FARM MANAGEMENT 325 



soil, how much is removed from an acre yielding 20 bus. of wheat? 



2. If a crop of clover yielding 2 tons per acre removes 100 lbs. 

 of mineral elements worth 53^c. per pound, what is the value of 

 fertility sold in two tons of clover hay? 



3. If a bushel of com removes 14c. worth of fertility from the 

 soil, how much is removed from an acre yielding 50 bus.? 



ROTATION MAINTAINS VEGETABLE MATTER 



Worn-out Farms. — One often hears the remark that a 

 certain farm is worn out or exhausted. The remark is 

 usually based on the fact that the farm in question no 

 longer yields good crops. Many farms that formerly yield- 

 ed from twenty to thirty bushels of wheat per acre now 

 yield but from five to ten bushels. When we consider the 

 fact that some of the land in Europe has been cultivated 

 for centuries and is still producing large yields, we must 

 conclude that it is much better, or that farms in this country 

 that are giving such low yields are not exhausted but are 

 simply not in good condition. 



Our faith in the latter conclusion is strengthened by the 

 fact that most of us know of instances where men have 

 taken these run-down farms, and after a few years have 

 been able to get as large yields from them as ever. 



From the facts at hand, we must conclude that very 

 likely the reason these farms are at present unproductive 

 is because conditions are not favorable for the liberation 

 of plant food. That is, the plant food may be present, but 

 is not soluble so that plants can get it easily. We have 

 learned that the most common way in which plant food is 

 made soluble is by the decomposition of vegetable matter. 

 We may believe, then, that the reason many farms are 

 unproductive is because some of the conditions necessary 

 for decomposition are lacking. 



Lack Vegetable Matter.^ — The condition we are most 

 likely to find lacking in these unproductive soils is a suffi- 

 cient supply of vegetable matter. A good rotation of crops 

 provides for maintaining the supply of vegetable matter 

 in the soil, because it provides that each field shall grow a 

 /;rass crop one or more years in every three to six years. 

 Grass crops have heavy root systems and, therefore, add 

 vegetable matter to the soil. 



One can get a good comparison of the amount of vege- 



