CONTENTS xvii 



CHAPTER IX. THE DRAINAGE OF FARM SOILS 



PAGE 



Drainage mainly a problem east of the Mississippi . .189 

 When drainage is needed . . . . . .190 



To dry put a wet soil ...... 191 



To deepen a shallow soil . . . . . .192 



To improve texture . . . . . . .192 



Many soils are well drained naturally . . . .194 



When it will pay to drain land . . . . .195 



How drainage affects the soil . . . . . .196 



It makes the soil wanner . . . . .196 



It ventilates the soil . . . . .197 



Draining a soil makes it more moist . . . 197 



Practical results from draining land . . . .199 



What kind of drains to use 200 



Surface drains ....... 200 



Underdrains 200 



When ditches are practicable . . . . .201 

 How to dig a drainage ditch ...... 202 



The grade . . 203 



The distance apart ....... 204 



Surface drainage by plowing into lands .... 204 



The action of underdrains ...... 205 



Planning a system of underdrains ..... 207 



The necessity for a plan ...... 207 



The outlet 209 



The grade 210 



Simple devices for establishing the grade . . . .212 

 The number and direction of the drains . . . .216 

 Distance between drains ...... 218 



The depth to lay the drains 219 



The kinds of tiles . 221 



The size of tiles 222 



Digging the ditch 224 



Placing the tiles ........ 225 



Filling the ditch 226 



Obstructions in tile drains ...... 227 



The cost of putting in tile drains ..... 228 



Other kinds of underdrains . . . . . .229 



Draining pot holes ....... 230 



Draining large swamps and marshes . . . . .231 



The large area of reclairnable swamp and marsh land 231 



