The Bulletin. 



31 



material treated with an eiiual amount of sulphuric acid; basic slag 

 is a bj-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 most extensively used in this State 

 as it is the more common carrier of phosphoric acid in our mixed 

 fertilizers. It is readily available and consequently acts quickly. 

 Bone meal either raw or steamed is very desirable, but is a more 

 expensive carrier of phosphoric acid than the others. Basic slag is 

 a desirable form since it contains lime as well as phosphate and con- 

 sequently assists in correcting any possible acidity. Phosphoric acid 

 in this form, however, is not as available as in acid phosphate. The 

 ground rock or floats undoubtedly furnishes the cheapest 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 ap- 

 plied in combination with stable manure or turned under with a 

 green crop, it has considerable effect the first year. 



An experiment was put out in 1910 on the Toxaway loam of the 

 Buncombe Farm to determine the relative value of rock and acid 

 phosphate, when applied alone, in combination with stable manure 

 and when turned under with a green crop. This is known as field 

 "D" and consists of eight one- twentieth acre plats. 



TABLE 8. RESULTS ON FIELD D, BUNCOMBE TEST FARM, 1910. 



The treatments and yields are given in table 8. Plat 1 of this 

 field received an application of blood, acid phosphate and sulphate 

 of potash at the rate that nitrogen, phosphoric acid, and potash are 

 removed by a one-hundred bushel corn crop. Plat 2 received the same 

 treatment except that rock phosphate was used instead of acid phos- 

 phate. Rock was always applied about twice as heavy as acid since 

 it costs approximately one-half as much per ton. The gain from 



