Relations of Higher Plants to the Formation of Nitrates 41 



obtaining the second half of its nitrogen supply, or that nitrate formation 

 is depressed at that time. 



Nitrates in soil planted to maize, potatoes, and oats 

 Experiments in 1910 



During the growing season of 1910, determinations of nitrates were 

 made under maize, potatoes, and oats. These were from four plats 

 planted to each crop, of which two plats were limed and two were unlimed. 

 An unplanted strip ran through the center of each plat. Soil samples 

 were taken on the planted and on the unplanted sections of each plat. The 

 sections are designated as "north ends," "middles," and "south ends." 

 The north ends and the south ends were both planted; the middles grew 

 no crop, but were given the same soil treatment as the remainder of the 

 plat. This consisted in cultivation on the maize and potato plats and 

 in scraping the surface on the oat plats. Soil samples were taken to 

 a depth of four feet on the north ends and on the middles, but to a depth 

 of only one foot on the south ends, except on May 12, when composite 

 samples from the north ends and the south ends were analyzed. 



The soil on which these plats were located was a heavy clay loam in 

 the same field as that in which most of these experiments have been 

 conducted. This particular piece of land was not uniform as regards 

 either production of crops or nitrates. Fortunately each crop was grown 

 on four separate plats, and in spite of irregularities in single plats the 

 average of the four plats in each crop gives fairly concordant results. 



The weather during the growing season of 1910 was drier than normal 

 and the early part of the season was unusually cool. The yield of oats 

 and of potatoes was about the average, but the maize crop was very 

 poor. The small maize crop was due to the soil rather than to the weather, 

 as no manure had been applied and this soil does not produce good yields 

 of maize unless it is well manured. It will be noticed from Table 14 

 that the nitrates under maize reached over a hundred parts per million 

 in the surface foot of soil; yet, in spite of this large quantity of soluble 

 nitrogen, the crop was very poor. Potatoes and oats made a much better 

 growth and reduced the nitrates considerably lower. This is another 

 example of the slight response of maize to nitrates on this soil. 



Planting was done on the following dates: oats (White Russian) on 

 April 28; potatoes (Enterprise) on May 16; maize (Pride of the North) 



