Practical Evaluation of Garbage Compost as a Fertilizer under Conditions in Puerto Rico

Abstract

Data are presented to show the relative economic inefficiency of garbage compost when compared with inorganic fertilizers and filter-press cake. The content of potash and phosphoric acid is higher in the garbage compost than in the filter-press cake, but the former is slightly lower in organic matter. They both have about the same nitrogen level. In a greenhouse experiment it was found that additions of garbage compost and filter-press cake increased sorghum yields in the absence of inorganic fertilizers. However, when nitrogen, phosphoric acid, and potash were applied at the rate of 100 pounds to the acre each the application of either compost or filter-press cake did not increase yields significantly. Under the conditions that prevail in Puerto Rico there is hardly any need for plants to process town wastes for fertilizer production. At current price levels, the cost of commercial garbage compost would be so high in relation to its fertilizer-element value, that it could not compete with commercial inorganic fertilizers. The product is so bulky that hauling and application costs would be too high under normal conditions. Furthermore, the organic-matter levels of Puerto Rican soils are not so low as to justify the use of such commercial composts. Under average farm conditions there are more practical means of raising soil organic-matter levels, if and when necessary.