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Proceedings of Indiana Academy of Science 



were calculated on a dry basis of the soil. The incubated samples were 

 calculated on a basis of 21.5 per cent of moisture as that was found to 

 be optimum, and it was endeavored to incubate them under as nearly 

 optimum moisture conditions as possible. The incubated samples with- 

 out ammonium sulphate added are shown in these tables as I ; those 

 with ammonium sulphate as II. 



TABLE I.— Series 1 East 



Discussion of Series 1 East (Corn and Wheat). 

 (Table I.) 



The fresh nitrate content of the wheat plot was low durinj? May and 

 the early part of June at which time the crop was draining heavily on 

 nitrates. By July 10 it had reached nearly 10 parts per million and 

 remained at this point with minor fluctuations until about September 1, 

 when it gradually went down because of dry, cool weather and the with- 

 drawal by the clover crop. The incubated samples were consistently 

 higher than the fresh. Those with ammonium sulphate averaged about 

 65 per cent higher than tho.se without, which fact seems to indicate that 

 suitable nitrogenous materials and not absence of sufficient organisms 

 was the limiting factor. 



The fre.sh nitrate curve of the corn plot is much the same as that 

 of the wheat, but it is higher at all times except early in the season. 

 The highest point of 22.04 parts per million was reached on July 29. 

 Rains during the season, when not hard enough to leach out the nitrates, 

 caused a rise in the fresh nitrate content. The incubated samples were 

 much higher in nitrates than the fre.sh samples during the whole season. 

 During the middle of the summer the addition of ammonium sulphate 

 had little effect, which fact tends to show that the efficiency of the nitri- 

 fying organisms in the soil at that time was greater than at other 

 seasons of the year. This instance seems to confirm the general theory 



