AbstractVarious sources of phosphate were applied to cigar-filler tobacco grown on an acid Mabí clay. The results were as follows: 1. Highest yields of cured tobacco were obtained from the application of calcium metaphosphate with the powder significantly outyielding the granular form. 2. All phosphate sources used, with the exception of simple and concentrated superphosphate, gave significantly higher yields of tobacco than the no-phosphate treatment. 3. Calcium and ammonium metaphosphate treatments significantly outyielded simple superphosphate in tobacco per acre. 4. Considering the price of tobacco received per acre, calcium metaphosphate powder gave the highest returns, but the granular form failed to give a significant price return over the no-phosphate treatment. 5. Dicalcium phosphate and potassium-calcium pyrophosphate, along with calcium metaphosphate powder, were the only sources which gave significant increases in price of tobacco per acre over the no-phosphate treatment. 6. The importance of the particle size of calcium metaphosphate on yields of tobacco was discussed. 7. A highly significant linear correlation was established between the percentage P2O5 availability of the phosphate fertilizer and yields of tobacco per acre.
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