156 



Irrigation and Drainage 



centage of water in the soil and the number of pounds of water 

 per cubic foot are given : 



Table showing the water content in the spring, in soil which the year before had 

 been fallow and not fallow 



66.32 56.97 



9.35 



This table shows that the fallow ground starts out in the 

 spring with 9.35 pounds of water to the square foot more than 

 the ground not fallow did in its upper four feet, besides having 

 a much higher percentage of available nitrogen in the soil. How 

 much greater the available nitrogen was is not known, except 

 that in another trial, ground which had been fallow the year 

 before produced practically the same yield as did a strip which 

 received a good dressing of farmyard manure. 



At the end of harvest the same year, samples of soil were 

 again taken on the ground which had been fallow and on that 

 which had not been fallow, the results standing as shown below: 



Table showing the water content of soil at the end of harvest, which the 

 preceding year had been fallow, and had not been fallow 



J round with oats 



-Ground with barley- 



Sum 34.13 



25.92 



8.21 



47.51 



39.30 



8.21 



The data of this table show very clearly that summer fallow- 

 ing exerts a marked influence upon the relation of the soil to 



