Título en español.

This study on the use of filter-press cake as a fertilizer material may be summarized as follows: 1. It is a byproduct of the sugarcane mills consisting principally of a mixture of cane fibers, sucrose, coagulated colloids including cane wax, albumoids, and phosphates of lime, plus sand and son. 2. It is a soft, spongy, lightweight, amorphous dark-brown to black material. When fresh from the filter-presses it contains about 60 percent of moisture, and about 15 percent when air-dry. 3. Its chemical composition averages 2.19 percent of N, 2.77 percent of P2O5, 0.44 percent of K2O, and 3.05 percent of CaO, plus considerable quantities of the minor elements. 4. It did not produce appreciable yield increases when used on sugarcane in combination with commercial mixed inorganic fertilizer. 5. It was beneficial to tomatoes growing on a Coto clay when used at a rate of 10 tons per acre, but yields were higher when commercial fertilizer was used. 6. Ten tons per acre significantly increased yields of peppers on a Juncos clay. 7. Pigeon peas and corn responded to neither filter-press cake nor regular fertilizers. 8. Tobacco yielded more when filter-press cake was used as a nitrogen source, but ammonium sulfate produced higher yields still when used to supply equivalent amounts of N. 9. Yams did not respond to the use of filter-press cake. 10. Filter-press cake alone did not produce as good results on sweetpotatoes as commercial fertilizer. 11. Filter-press cake increased the yield of yautías. 12. Plantains did not respond to filter-press cake when grown on a Lares clay. 13. Pineapples gave a mixed response to applications of filter-press cake. When damage caused by biological-parasitic factors was properly controlled, the filter-press cake applications did not increase yields. 14. The composition of filter-press cake, as compared with that of other organic fertilizers showed it to be about equal (except for low K2O) to animal manures but not to animal tankage or seed meals. 15. If applied about 6 weeks prior to planting, the decomposition of fresh filter-press cake will not produce "burning" on vegetable crops.Filter-press cake may be used advantageously as a fertilizer material if adequate attention is paid to its limitations and full use is made of its particular advantages. Its main disadvantages are its low K2O content and large bulk combined with low concentrations of nutrients. Its main advantages are its cheapness, slower release of nutrients, minor-element content, high water-holding capacity, high exchange capacity, and mulching properties. The following recommendations are made for its use on crops: 1. Apply yearly in small amounts rather than in very large applications once in 3 to 4 years. 2. Use more on light-textured soils, than on heavy clays. 3. Use carefully on very poorly drained soils, not applying the filter-press cake too deeply in the soil, which prevents proper decomposition. 4. Large applications must undergo thorough incorporation into the plowed layer. Surface application and incorporation with the upper inch or two of soil is better for small applications. For root crops, application in the hole below the seed makes better use of minimum quantities. 5. Filter-press cake should be applied to fast-growing crops such as vegetables and tobacco a few weeks before planting, especially if the filter-press cake is not well rotted. 6. Filter-press cake should be supplemented with potash fertilizer when used for crops or soils with high potash demands, about 30 pounds of KCl for every ton of fresh filter-press cake containing 60 percent of moisture. 7. The maximum yearly recommendations in tons per acre for specific crops are: Sugarcane 10, pineapple 30, root crops 20, ornamentals 10 to 20, coffee 20, tobacco 10, vegetables 10, and plantains 10