Aportes de nitrógeno y fósforo al suelo a través de la hojarasca en dos agroecosistemas de café (coffea arábica) bajo sombra en los andes venezolanos.

Abstract

During one year period , the contribution of nitrogen (N) and phosphorous (P) to the soil through incorporating dead leaves in decomposition in two coffee agroecosystems (coffee arabiga) located in the sector Vitu, Municipality of Pampan , Trujillo State, was evaluated. In system A, coffee plants were mainly in the shade of trees like Ficus caruca and Inga spp, while system B . consisted in coffee in the shade of trees like Inga spp., Persea Americana and Bixa orellana, among others. The research was carried out in three stages ; a fi el stage in which decomposition of dead leaves was determined by means of the “litter bags” method; and a laboratory stage where concentrations of nitrogen (N) and phosphorous (P) were determinated by means of the Kjedahl and blue molybdenus methods, respectively, the controbutions of these parameters to the organic humus were evaluated too. Concentrations of N and P in system A were 2,10 – 3,00 % of coffee, 1,30 – 2,07 % N of tree leaves and 0,07 – 0,12 % of coffee, respectively. In system B, the contribution were: 2,03 – 2,38 % of coffee, 1,90 – 2,69 % N of tree leaves , and 0,11 – 0,16 % of coffee, 0,07 – 0,15 % of tree leaves. The contribution of tree leaves to the organic humus in system A were: N: 83,16 (Kg/ ha/year) and of N: 104,97 (Kg/ha/year) for system B, respectively. Constributions of P for system A was of 3,61 Kg/ha/year) and of 5,73 (Kg/ha/year) for system B. A light increase of values from N and P in dead leaves was also noticed. These results can be attributed to the fact that system B has different shade trees with respect to system A; however, the concentration of N and P in the organic humus are generally similar. Coffee farming in the shade provides an adequate microclime in humidity and temperature, basic for the development of the plant in not best areas for that kind of farming; this fact confers it a great ecological importance. For comparing these results the SAS statistical pack and the one-way variance analysis were used.