186 DRY-FARMING 



ing a small amount of sodium nitrate it was reduced 

 to 583 pounds. If so large a reduction could be 

 secured in practice, it would seem to justif}^ the use of 

 commercial fertilizers in years when the dry-farm 

 year opens with little water stored in the soil. 

 iSimilar results, as will be shown below, were obtained 

 by the use of various cultural methods. It may, 

 therefore, be stated as a law, that any cultural treat- 

 ment which enables the soil-water to acquire larger 

 quantities of plant-food also enal^les the plant to 

 produce dry matter with the use of a smaller amount 

 of water. In dry-farming, where the limiting factor 

 is water, this princijjle must l^e emphasized in every 

 cultural o]:)erati()n. 



Methods of cnntrolling transpiration 



It would appear that at present the only means 

 possessed by the farmer for controlling transpiration 

 and making possible maximum crops with the mini- 

 mum amount of water in a properly tilled soil is to 

 keep the soil as fertile as is possible. In the light 

 of this principle the practices already recommended 

 for the storing of water and for the prevention of the 

 direct evaporation of water from the soil are again 

 emphasized. Dee]^ and frequent plowing, preferably 

 in the fall so that the weathering of the winter may be 

 felt deejjly and strongly, is of first im|)ortance in 

 liberating ]:)lant-f(jod. Cultivation which has been 



