From January 24 to February 5, Dr. William Terry Kelley was in the Dominican Republic as part of a Farmer-to-Farmer (F2F) assignment. During his trip, Dr. Kelly traveled to La Vega Province where he assisted smallholder chayote (tayota) producers in adapting sustainable soil management and fertilization techniques.
Farmers in the Jarabacoa region of the province are currently producing Tayota (primarily Sechium edule) on slopes approaching 40% with a raised trellis system. While this crop is profitable for these growers and is therefore economically viable, the production system that they employ is not sustainable for the soil nor the surrounding environment. Since the growers do not use any type of ground cover under the canopy of the crop, most chayote field suffered from high levels of soil erosion.
While most growers have adequate chemical options for traditional insect and disease control, many of them utilize highly toxic compounds that they apply with hand sprayers and little to no personal protective equipment This situation presents an avoidable danger to the producers, since many of those insects and pest could be controlled with milder compounds that would not pose such a danger to the growers. In general, the growers’ fertilization practices are sound, although they could possibly reduce nitrogen applications, particularly during dry parts of the season.
Dr. Kelley's Recommendations
In light of these issues, Dr. Kelley provided a series of recommendation that local chayota farmers can use to prevent soil erosion and improve soil fertility. To generate the following recommendations, Dr. Kelley first had to carry numerous visits to chayota fields and identify the soil and fertilization practices being employed. Next, he had to assess the problems they were facing and determine the best way to employ changes in their practices. Also, having found out that there was some resistance from growers to using cover crops because of their concern over the cover crop competing with the Tayota crop, Dr. Kelley felt it best to make a plan to prioritize three key areas:
- Reducing Soil Erosion: Growers are faced with a dramatic soil erosion problem where Tayota is produced on steep slopes. The most feasible way for the growers to alleviate this problem is to use a cover crop in conjunction with the Tayota crop. Not being totally familiar with the flora that will thrive in the tropical climate, Dr. Kelley made recommendations that several different types of covers be trialed in order to determine the best cover to use. This cover has to provide sufficient coverage to virtually eliminate soil erosion, must not compete economically with the crop and must be capable of thriving under the crop canopy and in the tropical climate. Growers would like to use a cover that provides some nitrogen to the soil which means a legume would be preferable or a legume mixture. Some of the possible species to try would be:
- White Clover
- Hairy Vetch
- Ladino Clover
- Perennial Peanut
- Annual Ryegrass (or a non-competitive native grass species that can be mixed with the above legume species).
- Ideally, these covers should be planted as the crop is initiated so that they can get established before the crop canopy is complete. Covers that are too aggressive could be killed down with paraquat and still leave enough residue to hold the soil in place. However, ideally a cover mixture that is low profile would be non-competitive to the crop and the legume would supply the needed nitrogen for the grass species and thus not compete with the crop for nutrients. The crop should not compete in sum with the crop for moisture as the cover will conserve much of the moisture present.
- Using Appropriate Pesticides:The growers do have some weed, insect and disease problems. For weed problems the growers are using paraquat in general. This is an appropriate use and can be continued. Most of the diseases are controlled by Mancozeb which they currently use, however, this should be rotated with another class of fungicide such as a stobylurin class fungicide, if available. This will reduce the possibility of resistance by the fungi to a single class of fungicide. There are several strobylurins available, although its difficult to assess which are available in the DR. Growers have limited insect problems and do have the insecticides necessary to control the pests that they do encounter. It seems stem borers, worms and mites are their main problems. They use some materials referred to in the table above that are useful for control of these species. However, one of these materials should be discontinued if at all possible. Agromate is a very toxic insecticide. Although it provides excellent control, it is very dangerous to be applied with the handheld application devices used in the DR and should never be used without personal protective equipment. There are numerous insecticides which would provide control of the pest species that they have and would be much safer for the grower and the environment.
- Fertilization:The growers use a number of different fertilizer materials. It was difficult to ascertain what total amounts of fertilizer are being applied to the crop. This was due to the various materials used and not being able to determine the exact amounts and timing of each material. Based on some of the information that I obtained, it appears that the fertilization is within the requirements of the crop for nitrogen. However, growers may be using more potassium than they require and could be using more phosphorous than needed as well. More information is required to fully determine a recommendation on this issue.