UVM Theses and Dissertations
Format:
Print
Author:
Castro-Tanzi, Sebastian
Dept./Program:
Plant and Soil Science
Year:
2014
Degree:
Ph. D.
Abstract:
In Costa Rica, more than forty thousand farmers cultivate arabica coffee. Many of them combine different forms of agroforestry (i.e. the inclusion of trees in crop systems) with intensive agronomic management'practices. In the light of anthropogenic climate change, coffee agroforestry represents a carbon negative system and a management practice to affront increased extreme weather conditions. However, by adopting this practice, farmers may be forfeiting revenues on the short term as resource competition by the plants in the shade canopy may trump potential yields.
In this dissertation I explore tradeoffs and synergies between crop productivity and ecosystem services in intensively managed coffee agroforestry systems in the Los Santos region of Costa Rica. I combined farmer self-reported data, coffee plant productivity assessments, and vegetation and soil surveys to carry out an agroecological analysis of agroforestry coffee systems. My research was driven by the following objectives.
1) Identifying soil, site and agronomic management factors associated with coffee productivity at the field and plant scale; 2) Understanding the vegetation and soil carbon storage potential of coffee agroforests and associated land uses; 3) Examining the effect of the proximity of shade canopy plants on coffee productivity potential in coffee agroforestry systems.
Results from my study indicate that coffee yields were higher in those fields receiving higher doses of essential macronutrients in the form of synthetic fertilizers. The concentration of soil exchangeable calcium and acidity, fungal disease pressure and elevation were additional factors partially explaining the variation of observed coffee crop yields. A partial budget analysis indicated that nitrogen inputs exceeded by 3.2 ± 0.3 times the crop requirements of this nutrient. Results from this study suggest that the' excess nitrogen and a continuous extraction of soil cation bases in the crop may be contributing to the acidification and fertility depletion of soils under coffee cultivation.
I estimated that 176 ± 10 Mg ha⁻¹ of carbon is assimilated in the vegetation's biomass and soil organic matter of coffee agroforestry systems. While this represents 1.6 times more carbon than what is found in the vegetation and soils of pastures in the same region, it only represents 0.6 of the amount observed in forests.
A review of scientific literature indicates that coffee monocultures tend to outperform agroforestry systems when it comes to coffee production in long term trials. However, my field research indicated that within the agroforestry coffee fields in Los Santos region coffee plants found in the vicinity of shade canopy plants bore more fruit when compared to those in isolated conditions. This suggests that facilitation tends to be the prevailing outcome of the coffee-shade canopy plant interaction in this agroecosystem.
In this dissertation I explore tradeoffs and synergies between crop productivity and ecosystem services in intensively managed coffee agroforestry systems in the Los Santos region of Costa Rica. I combined farmer self-reported data, coffee plant productivity assessments, and vegetation and soil surveys to carry out an agroecological analysis of agroforestry coffee systems. My research was driven by the following objectives.
1) Identifying soil, site and agronomic management factors associated with coffee productivity at the field and plant scale; 2) Understanding the vegetation and soil carbon storage potential of coffee agroforests and associated land uses; 3) Examining the effect of the proximity of shade canopy plants on coffee productivity potential in coffee agroforestry systems.
Results from my study indicate that coffee yields were higher in those fields receiving higher doses of essential macronutrients in the form of synthetic fertilizers. The concentration of soil exchangeable calcium and acidity, fungal disease pressure and elevation were additional factors partially explaining the variation of observed coffee crop yields. A partial budget analysis indicated that nitrogen inputs exceeded by 3.2 ± 0.3 times the crop requirements of this nutrient. Results from this study suggest that the' excess nitrogen and a continuous extraction of soil cation bases in the crop may be contributing to the acidification and fertility depletion of soils under coffee cultivation.
I estimated that 176 ± 10 Mg ha⁻¹ of carbon is assimilated in the vegetation's biomass and soil organic matter of coffee agroforestry systems. While this represents 1.6 times more carbon than what is found in the vegetation and soils of pastures in the same region, it only represents 0.6 of the amount observed in forests.
A review of scientific literature indicates that coffee monocultures tend to outperform agroforestry systems when it comes to coffee production in long term trials. However, my field research indicated that within the agroforestry coffee fields in Los Santos region coffee plants found in the vicinity of shade canopy plants bore more fruit when compared to those in isolated conditions. This suggests that facilitation tends to be the prevailing outcome of the coffee-shade canopy plant interaction in this agroecosystem.