AbstractThe effects of municipal biosolid yard-waste compost and fertilizer N applications on tomato (Solanum lycopersicum L.) growth, yield and fruit quality were evaluated in Lajas (Typic Haplusterts) and Juana Díaz (Cumulic Haplustolls) (Fortuna Substation), Puerto Rico, for three years. In Fortuna, an initial application of compost at 50 t/ha significantly improved yields over those in unamended soil, yet a second application of compost the following year at 50 and 100 t/ha, reduced yields. No residual effect of compost on tomato yields was detected the third year. In Fortuna, levels of N fertilization did not significantly affect tomato yields, growth or quality, except in the third year, when tomato yields were significantly higher in soils fertilized with 75 kg N/ha than yields from unfertilized soil. At Lajas, there was a significant crop response to fertilizer N in one of the two site years, when crop response to initial fertilizer N application was evaluated. Compost addition in Lajas did not improve yields or plant agronomic components for the first year of cropping tomato. The use of the SPAD chlorophyll meter may be a useful N diagnostic tool for tomato grown under drip irrigation and polyethylene mulch. In general, maximum SPAD values coincided with maximum yields, depending on the hybrid or variety planted; treatment effects were adequately separated out. The economic optimum N rate was relatively insensitive to fertilizer and tomato price fluctuations in the range selected. The calculated optimum N rate to achieve 99% yield goals was 143 kg N/ha, at sites with initial N application in Lajas, and 165 kg N/ha, respectively, for second and third applications of N in Fortuna, with maximum yields near 54 t/ha.
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