Improving Tropical Soils by Utilizing Organic Wastes

Improving Tropical Soils by Utilizing Organic Wastes

Summary

Lake Carite in Puerto Rico is surrounded by forest and farmland. The farmers utilizing the land surrounding the lake grow citrus, coffee, bananas and some annual crops. Some of the fertilizers and pesticides used by the farmers leach into the lake. In many tropical ecosystems, nutrients are held in the standing biomass and not in the soil. When the natural vegetation and nutrients are removed from the site, the fertility of the bare soil is low. In the absence of protection, the topsoil erodes, and the remaining soil does not respond well to fertilization. Consequently, the citrus crops are not responding to traditional fertilizer recommendations and fertilizer use is increasing. The local fruit processing plant and poultry farm near the lake have waste disposal problems. The project seeks a practical solution to the plants’ waste disposal dilemma and to the farmers’ soil fertility problems.

Objectives
1.) Construct compost piles primarily of fruit waste and poultry manure with seaweed, sand, calcium carbonate and leaves.
2.) Demonstrate to area farmers how to build compost piles.
3.) Demonstrate to area farmers how to use compost to increase organic matter in their soil.

Approach
The compost piles are housed on a demonstration farm in wire-mesh sided structures with concrete floors and tin roofs. The piles are turned regularly. Temperature, humidity and pH are monitored in all the compost piles on the demonstration farm to ensure adequate composting. These compost piles will be used as controls against which the performance of the compost piles of the participating farmers’ fields will be compared. In this way, a participating farmer’s compost pile can be adjusted and improved to obtain a better compost. There are many farmers participating in the project, both from the area and from surrounding counties.

Results
In addition to obtaining fruit waste and poultry manure from local sources, the project coordinators also purchase cow manure because they have learned it is helpful to keep a large stock on hand for the project. They have also found that the addition of seaweed increased the nutrient content of the compost. The compost piles constructed in the bins on the demonstration farm take nine weeks to mature. On some of the participating farms the compost piles produce fully useable compost after 12 weeks. The differences are likely due to composition and size of the piles and air temperature due to elevation. In all cases, the piles are turned every 20 days. Mature compost has been applied to citrus trees, used as a potting medium for nursery trees and as a soil amendment in vegetable gardens. The cooperators report that when the compost is applied to citrus trees, chlorosis was corrected, and the general appearance of the trees improved.

Outreach
Farmers are invited to attend workshops about composting through notices posted in local extension and NRCS offices. The cooperators have held more than 20 workshops for area farmers. The average attendance has been 12 with up to 30 people attending some workshops. Farmers who cultivate fragile land on the lake shore have been visited by project participants who tell them of the project and how they can benefit from it. The cooperators demonstrated composting to 200 people at an Earth Day gathering. They have received invitations from groups in other counties requesting demonstrations on compost pile construction. With the help of cooperating agencies, printed material has been produced covering composting and organic farming methods.

December 1998.