25 



far more efficient than sulphate of potash and nitrate of soda com- 

 bined. This conclusion is further emphasized by comparing plats 3 

 and 5, the latter having acid phosphate in addition to the sulphate of 

 potash and nitrate of soda, which No. 3 has, and showing a very 

 marked increase in growth over No. 3. Since plat No. 5 is very little 

 better than Nos. 2 and 4, it further emphasizes the conclusion arrived 

 at by comparing Nos. 1 and 3 — i. e., that nitrate of soda and sulphate 

 of potash have had very little effect on the growth of tobacco on this 

 soil. Plat No. 6, to which 200 pounds of lime was added, showed no 

 improvement over No. 5, which was otherwise treated the same. 

 (PI. Ill, figs. 1 to 4; PI. IV, figs. 1 and 2.) It was hoped that further 

 valuable results would be obtained by keeping each plant separate 

 through the harvesting, curing, and fermenting, thus obtaining the 

 effect of the different fertilizers upon the actual yield and quality 

 of tobacco. It was not possible, however, to carry out the last part 

 of the experiment. 



So far as the experiment was carried it indicates that the appro- 

 priate fertilizer for tobacco on this field is one containing a large 

 amount of acid phosphate and smaller amounts of nitrogen and potash. 



The experiment is an example of what any planter can easily try 

 for himself, and as the question is put to the soil of his own estate 

 and the answer given in the effect upon the crop he is growing, the 

 result can not fail to be far more satisfactory than any chemical exam- 

 ination that could be made. It should also be recognized that what 

 maj^ give excellent results on one soil may fail altogether on another. 



The writer had under observation another field, part of which was 

 treated with cotton-seed meal at the rate of 2,000 pounds per acre, 

 and another part given a liberal dressing of compost containing horse 

 manure, vegetable matter, and tobacco stems. The compost was 

 applied about three weeks before planting and the cotton-seed meal 

 the day before planting. The plants given cotton-seed meal grew 

 more rapidly, especially during their early life. It is probable that 

 the ingredients of the cotton-seed meal were immediately available, 

 and in case of the compost, which was not well decomposed, they 

 were not. 



The application of fertilizers is a question which has received very 

 little consideration in Porto Rico, but it is an important one, espe- 

 cially in relation to tobacco growing. It may be pardonable, there- 

 fore, to quote briefly from other sources. 



According to analyses reported by P. J. Davidson, of the Virginia 

 Agricultural Experiment Station, the entire plants of a tobacco crop 

 yielding 1,000 pounds of leaves per acre contain 66.85 pounds of nitro- 

 gen, 8.68 pounds of phosphoric acid, and 85.41 pounds of potash. 

 The leaves of such a crop contain 44 pounds of nitrogen, 5.89 pounds 

 of phosphoric acid, and 58.19 pounds of potash. The parts usually 



