MANURE, YIELD AND SOLUBLE SALTS IN SOILS. 



Increase in yield of potatoes due to manure and guano. 



17 



The increase in yield of potatoes associated with the manure, 

 in bushels per ton, has been : 



The comparatively small effect of the manure on yields on 

 the four poorer soils must be ascribed, in part, to the more in- 

 tense development of "tip-burn" on these soils. 



Taking the amount of water in potatoes at 78.9 per cent., 

 the mean increase of dry matter, per ton of manure, was, on 

 the four poorer soils, 47.73 Ibs. and on the four stronger soils 

 82.29 Ibs. 



!N"o observations were made which make it possible to state 

 the amounts of dry matter produced in the potato Tinea on the 

 different soil types ; but on August 16 four typical hills were 

 selected, one from each of the four sub-plots on each soil type 

 to which 15 tons of manure had been added, and the air-dry 

 weights of these vines was determined, from which the yields 

 of air-dry matter in vines, computed in pounds per acre, were 

 found to be as given in the next table. 

 2 



