INFLUENCE OF SOIL UPON YIELD. 



25 



The yield of grain of good quality increases in the same way, and the 

 yield of grain of poor quality decreases proportionately. It must be 

 remembered that by good quality of grain in. these early writings is 

 meant plump kernels and not necessarily what would be considered 

 wheat of good milling quality at the present day. The production of 

 proteids per acre decreased with the use of the incomplete fertilizers, 

 ashes and oil cake, and even with the bat guano. It increased, how- 

 ever, with the use of oil cake and ashes combined and of Peruvian 

 guano. ' The percentage of proteids was greatest in the unfertilized 

 grain and the percentage of starch least, with the exception of one 

 fertilized plot. 



The very evident effect of the fertilizers in this case was to produce 

 a more completely matured kernel. It will be noticed that the plots 

 producing grain of highest starch content were those having the 

 greatest proportion of plump kernels. 



Again, in 1884, Lawes and Gilbert a report results obtained from 

 manured and unmanured soils. These experiments cover a period of 

 si x t een years and are divided into two periods of eight years each. In 

 one of these periods the seasons were favorable for wheat, in the other 

 unfavorable. 



Favorable seasons. 



Unfavorable seasons. 



It is evident from this statement that the largest crops and best 

 developed kernels were obtained from the soils treated with barnyard 

 manure, and that these kernels contained the lowest percentage of 

 nitrogen. The crops on unmanured soil stood next in these respects, 

 except in yield. Those on the soil receiving ammonium salts pro- 

 duced the most poorly developed kernels and those of highest nitrogen 

 content, but gave larger yields than the unmanured soil. 



In the unmanured soil there was a very evident lack of plant food, 

 as indicated by the light crops. The effect upon the kernel was to 

 c-urtail its development, leaving it of light weight and with a relatively 

 high nitrogen content. 



a On the Composition of the Ash of Wheat Grain and Wheat Straw, London, 1884. 



