1920] SOILStt-FERTILIZERS. 725 



was carried on with nOO-^Mii. portions of tho soil in percolators, and the nitrates 

 were extracted at intervals of four weeks. 



It was found that usually niaxiinum nitrification toolc place during the first 

 four weeks, but in some cases it was delayed to the second and even third 

 period, and in some soils nitrification did not occur for a year or more. When 

 nitrification was carried on for several years, a second maximum occurred dur- 

 ing the second summer and a third during the third summer, but these were 

 much smaller than the first maxinuim. The average quantity of nitrates pro- 

 duced increa.sed with the total nitrogen of the soil. With the exception of 

 soils containing less than 0.02 per cent of nitrogen, the percentages of organic 

 nitrogen converted into nitrate were on an average fairly constant. 



There were wide variations in the amounts of nitrates produced by individual 

 soils. The adtlition of 1 per cent calcium carbonate caused most of the soils 

 which failed to nitrify without such addition to do so within the first four 

 weeks. Acid soils nitrified slightly less on an average than nonacid soils with 

 a low lime content. Some acid soils did not nitrify at all, while others showed 

 high nitrification. No other relation could be ti'aced between the amount of 

 nitrifi'oation and the chemical composition of the soil. 



The nitrification in subsoils averaged nearly the same as that in surface 

 soils. Subsoils having a low nitrification were usually low in lime and over 

 half of them were acid, while of those having a high nitrification several 

 were acid. The addition of phosphate or potash increased nitrification in 

 several of the soils, the phosphate being the more effective. 



The nitrifying capacity of 29 soils was found to vary from 2 to 232. Of 

 these, 8 had a nitrifying capacity of less than 25 and 3 had a capacity of more 

 than 100. 



The addition of manure to the soil ^-esulted in a decrease in the amount of 

 nitrates in the percolate. There was no agreement between the nitrifying 

 capacity of the soil and the nitrification of the manure. 



Supply of nitrogen in the soil, .T. W. Ames {Mo. Bui. Ohio Sta., 5 {1920), 

 No. 6, pp. 17.'f-n7). — Studies of the effect of cultivation and fertilization on the 

 nitrogen content of certain soils at the station are reported. 



On a soil which was unfertilized and unlimed and constantly cropped for 18 

 years it was found that the decrease in nitrogen content averaged 20 lbs. per 

 acre annually. On another soil, which was cropped with a 3-year rotation of 

 potatoes, wheat, and clover for 18 years, the decrease in nitrogen content was 

 about 40 lbs. per acre. 



Analyses of pasture .soils which had been cropped and cultivated for 20 years 

 showed a total decrease in nitrogen content for the period of 1,000 lbs. per acre. 

 Adjacent soil which was in grass during the 20-year period showed an increase 

 of 600 lbs. per acre. 



On soil continuously cropped for 16 years to corn, oats, and wheat it was 

 found that the largest decrease occurred in the corn plats and the smallest de- 

 crease in the wheat plats. The supply of nitrogen in limed soils did not decrease 

 as much as that in unlimed soils, whether fertilized or not. 



The hysteresis of aqueous solutions of humus soils, H. Puchner (Kolloid 

 Ztschr., 25 {1919). No. 5, pp. 196-201'. figs. i2).— Studies with peat are reported, 

 which showed that a clear dark yellow solution may be obtained by digesting 

 it with cold water. During the solution a faintly acid, s-omewhat aromatic odor 

 was noticeable. The solution obtained had an acid reaction, and on being kept 

 for several days a slimy brown substance was deposited, after which the clear 

 solution became alkaline. The residue from the incineration of the deposit con- 

 tained alumina, ferric and manganese oxids, lime, and magnesium sulphates, 



