THE IRKIGATION AGE. 



163 



Irrigation of Alfalfa 



By SAMUEL FORTIER, 



Chief of Irrigation Investigations, Office of Experiment btations. 

 U. S. Department of Agriculture, 



Experience in the growing of alfalfa for more than 

 two thousand years shows that it thrives best in the soil 

 and climate of arid and semi-arid regions. The abundant 

 sunshine, the warmth, and the deep, rich soil prevailing 

 throughout the western half of the United States seem to 

 be well suited to its requirements, and over half a cen- 

 tury's experience has shown that there is comparatively 

 little cultivable land in the West on which it can not be 

 grown. One finds the same varieties flourishing in Im- 

 perial Valley, California, 100 feet below sea level, and 

 maintaining a sturdy growth on the San Luis plains of 

 Colorado, 7,500 feet higher. Alfalfa makes a remarkable 

 growth in the warm sunshine of Arizona, yet it is rarely 

 injured by cold in Montana. 



One can not well overestimate the importance of al- 

 falfa to western farmers. The alfalfa field and the alfalfa 

 stack provide the best means of protecting stock against 

 enormous losses by starvation when the excellent pastur- 

 age available throughout the greater part of the year fails 

 either through drought in midsummer or by being cov- 

 ered with deep snow in midwinter. A single ton of 

 alfalfa may save the lives of many head of stock by pro- 

 viding feed during short periods of cold, stormy weather. 

 Alfalfa can not be excelled as a preparatory crop on soils 

 that have long been unproductive. Likewise, it maintains 

 the fertility of soils naturally rich in plant food, and if 

 used as a base of rotation makes possible abundant crop 

 yields of various kinds. In 1906 the chemist of the Colo- 

 rado Experiment Station* estimated the fertilizing value 

 of the stubble and roots of mature plants at $35 per acre 

 when measured by the commercial value of artificial fer- 

 tilizers on the market. Moreover, the yields are excep- 

 tionally high when irrigation, favorable climatic condi- 

 tions, and proper treatment are combined. Seven tons of 

 cured hay at three cuttings are obtained from the best 

 fields of Montana, while frequently 9 tons in five cuttings 

 are harvested in California. This large tonnage, together 

 with its high feeding value and the fact that it is con- 

 sumed by practically all farm animals, makes it not only 

 a convenient and useful crop to the grower, but a highly 

 profitable one as well. 



Notwithstanding its present importance and great 

 value in irrigation farming, the profits on the area now in 

 alfalfa can be greatly increased if more care and skill are 

 exercised in growing it. The western irrigator has sel- 

 dom been able, financially, to dig his ditches and prepare 

 his fields in such a way as to insure the most efficient 

 irrigation and the highest profits. In consequence, valu- 

 able water is wastefully applied to land that is in no 

 fit condition to be irrigated. On the large acreage in irri- 

 gated alfalfa this amounts to an enormous loss. This 

 fact, considered in connection with the importance of this 

 crop, the rapidly increasing area devoted to its growth, 

 and the large number of farmers who are settling in the 

 West and who will be for years dependent in a large 

 measure on alfalfa for a livelihood, would seem to war- 

 rant the collection and publication of any information de- 

 signed to improve the present practice. 



As its title implies, this publication deals with but 

 one feature, that of irrigation, and its scope is necessarily 

 limited to irrigated lands. There has been no attempt to 

 present or discuss at any length other phases of the gen- 

 eral subject of alfalfa growing,! and wherever mention 

 has been made of these it has been only to show their 

 relationship to irrigation. 



In the examination of alfalfa fields and the collection 

 of the data necessary for this publication, advantage was 

 taken of the organization of the irrigation investigations 

 of this office, which is well adapted for such a purpose. 



Colorado Station Bulletin 110. 

 tThese are treated in U. S. Dept. Agr., Farmers' Bui. 339. 



Through the state and territorial agencies of that divi- 

 sion and through co-operation with the members of state 

 experiment station and the state engineers it was possible 

 to obtain with a high degree of accuracy the conditions 

 and irrigation practice with reference to this crop through- 

 out the entire arid region. 



Irrigable Lands Adapted to Alfalfa. 



Perhaps the most essential conditions for the pro- 

 duction of alfalfa are abundant sunshine, a high summer 

 temperature, sufficient moisture, and a rich, deep, well- 

 drained soil. All of these essentials, save moisture, exist 

 naturally in the arid region of the United States, and 

 when water is supplied it makes the conditions ideal. Al- 

 though alfalfa can be successfully grown under a wide 

 range of soil conditions, yet all western lands are not 

 equally well adapted to its growth. For this reason those 

 who are seeking such lands with a view to their purchase 

 should first make a careful examination of the character 

 and depth of the soil, its behavior when irrigated, the 

 slope and evenness of the surface, the presence of injuri- 

 ous salts, and the facilities for drainage. 



One of the best indications of the character of the 

 soil is the native vegetation. When sagebrush, buffalo 

 grass or cactus is found on a tract it is reasonably certain 

 that the soil is fertile, easily tilled, and well drained. On 

 the other hand, the presence of greasewood, saltwort, 

 salt weeds, or similar plants is indicative of a heavier soil, 

 less easily cultivated and irrigated, and containing more 

 or less of the injurious salts usually grouped under the 

 common name of alkali. 



Figure 1. Soil Auger. 



In arid regions most cultivated plants are deep 

 rooted. They draw their supply of plant food and mois- 

 ture from considerable depths, and the deeper the soil 

 the larger is the feeding ground for the roots and the 

 greater is the capacity to store water. The presence of 

 any impervious stratum lying between the first and fifth 

 foot prevents deep rooting and the storage of moisture. 

 A hard stratum lying between the fifth and tenth foot is 

 likewise injurious, but to a less extent. The character of 

 the subsoil may be readily determined by boring holes, 

 with a suitable soil auger similar to that shown in figure 

 1, to a depth of 10 feet, if necessary, and taking samples 

 of soil at different depths. It will be possible usually to 

 find under irrigation in near-by fields soils similar to 

 those being examined, but if this is not possible a trial 

 may be made on a small scale to determine how the soil 

 acts under irrigation. In general, sandy loams irrigate 

 well; clay is hard to cultivate when wet, does not absorb 

 water readily, and bakes and cracks when drying; while a 

 soil which is too sandy will not retain sufficient moisture 

 to maintain crops. 



The most favorable condition for irrigating is a 

 smooth surface, with a uniform slope of 10 to 20 feet to 



