FEEDING VALUE OF CROPS 259 



condition of the soil, as to acidity or alkalinity, also in- 

 fluences the character and composition of crops. Crops 

 produced upon acid soils have a different appearance from 

 those grown upon mildly alkaline soils. An unbalanced 

 condition of plant food in the soil produces an unbalanced 

 crop growth. It is not possible, however, by the use of 

 manures or the selection of seeds, to entirely change the 

 composition of crops. In the extensive experiments by 

 Lawes and Gilbert (Rothamsted Memoirs, Vol. Ill), the 

 continued use of nitrogen and mineral manures for a 

 period of twenty years showed no material increase in the 

 amount of nitrogenous matter in the wheat. In similar 

 experiments with potatoes, in which nitrogenous ma- 

 nures alone were used, there was an increase of 0.05 per 

 cent, of nitrogenous matter. The sugar-beet has been 

 extensively changed in composition by cultivation. The 

 content of sugar has been increased from 8 to 16 per 

 cent. Wheat and other grains show material differences 

 in weight and composition when grown upon different 

 types of soil. Experiments have been made where wheat 

 grown from one lot of seed under different climatic and 

 soil conditions showed a difference of 18 bushels per acre 

 in yield, and 8 pounds per bushel in weight (Minn. 

 Expt. Sta. Bull. No. 23). Forage crops produced upon 

 soils of high fertility have a higher feeding value than 

 crops grown upon poor soils. At the Minnesota Experi- 

 ment Station, timothy and corn fodder grown on land 

 that had been manured and rotated, and similar crops 

 grown on unmanured land showed the following amounts 

 of protein : 



