108 THE AMERICAN FARMER. 



for the elements extracted from the soil by the production of crops, the exhaustion can be 

 largely prevented. Yet, even in such cases, it is found that for all soils a change by way of 

 rotation is the most satisfactory in the result upon both the soil and crops produced, most 

 writers on the subject claiming that the application or withholding of manures only serves to 

 retard or accelerate this process of exhaustion. 



As a general rule, the poorer the soil the greater the necessity of diversifying the crops, 

 consequently the greater the necessity of a rotation, and those crops that are wholly removed 

 from the soil in root, branch, and seed, will exhaust lands sooner than those that permit of a 

 portion remaining on the lands to fertilize it, such as stubble, etc. Even on the rich lands of 

 the West, it is found that special crops, such aa wheat, cannot be cultivated year after year on 

 the same soil without deterioration. &quot;When lands became unproductive among the earlier 

 cultivators of the soil, it was concluded that it was because such lands needed rest; hence, 

 the fallow system was introduced, which was a common practice among the Romans. Their 

 usual course was to permit the land to rest after each crop; a crop and a year s fallow 

 generally succeeding each other, although, where manure was applied, two and sometimes 

 several crops were taken between the fallowing peiiods. Among the ancient Egyptians the 

 fallow system was almost unknown, since their agriculture was confined to the banks and 

 lands adjacent to rivers having an annual overflow, which inundation caused a rich deposit of 

 mud to be left upon the surface yearly, thus furnishing a rich top-dressing sufficient to keep 

 the soil in constant fertility. The practice of changing the crops with more or less regularity, 

 although found to be attended with beneficial results, has never been quite satisfactorily 

 explained. 



Theories Relative to the Necessity of Rotation of Crops, Various the- 

 ories have from time to time been advanced relative to the cause of the failure or depre 

 ciation of the same kind of crops produced continuously from the same soil. One of these 

 theories formerly was, that plants, in growing, exuded or threw off from their roots waste 

 substances, which rendered the soil unfit, to a certain degree, for the production of the same 

 variety of plants, until time had neutralized the deleterious properties thus imparted, but 

 that those properties given off were not injurious to other kinds of plants. This theory is 

 now generally discarded. Another theory, and the one now generally adopted, is that differ 

 ent kinds of plants exhaust certain elements from the soil in different degrees, and that this 

 explains why a change in the production of crops is beneficial. This may be a true reason 

 to a certain extent, but it does not fully answer the question, since it is found that different 

 crops, requiring about the same elements of plant-food in similar quantities, do not affect 

 the soil in the same manner, or, in other words, that the slight difference in the proportionate 

 elements of plant-food of different crops does not account for the great difference between 

 the alternation of these crops, and the successive following of the same, as is the case with 

 wheat and corn, as instanced by the following from Prof. Blount, of the State Agricultural 

 College, Colorado: 



&quot; In the vegetable, as well as the animal kingdom, it is the infallible law of nature that 

 constant cropping and continual feeding of one thing to the exclusion of all others, tend to 

 reduce the strength, vigor, growth, and product. Now corn takes from the soil only about 

 6 pounds of its whole substance when dried, and wheat 7 pounds. All the rest of the mat 

 ter comes from the atmosphere in the shape of carbon, oxygen, hydrogen, nitrogen, etc. If 

 a succession of croppings be made, it necessarily takes from the soil these elements to a 

 greater or less degree. Both wheat and corn, chemists tell us, take up the same essential ele 

 ments, but they fail to make the process or operation clear enough to show why one crop 

 following itself lessens, and following another does not lessen the yield. Corn has its own 

 natural habit of extracting food from the soil; so has wheat. The operation of both cannot 

 be alike, or the exhaustion, lessening of the yield, and the same condition of the soil would 



