SOILS FEKTILIZEKS. 821 



phosphoric acid was largest in the corn plat, followed in order by oats, grass, 

 and wheat. The soil extracts varied widely in concentration at different periods. 

 Experiments in wire-gauze pots showed that in general the soils from which the 

 greatest amount of water-soluble constituents was recoverable produced the best 

 growth of wheat. Bottle culture experiments showed that the untreated extract 

 of the soil of the corn plat produced better growth of wheat than the extracts of 

 soils of other plats whether treated or untreated. The corn plat extract was 

 benefited least by treatment with absorbent substances liiie carbon black. Boil- 

 ing was especially effective in improving the extracts for the growth of wheat. 



An investigation of the causes of variation in soil fertility as affected by 

 long continued use of different fertilizers (pp. 82-91). — In studies similar to 

 those noted above determinations were made of water-soluble nitrogen, calcium. 

 Ijotassium, phosphorus, and total solids, under corn in 8 plats receiving dif- 

 ferent treatment to ascertain the causes of the differences in yield on these 

 plats. 



Very little difference was found in the moisture content of the plats. The 

 amount of nitrates recoverable varied considerably at different times during 

 the growing period of corn and as a rule the greatest amount of nitrates was 

 found in the high yielding plats early in the season. There were only slight 

 variations in water-soluble calcium, but a marked variation in the water- 

 soluble potassium, a close relation apparently existing between the field treat- 

 ment and the amount of water-soluble potassium. The higher content, however, 

 was not always associated with high yields. In general the amount of potas- 

 sium i-ecoverable decreased as the season advanced. There were only slight 

 variations in the water-soluble phosphorus of the different plats. Determina- 

 tions of total solids indicated that the least productive plats furnished extracts 

 of greater concentration than the plats which produced the greatest yields. 



Comparative physical and chemical studies of five plats, treated differently 

 for twenty-eight years (pp. 92-117). — The chemical and physical studies here 

 reported were made on plats of the long-time rotation experiments which had 

 received lime, lime and manure, and commercial fertilizers continuously for 

 28 years. 



The results were not conclusive as to the causes of differences in yield on the 

 differently treated plats. Alcohol digestion or extraction seemed to offer 

 promising means of determining the presence of crystalline organic bodies in 

 soils and the character of the organic matter of the soil appeared to be an 

 important factor in determining the differences in yield. 



The forms of organic nitrogen in soils (118-129). — Previous work by other 

 investigators on this subject is reviewed, and studies of the organic nitrogenous 

 compounds in soils of certain of the long-time rotation plats by the method of 

 Ilausmann modified by Osborne and Harris (E. S. R., 15, p. 221 ) are reported. 



The results indicate that the nitrogenous matter of limed soils is more resist- 

 eut to agencies of decomposition than that of inilimed soils. The decomposition 

 of the nitrogenous matter of limed soils apparently proceeds very gradually, 

 resulting eventually in from 16 to 21 per cent of the nitrogen being given off as 

 ammonia and from 21 to 34 per cent being converted into amino acids, the re- 

 maining 40 to 60 per cent of the nitrogen being either partially or almost wholly 

 unavailable for plant use. 



Studies in organic soil nitrogen, E. C. Latheop and B. E. Brown {Jour. 

 Indus, and Engin. Chem., 3 (1911), No. 9, pp. 657-660). — This is a brief account 

 of studies noted above. 



General composition of the grass lands contiguous to the general fer- 

 tilizer plats, W. Feear and J. W. White {Pennsylvania Sta. Rpt. 1910, pp. 

 163-235, pi. 1). — Continuing previous work (E. S. R., 23, p. 521), an account 



