Excerpt from page 30, THE COSTA RICAN ORGANIC HOME GARDENING GUIDE

ORGANIC FERTILIZERS FOR THE SOIL

To insure optimal soil fertility, it’s a good idea to add various types of soil amendments, which provide plants with the necessary minerals for vigorous growth and production. Included here are various raw materials that can be used for the garden.

Rock Phosphate
An important source of phosphorus for garden plants. Usually phosphorus is a limiting nutrient in tropical soils. Rock phosphate is now available in most agricultural supply stores and can be applied directly to the soil or mixed into compost. Add 4 kg of rock phosphate for 10 square meters of garden beds. This breaks down slowly providing the phosphorus to plants for more than one year. Called roca de fosfato.

Lime
An excellent source of calcium for the plants. Also acts to make acid soils more alkaline and unlocks soil fertility. Use dolomite limestone when possible, since it also contains more trace minerals. Add 2-5 kg per 10
sq. meters. Known as carbonato de calcio in Spanish.

Wood Ashes
A good source of potassium for plants. Dissolves readily to become available to plants. Also contains trace minerals. Add 2 kg/10 square meters. Called ceniza in Spanish.

Charcoal
Finely ground charcoal acts as raw food for humus making microbes, fungi and earthworms. It also acts to purify the soil and retain soluble nutrients for plants. Make your own from the charcoal that is screened from the ashes. Best mixed into compost at 1-2 cups/wheelbarrow load of compost. Carbón in Spanish.

Seaweed
Coastal gardeners can collect seaweed from the shore to use in compost. Wash the material before using to avoid salt build up in the soil. Seaweed extracts are now available in Costa Rica. An excellent source of trace minerals for plants. 1-2 tablespoons/gallon. Called extracto de algas in Spanish.

Fish Emulsion
A concentrate of recycled fish waste that has an NPK value of 5-2-2. Useful in correcting any minor deficiencies in soil fertility. Soluble nutrients become readily available to plants. Applied directly to soil as drench at 1-2 tablespoons/gallon of water. Emulsión de pescado in Spanish.

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