Resumen

CAMACARO, Selina; CHACON, Eduardo  y  MACHADO, Wilfre. Macro and micronutrients fertilization effects on the structure of Leucaena leucocephala (Lam.) de Wit.. Zootecnia Trop. [online]. 2002, vol.20, n.4, pp.433-447. ISSN 0798-7269.

An experiment was carried out at "La Antonia" Experimental Research Station of the Central University of Venezuela, located on an area of transition of tropical humid forest and dry forest, with the objective to evaluate the effect of the fertilization with macros and micronutrients on the structure of Leucaena leucocephala. Plots of this legume, established in single rows of 1x 2 m, on a pasture of Cynodon sp., was used. A random block design was used with sixteen treatments, including two controls (negative and positive), resulting of combining the nutrients K, Mg, Cu, and Zn with a missing element, applied at doses of 70, 20, 3, and 3 kg/ha, respectively. These elements were detected as deficient according to soil analysis (K: 32 ppm, Mg: 12 ppm, Cu: 0 ppm, Zn: 1.5 ppm, pH: 5.2). Four nondestructive samplings (end of rainy season: November 97, drought season: March 98, rainy season: July 98, and end of rainy season: November 98) were done to evaluate: height, number of branches, length of branches with diameter < 6 mm, and with diameter >6 mm, number of leaves, and length of leaves. Plot was grazed by growing cattle female, after samplings. Significant differences were detected (P<0.05), in all the structure variables evaluated, for effect of the fertilization. An important, although not significant effect, was observed with the element Cu in all the evaluated structure variables, followed by K and Zn, mainly in those variables that constitute important components of the edible biomass (height, number, and length of leaves, length of branches Ø < 6mm). On the other hand, the presence of Mg in the treatments 9 and 6 seemed to have caused a detrimental effect. It is considered that this response could be associated to the contribution by the deficient elements for the plant, and to additional contribution of S through the used sources. The obtained results would allow to make inferences on the modification of the structure of the plant to increase the biomass production and its utilization. It is recommended to continue the evaluations in the field combining different doses and these and other elements that could cause a desirable effect in the structure of the plant.

Palabras clave : Leucaena leucocephala; fertilization; structure; macronutrients; micronutrients.