899 



the surface. * * • In one series of trials the observation of the 

 solution was continued till conversion of nitrites to nitrates was com- 

 plete. This certainly occurred with all soils down to 4 feet below the 

 surface." 



It is of interest to note in this connection that Miintz has found the 

 nitrifying organisms in the disintegrating rocks of the Alps (see Exper- 

 iment Station Record, vol. iii, p. 114). 



The methods used by the author for x>reparing soil extracts and 

 determining the nitrates in the same are described. Details of the 

 latter (a modification of Schlosing's method) will be found in Trans. 

 Chem. Soc, 1880, 408; 1882, 345, 351. 



The quantity of nitrate which may be formed in soil under favorable circumstances 

 is very larj^e, and the process of nitrification very rapid. The most strikiujjj instance 

 I am aware of is furnished by one of Schlosing's experiments, in which * » * 

 during the 12 days of active nitrification, nitrogen was oxidized at the rate of 56 

 parts per million of dry soil per day. 



The greatest rate of nitrification I have noticed when working with ordinary ara- 

 ble soil (first 9 inches) from the Rothamsted farm, has been about 70 parts of nitro- 

 gen per million of air-dried soil in 119 days (0.588 per day). * -^ * 



Lawes and Gilbert (Trans. Chem. Soc, 1885, 415) working with the far richer Mani- 

 toba soils and with a higher temperature, obtained in two cases (soils from Selkirk 

 and Winnipeg) average daily rates of nitrification of 0.7 part of nitrogen per million 

 during 335 days, the rates during the earlier portion of this period being as high as 

 1.03, 1.24, 1.36, and 1.72 per million. The greatest proportion of nitrogen nitrified 

 in 335 days was 5.4 per cent of that originally present in the soil. 



Deh^rain (Ann. Agron., 1887,245; 1888, 292) working with a soil containing 0.16 

 per cent of nitrogen, obtained daily rates of nitrification varying from 0.71 to 1.09 

 per milliojx in 90 days. 



[The amount of nitrogen as nitrates at depths of from 9 to 27 inches in Rotham- 

 sted soils after bare fallow, are given in a table: If we add to the amount thus deter- 

 mined that found in the drainage water,] we arrive at 86.5 pounds of nitrogen per 

 acre as the quantity nitrified during the season of 1881-82, and 89.5 pounds as the 

 amount nitrified in 1880-81 (the periods covered in each case being from 14 to 15 

 months). * * * If a farmer could insure dry seasons, so that the nitrates produced 

 during a bare fallow shotild remain in the soil available for the succeeding crop, it 

 would pay h.im better to have an alteration of wheat and dry fallow rather than to 

 grow wheat continuously, but in the English climate no such favorable result can be 

 expected [and 30 years' experiments at Rothamsted have sliown that] wheat 

 after fallow, except in some of the earliest years, has not given the double produce 

 which should result from the presence of a double supply of nitrates. It is also 

 further evident that the fallowed laud has declined in fertility more quickly than 

 the land which has been continuously cropped. 



The construction of the drain gauges in use at the station is 

 described. These gauges have brought out the remarkable fact "that 

 a poor, arable soil, without vegetation, loses annually by drainage 

 nitrates equivalent to 2 cwt. per acre of sodium nitrate." 



Lecture V. — Nitrification of soil and mnmire (pp. 77-94). — The aver- 

 age monthly amounts of drainage, and nitrogen as nitrates in drain- 

 age water, from unmanured bare soils, 20 and 60 inches deep, for 13 

 years, and from unmanured wheat land for 12 years, are given in 

 tables. In the first case the drainage from 60 inches of soil was only 



