The effect of irrigation using secondary and advance treated wastewaters on soil properties under kikuyu grass production

The main objective of this study was to determine the effect of irrigating using three different types of waters, viz. secondary treated wastewater (STW), advance treated wastewater (ATW) and tap water (TW) on some important soil characteristics under kikuyu grass production. Kikuyu grass (Pennisetum clandestinum) is a very common and popular grass for urban areas and sports fields in Australia and was irrigated with above-indicated wastewaters and tap water for a period of 16 months (March 2016 - June 2017). No fertiliser was added during the study. Irrigation waters, soil extracted waters from different depths of the soils and soil samples from different depths were analysed for different parameters. Considerable changes occurred in soil characteristics over the period of study under different treatments. Soil saturated extract pH (pHSE) experienced an increase of more than 1 unit under irrigation with ATW while STW irrigated soil showed no appreciative change and TW irrigated soil evidenced a slight decrease of pH compared to initial soil pH. Also, a remarkable increase recorded for saturated extract electrical conductivity (ECSE) of top soils irrigated with treated wastewaters compared to soil’s initial ECSE. Variation of soil pHSE in conjunction with soil salinity and differences in nutrient levels amongst irrigation waters resulted in various grass yield from each treatment. Annual grass production of 16,241 kg of dry-matter per hectare (kg DM/ha) achieved from soil irrigated with STW where the recorded annual yields from ATW and TW were 7,028 and 14,216 kg DM/ha, respectively. Overall, the results from this study highlighted the benefits of using STW as irrigation water due to its lower cost of treatment compared to ATW, higher grass production and maintaining of soil pH within an ideal range