SOIL MULCHES 55 



Let the cylinders stand until the soil appears damp at the 

 surface in all the cylinders. This may require several 

 hours, and it may be necessary to replenish the water in the 

 supply tubes during this period of time. 



After capillary water appears at the top of the soil on all 

 the cylinders they should be treated as follows : 1 



No. 1. No treatment. 



No. 2. Cultivated one inch deep. 



No. 3. Cultivated three inches deep. 



No. 4. Covered with two inches of cut straw. 



Cylinders 2 and 3 should be cultivated by removing the 

 soil to the required depth into a wash pan by means of a 

 long-bladed knife. Thoroughly mix the soil and return it in 

 a loose condition to the cylinder. Just sufficient soil should 

 be returned to the cylinder to bring it to within one inch of 

 the surface. Discard any surplus soil. 



Cylinder 4, on which the cut straw is used as a mulch, 

 should be prepared by removing two inches of the soil and 

 replacing the soil with two inches of finely cut straw. 



When the mulches are in place, fill the supply tubes to the 

 same level with water. Cork the tubes to prevent evapora- 

 tion. Weigh the cylinders and record the weight in the 

 accompanying outline form. 



Repeat the weighings each day for six days. 



Determine the surface area of the cylinders and compute 

 the number of tons of water evaporated per acre in each case 

 during a period of one week. 



Tabulate your results in the accompanying outline form. 



1 The cylinders may be filled at one laboratory period and the 

 mulches placed in the cylinders at the next period. 



