620 Circular No. 7. 



the same amount. We shall therefore discuss the subject under the 

 folowing heads : 



1. The effects of lime on the soil and the crop. 



2. The general need of lime, including its loss from the soil. 



3. The forms and availability of lime to be used on the soil. 



4. Practical questions of supply, prices, and application of lime as 



viewed by the farmer. 



A great movement toward conservation is getting under way in the 

 United States — conservation of forests, of mines, of streams and of soil. 

 Speaking broadly, our American agriculture has been extensive. It has 

 met the need for more produce by taking up more and newer land rather. 

 than by an increase in the productive capacity of the old land. Indeed, 

 the usual course of development is the subjugation of the more readily 

 reclaimable land, followed by a more or less rapid decline in its produc- 

 tion, which is succeeded either by abandonment or by such intelligent 

 management as shall not only bring it again to its former productiveness 

 but even to surpass that condition. 



We take occasion here to divert attention to the fundamentally impor- 

 tant fact that the time has now come when American demand lur murt 

 produce can no longer be met by extensive or slip-shod methods or of 

 expansion of the producing area, but must be met by increase in the 

 unit production, that is, by increased acre-yields. It is true that there is 

 a considerable area of arid and swampy land to be developed, but the 

 process is expensive and the area totally inadequate. Increased yields is 

 the point upon which attention must be centered, and it is encouraging to 

 know that it holds large promise. There is no reason why American 

 farms may not equal or exceed the record of German farms on which the 

 yield of wheat has been raised from the indifferent amount of 12 or 15 

 bushels to an average of 28 bushels, or of English farms on which tne 

 average is 32 bushels. As a business proposition there is also involved 

 increase in the net income per acre. This paramount question has been 

 given national prominence through its public discussion by the Presidents 

 of two of the leading railroads. 



THE EFFECTS OF LIME ON THE SOIL AND THE CROP. 



Lime has three types of effect on soil productiveness : ( i ) Physiological 

 or Biological, (2) Chemical, (3) Physical. In this discussion we have 

 in mind primarily the base calcium rather than any particular compounds 

 of calcium, except as those may be mentioned. 



