112 



FlXDAMEXTAl.S OF FRVIT rRODlCTIO.X 



TaBI.K V2. WaTKK Soi.lBl.E XlTKATE IN PaHTS TEK Mll.LlON OK DuY SoIL" 



i,.\voi;igo por \i\oO 



Year 



Sod 



Surfaoo soil 



Tillage 



I'illago with oovor 

 crop 



1913 

 1914 

 1915 

 1916 



Averngo 



4 41 

 2 00 

 o 59 



3. IS 



IS. 25 

 14.01 

 21.05 

 16.29 



17.40 



oS . o< 

 37 27 

 IS 75 

 41.20 



33.01 



Subsoil 



iho sunmior. wherever the soils are of sueh nature that they encourage 

 shallow rooting the iuHuenee of these various systems of soil management 

 iipcMi moisture supply is probably a factor of equal or greater unportance. 

 However, it is neither difficult nor expensive to furnish trees growing in 

 sod with an adequate supply of nitrates through the use of certain fertil- 

 izers. Indeed, it is in orchards of this kind that nitrogenous fertilizers 

 have given some of the most striking results and the question maj- be 

 raised whether some nitrogen-carrying fertilizer may not be a more or 

 less constant requirement if orchards permanently under this method of 

 soil management are to be kept growing and producing most efficiently. 



Influt'wecl by Temperature and Soil Moisture. — The effects of moisture 

 and of temperature on the activity of nitrifying bacteria are shown by a 

 seasonal variation in nitrate content. For example, in Illinois soils -^'' 

 the most active season of nitrate production and accumulation is late 

 spring and early summer when optimum moisture and temperature 

 conditions are approached. Early autumn is the next most active 

 season, when these optimum conditions for nitrate production are fre- 

 quently approached. During the summer little nitrate is produced 

 unless the weather is cool and moisture plentiful; in winter there is no 

 evidence of nitrate production. 



Similar conditions are i-eported for orchard soils in Indiana^^ where 

 very little nitrate was found in late fall and winter, though maxima were 

 found in early summer and early fall. Orcharding, however, is carried 



