590 



Journal of Agricultural Research voi. xviii, no. h 



differences in the size of the plants and their fruitfulness brought about 

 by differences in the water supply, the date of blossoming was not affected 

 at all, the first blossoms in all boxes and in the field appearing August 7. 

 No important differences were observed in the time of final maturation 

 under the different treatments. 



Table XII. — Effect of differences in the moisture content of the soil on the growth and 

 development of soybeans, igi6 



It may be observed in passing that the wooden boxes placed in the soil 

 as indicated above have been found to be very satisfactory for conducting 

 field tests dealing with the effects of the water supply on plants. By the 

 arrangement of sloping covers on either side of the plants rainfall can be 

 very largely excluded, and losses of soil moisture from causes other than 

 transpiration are reduced to a minimum. Boxes of any convenient size 

 and length may be used, and placing the boxes in the soil insures a close 

 approach to general field conditions. 



The general plan as well as a summary of the results of the 1918 tests 

 on the effects of differences in water supply in combination with different 

 degrees of shading have been given in the preceding section on light in- 

 tensity. It is appropriate to give here further details of the water treat- 

 ments. The surface area of the soil in each 8-foot section of the boxes 

 was 8 square feet, so that nearly 5 gallons of water would be required to 

 supply the equivalent of a rainfall of i inch. The water was applied in 

 measured quantities by means of a garden hose. Although nearly all 

 water lost by the soil was through transpiration, it was found necessary 

 to water heavily each day in periods of hot and dry weather. The quan- 

 tities of water added weekly and the rainfall during the period of the tests 

 are shown in Table XIII. 



Soil moisture determinations were made at intervals during the season 

 from samples taken from the field and from the boxes. The samples 

 were taken to a depth of 1 2 inches — that is, to the bottom of the soil in 

 the boxes. Composite samples were made up from boxes receiving the 

 same quantities of water. The samples were taken in all cases just before 



