[shutt] NITROGEN COMPOUNDS IN RAIN AND SNOW 85 



per acre per annum. The most notable departure is for the year 

 ending February, 1909, when the amount reached 8-364 lbs per acre, 

 an amount which is, undoubtedly, abnormally high. As pointed out 

 in a former communication on the subject to the Royal Society, this 

 exceptional result was due to extensive bush fires which raged for 

 many weeks during the autumn of 1908 in Ontario, Quebec and 

 Northern New York.* The rain falling during this period was very 

 high in free ammonia and, although the precipitation was light, 

 it furnished per acre, approximately, one and a half pounds of nitrogen 

 in September and two and two-tenths pounds in October. 



This investigation was begun with the intention of continuing 

 it uninterruptedly for a period of ten years. We shall not, therefore, 

 at this time draw any final conclusion, but it would seem probable 

 from the data obtained that the amount of combined nitrogen furnished 

 by the precipitation in the neighbourhood of Ottawa per acre, per 

 annum, is approximately 6 pounds. 



Dr. N. H. J. Miller of the Rothamsted Experiment Station, 

 England, has compiled from all available sources a table giving the 

 nitrogen as ammonia and as nitrates in parts per million and pounds 

 per acre, as determined by various observers in the world.** The 

 results show wide differences, the nitrogen per acre ranging from less 

 than 2 pounds to nearly 20 pounds per annum. However, the larger 

 number of reports indicates considerably less than 10 pounds and very 

 probably the average, where the collections have been made in sub- 

 urban and rural districts, will not exceed the Ottawa figure. If 

 such be the case, it is obvious that the function of the precipitation 

 in restoring nitrogen to the soil is of no great significance ; the nitro- 

 gen so supplied would go but a small way towards replacing the 

 losses incurred in irrational farming methods or by the removal of 

 crops. It is, however, worthy of note that this nitrogen is supplied 

 in forms immediately and directly available to plant growth and that 

 the larger amount enriches the soil at a season when vegetation is 

 active. It is therefore a warrantable assumption that the rain 

 apart from its solvent action on the soil and its other important 

 functions directly assists our crops by supplying a portion of the 

 nitrogen required for their growth. 



At Ottawa, approximately two-thirds of the total precipitation 

 is as rain. As rain is decidedly and invariably richer than snow in 

 nitrogen compounds, it follows that much the larger proportion of 



"Transactions Royal Society of Canada, Vol. IV, Section III, pages 55-59. 

 * Composition of Rain water, Journal of the Scottish Meteorological Society, 

 Third Series, Vol. XVI, No. XXX, 1913. 



