The Influence of Various N-P-K Fertilizer Levels on Onion Production in Southern Puerto Rico

Abstract

An experiment was conducted on a San Anton (Cumulic Hasplustolls) fine loamy mixed isohyperthermic in the southern irrigated coastal plain of Puerto Rico, to evaluate the influence of various N-P-K levels on yield and quality of onion (cultivar Texas Grano 502). All P and K fertilizer were broadcast and mixed with the soil at planting. Half of the N fertilizer was broadcast at planting and half was banded 6 weeks later between rows and left uncovered. Mean yield differences attributable to fertilizer levels were not significant. The soil seems to have sufficient available native N to meet this crop's needs. This may be in part attributable to continuous fertilizer applications over the years for sugarcane production in this soil. An average onion production of 22 metric tons/ha was obtained. The world average production is 11 metric tons/ha. Based on the results obtained, the production of onions in th is soil is recommended for two reasons: 1) The high tonnage that can be obtained, and 2) the low investment on fertilizers if planted on soils of high fertility, especially if previously used for sugarcane and fertilized over a long period.