Phosphorus fertilization of peach palm (Bactris gasipaes) for heart-of-palm in nurseries and plantations

Abstract

Two trials in peach palm for heart-of-palm were carried out to evaluate fertilizer response and the predictive level of foliar and soil analysis as diagnostic tools of P deficiency. The first in a greenhouse in Guápiles, Limón, with 30 cm-high nursery plants of the Putumayo variety, by evaluating the application of 6 rates of P established on the basis of the buffer coefficient. Five Andisols and 5 Ultisols were used, all with deficient values of available P. After 6 months, measurements were made for height, fresh and dry weight of aerial biomass, P content in the plant and the level of extractable P by Modified Olsen and Mehlich 3. The second experiment was in Caño Negro, San Carlos, in a 2 year-old commercial plantation of the Tucurrique spiny variety. Response to P fertilization was evaluated in a P deficient Inceptisol of low fertility, using 6 rates also defined by the buffer coefficient. During a 2-year period, monthly measurements were made for fresh weight of reaped heart-of-palm; trimestral sampling of soil and foliage was done for the analysis of available P and total P, respectively. In the greenhouse test, a critical level of 10 mg l^-1 of P in Ultisols was estimated with the Modified Olsen solution, which was related to a minimum value of foliar P of 0.14%. Extractable P by Modified Olsen was not an efficient parameter for the diagnosis of P deficiency in Andisols. In the field, although all the treatments exceeded the control, no clear response to P fertilization was found after 2 years of evaluation; yields of the first year reaping varied between 14785 and 16238 kg ha^-1 year^-1 of fresh heart-of-palm and in the second year between 12109 and 13561 kg ha^-1 year^-1. The conventional methods of diagnosis of P deficiency through soil and foliar analyses were, in general, not useful to indicate a positive response of heart-of-palm to P applications. This reaffirms the need for research on alternative diagnostic methods for woody perennials, such as the analysis of soluble organic P, P in the soil solution, and the effect of mycorrhizas on the P supply to heart- of-palm.