22 T. Lyttleton Lyon and James A. Bizzell 



When the unplanted section at the north end was sampled, the north half 

 of the planted area was sampled on the same date; and the same was done 

 with the south part of the plat. The north and south halves were sampled 

 alternately. In 1909 all samples were taken from the south halves of the 

 plats, the unplanted and the planted parts corresponding exacth^ with 

 those of the previous year. These are referred to as " north ends/' 

 " south ends," " north middles," and " south middles." 



A comparison of the nitrate content of the unplanted and the planted 

 sections of the same plat serves to indicate what has been the effect of 

 the crop on the nitrate content of the soil. These figures for the years 

 1908 and 1909 are given in Table 3. 



A striking feature of the nitrate content of the soil during the growth 

 of maize is the close agreement between the nitrates in the planted and 

 those in the unplanted sections of the plats. This is particularly notice- 

 able in the analj'ses of July 27, previous to which the maize crop must have 

 absorbed about one half of its nitrogen, judging by what is known of the 

 life history of the plant. The previous heavj' draft on soil nitrates is 

 indicated by the analyses of June 22 and July 6, which show a lower 

 nitrate content in the planted sections of the plats. The analyses of July 

 27 indicate either that the production of nitrates is proceeding much more 

 rapidly in the cropped than in the uncropped soil, or that the maize crop 

 is absorbing part of its nitrogen in some form other than as nitrates. 



The analyses of August 10 show a decline of the nitrates on the planted 

 areas, while on the unfertilized plats the nitrates still continue to increase 

 on the unplanted spaces. From the standpoint of nitrogen utilization by 

 the crop, the decline in nitrates at this late date is difficult to explain. 



The analyses of April 22, 1909, made before the oats were planted, show 

 a continuation of the more rapid decline on the maize land than on the 

 uncropped spaces. The next analyses, June 24, show a marked decline 

 in the nitrate content of the cropped sections of the plats, as do also those 

 of July 12. B}' the latter date the nitrogen utilized by the oat crop has in 

 large part been absorbed. The last anah'ses, however, on August 7, show 

 a still greater decrease in the nitrate content, when a partial recover^'- 

 might be expected and when the nitrate content of the uncropped soil has 

 made a very great increase. 



Comparing the two crops, the following facts are significant: « 



(1) When nitrification is at its maximum in the maize land the cropped 



