Needs and Potential Use

Although our farmers have used phosphate fertilizers for more than 75 years, the amounts now used are still inadequate from the standpoint of both efficient production and soil conservation. That conclusion was reached in 1944 by the State Production Adjustment Committees of the State agricultural experiment stations working in cooperation with Department statisticians. Their estimates of the amount of fertilizers that could be used profitably under generally prosperous economic conditions are that for the whole country nearly four times more phosphate fertilizer is needed than was used before the war ( 1935-39) and more than twice as much as was used in 1944. The suggested increase over 1944 ranges from 25 percent in the Northeastern States to approximately 250 percent in the Corn Belt and Lake States.

Although 8 Corn Belt and Lake States account for 47 percent of the total suggested increase (compared to only 34 percent for the 20 States of the Southeast, Appalachian, and Northeast regions), the increased needs in the latter States should not be minimized. Those States have large acreages of rolling and eroded soils that should be in permanent pasture or are now producing only scant and poor vegetation. Many field experiments have shown that phosphate and lime are the primary essentials in the establishment of a good vegetative cover of high quality legumes and grasses.

Although in many of the States several times more phosphorus is added in fertilizers than is removed in crops, much of the consumption is concentrated in areas growing cash crops of high value per acre. In areas of concentrated use, phosphorus accumulation will no doubt lead to reduction in acre applications, but on large acreages of poor crop and pasture land increases in use are essential to good land use and conservation. Millions of acres of pastures in the Central States also need improvement through the use of phosphates. According to Donald B. Ibach of the Department, less than 6 percent of the permanent pasture in the humid region was fertilized in 1943.

The need for improving the phosphate status of many soils is also emphasized by the advances made in the development of better adapted and higher yielding crop varieties. It is evident that improved crop varieties make a greater demand on the soil for phosphorus and other elements than do lower yielding varieties, and that a higher phosphate level is necessary if full advantage is to be realized from crop improvement programs aimed at higher acre yields and greater efficiency in production.

Moreover, it is a well-established fact that poor crop quality and lower feeding value are more often associated with phosphorus deficiencies in soils than with deficiencies of any other mineral element. This is particularly true of pastures where phosphates increase not only the phosphorus content of the forage, but also the proportion of the more desirable and nutritious plant species.

Like other practices aimed at soil improvement and conservation and at greater efficiency in production, the practice of phosphate fertilization must be considered a part of a unified program of good soil management. Its place in this program varies with the soil, with the crop grown, and with the system of farming. It is a practice, therefore, that must be adapted to the individual farm.

THE AUTHOR

W. H. Pierre is professor of soils and head of the Department of Agronomy, Iowa State College, Ames, Iowa.

WATER FROM MOUNTAIN SNOW Snow was first measured for its water content in this country by Charles A. Mixer in Maine about 1900. He proved that snow a frozen mass of air and water varies too widely in density for its depth alone to show how much water it will make. In 1908 Dr. J. E. Church of the University of Nevada developed the Mt. Rose sampler, a forerunner of the Federal sampler currently used. With it, a snow sample can be taken and weighed and the snow readily converted into water inches. Now, a thousand or more snow surveyors face sudden storms, snowslides, and exposure to measure each year the snowfall in the Western States where irrigation farming is the backbone of cropland agriculture. The surveys usually start in December: measurements are taken on or about the first of each month until the spring thaws set in. The Soil Conservation Service is responsible for compiling the data.