Transport and Persistance of Agro-Chemicals in Soils Under Paddy Cultivation and Its Impact on Ground Water Pollution

摘要

For sustainable agriculture cultivation of paddy is essential. The crop requires a good amountrnof agro-chemicals and water to reap a good harvest. It is apprehended that under intensive andrnextensive cultivation and use of various chemicals along with large quantity of water for irrigation tornthe crop may invite the problem of soil pollution and/or leaching of the chemicals and subsequentrnground water pollution. To verify this perception an investigation was carried out with UGC fundingrnin Department of Soil Science CCS Haryana Agricultural University, Hisar to investigate transportrnand persistence of the three commonly used agro-chemicals namely Urea (source of nitrogen),rnButachlor (herbicide), and Carbofuran (pesticide), in two soils- a sandy loam (clay 20%, silt 26%)rnand a clay loam (clay 31 % and silt 41 %) with and without paddy crop subjected to intermittent andrncontinuous flooding methods of irrigation.rnThe studies were carried out in PVC columns in laboratory (without crop) as well as inrnlysimeters in screen house (with crop). The agro- chemicals were applied to the soils as per therntreatments reported below:rnA: Laboratory Study) Control (no application of agro-chemicals),rnⅡ) Urea @ 250 mg kg-1 soil (U),rnⅢ) U + Butachlor 50 EC @ 0.5 ml kg-1 soil (B),rnⅥ) U + Carbofuran (granules) @ 25 mg kg -1 soil (C),rnⅤ) U + B + C.rnThirty PVC columns of length 45 cm and diameter 5.4 cm were filled with both thernexperimental soils at 1.45 Mg m3 bulk density (fifteen for each soil) in 2 cm layers up to 32 cm. Thernfilled columns were kept vertically in a stand and after mixing the three chemicals in top 1 cm soilrnlayer, two water heads – constant and intermittent (7.5 cm) were maintained on the soil columnsrnthroughout the study period. The leachates were collected at 6,12, 24. 48, 120 and 240 hours afterrnirrigation and analysed for urea -N, ammonical – (NH4N), nitrate-N (NO3N) and total N, butachlorrnand carbofuran. Soil samples from top 1cm layer were also collected and analysed for residualrnpesticides.B. Screen House Study:rnScreen house study was carried out in steel lysimeters of 30 cm diameter filled with the twornexperimental soils at 1.5 Mg m3 bulk density. The soils were flushed with three pore volumes ofrnwater to leach down soluble material present in the soils and treated in top 1 cm layer with the threernagro-chemicals as under:rnⅠ) Control,rnⅡ) Urea @ 5.72 gm/lysimeter,rnⅢ) Urea + Butachlor @ 25ppm / lysimeter,rnⅣ) Urea + Carbofuran @0.825 gm / lysimeter.