56 EXPERIMENTS UPON WHEAT 



bushel, and value from a commercial point of view. The plant, 

 when starved, diminishes the number but not the quality of the 

 seed; even the proportion of "tail" corn is not above the 

 average on this plot. The proportion of corn to straw is the 

 highest on this plot, as though starvation resulted in con- 

 centrating the highest possible proportion of material on the 

 reproductive parts of the plant. 



The plot receiving minerals only differs very little from the 

 unmanured plot, but with each successive addition of nitrogen 

 on Plots 6, 7, and 8, the weight per bushel, the size of the 

 grain, and the value somewhat diminish ; at the same time the 

 proportion of straw to corn is much increased. The effect of a 

 given quantity of nitrogen in the directions thus indicated seems 

 to be intensified when it is applied as nitrate instead of 

 ammonia. 



Turning to the Plots 7, 10, 11, 1*2, 13, and 14, which receive 

 the same amount of nitrogen but vary in their mineral manures, 

 we get the highest weight per bushel, the largest grains, and 

 the greatest value on Plots 7 and 13, where potash is supplied ; 

 on these plots also the proportion of straw is at a maximum, 

 facts which depend upon the function of potash in the formation 

 of carbohydrates — starch in the grain, and woody-fibre in the 

 straw. The soda and magnesia applied to Plots 12 and 14 

 have rendered some of the potash of the soil available, and the 

 quality of the grain is better than on Plots 10 and 11. Plot 11, 

 receiving nitrogen and phosphoric acid, produces distinctly 

 worse grain than Plot 10, showing by far the smallest grains, 

 the lowest weight per bushel and value, and the highest 

 proportion of " tail " corn ; again demonstrating how the 

 continued use of phosphoric acid and ammonia has depleted 

 the potash in the soil of this plot. The plot receiving farm- 

 yard manure gives corn of about the same size and weight 

 per bushel and also the same proportion of corn to straw, as 

 Plot 7, which receives a medium amount of ammonium-salts. 



Turning now to the influence of season on the wheat crop, 

 Table XX. shows the yield of both grain and straw, the 



