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Representation of Solid and Nutrient Concentrations in Irrigation Water from Tailwater-Recovery Systems by Surface Water Grab Samples

Omer, A. R., Moore, M. T., Krutz, L. J., Kröger, R., Prince Czarnecki, J. M., Baker, B. H., Allen, P. J.
Journal of irrigation and drainage engineering 2017 v.143 no.11 pp. 06017013
agricultural land, alluvial plains, ammonium, infrastructure, irrigation, irrigation water, nitrogen content, nutrient content, nutrients, phosphorus, surface water, total suspended solids, Mississippi, Mississippi River
Tailwater recovery (TWR) systems are being implemented on agricultural landscapes to create an additional source of irrigation water. Existing studies have sampled TWR systems using grab samples; however, the applicability of solids and nutrient concentrations in these samples to water being irrigated from TWR systems has yet to be investigated. This is important if research using grab samples is used to quantify the application of solids and nutrients back onto the agricultural landscape. In order to test whether grab samples are representative of water pumped from TWR systems for irrigation use, this study compared concentrations of total suspended solids (TSS), total P (TP), total N (TN), total Kjeldahl N (TKN), nitrate-nitrite (NO3-NO2-) and ammonium (NH4+). Grab samples were collected simultaneously from the surface water and from their respective outflow of irrigation infrastructure in six TWR systems in the Lower Mississippi Alluvial Valley. Comparison of 14 irrigation events showed TSS, TP, TN, TKN, NO3-NO2- and NH4+ did not differ between surface water grab samples and irrigation water samples. No differences were found for TN, TP, NH4+, and TKN across sites, however, differences between sites did exist for TSS and NO3-NO2-. This research suggests surface water grab samples from TWR systems represent the solid and nutrient concentrations being irrigated at that moment of time.