20 T. Lyttleton Lyon and James A. Bizzell 



active nitrification was also the time during which the maize was making 

 its most active growth. The weather was warm and very favorable for 

 the growth of maize, which was an unusually good crop this year. It is a 

 striking fact that in spite of the pronounced growth of the maize at this 

 time the nitrates increased at a rate which gave no appearance of their 

 being used by the crop. The nitrate content under the crop and on the 

 unplanted soil is shown graphically in Diagram I. 



Between July 28 and August 10 there was a perceptible decline in the 

 nitrate content, and between August 10 and September 17 this decline 

 was very marked. It is strange that the diminution in nitrates should 

 take place after that period of growth during which the maize plant has 

 been shown to absorb fully one half of the nitrogen that it utilizes. 



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

 planted, show a much higher nitrate content in the soil in the spring fol- 

 lowing maize than in that following timothy, although the analyses were 

 made nearly a month earlier in 1909 than in 1908. Between April 22 and 

 June 24 there was a considerable loss of nitrates, as is to be expected in 

 view of the fact that the nitrogen absorption of the crop is greatest at that 

 time. The lowest figures for nitrates, however, were on July 12 and 

 August 7, although the crop could not have been making very heavy 

 drafts on the former date and had been harvested before the latter date, 

 and in the face of the fact that nitrification was at its maximum at those 

 dates under the maize crop. 



It would seem as if nitrate production is most pronounced during the 

 active growth of the crop on the soil, and decreases with the less vigorous 

 growth of the crop. The characteristic relations of the nitrate content of 

 the soil under timothy, maize, and oats are shown in Diagram II. 



Nitrates on the planted and the unplanted sections of the plats 



As before stated, a part of each plat was left unplanted in 1908 and 

 1909, but was otherwise given, as closely as possible, the same treatment 

 as was given to the planted section of the plat. When the planted section 

 of the plat was in maize the unplanted section was given the same culti- 

 vation; when oats were growing on the planted section, the unplanted 

 section was kept free from weeds by scraping the surface with a hoe. 

 In 1908 unplanted sections were maintained on the north as well as on 

 the south end of each plat for a distance of twenty-five feet from each end. 



