Guest post by Phil Roudebush, EXTENSION MASTER GARDENER, KANSAS
Don Juan Mora, a small-scale organic coffee farmer in Nicaragua, reached down and took a piece of organic material that was covered with a fungal mat from the soil on his farm. “When you see this, it means the soil is good and coffee plants will do well,” he said. As a master gardener back in the U.S., this made me think more about soil and its importance. A commonly used axiom in gardening and horticulture is the statement that “soil is not dirt.” This simple but profound gardening proverb suggests that healthy soil is a complex mixture of minerals, organic matter, air, water and millions of different living organisms (bacteria, archaea, fungi, algae, protozoa, nematodes, arthropods, earthworms, gastropods and more). We should think of healthy soil as a living, breathing organism which needs to be nourished in order to support plant and animal life. This concept has also been called the “soil food web” to denote the interdependent nature of these relationships.
Soil quality encompasses the characteristics of fertility, tilth (physical properties of soil) and biological activity. Organic farming uses various techniques to enhance soil quality, especially methods to increase and improve soil microorganisms. Symbiotic fungi are an important part of the “living soil” and those associated with plants are called mycorrhizae (from myco meaning fungus and rhiza meaning root).
Mycorrhizae are the most common symbiotic species on earth, with endomycorrhirzae ( or EM; also called arbuscular mycorrhizae) being the most frequent type, occurring in about 80% of plant species, including coffee. As their name implies, mycorrhizae are intimately associated with plant roots and actually grow into root tissue making a thick net around roots and extending for large distances into surrounding soil.
Like many crops, coffee associates symbiotically with EM. Numerous studies have shown the natural occurrence of EM in the soil of coffee orchards in Africa, South America and Central America, as well as the presence of mycorrhizal structures in coffee roots. The benefits of EM for plants are many: increased nutrient uptake, including phosphorus, calcium, magnesium, zinc, manganese, copper and iron; increased drought tolerance; protection against plant pathogens; and improved tilth (improved soil structure and aggregation). There is also evidence that coffee plants and the shade trees under which they grow “talk” with each other through shared EM and may use EM to develop their own symbiotic relationship. For example, some farmers claim that coffee from coffee plants grown in the shade of citrus trees will develop citrus aromas and flavors; if this is the case, then EM may be one way that shade trees influence the aroma and flavor compounds in coffee.
As mentioned at the beginning, the importance of organic coffee farming and maintaining healthy, living soil was noted during an Equal Exchange delegation to a coffee farm in Nicaragua in February 2015. We visited the farm of Don Juan, who grows organic, shade grown coffee on his farm near Boaca, Nicaragua. Equal Exchange purchases coffee beans from the Tierra Nueva Cooperative Union, of which Don Juan is a member. He and his son, Joel, help stimulate EM development by incorporating mulch, coffee seed hulls and ash into soil that is used to plant coffee seedlings. Young perennial plants have a high phosphorus requirement for optimal growth and EM are important for improving transport of phosphorus from soil into coffee seedlings. These same methods of soil amendment are used with mature coffee plants. The organic farming techniques utilized by Don Juan and thousands of other small organic coffee farmers are important for improving soil quality, improving plant health and ultimately improving coffee quality.