176 BOARD OF AGRICULTURE. [Pub. Doc. 



formed, there is great danger of its being lost in the drain- 

 age waters. Because nitritication goes on faster at the 

 higher temperatures, it follows that in the early spring, 

 while the land is still cold, nitrate nitrogen is much less 

 abundant than in midsummer, after the soil is Avarmed up. 

 As the nitrates which are formed are in o-reat danojer of 

 being lost if not speedily taken up by plants, it is important 

 to keep the land at all times covered with growing plants. 

 One of the factors of continued soil fertility is therefore 

 continued soil cultivation and continued growing of plants 

 upon the lands. 



The Maintenance of Soil Nitrogen. 



Every growing crop removes very considerable quantities 

 of nitrogen. The nitrates which are formed in the soil are 

 in danger of being leached out by drainage waters, or being 

 broken up into free nitrogen b}'^ the denitrifying organisms. 

 All of this is a constant drain on the land, and means a loss 

 of soil nitrogen. These facts have been known for many 

 years, and until recently there has been no satisfactory 

 answer to the question, " Is it possible to maintain the 

 supply of soil nitrogen ? " The amounts of nitrogen brought 

 to the soil in the form of nitric acid and ammonia in rain are 

 small, and are totally inadequate to meet the demands of 

 growing crops. 



To replace the nitrogen removed by crops, men looked 

 about for sources of availal^le nitrogen stored in the earth. 

 Large quantities of guano, found on islands which for gen- 

 erations had been the bre(^ding places of sea fowl, were used 

 until this store was exhausted. Then came the discovery of 

 enormous beds of nitrate of soda in South America, and this 

 nitrate of soda is still being used extensively for our agri- 

 culture. Like the guano, these beds will some time be ex- 

 hausted. Can we turn elscAvhere with surety? This brings 

 us to consider one of the most imi)ortant discoveries of 

 modern times. 



