THE SOIL AND THE PRODUCE. 1ST 



been again removed in tlie crops, which is not true in 

 all cases, then the field, at the end of the rotation, is in 

 the same state in which it was at the commencement, 

 before it had been manured. Accordingly, we may 

 assume, without great risk of error, that the produce of 

 different crops, which a plot of ground will yield in a 

 new rotation without manuring, will be in proportion 

 to the store of nutritive substances, ready for assimila- 

 tion, which it contains in its natural state. Hence from 

 the unequal products yielded by the two fields in that 

 state, we may, with an approximation to truth, infer 

 certain inequalities in the amount of food or in the con- 

 dition of the fields. 



Of course, inferences of this kind are admissible only 

 within very narrow limits ; for when we compare two 

 fields which lie in the same or in different districts, we 

 must remember that in each case various factors operate 

 upon the products, making these unequal, even though 

 the nature of the soil be otherwise identical. 



If, for instance, two fields, both unmanured, are 

 planted with one and the same cereal, it is by no means 

 a matter of indifference, as regards the produce of corn 

 and straw, what crop has preceded the cereal. If the 

 last crop in the preceding rotation was clover on the 

 one, oats on the other field, .the results will vary, even 

 though the condition of the soil in both was originally 

 identical ; and the produce reaped, in that case, indi- 

 cates merely the state into which the field has been 

 brought by the preceding crop. 



In hilly districts, a northern or southern aspect 

 makes a difference in the comparative character of two 

 fields ; so too does the height above the sea, on which 

 the quantity of the fall of rain depends. A fall of rain 

 received at a more favourable time by one field than 

 by another makes a difference in the amount of pro- 

 duce, even though the condition of the soil be the same 

 in both fields. 



Lastly, in judging, in the manner indicated, of the 

 state and condition of a field, the weather during the 

 preceding year must be taken into account. 



