BUEEAU OF SOILS. 177 



the Bureau, in charge of Prof. Franklin H. King. During the past year 

 exceedingly delicate methods have been devised for the analyses of 

 soils in the field. They are so sensitive that the amounts of nitrates, 

 phosphates, sulphates, and the like, which may be present, as indi- 

 cated by water solutions, can be determined to within 4 or 5 pounds 

 per acre 1 foot deep. With these methods it is possible to detect 

 throughout the jeav fertilizers which were applied in the spring, and 

 to trace the movement of these fertilizers from the place where they 

 were applied down through the different depths of the soil. It has 

 been found possible to show noticeable differences in the chemical com- 

 position of the soil in the same field, in some parts of which the crops 

 are growing well and in other parts of which they are but poorly devel- 

 oped. It appears that the time has arrived, looked forward to with 

 much interest by scientists and practical men alike, when an analysis 

 will show the need of any particular soil for certain fertilizers. It is 

 too early to make a positive statement of this kind, but the indications 

 are that this can soon be accomplished. 



A considerable amount of work has been done with these methods 

 on the soils of eastern North Carolina and of Wisconsin, and quite 

 recently many of the important soil types which have been established 

 by the Bureau in Georgia, North Carolina, South Carolina, Virginia, 

 Maryland, New Jersey, Pennsylvania, and Wisconsin have been ana- 

 lyzed by these methods. These types represent all grades of soil, 

 from the most productive to those which are quite unproductive; 

 soils that are adapted to truck crops, tobacco, fruit, wheat, and corn ; 

 and soils under a range of climatic conditions with rainfall varying 

 from 25 to 45 inches per annum. 



The results of this work have led us to look upon the soil moisture 

 as a great nutritive solution existing over the surface of the earth, 

 the composition of which is everywhere approximately the same. The 

 soil is a heterogeneous mixture of minerals, the predominant ones being 

 silica, feldspar, mica, and other like silicates, resulting i^rimarily 

 from the disintegration and decomposition of igneous rocks, spread out 

 often through the action of water over vast areas of land. All these 

 minerals are but slightly soluble, and it is not unreasonable to expect 

 that such a heterogeneous mixture of silicates in contact with water 

 should yield a soil solution having sensibly the same composition and 

 concentration. The older experimenters in Germany found that in 

 making up solutions for water culture or for sand culture, the con- 

 centration and composition of the nutritive solution must be the same 

 within relatively narrow limits for success in plant development. The 

 results of the past season indicate that the differences in the compo- 

 sition and concentration of the dissolved material in the soil moisture 

 of various types of soil of widely different localities and of different 

 agricultural values are little, if any, greater than the differences to 

 be found in one and the same type of soil under good and under poor 

 farm management. 



The "early truck" soil of the Atlantic coast maybe deficient in 

 plant food and may require fertilizers for the best development of the 

 crop, but even with such an application as would make these soils as 

 rich in plant food as the prairie soils of the Middle West, these light 

 truck soils could not economically be made to produce as large corn 

 crops as the prairie soils. The difference in the agricultural value of 

 these different types appears to depend not so much upon the chemical 

 composition as upon the physical properties of the soils, and espe- 



AGR 1902 12 



