By Andrew Margenot, PhD, Soils & Biogeochemistry, Univeristy of California, Davis
Nicaragua is a Central American nation that, though endowed with natural resources, is considered the second poorest country in the western hemisphere. This largely reflects a combination of political and economic instability due to civil war (1980-1990) and frequent exposure to natural disasters. Agriculture accounts for one-third of livelihoods of Nicaraguans, 80% of which involves family farms.
In contrast to the semi-arid, volcanic landscape of the western side, on the Caribbean coast we find ourselves in the lowland humid tropics with three-fold greater precipitation, albeit with soils of inherently low fertility. Soils in the Nicaraguan lowland tropics are highly weathered (Oxisols and Ultisols in USDA Soil Taxonomy), meaning they have low pH (acidic) and nutrient reserves, in particular calcium, magnesium, and phosphorus. A fragile but dynamic fertility cap exists at the surface (<20 cm) under the native humid rainforest vegetation in this region.
As is typical of forest ecosystems across the tropical belt, the thin but fertile topsoil represents the accumulation of scarce nutrients from the soil by plants. Deep roots mine the sparse nutrient elements throughout the soil profile, bringing them up into the plant biomass. These nutrients are redeposited to the soil in the form of plant litter. Under the wet and hot conditions of the tropics, the resulting rapid decomposition of plant litter returns these nutrients to the topsoil, where they are taken up by shallow roots before they can be leached downward.
To capitalize on the fertility at the soil surface, tropic forest is often converted into annually tilled fields. The loss of deep rooted tree species breaks the nutrient cycle and is further exacerbated by the net loss of nutrients through crop harvest. As a result, the soil fertility cap and thus productivity rapidly declines within several cropping seasons. Extensive fallowing or replenishment of nutrients (i.e., fertilization) is necessary to restore soil fertility.
On the Caribbean coast of Nicaragua, much of the agriculture is based on agroforestry, i.e. the management of tree species for food and fuel production. This reflects the high land to population ratio and the high suitability of this climate for tree crop species such as cacao and breadfruit from other parts of the world. Agroforestry mimics the nutrient cycling of native forests in these low fertility soils, and additionally offers reduced erosion and soil compaction, a risk of repeated tillage in a region already vulnerable to intense precipitation events.
Cacao (Theobroma cacao) is an example of an agroforestry species with high value as an export crop and intensive management, in particular in its early phases. Cacao cultivation begins with germination of seeds in sealed bags filled with wet sawdust, mimicking conditions of the forest soil-litter interface to coax the seeds to life. Once germinated, seeds are hand planted into individual nursey containers, which generally receive a fertilizer such as compost, urea, or even topsoil excavated from the forest. Cacao seedlings are carefully protected from the sun under shade cloth and maintained moist (e.g., sprinkler irrigation). Once seedlings are sufficiently robust, they are transplanted in soils receiving partial shade from over-story trees.
Though not a tree species, pineapple (Ananas comosus) is readily integrated into agroforestry management because of its semi-perennial nature, producing fruit for 3-5 years. Depending on the cultivar, which can vary by size and sweetness, pineapple is locally consumed as well as sold on domestic and foreign markets.
Breadfruit (Artocarpus altilis) is a common agroforestry species with little to no export value but high importance as a food crop. The deep-rooted trees are often resistant to hurricanes that tend to level other tree crops such as coconuts. A central ingredient to a key dish in creole cuisine, breadfruit is blended with coconut milk to make a smooth porridge that has a strikingly similar flavor to North American oatmeal. Breadfruit is tantamount to food security in this region, to the point that houses on the market are expected to have a breadfruit tree on the premises.
Coconut (Cocos nucifera) has value as both a local food and as crops for export. Its value varies by tree type (tall vs dwarf), and by utilization of specific product markets (oil, milk, water, etc.). The potential of coconut oil as a high value and shelf-stable product is increasing in regions like the Wawashang basin.
Given its importance for food security the Nicaraguan tropical lowlands and other regions, regional research efforts are focused on breeding and management of tree crop species. The Wawashang agroforestry center of La Fundación para la Autonomía y Desarrollo de la Costa Atlántica de Nicaragua (FADCANIC; “Foundation for the Autonomy and Development of the Atlantic Coast of Nicaragua”) focuses on such work. For example, FADCANIC runs a program on cross-breeding of coconut varietals from around the world, including Brazil, West Africa, and the Pacific Islands, in an effort to develop varietals better developed for the Nicaraguan niche. In order to increase participation by small-scale producers in the agricultural export markets, FADCANIC runs an extensive cacao nursery to provide affordable seedlings. These efforts exemplify the potential of basic investments in natural capital (e.g., seedlings, varietals) to enhance already ongoing practices by farmers. Furthermore, given the historically relatively low focus on agroforestry in agricultural science means that there is great untapped potential to improve agroforestry strategies toward food security.
Note: Content is based on a USAID Farmer-to-Farmer assignment on soil conservation in Nicaragua in May 2016. Photographs were taken in the Wawashang agroforestry center of FADCANIC. FADCANIC was founded in 1990, shortly after a statute by the government of Nicaragua recognized the autonomy of the Atlantic coastal regions. The mission of FADCANIC is to support the autonomy of the coastal region by improving the livelihoods of its citizens. Additional information on FADCANIC is available at http://www.fadcanic.org.ni/