194 THE SYSTEM OP FARM-YARD MANURING. 



conditions for the production of straw preponderate over 

 those for the production of grain, another is better 

 suited for the growth of clover, and so on. 



These conditions, according to their very nature, differ 

 in quantity and quahty. By conditions which can be 

 weighed and measured, we of course mean no other than 

 nutritive substances. 



The crops reaped from a field afford no indication of 

 the quantity of nutritive substances in the ground. 

 Consequently, the fact that the field at Miiusegast gave 

 twice as much corn and one-third more straw than the 

 one at Cunnersdorf, cannot lead to the inference that the 

 former was upon the whole richer in these proportions 

 in the conditions for the production of corn and straw ; 

 for we see that the Cunnersdorf field gave two years 

 after, without manuring, one-half more oat-corn and 

 straw than the field at Mausegast, and in the fourth year 

 above 60 per cent, more clover. Now some of the most 

 important food elements of corn are as essential to clover 

 as to the cereals ; and the food elements of oats are 

 identical with those of rye. 



A larger crop of any of the cultivated plants given by 

 one field over another merely indicates that the roots in 

 the one field, in their way downwards, have found and 

 absorbed in certain portions of the soil more particles of 

 the whole store of nutritive substances contained in it in 

 an available state than the roots in the other field ; but 

 not that the total sum was greater in the one than in the 

 other: for the field apparently poorer might in reahty 

 have contained a much larger total amount of nutritive 

 substances than the other, only not in a condition avail- 

 able to the roots. 



High returns are a sure sign that the nutritive sub- 

 stances of the soil are in a condition available to the 



