Coffee population density: A tree management technique to improve soil fertility

The objective of this study was to evaluate the effect of coffee tree population density on soil fertility levels after fourteen years of a field experiment. A field trial was established in 1977 at Londrina, State of Parana, Brazil, with four commercial coffee cultivars (Catuai Amarelo, Acaia, Icatu and Mundo Novo) in the following population densities : 893, 1020, 1190, 1429, 1786, 2381, 3571 and 7143 holes / ha with 2 trees / hole. In 1991 soil samples were collected from 0 to 20 cm soil depth from each plot for chemical analysis. Increasing plant population per unity of area increased soil pH, exchangeable Ca, Mg, and K, available P and organic carbon, and decreased exchangeable Al. These changes in soil fertility were greater under Catuai Amarelo than any other coffee cultivars. Increasing soil surface cover by tree canopy, decresing soil erosion, increasing residue management, decreasing nutrient depletion by leaching and improving nutrient cycling were found to be the possible mechanisms envolved in soil chemical improvement with increasing coffee tree population density.