Holgate, Leon Carl (2010-05). Irrigation Water Source: Effect on Soil Nutrient Dynamics and Microbial Community Composition. Master's Thesis.
Maintaining a supply of potable water is a growing concern in the USA, particularly in many southern and western states. One method of sustaining water supply in these areas is the use of greywater for commercial and residential landscape irrigation. Greywater is derived from residential use such as showers, laundering and bathing, and accounts for approximately 65% of residential waste water. I investigated the effects of municipal tap water, harvested rain water, washing machine and bath water (greywater) on the carbon and nutrient dynamics of soil, foliage and leachate and on soil microbial diversity. I also examined the presence or absence of E. coli in source water and leachate. There was a significant difference in leachate chemistry among irrigation treatments. Average leachate pH and conductivity was significantly lower in treatments irrigated with harvested rain water. Fertilization did not affect any of the leachate chemistries with the exception of orthophosphate-P, but significantly reduced carbon in soil without grass (blank) and domestic tap water treatments. E. coli colonies were detected in source water (greywater), but not in leachate suggesting that there was no movement through the soil profile. The results of principal component analysis (PCA) on whole-soil fatty acid methyl ester (FAME) profiles indicated distinct differences in soil microbial community composition due to irrigation with greywater as compared to rainwater, suggesting that water source may affect soil microbial community composition.