98 The Bulletin 



EFFECT ON YIELD OF PEAS. 



The most profitable yields were obtained on both fields from the plats 

 receiving 600 pounds of the normal fertilizer application. Considering 

 both hay and peas, the profit per acre was increased as the application 

 was increased, the profit from the use of 900 pounds being 5.9 times 

 greater than that from the use of 150 pounds per acre. 



PHOSPHORIC ACID. 



The results from the different experimental fields of the Piedmont 

 Section of JSTorth Carolina contained in this bulletin show conclusively 

 that phosphoric acid is the chief requirement of all the soils tested, 

 except those of the Tredell loam. With this exception, wherever it has 

 been applied the yields on an average have been markedly increased. 

 Chemical analyses show that the total supply in any of the types of soil 

 examined in the Piedmont Section which are farmed extensively is 

 below that commonly required for the production of maximum crops, 

 except the Iredell loam, the Mecklenburg loam, the Congaree silt loam 

 and the Congaree fine silt sandy loam soils. Twenty to twenty-five 

 large corn crops would require as much of this constituent as is con- 

 tained in the surface 6-^ inches per acre of most of the types occurring 

 in the Piedmont Section of the State. 



There are several sources from which phosphoric acid is commonly 

 obtained as a fertilizer. These are acid phosphate, bone meal, basic 

 slag, and ground phosphate rock or fioats. Floats is the name given 

 to ground phosphate rock; acid phosphate is the same material treated 

 with an equal amount of sulphuric acid; basic slag is a by-product of 

 the manufacture of steel from phosphatic iron ore, and bone meal is a 

 by-product of slaughter houses. 



Of these acid phosphate is the foremost extensively used in this State 

 it being the more available carrier of phosphoric acid. It is readily 

 available and consequently acts quickly. Bone meal either raw or 

 steamed is suitable but is scarce and is a more expensive carrier of 

 phosphoric acid than the others. Basic slag is a desirable form, if not 

 too expensive, for sour soils, since it contains lime as well as phosphate 

 and consequently assists in correcting any possible acidity. Phosphoric 

 acid in this form, however, is not as available as that derived from acid 

 phosphate. The ground rock or floats undoubtedly furnishes the cheap- 

 est source of phosphoric acid to be used in the permanent improvement 

 of the soils of this section. Phosphoric acid can be secured in this 

 material at about one-fourth of what it would cost in acid phosphate 

 and one-third as much as in slag. It is not readily available, but when 

 applied in combination with stable manure or turned under with a green 

 .crop, it usually has considerable effect the first year. 



By the use of the rock in the proper way, not only are the yields gen- 

 erally increased rapidly, but the soil will be enriched in phosphoric acid 

 about four times as fast. The practice of mixing rock phosphate with 

 manure as it accumulates in the stable is certainly commendable. We 

 advise the addition of 75 to 100 pounds to each ton of manure for the 

 soils of this section. Another method of using the rock phosphate is to 

 apply it to clover sod or a green catch crop. In this case we would rec- 



