Relations of Higher Plants to the Formation of Nitrates 45 



TABLE 16. Yield of Dry Matter and of Nitrogen in Crops, and Average Nitrate 



Content of Soil, 1910 



Crop 



Yield 



of dry 



matter 



(pounds) 



Yield 



of 



nitrogen 



(pounds) 



Nitrates in first foot 

 of dry soil (parts per 

 million) 



Nitrates in planted soil 

 when nitrates in un- 

 planted soil are taken 

 as 100 





Planted 



Un- 

 planted 



Planted 



Un- 

 planted 



Maize 



221 

 1,910 

 1,670 



3 



43 

 29 



167 



104 



90 



136 

 108 

 126 



123 

 96 

 71 



100 



Potatoes 



100 



Oats 



100 







oats, the relationship does not hold. Instead, the characteristic relation 

 of the kind of plant to the nitrate content of the soil is again repeated, 

 and this appears to hold, to a large extent, regardless of the relative 

 quantities of nitrogen removed by the crops. 



Experiments in 1911 



The plat experiments were continued in somewhat the same manner 

 in 1911, but none of the plats were limed. As before, each crop was grown 

 on four separate plats, thus removing to a great extent the error due to 

 local differences in nitrate formation. Another feature introduced in 1911 

 was the different methods of treatment of maize. Certain plats were 

 mulched with straw, others were scraped with a hoe in order to keep 

 them free from weeds without stirring the soil, and still others received 

 the usual cultivation. The maize was treated also in the following two 

 ways: (1) The crop was harvested on the first of August, the planting 

 having been done at the usual time; the object of the early harvest was 

 to ascertain the effect of the immature plants on the nitrates after the 

 crop was removed. (2) The maize was planted about a month later 

 than on the plats just mentioned and was harvested on August 1. This 

 gave a very immature crop (about eighteen inches high) at harvest 



Potatoes were grown as in 1910. 



Oats were treated in two ways: (1) on one set of oat plats the land 

 was plowed immediately after harvest and maize was planted; (2) on 

 another set of plats maize was not planted after removing the oats, but 

 the land was plowed and given the same cultivation as was given the 

 maize. The object in giving this treatment after harvesting the oats 



