Nickel, lead and manganese content of forages irrigated with different sewage water treatments: A case study of a semiarid region (Sargodha) in Pakistan

摘要

The use of sewage water for agricultural purpose has tremendously increased during the last few years due to shortage of water availability, especially in semi-arid regions. Despite of many nutrients recycling advantages of sewage water, farmers are not fully aware of its harmful chemical composition. Heavy metals toxicity in soil and crops results from the long term use of sewage effluent for irrigation purposes. The present study was conducted to assess effect of sewage water on the uptake of Ni, Pb and Mn in different forage species with respect to the nutrient requirement of the grazing ruminants inSargodha,Punjab,Pakistan. Five samples each of six fodder species viz., Trifolium alexandrinum, Cichorium intybus, Avena sativa, Medicago polymorpha, Brassica campestris and Medicago sativa were collected from three fields irrigated with canal water, mix water (canal plus sewage water) and sewage water respectively. Pb, Ni and Mn concentration in the forage species during different treatments varied from 0.624 to1.672 mg/g, 7.364 to 10.17 mg/g and 5.136 to 12.422 mg/kg respectively. High value of Pb and Mn concentrations was observed during sewage water treatment. Lead is a non-essential element and is a very toxic metal. But in the present investigation Ni and Pb level in forages were below the toxic level, so the ruminants feeding on these forage species had no chance of Pb and Ni toxicity. On the other hand, Mn concentration in the forage species under observation was below the critical level. So the grazing animals at this location need continued mineral supplementation of Mn to prevent diseases caused by Mn deficiency, and to support optimum animal productivity. The objective of this study was to examine the potential for forage analysis as indicators of likely mineral deficiencies or excesses of grazing livestock during different sewage water treatments.