Lysimeter Experiments 



37 



The nitrogen in the drainage water was all in the form of nitrates, 

 there being almost no organic matter and only traces of ammonia. The 

 quantity of nitrogen in pounds per acre, calculated from nitrates for each 

 of the tanks and for each year of the experiment, is given in table 17. 



Relation of nitrogen removal in drainage water to total flow of drainage 



In the five-years period thru which the experiments extend, great 

 variation is shown from year to year in the quantity of nitrogen that is 

 present in the drainage water. The range of nitrogen is greater for the tanks 



I 



/300- 

 /£50- 

 /200- 

 .'/50- 



//oo- 



/050- 



/OOO- 



950- 



900- 



B50- 



aoo 



Dra/nage 



-Jd. 



Fig. 8. relation of yearly flow of drainage water to yearly removal of 



nitrogen in drainage water, tank 4 



that had no vegetation than for those that were planted. The variations 

 are probably controlled largely by the quantity of drainage water, rather 

 than by weather conditions favoring a large formation of nitrates. In 

 years of large percolation the nitrates are usually high, and in years of 

 small percolation usually low, because a large volume of water is required 

 in order to remove all the nitrates from the soil. The relation of the 

 nitrogen in the drainage water to the total flow is shown in figures 8 

 and 9 for tanks 4 and 8. respectively. 



In 1910 the nitrogen content was high as compared with the flow of drain- 

 age water from both tanks, which may have been due either to a favorable 

 season for nitrification or to the thoro aeration to which the soil was sub- 



17 



