52 CAMBFELL'S SOIL CULTURE MANUAL 



The following of a harvester with a disk as shown in 

 illustration elsewhere, is one of the little things that mean 

 much. Especially is this true in the growing of winter 

 wheat in the more arid sections. There are two very 

 prominent reasons for this: 



First, by repeated experiments we have found it very 

 important in holding up the fertility of the soil to prevent 

 its becoming dry either before the crop is planted, during 

 its growth, or after it is harvested, in so far as it may be 

 possible. Especially is this true in July and August, 

 during which time the temperature usually runs high and the 

 humidity low, causing an enormous evaporation and rapid 

 drying out of the soil upon which the dead stubble of 

 wheat or other small grain is left standing with the sur- 

 face soil closely compacted by the rains or from irrigation. 

 The stubble itself strongly attracts the sun's rays. By 

 double-disking we are able to mix the stubble and coarser 

 roots among the loosened soil, forming a most ideal mulch 

 to prevent further evaporation, and if you have been care- 

 ful to conserve all your moisture in previous years, you 

 will soon find the firm soil beneath this mulch quite moist. 



INCREASING THE FERTILITY. 



This moisture, together with the nitrifying air that 

 freely permeates your mulch, together with the heat, 

 will develop more or less bacteria and nitrates, and really 

 increases the available fertility in lieu of depleting it, as 

 is true when the field is allowed to dry out under the 

 more common methods. 



Second, by the disking you prevent the loss of moist- 

 ure, this peculiarly desirable condition causing this moist- 

 ure to gather in the hard soil just beneath the mulch, 



