458 



EXPERIMENT STATION RECORD. 



TIk' ivsults of ik'ld cxiuuinationw liy tlies^e inethods of the water extracts of several 

 hundred oveu-dried sami)les of (5 typical soils of varying degrees of productiveness 

 from New Jersey, Maryland, and North Carolina are reported. From these results 

 and from those of analyses of air-dried samples of tyi)e soils from various parts of the 

 humid region of the United States the conclusion is drawn that " there is no a])j)ar- 

 ent relation between tiie dissolved salt of the soils, as determined by the methods 

 outlined a1)ove and the yield of crops, and that there are no constant differences 

 l)etM('en the <lifferent types of soil, although these types differ widely in tlieir agri- 

 cultural and crop values." 



Th<' extreme variations in the })rincipal constituents of tlie water extracts of the 

 () typical soils to which special attention was given were foun<l to be as follows: 



VitridtioiiK in principal conafttnenls of water c.rtrads ofti/pical soils. 



Windsor sand 



Norfolk tiand 



Sassafras loam 



Leonardtown loam 

 Cecil sandy loam.. 

 Cecil clav." 



Number 

 of anal- 

 yses. 



34 



98 

 80 

 02 

 57 

 120 



Parts per million of oven-dried soil. 



Phosphoric 

 acid (PO4). 



2. 65-12. 88 

 1.71-16.52 

 2.24-21.45 

 2.90-16.50 

 . 59-27. 59 

 2. 40-40. 60 



Nitric acid 



(NO3). 



0. 56-26. 62 



. 67-23. 76 



.50-38.40 



Trace-62. 00 



Trace-28. 41 



Trace-34. 12 



Potassium. 



10. 90-46. 11 



11. 64-44. 90 



7. 94-46. 80 



10.08-.51.66 



7. 47-72. 70 

 4. 93-83. 80 



Calcium. 



Trace- 47. 50 

 Trace- 46. 86 

 2. 84- 62. 72 

 2. 66- 34. 22 

 11.08-100.3.5 

 10. 70-102. 85 



The extreme variations found in analyses of air-dried samples of about 50 type 

 soils from different parts of the eastern half of the United States were as follows: 

 Phosphoric acid from 3.5 parts per million in Cecil loam (New Jersey) to 37.8 parts 

 in Allegan gravelly loam (Michigan), nitric acid from 1.4 parts in Orangeburg sandy 

 loam (Alabama) to 210.5 inConestoga loam (Pennsylvania), potassium from 5.2 parts 

 in Houston l)lack clay (Texas) to 84 in Mianu clay loam (Ohio), calicium from 2 parts 

 in Cecil loam (New Jersey) to 213.2 in Orangeburg clay (Alabama). 



The average of 147 of the analyses (the basis of selection of which is not stated) 

 is reported as follows: Phosi^horic acid 7.64, nitric acid 5.47, calcium 11.67, and 

 potassium 22.74; and the t'onclusion is drawn that "while these values will 

 undoubtedly vary somewhat as a result of wider investigations, it is believed that 

 they represent closely the average figures for the great majority of cultivable soils as 

 regards these several constituents, which the procedure used in this investigation 

 will show; and so far as the investigations have l)een carried, it may be stated, no 

 evidence has yet been found, except possibly in occasional samples, where the (juan- 

 tit)' of any one of these necessary plant foods was below the amount necessary for 

 the sujjport of a medium to good crop." 



Results of examinations of the water extracts of soils at different tlepths are cited 

 to show " that the soil proper does not contain materially more soluble plant food 

 than does the subsoil." Examinations of soil water obtained by means of the Briggs 

 centrifuge showed the soil solutions to be remarkably uniform, although the amounts 

 of water originally present in the soils varied from 10 to 25, and widely divergent 

 soil types were used. Data as to the effect of drying in increasing the solubility of 

 the soil constituents are reported. 



The authors state that in view of the results reported " the conclusion seems justi- 

 fied that, although differences in the dissolved salt content, or in the concentration 

 and composition of the soil moisture, may be a factor in the yield as well as quality 

 of a crop, it does not appear to be a major one in determining or controlling the wide 

 variations observed in crop yields on different soils. It appears further that prac- 

 tically all -soils contain sufficient plant food for good crop yield, that this supply 

 will be definitely maintained, and that this actual yield of plants adapted to the soil 



