18 The Bulletin 



would come in contact with about a hundred times as much iron and 

 aluminum oxide as limestone in the same length of time, and, of course, 

 there would be nearly a hundred times as much acid revert with these 

 bases as with the calcium base. On the other hand, the mixing of the 

 limestone with the acid before applying it to the soil assures the least 

 possible amount of reversion to these insoluble compounds. 



In Bulletin 140 of the ISTorth Carolina Experiment Station, published 

 in 1910, entitled "Fertilizer Experiments with Corn on the Piedmont 

 Red Clay Loam Soil," it is shown that 450 pounds of 14 per cent acid 

 phosphate to the acre was used for an increase, as an average of seven 

 years tests, of 10.9 bushels of corn and 814 pounds of stover to the acre. 

 This 450 pounds yearly acre application of acid phosphate contained 17 

 pounds of the element phosphonis, while the increase in the crop directly 

 attributable to the use of the acid phosphate contained only about 3 

 pounds of the element phosphorus, thus leaving 14 pounds of phosphorus 

 unaccounted for in the crop and locked up in available forms in the soil. 

 By this method of apjAication there had heen destroyed over 2,720 

 pounds of acid phosphate during the seven years, and only ahout J^SO 

 pounds utilized. This fact is not brought out in the discussion of the 

 experiment, however. 



In the April Bulletin, ISTo. 195, published in 1914, the experiments 

 with the fertilization of cotton on the Edgecombe Test Farm show that 

 600 pounds of 14 per cent acid phosphate was used for an increase in 

 the crop, directly attributable to the use of the acid, of 356 pounds of 

 seed cotton as an average of seven years tests. The annual application of 

 600 pounds of acid phosphate carried 22 pounds of the element phos- 

 phorus, while the increase in the crop of 356 pounds of seed cotton 

 carried about 2 pounds of phosphorus, leaving 20 pounds unaccounted 

 for in the crop and locked up in unavailable forms in the soil, except 

 what was turned back into the land with the stalks and leaves. By this 

 method of application, therefore, there had heen put into the soil J^,200 

 pounds of acid phosphate, and a little over 250 pounds taken out in the 

 crop. Ahout 3,950 pounds had, heen locked up in unavailahle forms and 

 lost. 



CITATION OF AUTHORITIES. 



Prof. George Roberts of the Kentucky Experiment Station, in his 

 bulletin on "Use of Ground Limestone in Kentucky, " says: "If acid 

 phosphate is being used on soil deficient in limestone, the addition of 

 limestone will increase the efficiency of the acid phosphate." The follow- 

 ing results obtained on the London Experiment Field, Kentucky Agri- 

 cultural Station, will illustrate this point: "In 1911 soil with no treat- 

 ment produced 13.7 bushels of corn; with acid phosphate 25.1 bushels; 

 with acid phosphate and lime 38.0 bushels." In 1912 soil with no treat- 

 ment produced 20.7 bushels of corn; with acid phosphate 22.2 bushels 

 of com; with acid phosphate and lime 51.9 bushels of corn. 



