HORTICULTURE 125 



through the lowest wet portions are absolutely necessary, as is the 

 case in humid sections. 



Before drainage work can be taken up with any surety of suc- 

 cess these underground conditions must be determined. If expen- 

 sive mistakes are to be avoided, the subsoil examinations must not be 

 neglected. The first method of making such examinations is that of 

 digging test pits. Under ordinary conditions a depth of 6 feet can 

 be reached without any difficulty. The test pit is also valuable for 

 showing the nature of the digging for which special methods may be 

 necessary. Another method is to use a soil auger, made of a 2-inch 

 wood bit and Mi-inch gas pipe, with which holes can be put down 12 

 feet, if gravel is not present. A long steel rod probe % inch in 

 diameter can often be used to advantage in soft ground. 



The kind of drain to be employed in farm drainage will be de- 

 termined largely by local conditions. Open ditches are sometimes 

 used for farm drainage, but more often for outlet and main drains. 

 The principal objections to the use of open ditches for form ditches 

 are the loss of land and the high initial cost if sufficient side slope is 

 given them. If side slopes are left steep the maintenance expenses 

 are high. 



Covered drains may be divided into the following forms: Tile, 

 lumber boxes, stone, brush, and mole-plow drains. Burned clay 

 tiles, chiefly in a round form and in 1-foot sections, have been in 

 use for more than four hundred years and have proved satisfactory. 

 They have been known to endure for one hundred years. Some 

 kinds of clay tile, when left upon the surface of the ground, will be 

 disintegrated by soil alkali and by freezing. 



Stone box drains have not been used to any extent in these dis- 

 tricts so far as known, but brush and loose rock drains have been 

 observed to fail by filling with sand and silt. 



If farm drains must be-laid along lines of water-loving trees and 

 within 100 feet of them, the drains should be open ditches to prevent 

 roots from obstructing them. The need of covered drains in orchards 

 requiring drainage has necessitated a method of removing the roots 

 without removing the tile. Tn California, cables are strung through 

 he tile and root brushes pulled through short sections. 



The questions of locating the lines and determining their sizes 

 and depths will have to be determined by judgment, applying the 

 fundamental principles herein stated. No general directions, such 

 as a gridiron, double main, and single line or parallel systems, com- 

 monly used for drainage in humid districts, can be given for this 

 kind of drainage. Such systems, with parallel lines 1 rod apart, 

 might fail entirely if applied to some irrigated fields. If after care- 

 ful examination the trouble is located as lateral seepage, a single line 

 should be laid across the line of greatest slope 2 to 6 rods below the 

 upper line of the wet spot. Such spots are usually small and one 

 line may be sufficient, but an outlet line or branch should be laid 

 through the low ground or basin. The distance down the slope af- 

 fected by a drain will vary from 300 to 2,000 feet, according to local 

 conditions. If the source is found to be in particular spots a branch 



