Evaluation of controlled-release fertilizers for northeast Florida chip potato production

Control led-release fertilizers (CRF) were compared with ammonium nitrate (AN) in a potato (Solanum tuberosum L.) production study at the University of Florida farm in Hastings, FL, in 2002. Treatments were no nitrogen (No-N), AN, and nine CRFs at 146 kg ha(-1) N and 225 kg ha(-1) N. CRF7 (146 kg ha(-1) N) resulted in highest total and marketable yields at 33.7 MT ha(-1) and 29.4 MT ha(-1), respectively. Tubers from the AN (225 kg ha(-1) N) and CRF9 (225 kg ha(-1) N) treatments had the highest specific gravity at 1.073. Nitrogen removal efficiency was highest in plants in CRF1 (43.0%) and CRF7 (47.3%) plots. Both were significantly higher than AN-treated plants. At 39 days after planting, NO3-N and NH4-N concentrations in lysimeter water samples were significantly higher in AN treatments. Leaf tissue N concentrations were sufficient throughout the growing season in all treatments except No-N.