Page 36 



BETTER FRUIT 



April 



Figure 10— BASIN METHOD OF IRRIGATION 



tity of water entering each furrow. Each 

 small stream should then be allowed to 

 run until the absorption which goes on 

 in its passage down the furrow has 

 sufficiently moistened the soil around 

 the roots. 



As regards the right time to irrigate 

 and the proper quantity to apply the 

 best guide is a close observance of the 

 crop itself. Sufficient moisture should 

 be given to the soil to enable the beets 

 to maintain a steady, vigorous growth. 

 When water is applied too early it pro- 

 duces leaves at the expense of roots, and 

 too late waterings cause the plants to 

 mature before they have their growth. 

 A depth of four to five inches over the 

 surface is usually applied at each water- 

 ing, and the number of applications 

 ranges from two to four in a season, 

 the ground being cultivated as soon after 

 each irrigation as practicable. 



The growing of potatoes in a commer- 

 cial way in some of the arid states is 

 rapidly becoming an important industry. 

 Its success is largely due to an inter- 

 change of other irrigated crops. A com- 

 mon rotation on the more fertile bench 

 soils of Greeley, Colorado, consists of 

 grain as a nurse crop to alfalfa the first 

 season, then two years of alfalfa, fol- 

 lowed by two years of potatoes. In the 

 San Luis Valley of Colorado the common 

 field pea is substituted for alfalfa, the 

 most common rotation being one to two 

 years of peas, one to two years of pota- 

 toes, followed by one to two years 

 of grain. 



The rotation of crops in potato grow- 

 ing has an important bearing on the 

 way in which the fields are prepared for 

 irrigation and the manner of applying 

 water. Neither the check nor the basin 

 method is suitable, since potatoes cannot 

 well be flooded. The choice lies between 

 furrows and flooding from field laterals, 

 since it is easy to change from the flood- 

 ing method followed in alfalfa, peas or 

 grain to the furrow method followed in 

 potatoes. In furrow irrigation the size 

 of the field, the slope and the character 

 of the soil cause the length of the fur- 

 row to vary from a minimum of 200 feet 

 to a maximum of 1,400 feet. From the 

 standpoint of the irrigator it is not advis- 

 able to increase the length beyond 660 

 feet. Sometimes the furrows are not 

 more than six inches deep, at other times 

 they are twelve inches deep. A common 

 practice is to have the bottom of the fur- 

 rows about twelve inches below the 

 crown of the plant. In most other 

 respects the irrigation of potatoes does 

 not differ from that of sugar beets. 



Gently sloping land is preferred for 

 irrigated orchards. A fall of ten to 

 twenty feet to the mile insures good 

 drainage, and the soil is not eroded by 

 small streams of water. On very flat 

 slopes the excess water from irrigation 

 frequently has to be removed by artificial 

 means, and on very deep slopes the diffi- 

 culties of applying water are greater. 



Furrow and basin irrigation are the 

 usual methods employed, but the former 

 is more common. In setting out land 

 for commercial orchards a section is 

 usually divided first into forty-acre divi- 

 sions and then into ten-acre tracts. The 



lateral ditches supply the divisions, and 

 individual owners control the respective 

 tracts. When the width of driveways is 

 deducted the length of a tract occupied 

 by trees is seldom more than 600 feet. 

 This distance governs the length of the 

 furrows. The watering of orchard trees 

 during the first season after transplant- 

 ing is most commonly done through two 

 furrows spaced four feet on each side of 

 the tree. As the roots expand more fur- 

 rows are added, and about the time the 

 tree begins to bear the entire space 

 between the rows is moistened, the num- 

 ber of furrows necessary to accomplish 

 this depending on the soil, depth of fur- 

 row, cultivation, etc. Evaporation is less 

 from furrow than from surface irrigation, 

 and deep furrows conserve more water 

 than shallow furrows. In citrus orchards, 

 where water is valuable, a depth of fur- 

 row of eight inches is common. 



In conducting a supply of water along 

 the upper margin of an orchard and in 

 distributing the flow evenly among a 

 large number of furrows, various plans 

 have been adopted. Although the earthen 

 ditch is still common it is no longer 

 regarded with favor. Wooden spouts. 

 Figure 12, or short lengths of pipe 

 inserted in the lower bank of the feed 

 ditch are cheap and fairly efi^ective. 

 Wooden flumes. Figure 13, with auger 

 holes about one inch in diameter spaced 

 every four feet are quite effective, but 

 the wood soon deteriorates, and in time 

 decays. The cement flume shown in 

 Figure 14 overcomes this objection, but 

 both interfere with the free use of teams. 

 For this and other reasons many orchard- 

 ists prefer to conduct the water in a pipe 

 and bring it to the surface through a short 

 standpipe located at the head of each 

 row of trees. This system is shown in 

 part in Figure 16. Each standpipe, 

 through the small openings made in its 

 shell slightly above the ground surface, 

 can supply all the- furrows belonging to 

 any one row of trees without interfering 

 to any appreciable extent with the free 

 passage of teams. 



The quantity of water that is applied 

 to orchards during an irrigation season 

 runs all the way from one to five feet. 

 Where more than three feet in depth is 

 used it is pretty safe to conclude' that 

 the excess is wasted. In districts of 

 scanty rainfall and heavy evaporation, 

 the most profitable crops are produced 

 with the use of twenty to thirty inches 

 in depth over the surface throughout the 

 season. One of the most productive 

 apple orchards in the vicinity of Wenat- 

 chee, Washington, is irrigated five times' 

 between the middle of May and the last 

 week in September, from four to five 

 inches in depth being applied at each 

 watering. In Southern California it 

 requires fully three inches per month 

 in depth over the surface, including both 

 rain and ditch water, to keep citrus trees 

 in a good condition. For the past seven 

 years the amount of irrigation water 

 which has been applied to the lands 

 under a canal at Riverside, California, 

 which serves about 9,000 acres, has 

 averaged twenty-seven and three-quarter 

 inches in depth over the surface. The 

 average rainfall of. this locality for the 

 seven years was ten and one-half inches, 

 thus making the total thirty-eight and 

 one-quarter inches, or a trifle more than 

 three inches per month. 



In the introductory paragraph of this 

 article it was estimated that the water 

 now diverted from stream channels and 

 other sources in excess of that required 

 to produce satisfactory yields is suffi- 

 cient to irrigate 7,000,000 acres of land. 

 Very little of this excessive use is 

 deliberate waste. A large part of the 

 water taken from natural streams is lost 

 before it reaches the fields of the farmers 

 and another large part of it results from 

 the failure to adapt methods to soil and 

 crop conditions and to the character of 

 the water supply. In deciding upon the 

 best method for given conditions all 

 these factors must be considered, and 

 the crop and the soil should be examined 

 often to see whether the water is being 

 properly distributed to the plant roots. 



