The Bulletin. 



47 



ents for most profitable returns, but it is certain that the fertilizer 

 should carry a much higher percentage of nitrogen than has been used 

 heretofore, if the soil is not well stocked with organic matter, and that 

 the phosphoric acid may be decreased. The indications are that for 

 the average soil of the Coastal Plain a mixture containing about 7 per 

 cent of available phosphoric acid, 7 per cent of nitrogen and 5 per cent 

 of potash will give close to if not the best results. 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, cotton-seed 

 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 28 pounds phosphoric acid, 28 pounds 

 of nitrogen and 20 pounds of potash, and 1,000 pounds would contain 

 70 pounds phosphoric acid, 70 pounds of nitrogen and 50 pounds of 

 potash. The required amounts of phosphoric acid in 400 and 1,000 

 pounds respectively of this mixture would be supplied by 175 and 438 

 pounds of 16 per cent acid phosphate; the nitrogen by 215 and 538 

 pounds of 13 per cent dried blood, and the potash by 100 pounds and 

 250 pounds of 20 per cent manure salt. Other materials or other 

 grades 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 specific number of pounds of phosphoric acid, nitro- 

 gen and potash that is desired, rather than a given weight of mixed 

 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 materials to make a formula 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 con- 

 taining 7 per cent of available phosphoric acid, 7 per cent of nitrogen 

 and 5 per cent of potash, or 28 pounds of phosphoric acid, 28 pounds 

 of nitrogen, and 20 pounds of potash, it is only necessary to divide the 

 number of pounds of plant food desired per acre (28, 28, and 20) by 

 the percentage composition of the materials to 'be used, as follows : 



