394 ANNUAL REPORT OF THE Off. Doc. 



soils, sandstone soils, shale soils, granitic soils, etc., and in that 

 part of the South Mountain district in this immediate vicinity you 

 have many finer divisions, even, such as "white flint," "gray flint," 

 "copperstone," "mountain stone," etc. A group of soils is desig- 

 nated by the soil series name. Thus the valley limestone soils were 

 named the llagerstown series because they were first ma])ped in the 

 vicinity of TTagerslown, ]Md. And in similar manner other names 

 have been selected to designate main groups or series of soils. 



Leaving the stone content and the gravel content out of con- 

 sideration we are accustomed to speak of soils as clays, sands and 

 loams, or some combination of these terms such as sandy loams, 

 clay loams, etc. What do these terms mean? Analysis of a true 

 clay will always show that the per cent, of exceedingly fine particles 

 is relatively high and where the amount is as much as 35 per cent. 

 of the soil mass it gives to the soil a definite character, in fact 

 seems the determining factor in the way the soil behaves when 

 worked. If plowed or cultivated when wet such a soil will clod 

 badly. Soils are sometimes found which analyze as much as 50 

 per cent, of clay, but I know of none so heavy in this state. A soil 

 that would be mapped as a sand, on the other hand, is composed 

 principally of particles much coarser than the gi^ains of clay. 

 Through such a soil water percolates rapidly and we think of it as 

 a droutliy soil. Between these two extremes, then, of sand and 

 clay, the coarsest soil particles and the finest there is a wide range 

 of sizes. A true loam is a mixture of a large number of differrnt 

 sized particles. Tt is a medium mixture in which clay, medium 

 and fine sands and silt are well balanced. When there is a little 

 too much sand for this medium mixture of loam the soil is called 

 a sandy loam, but where there is a little too much clay for the 

 same classification the soil is called a clay loam. This phase of 

 classification, as you will note, is based solely on the size of the 

 soil grains, and determines the so-called texture of the soil. 



But there are also stiff soils, mellow soils, mealy soils, and so 

 on. This is brought about by a difference in the arrangement of 

 the various sizes of soil particles. Two soils may analyze practi- 

 cally the same, i. e., their textures may show no material differ- 

 ences and yet after a rain the one has to be dried out much more 

 thoroughly than the other before it can be worked without clod- 

 ding. This is due to the differences in the soil structure. Suppose 

 we reduce this to fractions having a common denominator, as we 

 used to do in school. Some of you have tried packing apples in 

 boxes, and until experience has been acquired it is not easy to come 

 out even. If all apples were of the same size it would be an easy 

 matter. But there are all sorts of variations in size, and it takes 

 patience to work out the best combination. Apples of different 

 sizes have to be arranged to fill a given space, and there is almost 

 no limit to the number of combinations that could be made if we 

 did not assort and pack according to standard grades. 



Now soil particles vary as much in size, relatively, as do apples, 

 and hence the soil mixture is exceedingly uneven. All sorts of 

 combination packs have been made and in some of them the parti- 

 cles fit together so snugly that they do not readily crowd apart 

 when a little rootlet tries to find its way down among them. And 

 remember that in plant and tree growth a tiny rootlet always has 



