Effects of effluent irrigation on the variation of chemical element concentrations of soil extractions under field conditions

Sustainability of effluent-irrigated agriculture depends on balance of soil chemical elements. Effects of two water qualities and three irrigation quotas on the variation of soil chemical element concentrations during successive planting period of winter wheat(Tricicum aestivum L.) and summer corn(Zea mays L.) were studied under field conditions. The experimental results indicated that irrigation with effluent water at great quota increased soil salinity, but irrigation at small quota and middle quota decreased it under natural rain conditions. The effluent water used in this study could not result in secondary alkalization of soil. After one-year planting, the concentrations of Ca, Mg, Fe and Zn of soil increased but those of P, Mn, Cu, Cd and Ni decreased. Na and B of soil cumulated when soil was irrigated with effluent water at a great quota but decreased when did at a small quota; the variation of K of soil had an opposite tendency with Na and K. Effluent irrigation may supply soil with extra nutritious elements K and P for plants; however, decreasing irrigation quotas of effluent water can effectively control the accumulations of salt, B and Zn of soil or heavy metals of plants.