Relations of Higher Plants to the Formation of Nitrates 17 



TABLE 1 {continued) 



Plat 



Treatment 



Plat 



Treatment 



722 



160 pounds nitrate of soda 

 80 pounds muriate of potash 

 640 pounds rock superphosphate 



727 



320 pounds nitrate of soda 



80 pounds muriate of potash 

 320 pounds rock superphosphate 





723 

 724 



No fertilizer 



320 pounds nitrate of soda 



80 pounds muriate of potash 

 640 pounds rock superphosphate 



728 

 729 



640 pounds nitrate of soda 



80 pounds muriate of potash 

 320 pounds rock superphosphate 



No fertilizer 





725 



320 pounds nitrate of soda 

 80 pounds muriate of potash 

 320 pounds rock superphosphate 



730 

 731 



No fertilizer 



10 tons manure, 1905, 1C07 





726 



No fertilizer 



732 



20 tons manure, 1905, 1907 





On these plats samples of soil were taken, to a depth of eight inches, at 

 intervals during the growing season and after the timothy and oats had 

 been removed. The entire twenty- two plats were sampled on the same 

 day or on two consecutive days. The samples were removed from the 

 earth by means of a soil auger. Twelve borings were removed from each 

 plat and thoroughly mixed on an oilcloth surface, and a pint sample was 

 placed in a glass jar. The sample was brought to the laboratory and 

 moisture and nitrates we're determined — the former by drying to constant 

 weight at the temperature of boiling water; the latter by the phenol- 

 disulfonic-acid method, comparisons with a standard nitrate solution 

 being made by means of the colorimeter designed by Schreiner. 



In 1908 and 1909, when the plats were planted to maize and oats, 

 respectively, an unplanted space was left for twenty-five feet on the south 

 end of each plat. This unplanted space was cultivated when the plats 

 were in maize, receiving the same cultivation as did the planted part of 

 the plat. When the plats were in oats the unplanted space was kept free 

 from weeds by scraping with a hoe. Soil samples were taken from the 

 planted and the unplanted sections of each plat on the same dates, which 

 permits of a comparison of the effect of a certain soil treatment on the 

 uncropped as well as on the cropped soil. It also serves to show the rela- 

 tion of the crop to the nitrates in the soil, which is a very important factor 

 in their occurrence. 



In Table 2 is given a statement of the nitrate content of the planted part 

 of each plat on the dates sampled, during the three years. At the foot 



