Relations of Higher Plants to the Formation of Nitrates 19 



of the table is the average for all plats on the dates analyzed, and below 

 that is the average for all unfertilized and unmanured plats. The last, 

 by eliminating the effect of nitrate fertilizers, is a better index to the 

 normal course of nitrification than is the average of all the plats. 



The timothy had been on the land for two years previous to 1907 and 

 there was a good stand. Commercial fertilizers had been added to each 

 of the previous crops, and farm manure once. For the crop of 1907, farm 

 manure was applied as a top-dressing on October 2, 1906, to the plats 

 designated in Table 1, and commercial fertilizers were applied on April 23 

 and 24, 1907. Soil samples were taken on April 23, immediately before 

 the fertilizers were applied. The timothy was cut on July 23 and samples 

 for nitrates were taken the next day. The maize was planted on May 29 

 and cut on September 24. No fertilizer nor manure was applied to either 

 the maize or the oats. The oats were drilled in on April 23, the day fol- 

 lowing the first sampling for nitrates. They were harvested on August 6 

 and samples were taken on the following dsiy. 



Seasonal range of nitrates under timothy, maize, and oats 



A striking feature of the nitrate content of the timothy plats is the uni- 

 formity and scarcity of nitrates throughout the growing season. In all 

 except the nitrate-fertilized plats the nitrate content was higher in April 

 and August than during the period of more active growth. The land had 

 not been plowed for two years and was covered with a thick sod, neither 

 of which conditions was favorable for nitrification. The seasonal range 

 of nitrates under timothy resembled that under alfalfa in the experiments 

 of King and Whitson and in those of Stewart and Greaves. During the 

 first half of May, when growth first became active, there was a tendency 

 for the nitrates to increase, as is shown by the analyses of May 3 and May 

 14; there was then a decrease during the remainder of May and during 

 June, with a slight increase at the time of harvest which was continued 

 in the middle of August when the aftermath was growing. 



The timothy sod was plowed under in the autumn of 1907, but nitri- 

 fication had not proceeded very rapidly up to the time of the first analyses 

 on May 19, 1908. The most noticeable increase was between July 6 and 

 July 27, 1908. At the latter date there was a very large accumulation of 

 nitrates in the soil, probably the maximum of the season. This period of 



