Fertilizer type and species composition affect leachate nutrient concentrations in coffee agroecosystems

Abstract

Intensification of coffee (Coffea arabica) production is associated with increases in inorganic fertilizer application and decreases in species diversity. Both the use of organic fertilizers and the incorporation of trees on farms can, in theory, reduce nutrient loss in comparison with intensified practices. To test this, we measured nutrient concentrations in leachate at 15 and 100 cm depths on working farms. We examined (1) organically managed coffee agroforests (38 kg N ha -1 - year -1 ; n = 4), (2) conventionally managed coffee agroforests (96 kg N ha -1 year -1 ; n = 4), and (3) one conventionally managed monoculture coffee farm in Costa Rica (300 kg N ha -1 year -1 ). Concentrations of nitrate (NO3 - -N) and phosphate (PO4 3- -P) were higher in the monoculture compared to agroforests at both depths. Nitrate concentrations were higher in conven- tional than organic agroforests at 15 cm only. Soil solutions collected under nitrogen (N)-fixing Erythrina poeppigiana had elevated NO3 - -N concentrations at 15 cm compared to Musa acuminata (banana) or Coffea. Total soil N and carbon (C) were also higher under Erythrina. This research shows that both fertilizer type and species affect concentrations of N and P in leachate in coffee agroecosystems.