CAMPBELL'S SOIL CULTURE MANUAL 45 



at the time of plowing, and the climatic conditions before 

 and after plowing than by the absolute depth or time of 

 plowing. 



We desire to call attention to these facts on the start, 

 that we may prepare the student to more fully grasp the 

 real scientific principles 



SPRING PLOWING OLD LAND. 



The first and all-important work is the early double- 

 disking as explained in the preceding chapter. It is 

 nothing uncommon to see farmers double-disk by first 

 going over the ground one way and then cross-disk it. 

 This is not correct, for it results in a series of ridges and 

 trenches, leaving the surface very uneven. The trenches 

 left by the center of the disk each way over the field, ex- 

 poses the solid soil in the bottom to the direct rays of the 

 sun, causing an enormous evaporation resulting in a thick 

 hard crust which breaks into coarse clods when plowed. 

 The proper manner of double-disking is to lap half, which 

 leaves the surface smooth and thoroughly pulverized. 

 In the lapping of the half of the disk the last time over, 

 the last disks revolve at right angles with the disks that 

 precede. We cannot put too much stress upon this part 

 of the proper preparation of the soils. Bearing in mind 

 that the all-important element for the successful growth 

 of our crops is water, we must lose no opportunity of 

 conserving and storing the water from the earliest part 

 of the spring to late in the fall. 



WHEN TO PLOW. 



Evaporation and percolation are more fully explained 

 in chapters to follow. After thoroughly pulverizing the 

 surface to stop the evaporation we can do our plowing 

 a little later, regardless of the climatic conditions which 

 may exist, and we shall find the soil in a moist condition. 



