Abstract

MOLINA, Eloy  and  RODRIGUEZ, José Hernán. N, P, K and S fertilization and nutrient absorption curves on rice var. CFX 18 in Guanacaste. Agron. Costarricense [online]. 2012, vol.36, n.1, pp.39-51. ISSN 0377-9424.

An experiment of fertilization with N, P, K and S on rice (cv. CFX 18) was evaluated under flooded conditions in a Eutric Inceptisol in Guanacaste; also, the absorption curve of macro and micronutrients during the growing season was determined. The treatments were 0, 80, 120 and 160 kg.ha^-1 of N; 0, 40 and 80 kg.ha-1 of P₂O₅; 0 and 50 kg.ha^-1 of K₂O, and 0 and 20 kg.ha^-1 of S, for a total of 8 treatments with 4 replicates, in a randomized complete block design. Foliar analysis was performed at pre-flowering, and the yield of dry and clean grain was determined at harvest. In the treatment of 120 kg.ha^-1 of N, 40 kg.ha-1 of P₂O₅, 50 kg.ha^-1 of K₂O, and 20 kg.ha^-1 of S, 5 whole-plant samples were taken  at 28, 43, 66, 79 and 93 days after germination, for dry weight determination and chemical analysis of nutrients and for development of the absorption curves as a function of plant age. There was a significant response in yield to N, P, K and S. The treatment of 120 kg.ha1 of N, 40 kg.ha^-1 of P2O5, 50 kg.ha^-1 of K₂O, and 20 kg.ha^-1 of S presented the highest grain yield, in a soil  that had an adequate content of P and K, but low in S. These same treatments brought about the higher foliar contents of N and P and were significantly different from treatments with no N and no P. The nutrient absorption curve was directly related to biomass production. Most of the absorption of nutrients occurred during the reproductive and ripening stages. The maximum absorption of N, P, K, Ca, Mg and S was 61, 25, 197, 17, 11 and 9 kg.ha^-1 , respectively

Keywords : Rice; fertilization; uptake; nitrogen; phosphorus; potassium.

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