LARGE IRRIGATION FURROWS 171 



Irrigating by Large 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 followed 

 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 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 summer irrigations is all 

 that is required to carry the trees through. It is obviously adapted only 

 to land of slight and uniform grade. Irrigation 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 multiplied. In this case the water is admitted to the 

 furrows from a board flume. Large furrows are often used in a bear- 

 ing orchard, the furrows being filled from a lateral ditch, this lateral 

 being parallel to the main ditch. In this case the board dam is used 

 to divert the lateral into one large furrow after another, and when the 

 furrow is filled dirt is thrown in to prevent the reflow of the water into 

 the lateral. 



The great variety in large furrow practice is suggested in the fore- 

 going. A systematic manner of proceeding is that of Mr. A. Trost, of 

 Palermo, California, as described by himself : 



The soil is red, gravelly clay, the upper 12 inches without rocks; below this 

 the gravel is more rock. At the depth of 3 or 4 feet the red clay changes 

 into a whitish one and water enters it very slowly. My orchard is 12 acres 

 1,120 feet long from north to south and 510 feet from east to west. The north- 

 east corner is the highest. Here the water ditch enters, and I run my head 

 ditch along the east side from north to south. There are 51 rows of trees in 

 that direction, the north and south outside rows being olives. There are 23 

 orange trees in the row from east to west and 1 olive tree on the west end. All 

 trees are 20 feet apart. I use 24 miner's inches per day for 5 days in the fol- 

 lowing manner : I use 4 furrows about 5 or 6 inches deep and about 3 feet 

 apart between rows, leaving the rows nearest the trees from 5 to 6 feet from 

 the trunks. The 4 lower rows on the west side I cross furrow with 2 furrows 

 between the trees. I divide the 24 inches into 51 equal streamlets by using one 

 gate for each 4 rows. First turn this amount into the furrow south nearest to 

 tree. When the water has moved to the olive tree, I divide the water between 

 the 4 furrows for the lower 6 trees and through the cross furrows. The next 

 morning I divide the water at the tenth tree for the 4 furrows. On the third 

 day I let only one-half the water go down in the furrow south of tree, the 

 other in the one north nearest to tree. On the fourth day I turn part of it in 

 the middle furrows near the head ditch, and by the fifth day I have my place 

 equally wet from one end to the other, taking care that the top soil near the 

 trunks of trees remains dry on the surface. I keep the soil around the trunks 

 of the trees about 2 inches higher for a width of 3 feet. In this way I use all 

 the water without running any off, and lose only the evaporation. The whole 

 amount of water used is 120 inches, equal to 10 inches or 130,000 gallons per 

 acre, or 4.5 acre-inches, or 1,200 gallons per tree. 



I irrigate about every four weeks, running the water five days and turning 

 it on again three weeks after it is taken off. I have irrigated as early as the 

 1st ^ of April and as late as the middle of October, depending on late rains in 

 spring and early rains in fall ; usually from five to six irrigations per year. After 

 four or five days I cultivate 14 feet wide between the trees from 6 to 8 inches 



