Nutrients and environmental quality

When growers strive for maximum production, the use of large amounts of fertilizer can result in nutrient losses, especially nitrate losses, in drainage water. A recent study of nitrate leaching in pineapple (Reinhart, 2000) showed that the loss of nitrate below a depth of 30 cm was greatest where large amounts of N (more than 300 kg ha-1 applied to a soil with high residual nitrogen) in inorganic fertilizer were applied prior to planting. Losses were negligible where manure was used in lieu of inorganic fertilizer (Reinhart, 2000). Foliar fertilization with over 700 kg N ha-1 did not increase leaching losses. Chemical losses through runoff and soil loss may also be significant when pineapple is cultivated on ridges on slopes without soil cover. They reached 63 kg N ha-1 year-1, 44 kg K ha-1 year-1 and 56 kg Ca ha-1 year-1 in an experiment on volcanic soils in Martinique (Khamsouk, 2001). Nitrogen losses due to leaching, runoff and erosion may be an important problem, especially in tropical islands, such as Hawaii and the Caribbean, which have fragile ecosystems. Further studies are needed to better understand and predict nitrogen dynamics in pineapple cropping systems.

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