Nutrient management in growing media on growth and yield of red oak lettuce under smart greenhouse system

Abstract

This study was to investigate the utilization of organic fertilizer in soilless media (rice husk: rice husk charcoal: coconut dust: cow manure: soil = 1:1:1:1:0.25 by volume) for red oak lettuce production under a smart greenhouse system (controlling the average temperature at 30±3 ºC). The experimental design was a complete randomized design (CRD) with 11 treatments. Treatments were consisting of control (no fertilizer), 20.90 kg N/rai of chemical fertilizer, powder organic fertilizer, granular organic fertilizer, and cow manure at the rate of 10.90, 20.90, and 30.90 kg N/rai). All fertilizers have been applied once before planting and the harvest was done three times. The results in the first harvest revealed that the chemical fertilizer applied at 20.90 kg N/rai gave a significantly higher yield of red oak lettuce, which was 61.48 g/plant. However, the second and third harvesting yields of red oak lettuce under the chemical fertilizer treatment were lower, which was not significantly different from the control treatment. Although the application of granular organic fertilizer at 30.90 kg N/rai gave a lower yield fresh weight of red oak lettuce (36.95 g/plant) than that under the 20.90 kg N/rai of chemical fertilizer treatments, the result in the second and third harvests showed that the application of granular organic fertilizer at 30.90 kg N/rai gave consistent productivity and showed the highest yields, which were 35.35 and 35.76 g/plant, respectively. The result from this study could be concluded that the application of granular organic fertilizer at 30.90 kg N/rai was considered the appropriate rate for red oak production under the smart greenhouse system, which gave the highest average yield from 3 harvest cycles.