QUESTIONS 93 



the top of each equally, and keep a good supply of water in the top of each. 

 In which soil is the downward movement of the water most rapid? 



6. Water-holding Power of Soils. In the above exercise, the amount 

 of water poured into each may be measured, and the pouring may be con- 

 tinued until each lot of soil has taken up all the water it.will hold; that is, until 

 all the soil is wet and the surplus water begins to run through at the bottom. 

 The water-holding capacity of the two samples may then be compared. 



7. The above exercise may be varied by weighing the two samples of soil 

 while dry, before any water is poured on. Then weigh the samples after each 

 is thoroughly saturated -with water. Compare the weights and calculate the 

 percentage in each case. 



8. The effect of a mulch may be studied by placing a layer of straw or 

 carpet over dry soil in the garden. The next day remove this straw or other 

 mulch and compare the soil which has been thus covered, with that around it. 



9. Take two deep boxes of soil, say six to ten inches in depth. The soil 

 should be alike in each and should be moistened well when the exercise is 

 started. Weigh each. Leave the soil loose by scratching with a kitchen fork 

 over the surface in one of the boxes. Pack the surface of the soil in the other 

 box with a brick or block of wood so that a crusty surface may be formed. 

 From day to day for about a week compare the evaporation by weighing the 

 two samples. 



10. Organic Matter Aids in Holding Water. Test the water-holding 

 capacity of organic matter when added to garden soils. To one sample of 

 soil add half its volume of black humus soil from a peat bog or from a compost 

 heap. This is to be compared with another sample of soil without the added 

 humus. Put them in lamp chimneys and weigh each. Pour in water from 

 above until saturated. Reweigh and determine the percentage in each case. 

 This will prove the immense water-holding capacity of humus and organic 

 matter. 



QUESTIONS 



1. Tell of the quantities of water required by plants during the growing 



season. 



2. What is the average annual rainfall of your region? How much of this 



falls during the months of crop growth? 



3. Explain how crops can be grown when so little rain falls during the grow- 



ing season. 



4. What are the three conditions of soil water? 



5. What is free water? How can it be detected in soils? 



6. Of what use is free water in soils? 



7. What is the direct use of capillary water? 



8. Tell how hygroscopic moisture may be detected in soil which is apparently 



very dry. 



9. Tell how water in each of the three conditions is moved from place to 



place in the soil. Explain for each condition. 



10. Explain the different ways by which a grower can increase the capacity 



of his soil for holding capillary water. 



11. What are the chief sources of loss of moisture from soils? 



12. What do you mean by dust mulch? Of what use is it? 



13. What relation have cover crops to the moisture-holding power of soils? 



14. How and to what extent does humus aid in the holding of moisture? 



15. Explain the effects of wind breaks. 



Reference. U. S, Farmers' Bulletin 266, Management of Soils to 

 Conserve Moisture. 



