538 EXPERIMENT STATION RECORD. 



for the denitrification experiments contained sodium nitrate 121.5 mg., potassium 

 phosphate 20 mg., calcium carbonate 1 gm., starch 1 gm., and water 100 cc. In later 

 experiments the medium used in the study of nitrification consisted of ammonium 

 sulphate 3 gm., potassium chlorid 2 gm., potassium phosphate 2 gm., magnesium 

 sulphate 1 gm., ferrous sulphate O.S gm., in 1,000 cc. of water; for the study of deni- 

 trification it was the same as that used in the nitrification tests except that 3.86 gm. 

 of sodium nitrate was substituted for the ammonium sulphate. In the culture tests 

 25 cc. of water was added to 25 cc. of these solutions, 0.5 gm. magnesium carbonate 

 being also added, and in case of the denitrification medium, 2 gm. of organic matter. 

 The temperatures employed in the experiments were 22 to 25° C, 24 to 32°, 35 to 

 37°, and 40 to 42°. Qualitative tests for ammonia, nitrates, and nitrites were made 

 at frequent intervals during the experiments and quantitative determinations of these 

 substances were made at the end. 



The solid medium used was made up as follows: For the study of nitrification dry 

 quartz sand 4 kg., ammonium sulphate 2.5 gm., potassium phosphate 0.2 gm., water 

 500 cc; for the studj^ of denitrification the medium was the same except that 3.5 

 gm. of sodium nitrate was substituted for the ammonium suli^hate. These mixtures 

 w'ere brought to dryness on a water l)ath and 100 gm. of magnesium carbonate added. 

 The sand containing nitrate received in addition 200 gm. of organic matter prepared 

 from dry peat soil. The proportions of water used varied from to 16 per cent. 



Nitrification and denitrification were also studied in 2 soils, one rich in carbona- 

 ceous matter, the other poor in this substance. In one series of experiments the 

 soils were used Avithout addition of any kind; in the second series ammoniacal 

 nitrogen was applied at the rate of 19.6 mg. per 150 gm. of soil; in the third series 

 nitric nitrogen was added at the rate of 18.15 mg. per 150 gm. of soil. The humidity 

 in the different experiments ranged from to 16 per cent. The experiments were 

 continued from 2 months to 70 days, the gain or loss of nitric nitrogen being detei'- 

 mined at their close. 



Among the conclusions drawn from these investigations are the following: In a 

 liquid medium the denitrifying organisms act most energeticallj^ at a temperature 

 which very perceptibly retards the action of the nitrifying organisms. The rapidity 

 of nitrification of ammonium sulphate in solid media was directly proportional to 

 the quantity of water present. Perceptible denitrification occurred in such media 

 only when the percentage of moisture was small. In similar experiments with soils 

 the results were more decided, especially when the i)roportion of sodium nitrate was 

 increased. Denitrification took place to a marked extent only when the proportion 

 of humidity was less than 6 per cent, an amount insufficient to promote the activity 

 of the nitrifying organisms. The latter became decidedly active when the humidity 

 rose to 10 per cent. In soils containing a small amount of moisture denitrification is 

 proportional to the amount of organic matter present. 



The results thus show that water is an important factor in controlling the action of 

 the oxidizing and reducing organisms in the soil and in transforming and conserving 

 the nitrogen compounds present. 



Reclamation of salt marsh lauds, T. H. Me.vxs ( f'. ,S'. Depf. Agr., Bureau of 

 Soiln Circ. S, ]>p. 10). — This is a report of a preliminary investigation of the character of 

 the soils of the tide marshes around Oyster Bay, Long Island, and of the possiltilities 

 of reclaiming them for agricultural purposes. Among means of reclamation the cir- 

 cular V)riefly discusses the exclusion of the sea water and removal of excess of w'ater 

 by ditching, underdrainage, and pumping; the washing out of the salt; and the adop- 

 tion of a sj'stem of cropping and cultivation adapted to the conditions. Mechanical 

 and chemical analyses of several samples of tide marsh soils from the locality named 

 are given, with a discussion of the agricultural value of such soils. It is stated that — 



"Salt marsh lands have long Ijeen considered the most fertile and valuable of lands. 

 Practically no reclamation has been attempted in America, and that which has been 



