24 The Bulletin. 



organic matter in the soil. Experiments show that phosphoric acid 

 is the most needed contitiient for the production of cotton, it having 

 produced about two-thirds of the increased yield and profit, and 

 nitrogen and potash combined about one-third. It is not possible, 

 with present results, to say just what is the best proportion of these 

 three constituents for most profitable returns, but it is certain that 

 the fertilizer should carry a very high percentage of phosphoric acid 

 and comparatively low percentages of nitrogen and potash. The 

 indications are that a mixture containing 10 or more per cent phos- 

 phoric acid and 2 per cent each of nitrogen and potash will give 

 close to, if not the best returns. This mixture should be used for best 

 results at the rate of at least 400 pounds per acre, and as much more 

 as one can afford up to 1,000 pounds. 



The nitrogen may be all derived from blood, tankage, cottonseed 

 meal, or similar products, or in part from one or all of these, and in 

 part (up to one-half) from nitrate of soda or sulphate of ammonia. 



Kainit, manure salt, sulphate or muriate of potash may furnish 

 the potash, and acid phosphate the phosphoric acid. Four hundred 

 pounds of the above mixture would contain 40 pounds phosphoric 

 acid, and 8 pounds each of nitrogen and potash, and 1,000 pounds 

 would contain 100 pounds phosphoric acid and 20 pounds each of 

 nitrogen and potash. The required amounts of phosphoric acid in 

 400 and 1,000 pounds respectively of this mixture would be sup- 

 plied by 286 and 715 pounds of 14 per cent acid phosphate; the 

 nitrogen by 61^ and 154 pounds of 13 per cent dried blood, and the 

 potash by 40 pounds and 100 pounds of 20 per cent manure salt. 

 Other materials or other gTades of these same materials may be used, 

 and it will not be difficult, knowing just what they contain, to use 

 such quantities of them as will be necessary to furnish the required 

 amount of plant food, having in mind that it is the specfic number 

 of pounds of phosphoric acid, nitrogen, and potash that is desired, 

 rather than a given weight of mized fertilizer. 



It is not more, but perhaps less, difficult to calculate the number 

 of pounds of nitrogen, phosphoric acid, and potash to be applied per 

 acre to any given crop from materials which are to be had than to 

 estimate the exact number of pounds of the materials to make a for- 

 mula of a certain composition: as for example, in an 8-2-2 goods. 

 The question of filler does not have to be considered in doing this, as 

 is necessary in making a fertilizer formula in the usual way. When 

 it is desired, for instance, to apply the equivalent of 400 pounds 

 per acre of a fertilizer mixture containing 10 per cent of available 

 phosphoric acid, and 2 per cent each of nitrogen and potash, or 40 

 pounds of phosphoric acid and 8 pounds each of nitrogen and potash, 

 it is only necessary to divide the number of pounds of plant food 

 desired per acre (40, 8, and 8) by the percentage composition of the 

 materials to be used, as follows: 



