120 THE ESSENTIALS OF AGRICULTURE 



escape of some nitrogen into the air. This leaves all of the first 

 crop of clover on the ground, a circumstance which adds much 

 more organic matter than if it were "fed to stock and the manure 

 returned to the land. 



The loss in phosphorus and potassium is larger than under 

 live-stock farming, and on poor soils or under permanent sys- 

 tems of agriculture these must be purchased in commercial 

 fertilizers. Some such system of grain farming and green 

 manuring can be made remunerative where properly handled. 

 Older countries make much wider use of such systems than 

 does the United States. 



147. The business side of maintaining soil fertility. It is 

 easier to plan a system of soil building than it is to put this 

 plan into effect. The one requires knowledge, the other knowl- 

 edge and business judgment. To handle worn-out soil so as 

 to build up its fertility and make a living from it at the same 

 time is a very difficult matter. Both capital and time are 

 required. Even with abundant capital and time there are still 

 many problems whose solution requires keen intellect and the 

 best of business judgment. Too often, however, the farmer 

 neglects to provide the green manure crop or fails to purchase 

 the required amount of commercial fertilizer. A system of live- 

 stock and grain farming is safest and most profitable for most 

 regions of the United States. 



QUESTIONS AND PROBLEMS 



1. What proportion of the organic matter may be returned to the soil 

 when the crops are fed to live stock ? 



2. What proportion may be returned to the soil when a system of grain 

 farming is followed ? 



3. Explain fully how it is possible to maintain the fertility of the soil on 

 a live-stock farm. 



4. Explain fully the means necessary to establish a permanent system 

 of agriculture on a grain farm. 



5. What percentage of the elements of plant food contained in the feed 

 may be returned to the soil in live-stock farming? in grain farming? 



