Circular No. 26. (Revision of No. 14) February, 1910. 



MASSACHUSETTS AGRICULTURAL EXPERIMENT STATION. 



AMHERST. 



FERTILIZERS FOR POTATOES. 



WILLIAM P. BROOKS, Director. 



There is general agreement that fertilizers rather than manure 

 should generally be used for the potato. The principal reasons are : 



1. The chances that the crop will be free from blight, rot and 

 scab are greater on fertilizer. This does not of course mean that 

 immunity from any of these troubles is certain if fertilizers only are 

 used. 



2. The period of growth is relatively short and the plant food 

 supplied should be in highly available forms. High grade fertilizers 

 are superior to ordinary farm manures in this particular. 



Manure may be used for this crop with greatest safety and profit 

 on the lighter soils deficient in organic matter and humus. The 

 quantity should be moderate and it should be applied broadcast and 

 plowed or deeply harrowed in rather than placed in hill or drill. It 

 will usually pay to use some fertilizer in connection with manure. 



Experiments with fertilizers for potatoes on the Station grounds 

 on soils which are retentive in character indicate : 



1. Method of Application : The application of all the fertilizers 

 in the drill, making it cover a strip some 10 to 15 inches in width is 

 likely to give a better crop than broadcast application of all the fer- 

 tilizers used. 



2. The Nitrogen Supply: 



(a) When grown upon a clover or mixed grass and clover sod, a 

 relatively low percentage of nitrogen in a potato fertilizer is sufficient. 



(b) In order to make it safe to apply the entire amount of fertil- 

 izer needed for the crop at planting time, the nitrogen should be 

 derived from materials possessing a varying rate of availability, 

 such, for example, as nitrate of soda, sulfate of ammonia, dried 

 blood and tankage. 



3. Phosphoric Acid Supply : There is little doubt that the pres- 

 ence of a liberal amount of available phosphoric acid in fertilizers 

 for potatoes is favorable to early maturity and whenever the tops 

 usually make a rank growth, or where an early crop is important this 

 element should be relativelv abundant in the fertilizer. 



