NEARNESS OF ELEMENTS OF FOOD IN SOILS. 193 



tion, which likewise draws its nutriment from the sur- 

 face soil, found in the third year much less nutriment 

 than the rye plant which had preceded it. 



The elevations of the lines a b (Fig. I.) andy g (Fig. 

 III.), taken inversely, show how much relatively greater 

 has become the distance between the particles of the 

 nutritive substances for the barley plant. The barley- 

 corn requires for its formation the same nutritive sub- 

 stances as the rye-corn. Now, as the produce of the 

 rye-corn was to that of the barley-corn in the proportion 

 of 22 : 12, this means, taken inversely, that the distance 

 between the nutritive substances for the barley-corn had 

 increased from 12 to 22. 



In the third year, the roots of the barley, for the 

 same length, found scarcely half as much nutriment for 

 grain as the rye had found. 



This exposition is not intended to supply a standard 

 for measuring the distances between the available par- 

 ticles of nutritive substances in the ground, but merely 

 to define more accurately what is meant by the exhaus- 

 tion of land. The farmer who has a clear view of the 

 causes upon which depends the reduction of crops by 

 continuous cultivation, will thereby the more easily find 

 out and apply the means to make his field as productive 

 as before, and, if possible, even to increase its fertility. 



Beside the general differences of all the crops in the 

 Saxon experiments, we are further struck with the in- 

 equality in the proportion of corn and straw. 



To 10 parts by weight of corn, the yield of straw 

 was respectively at Cunnersdorf 25 parts by weight, 

 at Kotitz 23, at Oberschona only 21, and at Miiusegast 

 only 20. 



A more careful examination of the table shows that 

 the difference is mainly in the produce of corn. 



The fields at 



Cunnersdoi-f. Kotitz. Oberbobritzsch. 



Yielded in straw 2951 Ibs. 3013 Ibs. 3015 Ibs. 



that is, within a few pounds, the same quantity of straw, 

 while the amount of corn was in 



