YIELD RESPONSE OF BELL PEPPER AND TOMATO TO CONTROLLED-RELEASE FERTILIZERS ON SAND

In fall (September-December) 1991, bell pepper (Capsicum annuum L. cv. Jupiter) and in spring (February-June) 1992, tomato (Lycopersicon esculentum Mill cv. Sunny), were grown with controlled release (CR) nitrogen (N) and potassium (K) fertilizers on EauGallie fine sand (sandy siliceous hyperthermic Alfic Haplaquod). Production system was the full-bed polyethylene mulch with seepage (modified furrow) irrigation. For bell peppers, the CR-N and -K source was an 18N-OP-15K analysis resin-coated (RC) fertilizer, applied at 0, 25, 50, and 75% of the total N and K. The remaining N and K was supplied from soluble (SF) NH4NO3 and KNO3. The 50% PC N and K treatment increased early marketable yields and fruit size of pepper compared with the 100% SF (P<0.05), From early to mid-season, soil nitrogen (NO3)- and ammonium (NH4)-N concentrations were higher with decreasing CR-N rates. However, residual soil NO3 and NH4 concentrations and macronutrient concentrations in shoots and in fruits were similar with CR and SF. For tomatoes, N and K were applied at two rates, 1x and 1.5x, where the 1x rate was equivalent to 195 N/ha and 324 K/ha. Fifty percent of the N or K was replaced by polymer and sulfur-coated urea (PSCU) or resin-coated urea (RCU) and resincoated K (RCK). None of the CR-N and -K treatments improved fruit size or marketable yields compared with the NH4NO3-KNO3 control. Higher N and K rates increased seasonal yield of marketable fruits (P<0.05). Residual concentrations of soil NH4- and NO3-N and K were similar with CR and SF.