Tomato Growth, Nitrogen Uptake and Soil Mineral N as Affected by Controlled Release Fertilizers in South Florida.

Abstract Tomato growth, N uptake and soil mineral N content after applying two controlled release fertilizers: polymer coated urea (PCU) and polymer sulphur coated urea (PSCU) were investigated in this field experiment. The results showed that treatments with controlled release fertilizers (PCU or PSCU) or their combination with liquid fertilizer (4-0-8) had higher dry weight, N accumulation in shoot than treatments with soluble ammonium nitrate (AN) at three sampling dates. PCU, PSCU plus 4-0-8 and PCU plus 4-0-8 had significantly higher tomato yield than AN plus 4-0-8 and AN only. PCU had the highest yield, followed by PSCU plus 4-0-8 and PCU plus 4-0-8, AN plus 4-0-8 and AN. PCU had the highest apparent nitrogen use efficiency (ANUE) in shoots +fruits, next was PCU plus 4-0-8, followed by PSCU plus 4-0-8, PSCU, the lowest ANUE in shoots plus fruits was from AN plus 4-0-8 and AN (farmer traditional soluble N fertilization practice). Applying controlled release fertilizers (PCU or PSCU) increased soil residual NH4-N and NO3-N content also. This study suggested that applying controlled release fertilizers (CRF) may improve tomato growth and enhance nitrogen use efficiency and increase tomato fruit yield and increase soil mineral N residual. The treatments with combination of 5/8 PCU or PSCU plus 3/8 4-0-8 achieved better tomato yield also. The two combination treatments by CRF with 4-0-8 might be recommended to tomato growers in order to reduce the amount of CRF applied and increase economic return for growers.