Soil Moisture Mapping of Potato Farms Utilizing Four Irrigation Practices: Seepage, Subsurface Drip, Tile Irrigation, and Surface Drip, Poster Board #184

Alternative irrigation practices are being investigated for potato production in Northeast Florida to reduce fresh water consumption and increase soil moisture uniformity. In this region, potato is traditionally supplied water though seepage irrigation by pumping water through furrows spaced 60 feet apart, allowing water to flow down into the soil profile and raise the water table up from an impermeable clay layer to the root zone. Excess water is drained into ditches at the end of a field and directed out of the agricultural system. The average potato irrigation requirement was estimated to be 457 to 508 liters/m²/yr. The seepage system commonly results in uneven soil moisture at root zone across the field including the areas furthest from the furrows, leading to uneven growth and yield of potato plants, especially during dry periods. Commercial potato growers have implemented alternative irrigation methods on their farms with the objective to reduce irrigation water volume application and increase water distribution efficiency in comparison to previously established seepage irrigation systems. The objective of this study was to investigate the soil moisture spatial pattern obtained from spot measurements carried out in different irrigation strategies for potatoes. These alternative methods included: a) subsurface drip irrigation, using 2–4 drip tapes installed between furrows 12 inches below the soil surface; b) tile irrigation, using a network of 4-inch pipes buried 24 inches below the soil surface to supply water; and c) surface drip irrigation, using one drip tape per potato row placed above the planted seed piece. Seepage irrigation sites located beside the alternative irrigation systems were also evaluated for comparison. Soil moisture was measured throughout the fields at the root zone, 20 cm below the soil surface using a time domain reflectometer (TDR-300) in conjunction with a mounted GPS and repeated three times throughout the season. Soil moisture variability was evaluated using geostatistical analysis based on the empirical semivariogram. Contour maps were created of each irrigation method to describe the distribution of soil moisture. Spatial soil moisture patterns were found to be correlated with the slope and the distance from the furrow irrigation and drainage ditches. The field water table was raised quickly and more uniformly using subsurface drip irrigation and tile drainage than seepage at determined points of the area, especially the central area between furrows. Drip irrigation showed the greatest uniformity of soil moisture at the root zone compared to other irrigation methods.