User:Michael.C.Wright/sandbox/Scratch: Shade-grown coffee

Positive
Coffee trees grown under shaded conditions require less fertilization than trees grown in full sun. For this reason, shade-grown coffee is beneficial to producers who can not afford the cost of fertilization required for intense cropping systems under full sun.

Shade trees protect coffee trees from heavy wind, rain, and sun irradiance. These benefits are especially helpful in environments less favorable to sustainable production. For example, proper shade trees can buffer coffee trees from prolonged droughts and extreme temperatures.

If the litter from the shade trees (fallen leaves and branches) is allowed to decay on the ground, nutrients taken up by the shade tree can be returned to the system.

Shade conditions can reduce incidences of certain pests such as the Asian white stem borer.

Negative
Shade trees compete with coffee trees for water and nutrients. In regions where either resource is limited, competition is exacerbated.

Reduced nutrient availability, namely nitrogen, reduces coffee tree yield when compared to intense cropping systems in full-sun conditions.

The shade trees must be maintained (regularly pruned, weeded, fertilized, etc) and this adds to the cost for the coffee producer. Rigorous evaluation and management of the companion trees is required in order to realize the advantages of shade-grown coffee.

Shade trees contribute to increased humidity and ground litter from fallen leaves and branches. These conditions are beneficial to the proliferation of certain coffee pests and diseases, such as coffee berry borer and American leaf spot.

Revenue potentials are lower for shade grown versus full-sun management systems.

Coffee leaf rust
There is a complex interaction between shade, meteorological effects such as rainfall or dry periods, and aerial dispersal of coffee leaf rust. Researchers have found that shade may suppress spore dispersal under dry conditions but assist spore dispersal during wet conditions. The researchers acknowledge the need for further research on the topic.