822 EXPERIMENT STATION RECORD. 



is here given of a detailed study of samples of soil from the roadways sur- 

 roundins: and running through the long-time rotation plats at the station for 

 the purpose of determining if possible the differences between the character of 

 soil of these roadways and of the differently treatetl plats, of which studies 

 were not made at the time the rotation experiments were undertaken. The 

 studies reported included "(1) an examination to determine the average mechani- 

 cal composition of the soil — i. e., the proportions in which particles of different, 

 specific dimensions, enter to make the entire soil, surface and subsoil; (2) a 

 chemical examination, more complete than usual, into the composition of the 

 mineral matters of the soil ; (3) a general study of the soil's organic materials." 



Among the mox'e important facts brought out by these studies are that 

 although formed by the weathering of limestone rocks the soil contained 

 little if any calcium carbonate, while magnesia although less abundant than 

 lime in the original rock was present in the soil in considerably larger amounts 

 than lime. Quartz formed a large fraction of the undecomposed portion of the 

 rock remains in the soil. The remainder of the undecomposed rock was chiefly 

 an aluminum-potassium silicate with smaller quantities of soda, lime, magnesia, 

 and iron. Manganese was present in small quantity and titanium was quite 

 abundant. The surface soil was distinctly acid. The " active humus "' content 

 was 1.96 per cent in the surface soil and 1.08 in the subsoil. Pentosans were 

 present in the organic matter to the amount of 0.142 per cent, forming 4.65 and 

 4.47 per cent, respectively, of the active humus of the surface and subsoil. 

 The surface and subsoil, free from hygroscopic moisture, contained 0.1492 and 

 0.0676 per cent of nitrogen, respectively. The nitrogen content of the organic 

 matter of the surface and subsoil was 4.18 and 3.98 per cent, respectively. The 

 surface soil contained only 0.076 per cent carbon dioxid, the subsoil 0.143 per 

 cent. There was 0.5 per cent of lime in the surface soil and a little less in the 

 subsoil. The surface soil contained 0.7 per cent and the subsoil 0.9 per cent of 

 magnesia. The soil contained 3.5 per cent of potash, three-fourths of which 

 was in the undecomposed rock residues. The available potash by the Dyer 

 method was 0.0111 per cent in the surface soil and 0.00817 per cent in the 

 subsoil. Phosphoric acid was present to the amount of 0.13 and 0.1 per cent, 

 respectively, in the surface and subsoil. The available phosphoric acid by the 

 Dyer method was 0.008 per cent in the surface soil and 0.002 per cent in the 

 subsoil. In spite of the fact that this soil appears to be fairly well supplied 

 with phosphoric acid, it has always shown a marked advantage from the 

 application of phosphates. This is ascribe<l to the presence of iron and alumina 

 in large amounts and in conditions favorable to the formation of rather in- 

 soluble phosphates. Of the iron present in the surface soil about one-third 

 was found to be in the ferrous condition, a smaller proportion of the ferrous 

 iron being found in the subsoil. 



The methods used in the soil study are described. 



Contribution to the study of phosphoric acid in soils and fertflizers, W. B. 

 Ellett and H. H. Hill (Virginia Sta. Rpts. 1909-1910, pp. U-65, figs. 8).— This 

 is a preliminary report upon laboratory and pot experiments which have been 

 going on for several years to determine what becomes of the phosphoric acid 

 from fertilizers left in the soil after the removal of the first crop, and to what 

 extent this residual phosphoric acid becomes unavailable. The experiments 

 were made with various typical Virginia soils and the phosphates used were 

 phosphatic slag, and tricalcium, dicalcium, and monocalcium phosphates. 



The experiments with various solvents used to determine the availability 

 of the phosphoric acid showed " that the substances found in the different soil 

 types fix phosphoric acid from water solutions into compounds of different 

 solubiilty. The hydroxids of iron and aluminum lock up or fix 60 to 70 per 



