QUESTIONS 107 



Questions. (a) What is meant by capillary movement of soil water? 



(6) In what direction does capillary water move in soils? (Consult text.) 



(c) What determines the direction of movement? 



To Study the Power of Soils for Holding Capillary Water. Procedure 

 Fill ;i small baking-powder can having a perforated bottom, with air-dried, 

 coarse sand. Determine the weight of the soil by subtracting the weight of 

 the can from the weight of can plus the dry soil. Pour water on the soil until 

 thoroughly wet. Allow all free water to dram out, and determine the per cent 

 of capillary water retained. (Use weight of air-dried soil as basis.) Repeat 

 the experiment by using an air-dried, fine sand, a crummy silt loam, and a 

 peat or a muck. Record results in tabulated form. 



Questions. (a) Name the factors determining the water-holding power 

 of soils. 



(6) Of what importance is the fact that soils can retain moisture? (Con- 

 sult text.) 



To Determine the Effect of Organic Matter on the Water-holding Power 

 of Soils. Procedure. Take a baking-powder can one-half full of the same 

 air-dry, fine sand used in the previous exercise and mix with it an equal volume 

 of pulverized peat, or some other suitable organic matter. Determine the water- 

 holding power of this mixture. (Allow the organic matter to become well 

 soaked before draining off the water.) Compare results with those obtained 

 in the previous experiment. 



Questions. (a) What is the effect of organic matter on the per cent of 

 capillary water held? 



(6) Does this mixture actually contain more capillary water than the fine 

 sand alone? Determine. 



(c) How may the water-holding power of a sand be increased? Of a 

 silt loam? 



To Determine to What Extent Weeds Use Soil Moisture. Procedure. 

 Secure a pint sample of soil (to depth of at least 8 inches with soil auger) from 

 an area in the garden or field where weeds are growing thick and thrifty. 

 Collect a similar sample from another portion of the same field or garden where 

 land has been well cultivated and weeds killed. (Do not collect these samples 

 soon after a rain, but rather near the close of a dry period.) Place these 

 samples in baking-powder cans to prevent drying out. Weigh, and dry at 

 temperature of 105 C. or 221 F. Determine the per cent of moisture in the 

 two samples. (Use weight of soil as collected in field for basis.) 



Question. (a) Name several reasons why weeds should be destroyed. 

 (Consult index.) 



Field Studies. Determine if possible why some soils dry out so easily. 



Observe different conditions which aid soils to trap water. 



Observe the effect of a good soil mulch and of any other kind of mulch. 



QUESTIONS 



1. What is the relation of moisture to soil fertility? 



2. What use do plants make of water? What is the importance of moisture 



in the soil itself? 



3. What can you say concerning the amount of water used by crops? 



4. What is meant by "water requirement" of a plant? How do crops differ 



in this respect? 



5. About how much water is lost by evaporating from the soil in growing 



a crop? 



6. What are the factors which influence the water requirement of crops? 



7. Tell of the importance of rainfall at the right time during growth. 



8. What is dry-land farming? What is the limiting factor of production in 



this kind of farming? 



