Long-term impacts of pasture irrigation with treated sewage effluent on nutrient status of a sandy soil in Zimbabwe |
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Authors: | W Gwenzi R Munondo |
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Affiliation: | (1) Department of Civil Engineering, University of Zimbabwe, P.O. Box MP167, Mt. Pleasant, Harare, Zimbabwe;(2) Soil Science & Plant Nutrition, School of Earth & Geographical Sciences (South), University of Western Australia, 35 Stirling Highway, 6009 Crawley, Perth, WA, Australia;(3) Tropical Resources Ecology Program, Department of Biological Sciences, University of Zimbabwe, P.O. Box MP167, Mt. Pleasant, Harare, Zimbabwe |
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Abstract: | Declining freshwater resources and the need to safely dispose wastewater have led to a rapid increase in wastewater reuse
in developing countries. However, empirical evidence on the effects of effluent-irrigation on soil fertility is limited. The
study investigated the nutrient status of a sandy soil after 26 years of effluent irrigation. Soil samples from effluent-irrigated
and non-irrigated sites were analysed for pH, electrical conductivity (EC), soil organic carbon (SOC), total and plant available
forms of N and P, exchangeable bases and trace metals. Analysis of effluent quality showed that, besides Cr and Cd, all measured
parameters were within acceptable limits for wastewater irrigation. Our results revealed that effluent-irrigation significantly
(P < 0.05) enriched the soil with essential nutrients for plant growth, which are commonly deficient in most soils of Zimbabwe.
Effluent-irrigated soils had significantly (P < 0.05) higher pH, EC, SOC, total and available N and P and, exchangeable Ca and Mg at 0–30 cm-depth. However, apart from
Cr accumulation, effluent irrigation significantly (P < 0.05) depleted Zn, Cu and Cd probably due to plant uptake and enhanced mobility under acidic soil pH. Cr accumulation and
depletion and mobility of Zn, Cu and Cd in effluent-irrigated soils could threaten the sustainability of the practice. We
recommend a review of the current management practices based on crop water requirements, effluent quality and environmental
considerations. |
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Keywords: | Effluent irrigation Nutrients Pasture Wastewater |
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