Soil Salinity Under Seepage Irrigation and Irrigation Drainage Tile in Northeast Florida.

Salinity of irrigation water has been a concern for growers in the Tri-County Agricultural Area (TCAA) for many years.  This issue becomes most apparent during low rainfall years when salts can become concentrated in the soil due to evaporation and reduced leaching.  In an effort to reduce water use and nutrient loading to the Lower St. Johns River, alternative irrigation practices, including Irrigation Drainage Tile (IDT), are being evaluated in the TCAA; however, IDT drainage has also been hypothesized to reduce saline soils by improved leaching of salts from the soil profile. This research was conducted to evaluate whether IDT irrigation and drainage could reduce soil salinity as compared to conventional seepage irrigation (SI) and drainage. Soil samples were collected from SI and IDT fields on six farms between 2013 and 2015. For both SI and IDT fields, soil samples were collected at three distances from the water furrow or IDT pipe. At each sampling location, 30cm composite samples were collected from four sample depths below the surface, with three replicates. Soil salinity was assessed using the saturated paste method. Overall results indicated that IDT field soils were significantly lower in salinity than SI fields in five out of six farms. Overall reduction in soil salinity by IDT for all six farms was 32.1% and 39.2% in 0-30 and 30-60 cm depths respectively in Fall 2014, and 6.6% and 30.1% in Summer 2015. In conclusion, IDT has the potential to significantly lower soil salinity compared with SI systems.