Il6 SOILS AND FERTILIZERS 



surface well waters. In the soil, the ammonium com- 

 pounds may be oxidized and form nitrates. Com- 

 pounds as ammonium chloride or ammonium carbonate, 

 if present in a soil in excessive amounts, will destroy 

 vegetation in a way similar to the alkaline compounds 

 in alkaline soils. 



128. Nitrogen in Rain-water and Snow. — The 



amount of nitrogen which is annually returned to the 

 soil in the form of ammonium compounds dissolved in 

 rain-water and snow, is equivalent to from 2 to 3 

 pounds per acre. At the Rothamsted experiment 

 station the average amount for eight years was 3. 37 

 pounds. 43 When a soil is rich in nitrogen the gain 

 from rain and snow is only a partial restoration of that 

 which has been given off from the soil to the air or 

 lost in the drain waters. The principal form of the 

 nitrogen in rain water is ammonium carbonate which 

 is present in the air to the extent of about 22 parts per 

 million parts of air. 



129. Ratio of Nitrogen to Carbon in the Organic 

 Matter of Soils. — In some soils the organic matter is 

 more nitrogenous than in others. In those of the 

 arid regions the humus contains from 15 to 20 per 

 cent, of nitrogen, while soils from the humid regions 

 contain 4 to 6 per cent. 44 In some soils the ratio of 

 nitrogen to carbon may be 1 to 6, while in others it 

 may be 1 to 18 or more. That is, in some soils there 

 is 1 part of nitrogen to 6 parts of carbon, while in 



