(221) Controlled-release Nitrogen Fertilizer Release under Field Temperature and Precipitation Conditions for Potato Production in Northeast Florida

Abstract

Potato production in the Tri-County Agricultural Area of northeast Florida accounts for nearly half of the state's $120 M, 18-K hectare annual crop. Concern over nitrate movement into watersheds from potato production have stimulated research into alternative fertilizer sources and practices. This study evaluated the potential of several controlled-release fertilizer (CRF) products to release nutrients over a 100-day growing season under field temperature and precipitation conditions. In 2003 and 2004, 6 and 3 CRF products were evaluated, respectively. Meshbags containing 3 g of product mixed with 200 g of soil were buried 15 cm below the top of the potato row. Meshbags were removed at 2-week intervals. Samples were dried and sieved to remove soil. Fertilizer prills were ground and mixed with DI water to dissolve residual fertilizer. Samples were analyzed for total N by the Dumas (combustion) method (2003) or for TKN (2004). In 2003, initial release (after 20 days) ranged from 23% to 85% for the six products. In 2004, initial release (after 9 days) ranged from 34% to 65% for the three products. In 2003, total N release from CRF prills after 104 days ranged from 72% to 99%. In 2004, total N release from samples ranged from 79% to 92% release after 91 days. The shape of the release curve described some release patterns comparable to water-soluble fertilizers while others exhibited sustained-release properties. If release characteristics are designed to match potato plant uptake requirements in time and quantity, CRF products may be used to reduce off-site N movement while maintaining potato production.