74 Elementary Principles of Agriculture 



of the plows in any direction. Sometimes underground 

 drainage ways are provided. These are often made by 

 digging narrow ditches to the proper depth and filling 

 partly with coarse stones, logs, etc., before refilling. The 

 surplus water finds an outlet through the spaces between 

 the stones. Regular drainage tiles are now most often 

 used in place of loose stone. They may be secured in 

 any size to suit the local conditions. Many fields have 

 been greatly improved by placing rows of tile drains 

 every thirty feet or so. The prompt drainage of some 

 soils is just as important as the conservation of water 

 in others. An excess of water delays the warming of the 

 soil in spring, and prevents the growth of the roots. 



QUESTIONS 



1. In what three forms does water exist in the soil? 2. Explain 

 capillary water. Hygroscopic water. 3. Between what per cents 

 of water content do plants grow most vigorously? 4. Can an irri- 

 gated field have too much water? 5. What becomes of the rains? 

 6. What can the farmer do to make use of a greater amount of 

 the average rainfall? 7. About how much water is used for every 

 pound of dry matter made by growing cotton, or corn? 8. Why is 

 soil drainage important? 9. How should open drains be made? 10. 

 What is a tile drain? 



