426 EXPERIMENT STATION RECORD. 



"At the end of 50 days, under very favorable conditions, a large portion of 

 the active nitrogen produced from cotton-seed meal was still in the form of 

 ammonia. 



"While the rank of nitrogenous fertilizers measured by the nitrates formed 

 varies according to the nature of the soil, the relative production of active 

 nitrogen is much less variable and depends upon the nature of the material. 

 This offers a method for comparing the values of different nitrogenous fertil- 

 izers. ... In most cases a greater quantity of nitrogen was taken up by the 

 plants than would be produced in the jars, due to more favorable conditions in 

 the pots for the transformation of nitrogen to active forms. 



" Nitrogen content of the crop, as a rule, increased with the active nitrogen 

 produced in the soil. 



"All soils yielding less than 7 parts per million of nitric nitrogen, or 9 parts 

 of active nitrogen in the jars, were highly deficient in the pot tests. In no case 

 was the crop larger than 8 gm., and the addition of nitrates increased the crop 

 four-fold or more. 



" Soils yielding 7 to 22 parts per million of nitric nitrogen, or 9 to 27 parts of 

 active nitrogen, appear to be deficient in nitrogen. 



" Of nine soils yielding 27 parts per million of active nitrogen in the jars, 

 four ai)i)eared to supply sufiieient nitrogen to the crop, two responded slightly 

 to nitrates, while three resiionded considerably. 



"The soils containing 0.02 per cent nitrogen were very deficient in nitrogen 

 and produced the smallest quantities of active nitrogen. On an average, the 

 production of active nitrogen increased with the nitrogen content of the soil, 

 though the results with individual soils were irregular. 



" Six soils containing an average of 0.12 per cent total nitrogen contained an 

 average of 59 parts per million of active nitrogen, this being 5 per cent of the 

 total. Six soils, with an average nitrogen content of 0.8 per cent, and five with 

 an average of 0.026 per cent, contained 21 and 7 parts per million of active 

 nitrogen, being 2.5 and 2.7 per cent of the total. The nitrogen of soils contain- 

 ing high percentages appears to be more available than that containing low 

 percentages. 



" The production of active nitrogen in the soil can probably be developed into 

 a method for the determination of the needs of the soil for nitrogenous fertilizers. 



" Certain of the soils subjected to study contained a considerable proportion 

 of their active nitrogen in the form of ammonia. . . . 



"At the end of 4 or even 8 weeks a large portion of the active nitrogen pro- 

 duced from organic nitrogen fprtilizers was present as ammonia, even though 

 the conditions were very favorable for their conversion into nitrates. It appears 

 that ammonia must play a not insignificant part in plant nutrition, when fer- 

 tilizer or manure is applied." 



Absorption by soils, H. E. Patton and W. H. Waggaman ( XJ. 8. Dept. Agr., 

 Bur. Soils Bui. 52.- pp. 0.5, figs. S). — This bulletin summarizes the literature 

 relating to the absorption of solids fi-om solution, and reports results of in- 

 vestigations carried on in the laboratory of the Bureau of Soils in continuation 

 of the general work on soil absorption which has been under way for several 

 years. 



After a resum§ of earlier work, the bulletin takes up in detail the results 

 of investigations on selective absorption with carbon, gelatin, soil, paper, 

 cotton, barium sulphate, kaolin, clay, copper hydroxid, dyes, etc. ; absorp- 

 tion by soils of picric acid and dyes from various solvents; distribution 

 of different soluble salts between absorbent and solvent ; rate of absorption 

 (formulas) ; energy changes (heat evolved) ; condition of the absorbed sub- 



