EXPERIMENTS WITH POTATOES. 157 



Much better crops were obtained when phosphoric acid and 

 potash were used than when potash was used alone or with 

 nitrogen only. The chemicals were added in the proportion of 

 nitrogen 25.6 pounds, phosphoric acid 57 pounds and potash 

 •80 pounds per acre, or if mixed, the composition would be nitro- 

 gen S-5%, phosphoric acid 12.4%, potash ij^c. 



The Connecticut Experiment Station* made experiments to 

 compare the effect of muriate with that of sulphate of potash 

 on the starch content and yield of tubers. The potatoes were 

 grown on very poor soil which was dressed with 400 pounds 

 nitrate soda, 615 pounds acid phosphate and 120 pounds of 

 muriate or sulphate of potash. The yield was increased from 

 43 to 228 bushels of salable tubers per acre. Doubling 

 the potash, applying 240 pounds per acre, increased the yield 

 only tw^elve bushels per acre over what was produced when 120 

 pounds were applied. ^Muriate produced a somewhat greater 

 yield than sulphate, but the tubers contained slightly, more water 

 and less starch than when sulphate was used. 



The evidence in regard to the relative effect of sulphate and 

 muriate of potash on potatoes is somewhat conflicting. Most of 

 the experiments made in this country and Europe show that sul- 

 phate produces better tubers with less water and a slightly 

 higher starch content, but the difference is slight. Some Ger- 

 man experimenters, Pfeifferf and others, have recently pub- 

 lished results of experiments showing that pure muriate has no 

 injurious effect on the tubers, but impurities, noticeably chloride 

 of magnesia, are influential in depressing the proportion of 

 starch. 



An analysis of the ash of the potato shows it to be exceed- 

 ingly rich in potash, and the fact has led many to believe that 

 a potato manure should contain a large amount of this element, 

 but when we consider the small amount of ash a potato contains, 

 we find the amount removed by an ordinary crop (58 pounds) 

 is not greater than is taken up by any other farm crops. Two 

 tons of mixed hay would take away sixty-three pounds, while 

 two tons of red clover would take eighty-eight pounds of potash. 



In preparing a field for any crop it is more essential to consider 

 the special needs of the soil, to render it fertile, than the special 



* Report l?95,'p. 1-24. 



t Die Land. Vers. Stat. Bd. 49, p. 49. 



