84 Physics of the Soil. 



Warington determined the distribution of nitrogen in 

 some of the Rothamstead soils to a depth of 9 feet in 9-inch 

 sections. The results he found are given in the table be- 

 low: 



Nitrogen in soils at various depths. 



In these two cases the nitrogen decreases" downward until 

 about four feet and below this depth to nine feet the 

 amount remains nearly constant. It will be seen that the 

 amount is very large in the aggregate. Enough for more 

 than 240 crops of wheat, 40 bushels per acre, could it ?.ll 

 be used. 



99. Amount of Nitric Acid in Soils. The amount of the 

 available nitrogen in soils, or nitric acid, is seldom a large 

 quantity and while crops are growing the quantity is still 

 smaller. 



Warington states that the nitric nitrogen in the soil 

 seldom reaches 5 per cent, of the total amount present, and 

 in the surface three feet of the arable soil referred to in 

 (98) this would represent 360.6 Ibs. of nitric nitrogen and 

 1,650 Ibs. of nitric acid per acre; enough, if it could all be 

 used, to give a yield of 211.4 bushels of spring wheat per 

 acre. 



100. ITitric Acid in Fallow Ground. The amount of ni- 

 tric acid in fallow ground was determined to a depth of 4 



