In many areas of the region where water supplies are limited, farmers are installing underground pipes, or gated, aboveground surface pipes and hose in an effort to avoid the losses of water that occur from open irrigation ditches. To reduce losses from open ditches, farmers are urged to destroy the weeds in them or to line the ditches if seepage ,losses are high. Much water is being saved in Arizona through the extension of concrete ditch lining and the laying of concrete tile. Nearly one-third of the irrigation delivery facilities in Arizona in 1956 were of this type nearly 3 thousand miles of irrigation line, compared to about 200 miles in 1949.

In the lower Rio Grande Valley, the most concentrated irrigated area of Texas, seriously reduced surface supplies of water originating from the Rio Grande River have forced farmers to develop water supplies from groundwater sources. The amount of land irrigated from these sources increased from 23 thousand acres in 1951 to 160 thousand acres in 1954.

The diversion of rich valley lands to homesites, industry, cities, and superhighways also has had a pronounced effect on irrigation trends in the Southwest. As rising land costs and taxes force farmers to move from the deeper, More level valley soils up on to the coarser, shallower, undulating terrace and foothill soils, land leveling for the usual surface methods of irrigation becomes so difficult and expensive that farmers have had to turn to sprinkler irrigation. Frequent light applications of water by sprinklers on these coarser textured, shallower soils, however, enables the farmer to increase his irrigation efficiency and control erosion more effectively than if he applied the water by conventional surface methods.

Two OTHER DEVELOPMENTS that have contributed to the improvement of soil use and management in this region pertain to irrigated pastures and fertilization of nonirrigated rangeland.

I mentioned the vast acreage of valley basin and terrace soils in the region. These soils frequently are heavy or shallow and may be underlain by dense clay subsoils or cemented hardpans. Because the irrigated pasture plants that are used generally have a shallow root system, they can produce profitable yields of forage on these soils. Ladino clover is a key factor in the development of the irrigated pasture acreage in California, for it produces abundantly on heavy soils and those underlain by impervious subsoils. Relatively efficient water use is obtained because the fine texture and impervious subsoils reduce water percolation below the root zone of the shallow-rooted plants. The irrigated pasture was estimated in 1957 to be 600 thousand acres, about half of which has been seeded since 1945. An increasing number of farmers are using irrigated pastures in their rotation systems. It has been estimated that more than 8 thousand acres of riceland are rotated with pastures.

A spectacular development in improved land use in the region involves some of the 10 million acres of non-irrigated rangeland that lies above the cultivated valleys in California. Early experiments on range fertilization indicated that pronounced increases in the production of native clovers could be obtained on some range soils by the application of sulfur and phosphate fertilizers. Many areas of range did not respond to this treatment, however, and estimates published in 1950 indicated that only 27 thousand acres of dryland pasture or range in California were fertilized.

Experiments with range fertilization conducted since 1950 revealed why the earlier attempts to improve production on a wider number of range soils failed. The solution to the problem apparently involved larger amounts of fertilizer and the introduction of new species of grasses and clovers that are more responsive to the applied fertilizers than the native range plants. The grasses are Harding, smilo, Veldt, orchard, and tall fescue. The clovers are rose, crimson, and subterranean (or subclover). In the fall of 1953 at the Hopland Range Station of the University of California, the application of 500 pounds of a 16-20 0 fertilizer an acre increased the acre yield of dry matter from 240 pounds on the unfertilized plot to 2,420 pounds on the fertilized plot. Just how many more acres of rangeland will respond thus to treatment is unknown, but estimates by the experimenters indicate that significant increases in forage should be expected on most of the 10 million acres.

As more irrigation water becomes available in California through the development of its water resources program, significant expansion of irrigated pastures and other shallow-rooted field crops on the terrace soils that have been devoted to nonirrigated range can be expected. The effective development and management of these soil resources is of vital importance to California agriculture, for it is one means of replacing the soils lost annually in the valleys to urban and industrial developments.

AMONG ALL THE SOIL MANAGEMENT regions in the United States, probably none is more seriously affected than this one by the pressure of urban development and industrialization.

Out of a total of about 17.5 million acres of tillable land, California has lost more than 2.75 million acres to nonagricultural use, according to a1956 estimate of the Soil Conservation Service. More than 800 thousand acres of this diversion has taken place since 1942. Average annual figures for 1952-1955 indicate that it is being lost at the rate of 100 thousand acres a year.

California is not the only State in the region that is losing its most productive agricultural lands. A 1956 report of the Arizona Agricultural Experiment Station indicated the Salt River project has lost one-fifth of its acreage to subdivisions or other nonagricultural use. When it was first developed in 1917, this project of 240 thousand acres was the second largest irrigation project in the United States.

As farmers are forced by higher land prices, operating costs, and taxes to move from the more fertile, well-drained valley lands on to the poorer valley basin lands and terraces, they will be confronted with the task of achieving, maintaining, and increasing present levels of production on inherently less productive lands.

Since adequate supplies of irrigation water must be available to the new areas, additional sources of surface and ground water must be developed. Better irrigation methods will have to be used to conserve water and to avoid creating drainage problems from over-irrigation. Valley basin lands currently unproductive because of high water table will have to be drained; those affected by salt and alkali will have to be reclaimed.

Successful management of the terrace lands above the cultivated acreage will require more economical land-leveling techniques, improved irrigation methods, better cropping, and better rotation systems to reduce erosion.

The development of new irrigated acreages in the region to replace those diverted to nonagricultural use will require the adoption of the best soil-management and conservation practices available. To increase production in this area is a challenge for every agricultural scientist and farmer, for present techniques must be improved and new ones developed.