CULTURAL METHODS IN ORCHARDS 



157 



Table XXXVI 



SUMMARY OP MOISTURE DETERMINATIONS (wOBURN) 

 UPPER 9 INCHES 



136. Effect of temperature. — The temperature of the 

 surface soil can be affected somewhat by the soil treatment 

 and the nature of the soil covering. To what extent a few 

 degrees difference in temperature may affect the activity 

 of the soil flora cannot be stated definitely, but it is possible 

 that the effects are greater than the small differences of 

 temperature would indicate. Many factors are involved 

 in affecting the soil temperature, but the greatest are the 

 temperature of the air and the absorption of the sun's rays. 

 (Fig. 27). The .work of Bouyoucos^ shows that a difference of 

 as much as five degrees of temperature may obtain between 

 a soil which is tilled and one which lies bare or is in sod. 

 The following table shows the data as a monthly average: 

 1 Bouyoucos, G. J. Mich. Agr. Exp. Sta. Tech. Bull. 17. 1913. 



