598 Report of the Department op Field Crops op the 



for commercial manures on a farm of forty or fifty acres is not 

 unusual. It is probable, therefore, that in this locality there is 

 no direction which offers so promising an opportunity for the 

 practice of economy. 



The Quantity op Fertilizer. 



It is fair to inquire, first of all, whether the quantity of fertil- 

 izers which is used on Long Island farms is not often excessive. 

 In many instances as much as one ton of high grade superphos- 

 phate is used per acre. Potato growers often fertilize their land 

 at this rate. Is this profitable? The results of two years' experi- 

 ments reported by Dr. Van Slyke, in Bulletins Nos. 93 and 112, 

 indicate that it is not, when only the immediate crops are con- 

 sidered. In these experiments three quantities of fertilizer were 

 applied, viz., 1,000 lbs., 1,500 lbs. and 2,000 lbs. per acre and in 

 every instance the largest profits resulted from the use of 1,000 

 lbs. Slightly larger crops were obtained with 2,000 lbs. than 

 with 1,000 lbs. of fertilizer, but the greater yield from the former 

 quantity did not equal the greater cost. Moreover, the second 

 year's effect of the different quantities of fertilizer, although quite 

 marked, was practically the same with 1,000 lbs. and with 

 2,000 lbs. 



These facts are not surprising when we consider the quantities 

 of plant food which are applied to the soil in one ton of fertilizer 

 as compared with the amounts of nitrogen, phosphoric acid and 

 potash actually removed by a fairly large potato crop. Assum- 

 ing that the tops are returned to the soil, the average of analyses 

 herewith reported shows that a potato crop of 200 bushels re- 

 moves from the soil about 36 lbs. nitrogen, 13 lbs. phosphoric 

 acid and 60 lbs. potash. 



If the fertilizer used is made after the formula so commonly 

 in favor on Long Island, viz., 4 per cent N, 8 per cent P2 O5 and 

 10 per cent K2 O, the needs of the crop and the plant food sup- 

 plied by 2,000 lbs. would compare as follows: 



