20 Journal of Agricultural Research voi. xvi, no. 2 



PREPARATION OF SOILS 

 To obtain soils for the pot tests, quantities of field soil were taken 

 from the surface 6 inches, sacked, transferred to the station where each 

 soil was mixed over and over without drying, sieved, and potted. Equal 

 weights of a soil were put in galvanized-iron paraffined culture pots 

 9.25 inches in diameter and 11 inches high. The soil was compacted to 

 that of a good seed bed by dropping the pots a prescribed number of 

 times onto the floor from a height of about 3 inches. The pots were, 

 kept in the greenhouse and maintained at the desired moisture contents 

 by weighing two to three times a week and replenishing the evaporated 

 moisture with pure distilled water through an open tube extending from 

 above the surface of the soil to an arch at the bottom of the pot. The 

 surface of the soils of all pots except those kept fully saturated with 

 water was cultivated from time to time to give a very thin dust mulch. 

 The wheat stubble and growing clover were in the pots when sampled. 

 The samples were taken to represent the entire depth of soil in the pot 

 by the use of Noyes' bacteriologists' soil samplers (jp), and all determi- 

 nations were made from these samples. ^ 



NITRATES AND NITRIFICATION WITH LIME AND FERTILIZER 



TREATMENTS 



The nitrates were determined by the phenoldisulphonic-acid method 

 modified for the accurate determination of soil nitrates.^ The results 

 are held to be equally accurate for all the soils, since the modified method 

 takes into consideration the obtaining of a clear solution, the presence of 

 soluble salts and interfering organic matter. The nitrification tests were 

 made by the beaker method. One hundred gm. of each soil except 

 the peat, of which 50 gm. were used, were placed in half -pint jelly glasses. 

 Five cc. of a 2 per cent ammonium-sulphate solution were added and the 

 soil was incubated for six weeks at 20° to 2 1 ° C. The moisture content at 

 the end of the period of incubation was in every case within i per cent of 

 what it was when the soils were sampled. Table I gives the acidity, 

 crop yields, and nitrate data for each soil with the different lime and fer- 

 tilizer treatments. 



The quantities of nitrates found in the untreated soils before incuba- 

 tion showed that nitrification had taken place in every one of the acid 

 soils. The amounts of nitrate present in the untreated soils when sam- 

 pled were in proportion to their total nitrogen contents rather than in 

 any relation to their acidities. The presence of growing clover in some 

 of the pots lowered the ratio of the nitrates before incubation to those 

 after incubation. Those pots which contained large growths of clover 

 when sampled and which had received applications of lime alone con- 

 tained less nitrates than the unlimed pots, which contained little or no 



1 The pots used in this investigation were chosen from a series of different investigations on soil-acidity 

 problems, and hence the lime and fertilizer treatments for each soil were not the same. 



2 Noyes, H. A. the accurate determination of soil nitrates by the phenol disulphonic-acid 

 METHOD. To be published iu Jour. Indus, and Engin. Chem. 



