Development of Nitrogen Fertilization Best Management Practices (BMPs) for Potatoes in Florida

With approximately 25,000 acres of winter and spring potatoes, Florida is an integral part of the supply chain for freshly harvested potatoes in spring in the United States with a crop value of $135 million in 2007. BMPs are being developed to increase nitrogen (N) use efficiency for potato production and to reduce N losses to the environment. The objective of this study was to determine an optimal N fertilizer rate for commercial chipping potato production in northeast Florida.  Field experiments were conducted during Spring 2011 in Hastings, FL. The study was performed on three commercial farms growing ‘Atlantic’ potato.  Water was supplied through seepage irrigation into furrows 60 feet apart, thereby raising the water table to the rootzone. A randomized complete-block design with 4 replicates included total N ranging from 112 to 335 kg N/ha from ammonium nitrate, wherein all treatments received 56 kg N/ha at fumigation 30 days before planting. At emergence, N was sidedressed at 0, 56, 112, or 168 kg N/ha from liquid urea ammonium nitrate (UAN). Subsequently, a second sidedress of 56 or 112 kg N/ha from UAN was applied at the 6–8 inch growth stage. Total and marketable yield, specific gravity, plant dry weights, and N accumulation in the plants, tubers, leaves/stems were evaluated. Soil N content was recorded throughout the season.  Plant tissues (leaves/stem and tubers) accumulated from 101 to 157 kg N/ha. No difference in potato yields were observed between N rates at any location. Total marketable potato yield ranged between 250 and 320 cwt/ac. There were no differences in potato yield and tuber specific gravity between N rate of 56 or 112 kg/ha applied at 6–8 inch growth stage. In two out of three locations, significant increase in tuber specific gravity was achieved with N fertilizer rates above 112 kg N/ha from the ‘at emergence’ application. The preplant N fertilizer application did not increase soil N availability at plant emergence, with soil N content averaging 26 kg/ha which is similar to the soil N content at pre-plant. Reduced soil N content coincided with recent heavy rainfall events.