488 



Journal of Agricultural Research 



Vol. XII. No. 8 



stone, in increasing the nitrate content of Colby silt loam and Plainfield 

 sand; the heavier applications gave the highest nitrate accumulation. 

 In the case of the magnesium carbonate with Colby silt loam soil, the 

 increased accumulation reached as high as 8 mgm. The increase in 

 nitrate in the Plainfield sand ran parallel with that in the Colby silt loam 

 where similarly treated, though the accumulation in the sand was much 

 smaller, since this soil is low in organic matter. 



t :^ 3 -^ S 6 7 Q 9 /O imJ3 

 I month 



I £ i 'f 5 b 7 6 9 

 2mor,ih% 



3 fVoni/is 



Fio. lo. — Diagram showing the influence of calcium carbonate, magnesium carbonate, limestone, and 

 monocalcium phosphate on nitrate accumulation of Colby silt loam. 



i=no treatment. 



3= one-fourth calcium carbonate. 



3= one-half calcium carbonate. 



4= full calcium carbonate. 



5= one-fourth limestone. 



6= one-half limestone. 



7= full limestone. 



8= one-fourth magnesium carbonate. 



9= one-half magnesium carbonate. 

 io= full magnesium carbonate. 

 11= O.I per cent monocalcium phosphate. 



1 2= O.I per cent monocalcium phosphate+one-fourth calcium carbonate. 

 13=0.1 per cent monocaldum phosphate-1-full calcium carbonate. 



The monocalcium phosphate apparently did not favor nitrification in 

 the Colby soil, while in the sand this substance proved beneficial. A 

 combination of the phosphate and calcium carbonate did not increase 

 nitrification beyond that obtained from the use of calcium carbonate 

 alone. The effect of these substances on the reproduction of soil 

 organisms and on the formation of nitrates was similar. A review of 

 the entire data is shown graphically in figure 10. 



