LABORATORY EXERCISES 107 



43. Drainage. 



Materials. Two flower-pots with soil; two geraniums or other 

 flowers growing in pots. 



Set one geranium in a dish of water. Plant corn in two other pots, 

 and stand one in a dish of water. Keep water constantly in the dishes 

 under the two pots, and water the other two in the usual way. Notice 

 the effect of the excess of water on the geranium and on the germination 

 and the growth of the corn. If the corn in the wet pot grows, empty 

 both pots and examine the roots. In which do the roots go deeper? 

 What is the effect of flooding on field crops? On trees? Some crops 

 will live on soils that are so wet that other crops would be killed. What 

 ones? What kind of material underlies the soil in your neighborhood at 

 depths of three to ten feet sand, gravel, clay, rock? This can be 

 answered by observing cuts in the roads. Is the soil naturally well 

 drained? 



44. Laying Tile Drain. 



If possible, practice laying a tile drain. For directions see King, 

 Physics of Agriculture, pp. 286-328. 



if 



45. Temperature of Soils. 



Materials. Four or more cigar-boxes or other small boxes, soil, 

 thermometers, lime or chalk dust. 



Fill each box with soil. Water one box so as to keep it rather wet, 

 cover the surface of one with lime, set these and a third one so that 

 they will face the sun in a window. Set another so that it will not 

 face the sun, that is, give it a "north slope." Take the temperature 

 of each from time to time. 



A field trip may also be taken to get the temperatures of wet and 

 dry soil, north and south slopes, tilled and untilled land. 



WTiat effect does color have on temperature? Why? What effect 

 does the water have? Why? Cut a square hole in a piece of paper. Hold 

 this perpendicular to the sun's rays. Hold another piece of paper back 

 of this. Measure the area covered by the sunshine. Now incline the 

 second piece of paper and again measure the area of sunshine. Why 

 does the slope affect the temperature? 



46. Absorbent Power of Soil. 



Materials. Tin can with holes in bottom, soil and manure. 

 Mix water with the manure so as to get manure water. Fill the 



