Abstract
Paucity of quality fresh water for agriculture has made waste water (WW) application a popular option. Available data on chemical composition of different waste water, their effect on soil fertility, soil heavy-metal content, crop yield and quality parameters and maximum permissible limits (MPL) of different International environment protection agencies and governments of different countries has been summarized. Chemical composition of WW varied remarkably with respect to their heavy-metal content, pH, electrical conductivity (EC), biological oxidation demand (BOD), chemical oxidation demand (COD), alkalinity and hardness. Field application of all types of waste water significantly increases soil OC percentage, soil EC, cation exchange capacity (CEC), total and DTPA-extractable heavy-metal/micro-nutrient content, available macro-nutrient (N, P and K) content with significant decreases in calcium carbonate content of surface soil. However, high content of nitrogen, phosphorus and potassium strengthens its high fertigation/manural value for field crops. Significantly higher heavy-metal accumulation in soils irrigated with WW than ground water has been observed in surface layer than the lower depths of soil profile. Since crop genotypes and even crop cultivars within genotypes respond differently to waste water irrigation, their selection becomes more important under such situations. More importantly, carbon sequestration through WW irrigation could sustain long-term soil fertility. Periodic monitoring of chemical composition of waste water, soil and crop produce is however, suggested for safe and long term use of waste water.
Highlights
Water is a vital to all living creature, as it makes up to 50-97% of plant and an imal and about 70% of average human body weight[1], but regrettably it is the most poorly managed resource in the World[2]
Estimates revelled that agriculture sector consumes maximu m of the Ground water (GW) and ~80 per cent of actual water resources are utilized in agricu lture for irrigation purpose
Leather co mp lex effluents mixed with municipal surface water (SW) fro m Ludhiana (India) were reported to contain 0.41 mg Cu L-1, 20.1 mg Fe L-1, 0.39 mg Mn L-1, 2.25 mg Zn L-1, 4.03 mg Al L-1, 0.04 mg As L-1, 8.31 mg Cr L-1 and 0.20 mg Ni L-1, in Pakistan elucidates ghee industry effluents as most representing 42, 155, 98, 31, 50, 4, 1400 and 52-t imes, injurious to soil and plant health, because of its high electrical conductivity (EC) respectively higher heavy-metal content than GW, due to (~8.14 d S m-1) than effluents fro m text ile, chemical juncture mixing of industrial effluents[23]
Summary
Water is a vital to all living creature, as it makes up to 50-97% of plant and an imal and about 70% of average human body weight[1], but regrettably it is the most poorly managed resource in the World[2]. The total value of these nutrients would be around 1.78 million US$ annually [11] These findings recapitulates that WW have great potential as manure when used for irrigation to crops. 30.0 to 120.0 mg L-1) of total nitrogen (TN) in WW for agricultural use has been standardized by different agencies/Governments (Tables 1 and 2). MPL standardized by different agencies/Govern ments for heavy-metals revealed wide variat ion. Total concentration of soluble salts (EC) should be in between 3.0-5.0 dS m-1, a MPL suggested by different agencies/Governments
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