Moisture of the Soil. 



489 



cases it may be necessary to throw up ridges to produce the 

 proper degree of warmth for germination, but even then the 

 ridges should be slight. Nothing could be better calculated to 

 dry out a potato field or a corn field than throwing the ground 

 up in high ridges, leaving a large surface exposed to the action 

 of sun and wind. 



In fruit plantations Which are in a proper state of cultivation, 

 a small-toothed or even spike-toothed cultivator will be found 

 sufiicient to maintain the surface mulch. 



The following figures show how much the use of the cultivator 

 may do to save moisture: In our determinations of soil moisture 

 we found, on July 1st, in a plot where 14,080 lbs. of green forage 

 per acre had been cut from one-half of it but 6.73 per cent, of 

 moisture, while on the open cultivated space between plots, 

 within five feet from where the other sample was taken. 10.54 

 per cent, of moisture was found. July 6th samples were again 

 taken. The percentage of moisture in the standing oats was 

 4.07, and in the open cultivated space 13 per cent. This clearly 

 illustrates the difference in the amount of soil moisture retained 

 by frequent surface tillage compared with that which is found 

 where a crop of grain covers the soil. 



The roller in its relation to soil moisture is an implement whose 

 value depends largely upon local conditions. There is no tool 

 which requires more judgment as to its proper use. On light, 

 loose sandy or gravelly soils, where every 

 effort must be made to solidify and pack 

 the particles closely together, the roller must 

 be used repeatedly. The difficulty of such 

 soils is that the spaces between the grains 

 are so large that the water is permitted to 

 pass through freely and is lost by percola- 

 tion. The capillary openings are so large 

 that there is very feeble rise of the water 

 to take the place of that used by plants and 

 lost by evaporation (Fig. 142). The roller 

 lessens the size of these pores in solidifying 

 the soil and the capillary force is then 

 strong enough to draw the water to the surface (Fig. 143). If 



142.— Coarse gravelly soil, 

 ^hoMinK its loose struc- 

 ture. 



