Effects of greywater irrigation on plant growth, water use and soil properties

Glasshouse experiments were conducted to examine the effects of greywater irrigation on the growth of silverbeet plants, their water use and changes in soil properties. The experimental treatments included in the study were: irrigating with 100% potable water (control, treatment T 0), irrigating with 100% greywater (treatment T 1), irrigating with a mixture of greywater and potable water in 1:1 ratio (treatment T 2) and irrigating alternate with potable water for one irrigation and greywater for the next (treatment T 3). The pH and EC values of the greywater used in the study were 10.5 and 1358 μS/cm respectively. Results showed that greywater irrigation had no significant effect on soil total N and total P after plant harvest, but there were significant effects on the values of soil pH and EC. Furthermore, there were no significant effects of greywater irrigation on plant dry biomass, water use and number of leaves. For the treatment that involved irrigating with 100% greywater (treatment T 1), there was a significant increase in soil pH and EC when compared with the control and the other two irrigation treatments. The study indicated that irrigating silverbeet plants with potable water and greywater in an alternate pattern (treatment T 3) had soil pH and EC levels similar to that of irrigation with 100% potable water. This also meant that irrigating alternate with potable water and greywater could reduce some of the soil health risks associated with the reuse of greywater.