228 



FERTILIZERS FOR VEGETABLES 



that is rather poor in organic matter, I should cut down the 

 amount of nitrate even more and increase the amount of 

 tankage, and I should in that case supply rather more of the 

 phosphoric acid in the form of tankage than in the form of 

 acid phosphate, that is, where soil is lacking in organic mat- 

 ter, but potato soil ought never to be allowed to get into that 

 condition. As to the amounts to use, I do not think it is 

 good economy on good potato soils to use less than five hun- 

 dred pounds an acre, and only under very exceptional condi- 

 tions do I think it is good economy to use more than a thou- 

 sand pounds. I think it is a good plan for you to experiment 

 some in regard to amounts and find out what amounts you 

 can use most profitably. Dowm on Long Island some years 

 ago, experiments were made in which five hundred, a thou- 

 sand, fifteen hundred, a^nd two thousand pounds of fertilizer 

 were used. Results showed that when a thousand pounds 

 of fertilizer per acre were used, we got the largest return 

 in net receipts. While there was a larger potato crop with 

 fi.fteen hundreds pounds of fertilizer than with a thousand 

 pounds of fertilizer, it was not enough greater to pay for the 

 extra five hundred pounds used. 



President Greffrath : Which way do you think it the 

 best to apply the fertilizer to potatoes? There are a large 

 number of potatoes being planted with the planter, and the 

 planter, as I understand it, applies the fertilizer direct. 



Professor Van Slyke: There is one point in connection 

 with the amount of fertilizer used and the method of apply- 

 ing that should be taken into consideration. It is highly im- 

 portant to keep the fertilizer from coming into contact with 

 the potato seed. All these materials used in our fertilizers 

 are concentrated chemical compounds, and when they come 

 into contact with any seed, or for that matter with any living 

 plant, beyond a certain concentration, they injure the veget- 

 able growth. So it is desirable, in the fi.rst place, that in 

 putting in the fertilizer with potatoes, or with any other 

 seed, it be kept as far as possible from coming in direct con- 

 tact with the seed. It is obvious that if you are putting on 

 five hundred pounds of fertilizer, it is a good deal easier to 

 keep from injury than if you are putting on a thousand 



