PRACTICE III 



EFFECT OF DRAINAGE ON TEMPERATURE OF A SOIL* 



Two wooden trays 2 three by four feet and eight inches deep, 

 without legs, the bottom resting on the ground, one lined with 

 zinc to prevent drainage and the other made so as to allow drain- 

 age, are filled with the same kind of soil. Water is added to each 

 until drainage begins in the latter. 



Each tray should be divided into plots of equal size. After 

 the soil is dry enough to work properly, wheat, corn, water- 

 melons, etc. should be planted in their respective plots in each 

 tray, the same number of seeds in each plot. It is convenient to 

 plant 50 or 100 seeds of each kind in this and the following 

 practice. Each student may look after the planting of a single 

 plot, but should make observations morning and evening on all 

 plots in both trays, and keep accurate records of the number of 

 plants that have come up. 



After the plants begin to come up the temperature in each tray 

 at one, two, and four inches in depth is read and recorded hourly 

 on a clear day from 6 A.M. to 6 P.M. 



Explain differences in temperature. 



Why is clay land so often cold ? 



Why are these seeds used ? 



REFERENCES. 



"Soils," Lyon and Fippin, pp. 163, 242-244, and 463. 



"The Soil," Hall, pp. 130-132. 



" Physical Properties of Soil," Warington, pp. 174-178. 



"The Soil," King, pp. 225-227 and 237-238. 



" Soils," Hilgard, pp. 301 and 307. 



1 This and the following practice logically come later in the course, but the season 

 here makes it necessary to give them early in the first semester, but later in the sec- 

 ond semester. Best results may be obtained by conducting these practices before the 

 weather gets too cold in the fall or too hot in the spring. 



2 Where it is possible it may be better to conduct this and the following practice 

 in the field, where the conditions of soil and temperature will be more nearly normal. 

 Instead of the undrained tray a zinc box may be put into the ground. It will then be 

 well to place in this box the soil removed to make room for it. Some frames will be 

 needed to mark the limits of the plots, 



