High-density plantain plantations: Lessons from Latin America
Latin America invented the large-scale cultivation of bananas for the export market. Researchers there are now perfecting an intensive production system that promises better returns to farmers.
- Carefully selected offset corms, graded for size, being grown in a farm nursery. Credit: L. Pocasangre/Bioversity International
Banana and plantain farmers who try to obtain better yields by increasing the number of plants in their field will eventually be confronted with the law of diminishing returns. Tightly packed plants compete with each other for nutrients, water and sunlight. The results are smaller bunches and a longer wait between planting and harvesting.
Nevertheless, when Sylvio Belalcázar and his team based at the Instituto Colombiano Agropecuario, now CORPOICA, were asked in the late 1970s to breathe new life into the cultivation of plantain, they started experimenting with high-density planting to realize economies of scale. "The demand for food was growing," recalls Belalcázar, "and we had to find a way to increase yield without increasing production costs so as to avoid a rise in the price of plantain."
The lessons learned as they tested and fine-tuned the practice in various locations have now been distilled into a practical guide by some of the Bioversity scientists and partners who took part in the scientific validation of high-density plantations in Latin America and the Caribbean. The guide, currently available in Spanish only, concentrates on those aspects of high-density planting that are fundamental for achieving the best returns: the preparation of uniform planting material and irrigation.
A high-density plantation contains at least 2000 to 2500 plants per hectare, roughly double the 1000 to 1500 plants per hectare of a conventional plantation. But there is more to successful high-density planting than just increasing the number of plants per hectare. Success depends on starting with good-quality planting material of uniform size, and then making sure that the plants grow in lockstep.
Farmers are advised to start with tissue-culture plantlets—a practice currently popular mostly in China and the Philippines where the price of in vitro plants is low—or microcorms, which are obtained from the offshoots or suckers that grow at the base of the plant. The suckers are collected when they are still small and are carefully prepared to eliminate any damaged tissue before being planted in bags. When they are large enough the plants are sorted by size and planted out in the field. Most farmers will prefer to set up their own nursery to replant their fields. The guide recommends replanting after every harvest but Luis Pocasangre, scientist for Bioversity's Commodities for Livelihoods (CfL) Programme in Latin America, adds that they can also wait and replant after two harvests. "Two crop cycles is OK," he says, "but no more."
Farmers must start with uniform planting material in order to prevent larger plants from stunting the development of smaller ones growing in their shadow. The guide also advises farmers to spread their harvest by planting different parts of their fields at different times of the year. "But farmers might decide to concentrate their harvest at the one time of the year when production is low, and demand and prices are high," says Charles Staver, who coordinates projects on sustainable production in Bioversity's CfL Programme. Of course, if many farmers do the same the price differential will decline, but even in the absence of a monetary incentive farmers may prefer concentrating production, he adds. Those who opt for spreading their harvest have to find steady buyers for their bananas.
High-density plantations are taking off across the region. In Nicaragua, Piero Cohen, a particularly successful farmer who owns a 650-hectare high-density farm in Chinandega, exports part of his production to the US, El Salvador and Honduras, where much of it is sold fresh or processed into chips. In the Dominican Republic, where about 5000 hectares are planted at high densities with a hybrid (FHIA-21) developed by the Fundación Hondureña de Investigación Agrícola, Dominican farmers sell to companies that make banana chips as well as to local supermarkets. According to Ramon Jimenez of the Instituto Dominicano de Investigaciones Agropecuarias y Forestales, the hybrids are so popular that farmers are looking for more planting material to start up production in new areas and to replant old fields. But nowhere are FHIA hybrids more popular than in Cuba, where farmers have succeeded in cramming as many as 4000 plants per hectare into their fields. The plants are replaced every year, mainly because if the farmers didn't uproot them, hurricanes would.
FHIA hybrids offer the possibility of reducing or eliminating pesticides. Indeed, the primary motivation of Cuban farmers who use them is the lack of money to buy pesticides. But even without the help of disease-resistant varieties, high-density planting reduces the build-up of pests such as weevils and nematodes, because the fields are regularly replanted with material that mostly does not contain pests.
High densities are also said to create a microclimate that hinders the development of the fungus causing black leaf streak (better known as black Sigatoka). Farmers who are growing susceptible varieties and have always used pesticides will probably continue doing so, notes Staver, but high-density planting offers them opportunities to cut down on pesticide use. There is similarly no proscription against using herbicides to remove weeds, as an alternative to removing them by hand or mechanically until the crop plants can shade them out. Weeds compete for nutrients and water and are not compatible with successful high-density planting, explains Pocasangre, who also stresses the importance of a constant supply of water.
Plantains require at least 2000 mm of water a year to ensure normal development, and dry spells during the critical period of fruit formation can translate into the loss of up to 70% of production. To avoid such mishaps, farmers are advised to irrigate their field. Maintaining an irrigation system and a nursery on top of managing a field of thousands of plants is obviously not within the reach of resource-poor farmers. Even though economic studies in Costa Rica have shown that high-density planting can increase net returns by up to US$1000 per hectare per year compared with low-density semi-perennial systems, the barrier to entry is high.
"High-density planting is for relatively well-off farmers who have the capacity to scale their investments in response to commercial opportunities," notes Thierry Lescot, a banana scientist at the French agricultural research and development institute, CIRAD.
Staver agrees that "many challenges exist to adapt components of this intensive production system to the conditions of small farmers". Higher-quality and more-uniform planting material, as well as more frequent replanting, are some of the practices that will be tested by farmer groups in four Latin American and Caribbean countries in a new Bioversity project funded by the Regional Fund for Agricultural Technology (FONTAGRO). The objective is to see which combinations of technologies contribute to improving the livelihoods of farmers who have less to invest than those who have already adopted high-density planting.
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