Testing of Controlled Release Fertilizer Programs for Seep Irrigated Irish Potato Production#

Abstract

A Best Management Practices (BMP) program has been implemented for Northeast Florida potato (Solanum tuberosum) producers to reduce the potential for nitrate (NO3) leaching from the 9000 ha of land in potato production in the St. Johns River watershed. Controlled release fertilizers (CRFs) could supply nutrients to potatoes while reducing the potential for off‐site movement of nutrients thus, providing a long‐term solution to the problem of NO3 leaching on sandy soils. The objectives of this project were to evaluate the quality and quantity of potatoes fertilized with CRFs and soluble fertilizers and to determine the influence of nitrogen (N) source on N use efficiency (NUE). Fertilizer treatments were: (a) no N control; (b) ammonium nitrate (AN) and urea; (c) polymer coated urea (PCU) and polymer sulfur coated urea (PSCU); (d) polymer coated 11‐11‐11 product; and (e) polymer coated 15‐9‐12 product. Fertilizers treatments were each applied 112, 168, and 224 kg ha−1. The highest total and marketable yields were obtained with CRF 15‐9‐12 (224 kg N ha−1), PCU + PSCU (168 kg N ha−1), and AN + Urea (224 kg N ha−1) averaging 44.2 and 39.9 MT ha−1 respectively, across the three treatments. Total and marketable yield for the no N treatment were 11.2 and 9.3 MT ha−1, respectively. All leaf N levels were within the sufficient range except for plants in the no N, AN + urea (112 kg N ha−1), PCU + PSCU (112 kg N ha−1), and CRF 11‐11‐11 (112 and 168 kg N ha−1). Nitrogen removal by plant tissue ranged from a high of 94.3 kg N ha−1 to a low of 10.7 kg N ha−1 for the 15‐9‐12 (224 kg ha−1) and no N treatments, respectively. At low N rates, CRFs had higher NUE than the soluble fertilizers. Nitrogen use efficiency was similar among all fertilizer sources at higher N rates. #This research was supported by the Florida Agricultural Experiment Station and approved for publication as journal series no. R‐09126.