Print PageModern agricultural systems rely on the use of synthetic fertilizers to provide important nutrients for crop development and production. The main nutrients added are nitrogen (N), phosphorous, and potassium. During 2008, worldwide production of N for fertilizers exceeded 100 Gg. The novel abundance of N -otherwise a limiting nutrient- has been linked to important changes in ecosystem properties and functions. Typifying this model, high doses of fertilizers are commonly used in Costa Rican coffee agroecosystems. The consequences of this practice on the soil nutrient contents and the nutrient plant uptake efficiency are not quite well understood.
With the goal of understanding which management, soil, and environmental factors explain the yield gap in coffee farms in the Tarrazú region of Costa Rica, a field survey of 40 farms was carried out between 2007 and 2009. This included the collection of soil samples, characterization of the shade tree community, counts of standing coffee berries to estimate potential productivity per plant, and characterization of the coffee plants. Additionally, farm owners provided production and fertilizer application records for each farm. This presentation addresses the following questions: what are the consequence of fertilizer application on soil nutrients, and how does soil nutrient content relat e to the coffee production potential.
Results/Conclusions
We found that 92.5% of farmers regularly applied synthetic compound fertilizers. Conventional farmers added a mean dose of N of 213.9 ±23 kg ha-1 year-1, with a range 94.9 to 423.2 kg ha-1 year-1. Other agrichemicals were also commonly employed. We found a moderate negative linear relationship (R2=0.34, p-value=0.001) between the dose of applied nitrogen and the soil pH. This leads us to conclude that the widespread application of nitrogen-based synthetic fertilizers is contributing to higher rates of soil acidification. Soil pH was highly positive correlated with the cation exchange capacity of soils. A negative strong significant correlation between the number of stems per coffee plant and the average berries per branch was seen on soils with a calcium (Ca+) concentration lower than 5 cmol (+) l-1. This relationship was not significant in farms with higher soil Ca+ concentration. Coffee cup aroma showed a positive significant response to an increase of soil magnesium and calcium. We consider that the indiscriminate use of fertilizers will have negative consequences on the soil fertility and negative consequences on coffee production.
