122 EXPERIMENT STATION RECORD. [Vol. 3T 



It was found that " ammoniiiin hydroxid in 4 per cent concentration will, In 

 certain soil types, extract more phosphoric acid from the air-dry soil than will 

 1 per cent hydrochloric acid, and in only one sample of eight different soil 

 types did hydrochloric acid extract appreciably more phosphoric acid than did 

 the ammonia. There appears to be no relation between the amounts of phos- 

 phoric acid extracted by ammonia from the unleached soil and that extracted 

 after leaching with 1 per cent hydrochloric acid, although in both instances 

 there is usually a greater quantity of phosphoric acid extracted by the ammonia 

 than is extracted by the acid. The amounts of humus-phosphoric acid present 

 in the eight soil types studied when compared with the known fertility of these 

 soil types do not support the theory that a high humus-phosphorIc acid content 

 is a necessary factor in soil fertility. . . . 



" There is no relationship detectable between the total nitrogen content of 

 the soil and the phosphoric acid extracted by the different treatments. The 

 amount of ' humus ash ' present in an ammonia extract is extremely variable, 

 even when the extractions have been carried out under Identical working condi- 

 tions. A minimum of 6.7 per cent and a maximum of 32.6 per cent of ash 

 were found in the ' humus ' extracted from the eight mineral soil types studied. 

 S«ch a wide divergence can be accounted for only by the presence of consider- 

 able amounts of clay or absorbed mineral materials. . . . 



"The ' huinilication ' of vegetable materials in contact with a mineral soil 

 for an entire year did not Increase the humus-phosphorlc acid over that con- 

 tained in the original subsoil. The phosphoric acid present in the ammonia 

 extract of soils can not be correlated either with the amount of organic matter 

 present or with the known fertility of the soil tj'pe. Inasmuch as this phos- 

 phoric acid does not represent a definite chemical entity, there appears to be 

 no valid reason why determinations of humus-phosphorlc acid should be made. 

 It is pointed out that the conclusions drawn In regard to colloidal absorption 

 of phosphoric acid apply with equal force to determinations of humus-potash, 

 that in all probability organically bound potash does not occur in the soil In 

 appreciable amounts." 



Twenty-four references to literature bearing on the subject are appended. 



Soil survey of Buchanan County, Missouri. B. W. Tillman and C. E. Deak- 

 DORFF (U. S. Dept. Agr., Advaticc Sheets Field Operations Bur. Soils, 1915, pp. 

 46, fig. 1, map 1). — This survey, made In cooperation with the Missouri Exi)eri- 

 raent Station, deals with the soils of an area of 258.560 acres In northwestern 

 Missouri, which is divided Into upland and level flood plain. The upland ranges 

 from hilly to rolling and undulating, and is thoroughly, and In places exces- 

 sively, drained. The bottom land drainage is generally Imperfect. The soils of 

 the county are of loessial, glacial, residual, and alluvial origin. 



Including marsh. 15 soil types of 10 series are mapped, of which the Knox 

 silt loam. Marshall silt loam, and Wabash silt loam cover 33.6, 32.6, and 11.8 

 per cent of the area, respectively. 



Soil survey of Polk County, Nebraska, J. M. Snyder and T. E. Kokjeb 

 (U. S. Dept. Agr., Advanee Sheets Field Operations Bur. Soils, 1915, pp. SO, 

 fig. 1, map 1). — This survey, made In cooperation with the Nebraska Soli 

 Survey, deals with the soils of an area of 275.200 acres in east-central Nebraska. 



"About two-thirds of the county consists of uplands of the loess plain and 

 has a flat to undulating topography. On the north there is an abrupt break 

 from this upland, and a strip of roughly rolling land Intervenes between It 

 and the broad valley of the Platte River. The alluvial lands of the valley are 

 generally level or undulating, with local surface inequalities." The upland 

 soils are of loes.sial origin. 



