1910] Pendleton: A Study of Soil Types IV, 



APPENDIX A 

 METHODS AND TECHNIQUE 



Collection of Samples 



There was difficulty in finding types that would meet the requirements of wide 

 distribution and of differing from one another as to series as well as texture. The 

 types chosen were: 



Diablo clay adobe, a residual soil. 



Altamont clay loam, a residual soil. 



San Joaquin sandy loam, an "old valley filling" (old alluvial soil). 



Hanford fine sandy loam, a recent alluvial soil. 



The first task was the collection of the samples of soil for study in the Labors 

 tory and in the greenhouse. Of course, there were kept in mind the errors and 

 difficulties involved in the collection of representative samples. The selection of 

 the localities in which to collect samples was frequently made in consultation with 

 the persons who had originally mapped the areas under the Bureau of Soils. 

 This was done so that the soil chosen might as nearly as possible represent what 

 the surveyor had in mind as characteristic of the type within the area. It was to 

 be expected that the ideal type which one man would use as a guide as he did the 

 mapping in one area would not always be identical with that which another man 

 might use in mapping another area, despite the aid of the inspector in keeping the 

 ideal types of the field men as nearly alike as possible. Some of the accompanying 

 index maps, showing the places where the soil samples were collected, are dupli- 

 cates of the same locality. As the dates show, one is a portion of a less recent, 

 and the other of a more recent survey. In many cases the index maps have been 

 copied from the manuscript maps, a number of surveys in this state not yet being 

 published. For a discussion of the differences in these maps, see below the section 

 on The Criticism of the U. S. Bureau of Soils Method of Surveying. 



Not only were the field men questioned about the locality, but as nearly as 

 possible an exact designation was obtained on the soil map itself. In the collec- 

 tion of some of the samples the writer had the good fortune to have the assistance 

 of the man or men who actually mapped the soils in question. Sometimes there 

 was no trouble at all in locating a typical body of the soil where a sample might 

 be taken. On the other hand, as in the case of the collection of the Hanford fine 

 sandy loam from Woodbridge (nos. 15 and 16), more than two hours were spent 

 in driving about, trying to find a place that seemed a typical line sandy loam. 

 Experience shows that the personal equation in field work is very important and 

 is hard to control.* 5 



No special attempt was made to obtain virgin soil, for the types of soils that 

 had been selected for study were mainly agricultural, ami most of the soils have 

 been at some time under cultivation, if they are not now. Also, there has been 

 little, if any modification of the agricultural soils by the addition of fertilizers. 

 Hence the small tracts of the Hanford fine sandy loam, for instance, that are still 

 virgin are largely non-agricultural, waste land areas, and would not illustrate the 

 properties of the type as a whole. Not so large a part of the San Joaquin sandy 

 loam is under cultivation now, though almost all of it has been farmed to grain 

 in the past. The two minor types studied, the Altamont (day loam and the Diablo 

 clay adobe, being of residual origin and occupying rolling to hilly or mountainous 

 land are also not very extensively farmed. The topography is the limiting factor 

 in most cases. 



43 Fippin, E. O.. Practical Classification of Soils, Proc. Amer. Soc. Agron., vol. 3 (1911), 

 pp. 76-89; Increasing the Practical Efficiency of Soil Surveys, Proc. Amer. Soc. Agron., 

 vol. 1 (1907-1909), pp. 204-06. 



