Relations of Higher Plants to the Formation of Nitrates 69 



implanted soil of the other maize plats, owing to the fallow of the previous 

 year, that only on the late-planted plats are the nitrates at any time actu- 

 ally higher under the crop than on the bare soil. 



The relations of the crops to nitrates are well brought out in Table 23 

 and in diagrams XVII to XXIV. The figures on which these diagrams are 

 based have been obtained by considering the nitrates in the bare spaces as 

 100 and calculating, on that basis, the nitrates in the planted sections of the 

 plats. These percentages are then grouped into periods embracing all the 

 analyses before planting, and the analyses after planting by months or such 

 parts of months as elapsed before harvest. 



The mulched maize plats, represented in Diagram XVII, show a maxi- 

 mum nitrate content in July, at which time the nitrates were higher under 

 the maize than in the bare soil. After that there is a decrease to September 

 and a slight increase in October. 



BEFORE t72//V£- 



<yuiY 



AUGUST 



SEPT 



OCT 



DIAGRAM XVIII. — Relative nitrate content of soil under maize scraped, 1912 



The scraped maize plats, represented in Diagram XVIII, show a maxi- 

 mum nitrate content in July, but it is not so high under maize as in the 

 unplanted soil. There is a decrease after July. 



The cultivated maize plats, represented in Diagram XIX, correspond in 

 the main with the previous plats. All these maize plats exhibit the charac- 

 teristic stimulation of nitrate formation in midsummer and partial inhibi- 

 tion in late summer and in the fall. 



