DESIGN, CONSTRUCTION, AND INSTALLATION OF LARGE DRAINAGE LYSIMETERS FOR WATER QUANTITY AND QUALITY STUDIES

Abstract

Six large drainage lysimeters (4.85 3.65 1.35 m) were designed, constructed, and installed for quantifyingcrop coefficients and water quality impacts of drip and seepage irrigated watermelon in south Florida. Monitoring systemsdesigned for the lysimeters included water quantity (irrigation, rainfall, runoff, drainage, soil moisture, and water tabledepth) and quality (nutrient concentrations in the root zone, saturated zone, drainage, and runoff). Lysimeters, made of mildsteel plate, containing two plastic mulch plant beds and an irrigation ditch, were installed in a watermelon field. The soilprofile (A and E horizons) was reconstructed using native soil from the field. Bi-weekly soil solution and saturated zonesamples, and event-based drainage and runoff water quality samples were collected and analyzed for nitrogen (NH4-N,NO3-N, TKN) and total phosphorus. The watermelon crop was planted on plastic mulch beds. Four lysimeters received dripirrigation and two received seepage irrigation. Preliminary data for the first six weeks of watermelon crop for the drip andseepage irrigation systems indicated that lysimeters were working properly. Seepage lysimeter systems had higher ETccompared with drip irrigated lysimeters due to wetter soil and high evaporation losses during irrigation. Water quality datashowed that total dissolved nitrogen discharges from the seepage lysimeters were higher than the drip lysimeters. Lowernitrogen loadings for the drip lysimeters were mainly attributed to higher soil water storage capacity and fertigation. Thedesign and installation described in this study will be helpful for future studies with large lysimeters.