112 Bulletin No. $4, 



weeds. A determination of the per cent of water in each of the 

 five upper feet in each area May 23 gave the following results: 



Cultivated. Uncultivated 



First foot 7.3 3.8 



Second foot 12.6 8.1 



Third foot . 15.6 10.5 



Fourth foot 15,0 1 1.6 



Fifth foot . 1 2. 1 1 1.7 



Totals 62.8 45.7 



It will be seen that as a whole the upper five feet of soil in 

 the cultivated area contained over a third more water than the 

 upper five feet in the uncultivated area. But when only the avail- 

 able water in each is taken into consideration, the difference is 

 much greater- Plants cannot remove all the water a soil contains. 

 In such a soil as the above, at least five per cent would be left in 

 it after the rootlets had removed all they had power to remove. 

 Making this deduction, the soil in the cultivated area would be 

 found to contain about twice as much available moisture as that 

 in the uncultivated area. Making the statement in another form, 

 the loss of water from the uncultivated area from March 5 to May 

 25 exceeded the loss from the cultivated area by the equivalent of 

 over 2 inches of rainfall. To replace this loss from a ten-acre 

 field would necessitate the running of a stream of 100 miner's in- 

 ches for about ten hours. 



In order to produce the best results the soil must be so culti- 

 vated, however, that it is not left broken up into large clods that 

 will permit the air to reach the underlying strata. The finer and 

 looser the surface mulch the better, and in our arid region it needs 

 to be deeper than elsewhere. 



Weeds injure growing crops by appropriating the available 

 plant food and by removing water from the soil. While a soil 

 may be very fertile, there seldom is present enough plant food, in 

 the form necessary for the use of plants, to support a crop of 

 weeds and a crop of fruit, grain, or vegetables at the same time. 

 But weeds usually do the greatest injury by removing from about 

 the roots of the crop the water needed by it. Not only do weeds 

 require water for their increase in size, but water is continually 

 evaporating from the surface of their leaves. While they may 



