JOURNAL OF MMIWL RESEARCH 
Vot,. XXVII Washington, D. C., March i, 1924 No. 9 
THE MOVEMENT OF WATER IN IRRIGATED SOILS 1 
By Carl S. Scofield 
Agriculturist, Office of Western Irrigation Agriculture, Bureau of Plant Industry , 
United States Department of Agriculture 
INTRODUCTION 
Irrigation is a relatively new feature of agriculture in the United 
States. As yet there has not been time to accumulate a fund of experience 
in irrigation to correspond to our knowledge of farming under conditions 
of ample rainfall. We are now practicing irrigation under a great variety 
of conditions as to climate, soil, and character of water supply, and are 
gaining experience rapidly. Large investments have been made in 
irrigation works and in the improvements and equipment on irrigated 
land. These investments include not only money but even in larger 
measure the labor of the farmer and home maker, which have been 
applied in the belief that irrigation farming is no less permanent than 
farming under conditions of adequate rainfall. The structures installed 
for the storage and diversion of irrigation water have been built to last for 
generations. It is clearly the expectation that the lands to be served by 
this water will continue to be productive as long as the works shall stand. 
Yet our own experience, which covers but little more than half a century, 
shows that there is a real danger that some of our irrigated lands may 
become unproductive within a few years. The causes of this uncertainty 
as to the future are found in what is known as the alkali problem. 
The present paper deals with certain aspects of the alkali problem 
which as a whole relates to the soluble salts in the soil solution. These 
salts, which are derived from the processes of rock decomposition and 
soil formation everywhere, do not accumulate in the soil except in arid 
regions where the evaporation exceeds the rainfall. In regions of abundant 
rainfall the soluble products of rock decomposition are continually 
leached away from the soil and carried to the sea. 
In attempting to present an account of the alkali problem in relation 
to irrigation farming it seems desirable to consider first the physical 
relations existing between the water and the soil. An understanding of 
these relations is essential to a comprehension of the alkali problem. In 
an irrigated field the soil acts as a reservoir to hold water for the use of 
plants. As a reservoir it has definite limits of capacity, both as to the 
quantity of water it may hold within the zone occupied by plant roots 
and as to the time required to fill it with water. These limits and the 
factors which determine them need to be understood as clearly as our 
knowledge permits, both by the farmer who operates the land and by 
the engineer who designs and constructs the irrigation works. 
1 Received for publication Feb. x8, 1924. 
Journal of Agricultural Research. 
Washington, D. C. 
(617) 
Vol. xxvn. No. 9 
Mar. 1, 1924 
Key No. G-374 
81990 - 2 ' 
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