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Municipal Waste Water - An Alternative Resource Effective For Water And Crop Productivity And Its Characterization In Indian Sub-tropics

Congress: 2015

Keyword(s): Sub-theme 10: Management of water resources,
Abstract The use of urban wastewater in agriculture is a centuries-old practice that is now receiving renewed attention with the increasing scarcity of fresh water resources in many arid and semi-arid regions of the world. In India, agriculture primarily depends on the onset and availability of rainwater, mostly occurring during wet months of a given year, as major part of Indian sub-continent possess dry ecosystem (67-70%), erratic and uneven distribution pattern, faces scarcity even some pockets under sub-humid regions of the country. Water resources and its proper utilization, management is severe lacuna due to man-made and natural causative factors, resulted poor WUE (water use efficiency) at its field level. In this context, irrigation with wastewater gives the opportunity to solve the problems of its disposal, reuse and water conservation as well. Field experiment was conducted with wheat crop at the university research farm of Bidhan Chandra Krishi Viswavidyalaya (State Agricultural University), West Bengal, India during consecutive three years of 2009 - 10 to 2012 - 13 to examine the effect of wastewater application on the physico-chemical properties of the soil following the standard analytical procedure described by Jackson (1973). Soil pH was measured with a pH meter and soil EC was measured by a conductivity meter on a soil to water ratio of 1:2.5. Total N was determined using the Kjeldahl procedure (Bremner and Mulvaney, 1982). Concentrations of soluble Ca and Mg were measured using the EDTA titration method and Na and K was measured using flame photometer (Richards, 1954). Phosphorus was determined using Olsen extraction (0.5 M NaHCO3) method (Olsen and Sommers, 1982). The S was determined turbidimetrically by spectrophotometer at 420 nm wavelength (Page et al., 1982). Fresh groundwater and wastewater was collected from the city of Kalyani Municipality, West Bengal, India, which was used to irrigate wheat crop for consecutive three years. In this study, properties of wastewater - irrigated soil were compared with freshwater - irrigated soil. The experiment was formulated in factorial completely randomized design with five water quality (fresh water, fresh water and wastewater in the ratio 1:7, 2:3 and 3:4; raw wastewater) of main treatments and two sub-treatments of no-fertilizer and recommended dose of fertilizer replicated thrice. On an average, 153 mm of waste-(water) was applied from the sources in respective three irrigations to the wheat crop in each year. The amount of water applied in each irrigation was the same. It reveals from the experimental findings that the post-experimental field soils (both physical and chemical) were remarkably influenced due to the application of various water resources. The application of wastewater reduced the bulk density of the surface soil and slightly increased the porosity. The unsaturated hydraulic conductivity and water holding capacity of the soil was improved with wastewater irrigation. Soil pH increased due to wastewater application but decreased, to a smaller extent, due to fertilizer application. Soil EC increased both with wastewater and fertilizer application; both soil quality parameters changed proportionately in the 0−22 cm soil layer with wastewater irrigation. But, at the deeper layers, they were not affected by wastewater application. The organic C and total N level of the soils irrigated with wastewater were higher than fresh water irrigated soil. The organic C increased by 8.38% under fresh water irrigation in the top 20 cm soil layer. The N content of the soil showed similarities with the organic C contents. Available P and S concentrations were greater in the soil irrigated with raw wastewater compared to the soil irrigated with fresh water. The exchangeable cations: Mg, K, Ca and Na also increased with wastewater application. From the findings, it may be concluded that the application of wastewater for irrigation over 3 years, did not negatively affect soil physical properties, rather it improved some of them. Compared to the soils irrigated with fresh water, the soils irrigated with wastewater showed only small increase in porosity, hydraulic conductivity and water retention capacity but decrease in the bulk density. Soil chemical properties such as pH, EC, organic-C, N, P, K, Na, Ca, Mg, and S also slightly increased with wastewater irrigation over time. Though increase in EC is a concern, but it remained well below the permissible limit for agricultural soil. Thus, irrigation with wastewater improved soil fertility. Key words: hydraulic conductivity, irrigation, municipal wastewater, physico-chemical properties, soil water retention
2011 IWRA - International Water Resources Association - - Admin