and 2 per cent). Calcium pectinate beads of different combinations were synthesized via ion gelation method. Calcium pectinate beads were characterized based on the recovery yield of beads, while surface characterization was done through Scanning electron microscope (SEM) and optical microscope to understand the topography of beads and assess the size of the beads respectively. Pore volume and surface area were also studied using BET (Brunauer-Emmett-Teller) analyzer. Results: The yield of calcium pectinate beads were higher while using the concentration of pectin @ 4 per cent and CaCl2 @ 2 per cent as cross-linking agent. The spherical and smooth surface of beads was achieved with the concentrations of 6 and 2 per cent pectin and CaCl2 respectively, while beads were flat and smooth with concentration of pectin @ 4 per cent. Similarly, complete solubility of pectin was not achieved with concentrations of 8 and 10 per cent. BET results of beads showed that beads are non-porous in nature. Conclusion: Pectin and CaCl2 concentrations @ 6 and 2 per cent respectively were found to be ideal for the delivery of agrochemical based on the yield and surface morphology.

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Field experiments were carried out during summer seasons of 2017 and 2018 to study the effect of preceding (Rice-Okra) crops herbicide residue on weed, growth, yield and economics of succeeding blackgram. Residual effect of butachlor at 1.25 kg/ha on 3 days after transplanting (DAT) fb hand weeding (HW) on 40 DAT imposed in the first season rice crop and followed by hand weeding (HW) twice at 20 and 40 days after sowing (DAS) (T6) in okra and blackgram significantly influenced the reduction of weed dry weight accumulation by 8.75 and 7.44 times in mainland and island ecosystem, respectively at 20 DAS. The same treatment recorded the highest weed control efficiency (WCE) of 88.6, 86.5 and 86.2, 80.7 % observed at 20 and 40 DAS under mainland and island ecosystem, respectively. Among, the weed control treatments, residual effect of butachlor at 1.25 kg/ha on 3 DAT fb HW on 40 DAT to rice and HW twice at 20 and 40 DAS (T6) to okra and blackgram has recorded 64.8 and 65.0% higher seed yield of blackgram under main and island ecosystem, respectively.

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