Agronomy Research Expertise in Montpellier and Languedoc-Roussillon (South of France)

Agronomy : crops and cropping systems

Keywords :

Nitrogen cycle and the role of shade legumes in coffee cropping systems in Costa Rica

2. Minimizing the impact of cropping on biogeochemical cycles

2. Minimizing the impact of cropping on biogeochemical cycles

In Central America, agroforestry systems provide an alternative to intensive high-input coffee monoculture systems which have trouble reconciling production, environment-friendliness and cost-effectiveness. Agroforestry systems have a carbon storage potential, while also reducing nitrate leaching and emissions of nitrous oxide, a major greenhouse gas. However, in Costa Rica, many coffee plantations under monocropping systems or intercropping with highly pruned shade legumes are still conventionally managed with high quantity nitrogen fertilizer applications (200 kg N/ha/year). There is nevertheless an increase in the use of alternative practices with organic fertilizers and more sustainable management of shade legumes. It is essential to gain insight into the mechanisms and to quantify changes in nitrogen dynamics as a function of the associated woody plant species, its management, fertilizer inputs and field conditions in order to be able to assess the efficacy of nitrogen fertilizer applications, groundwater nitrate contamination and nitrous oxide emissions.

To assess the impact of cropping practices on nitrogen dynamics, the joint research unit Functional Ecology and Biogeochemistry of Soils and Agro-ecosystems (UMR Eco&Sols), in collaboration with its partners CATIE and ICAFE, established nitrogen flow balances in different reference coffee agroforestry systems as compared to monoculture systems. The studies revealed that generally under conventional cropping systems there was low fertilizer use efficiency by coffee trees and shade trees, as well as a high nitrate loss potential in drainage water along with relatively high nitrous oxide emissions. In addition, the findings showed that, as compared to monocultures, shade legumes (Erythrina poeppigiana) had a very positive impact on soil nitrogen availability and coffee production, especially in organic farming systems. Shade legumes thus enable high atmospheric nitrogen fixation and high recycling of this nitrogen when leafy branches are pruned.

Jean-Michel Harmand,

Publication date: 30/05/2010



Update on 19/04/12


Extrait du site