OBSERVATIONS ON SOIL MOISTURE. 183 



PALL PLOWED SPRING PLOWED — UNPLOWED. 



A piece of garden soil cultivated thoroughly without plowing for 

 two years contained, on April 23, 18.9 per cent of water. A strip of 

 garden near by, plowed early in the spring, contained, at the same 

 date, but 16.6 per cent of water. On June 15 the strip plowed in 

 the spring contained 18.4 per cent of water. The strip cultivated 

 without plowing contained 21.5 per cent of water. And a third strip, 

 near the others, plowed late the fall before, contained 20.3 per cent of 

 water. 



WIND-BREAKS. 



By Forest Trees. 



Several series of samples were taken to determine the effect wind- 

 breaks have in checking the evaporation of water from the soil. On 

 November 5 a series of samples was taken in a field north of a belt 

 of forest trees, consisting of five rows of soft maple nearly thirty feet 

 high and ten rows of catalpa about twenty feet high. The trees were 

 from four to six feet apart in the rows, and the rows were about eight 

 feet apart. There were very few branches near the ground. The 

 field north of these trees had grown a crop of corn, but this had been 

 cut and removed from the field. Duplicate sets of samples were taken 

 every two rods, beginning one rod from the trees and going fifteen 

 rods into the field. The averages of the six samples taken at each 

 distance from the trees are given in the diagram (Fig. 4). It will be 

 seen that there is a general decrease in per cent of water as the dis- 

 tance from the trees increases, excepting the irregularity at the distance 

 of seven rods from the trees. The decrease in per cent of moisture is 

 noticable for the first ten rods from the trees. From that point on 

 the per cent is quite uniform. 



It must be remembered, first, that the trees made by no means a 

 model wind-break, having but few limbs low down; second, the corn 

 grown on the field probably acted as a wind-break itself. The corn, 

 by checking the wind, would probably protect the interior part of the 

 field more than the part near the trees. The trees, on the other hand, 

 would naturally be expected to protect most the part of the field near- 

 est them. The two wind-breaks, while in no sense destroying each 

 other's efiFect, yet would give more uniform protection to the field and 

 thus make the effect of either wind-break less easy to be determined. 



