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Journal of Environmental Quality Abstract -

Nitrogen Loss from Coffee Agroecosystems in Costa Rica: Leaching and Denitrification in the Presence and Absence of Shade Trees


This article in JEQ

  1. Vol. 24 No. 2, p. 227-233
    Received: Apr 25, 1994

    * Corresponding author(s): drzak@umich.edu
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  1. Liana I. Babbar and
  2. Donald R. Zak *
  1. School of Natural Resources and Environment, Univ. of Michigan, Ann Arbor, MI 48109-1115.



Coffee (Coffea arabica L.) management in Costa Rica is changing from traditional agroecosystems, where coffee is grown beneath a tree overstory, to management systems where shade trees are removed and N fertilizer is applied at high rates (ca. 300 kg N ha−1 yr−1). Although fertilization increases coffee bean production, it also increases the potential for substantial loss of N to groundwater and the atmosphere. We investigated NO3 leaching and the factors controlling denitrification in shaded and unshaded coffee plantations in the Central Valley of Costa Rica; both plantation types were fertilized with 300 kg N ha−1 yr−1. Nitrate leaching was quantified using porous ceramic cup lysimeters placed 60 cm below the soil surface. Losses were estimated by multiplying the soil water NO3 concentration by the monthly soil water excess, determined as the difference between precipitation and actual evapotranspiration. In addition, a laboratory experiment was conducted to investigate the influence of NO3, C, and O2 availability on N2O production and total denitrification (N2O-N + N2-N). Annual leaching losses of NO3 were almost three times greater in unshaded plantations (24 kg NO3-N ha−1 yr−1) than those in shaded plantations (9 kg ha−1 yr−1). In contrast, mean total denitrification rates in control soil samples from shaded plantations were 60% higher (732 µg N2O-N kg−1 d−1) than in unshaded plantations (455 µg N2O-N kg−1 d−1). Carbon additions elicited the largest increase in denitrification, generating nearly a threefold increase (+ C = 8396 µg N2O-N kg−1 d−1; −C = 2985 µg N2O-N kg−1 d−1) in both plantation types. Anaerobic conditions also significantly increased denitriflcation (+ O2 = 4331 µg N2O-N kg−1 d−1; µO2 = 6656 µg N2O-N kg−1 d−1). In both plantation types, the potential for N loss via NO3 leaching was small compared with that for gaseous N loss.

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