LAYING OFF LARGE FURROWS 175 



chiefly in introducing the water more deeply in the soil as will be 

 shown later, and this is done by using fewer and deeper furrows. 



Irrigating by Largie Furrows. Where one to four furrows are 

 used, these are large furrows, while the small-furrow system uses 

 from five to eight or more between two rows of trees. Large furrows 

 are made with the double-moldboard plow, or with a single plow fol- 

 lowed by the "crowder," or by plowing out dead furrows between 

 the rows, etc. Their number depends upon the size of the trees and 

 the fitness of the soil for lateral seepage. They are wide enough and 

 deep enough to carry or hold a large stream of water. This method 

 is used chiefly for winter irrigation on land which is so nearly level 



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2_ r js -.'i.^L. 



SOUTH FURROW 



NOKTH FURROW 



Large furrow. 



Large furrow irrigation of orange trees at Palermo, Butte County, Cal. 



that the water will flow slowly into the furrows and stand there until 

 it disappears by percolation. It is also used where one or two sum- 

 mer irrigations are all that is required to carry the trees through. It 

 is obviously adapted only to land of slight and uniform grade. Ir- 

 rigation by a single furrow cut near to the row of trees is a widely 

 prevalent method with young trees. When the trees are larger, or 

 when inter-cultures are undertaken, the large furrows are multi- 

 plied. In this case the water is admitted to the furrows from open- 

 ings in a board flume or the furrows are filled from a lateral ditch; 

 this lateral being parallel to the main ditch. In this case the board 

 dam is used to divert the laternal into one large furrow after an- 

 other, and when the furrow is filled dirt is thrown in to prevent the 



