Page 498 - FRUTAS DEL TRÓPICO

498 Frutas del trópico

Optimizing nutrient management
In common with many plants, tropical fruit trees require 16 elements for growth, macronu-

trients (C, H, O, Ca, S, N, P, K, and Mg) and micronutrients (Fe, Zn, Mn, Mo, B, Cu, and Cl).

Properly managing N, P, K, Mg, Fe, Zn, Mn, and Cu are important for calcareous soils. Iron

deficiency is the most common symptom for plant grown on calcareous soils. If these nutrients

are provided adequately to tropical fruit trees grown on calcareous soils, they can be as pro-

ductive as grown on acidic soils.

Nitrogen (N): The loss of nitrogen through the volatilization of ammonia is significant for

ammonium N fertilizer applied on calcareous soils. Ammonium N fertilizer should be incorpo-

rated or introduced into the soil through irrigation. Also, nitrate N fertilizer is readily leached
through gravelly calcareous soils, as a result of over-irrigation or heavy rainfall.

Excessive nitrogen fertilizer is also reported to reduce some tropical fruit tree flowering

and fruit sets. We evaluated relationship between nitrogen fertilization and lychee flowering

and found that the timing and rate of nitrogen fertilizer significantly affected soil and leaf nitro-

gen status. High nitrogen concentrations in the leaves were associated with vegetative flushing

and reduced flowering and yield (Table 3).

Phosphorus (P): Phosphorous fertilizers applied in calcareous soils are fixed by calcium
carbonate (calcite) through adsorption and precipitation. Consequently the availability of P in

calcareous soils is relatively low. However, repeated applications of large amounts of P fertilizer

results in the accumulation of P in most cultivated calcareous soils. Accumulated P is slowly re-

leased into the soil solution to become available to plant roots. Therefore growers should use

less P fertilizer if their soils already have high residual P.

Universidad Autónoma de Chiapas