Conditions Modifying Duty of Water 201 



will be more readily appreciated after a study of the results 

 given in the following table: 



*Table showing the difference between the effectiveness of mulches developed from 

 different kinds of soil 



Loss of water per 100 days > 



Mulch Mulch Mulch Mulch 

 Black marsh soil : No mulch 1-in. deep 2-in. deep 3-in. deep 4-in. deep 



Tons per acre 588 355 270 256.4 252.5 



Inches of water 5.193 3.12 2.384 2.265 2.23 



Per cent saved by mulches 39.54 54.08 56.39 57.06 

 Sandy loam : 



Tons per acre 741.5 373.7 339.3 287.5 315.4 



Inches of water 6.548 3.3 2.996 2.539 2.785 



Per cent saved by mulches 49.6 54.24 ' 61.22 57.47 

 Virgin clay loam: 



Tons per acre 2,414 1,260 979.7 889.2 883.9 



Inches of water 21.31 11.13 8.652 7.852 7805 



Per cent saved by mulches 47.76 59.38 63.13 63.34 



The results in this table were secured by filling cylinders of 

 galvanized iron, having a depth of 22 inches and a cross-section 

 of -fa of a square foot, with the soil named, by thorough tamp- 

 ing, and then removing a depth of these soils equal to 1, 2, 3 

 and 4 inches, returning enough of each kind in a loose, crumbled 

 condition to fill the cylinders again level full, thus forming 

 mulches of the respective depths. Under these conditions, the 

 soils were exposed in the open field during 42 days to the normal 

 atmospheric conditions, except that during times of rain the 

 cylinders were covered. Water was added every 10 days to the 

 reservoirs shown in Fig. 36, bringing the lowered surface back 

 to a standard level. 



It will be seen that while the black marsh soil lost water 

 through the unmulched surface at the rate of 5.88 tons per acre 

 per day, the sandy loam lost water at the rate of 7.42 tons, 

 and the virgin clay loam at the rate of 24.14 tons per acre per 

 day ; the latter exceeding the two former more than three- and 

 four- fold. And, then, when the losses through mulches of cor- 

 responding depths are compared, it will be seen that although 



*Fifteenth Ann. Kept. Wis. Agr. Expt. Station, page 137. 



