Two axial experiments were carried out in two soils of the Northeast of Brazil from 1987 to 1992 to study the response of coconut to urea, simple superphosphate and potassium chloride. Nitrogen was found to affect the number of fruit in the Quartz Sand Soil. The critical level for nitrogen in leaf 14 was 17.18 g kg-1 which was reached when 1.538 kg of N was applied per plant/year. In the same soil, simple superphosphate did not influence the number of fruit while the response to potassium chloride was linear. In the Yellow Podzolic, response was observed for all fertilizers studied. The effect of urea on leaf nitrogen content was linear. The leaf critical level for phosphorus was 1.21 g kg-1, reached when 2.01 kg per plant/year of simple superphosphate was applied. There was no significant effect of potassium chloride on the potassium leaf content, but it was observed for chlorine whose critical level (6.07 g kg-1 on leaf 14) was reached when 2.06 kg of potassium chloride per plant, per year were applied.
critical levels; nitrogen; chlorine