124 



Journal of Agricultural Research 



Vol. XVI, No. 4 



influence; of nitrates 



The compounds used in this series were sodium nitrate, potassium 

 nitrate, calcium nitrate, magnesium nitrate, manganous nitrate, and 

 ferric nitrate. The quantity added to the soil was such that in each case 

 equivalent quantities of nitrate in the various forms were added to the soil. 

 Hence, the varying factor is the electro-positive ion, the electro-negative 

 remaining the same in each case. The average results for a number of 

 closely agreeing determinations are given in Table XIII as percentages of 

 nitric nitrogen found in loo gm. of soil, the untreated soil being taken as 

 loo per cent. 



Table XIII. — Percentage of nitric nitrogen formed in loo gm. of soil containing 2 gm. 

 of dried blood and varying am,ounts andform.s of nitrate salts 



[The untreated soil is considered as loo per cent] 



Sodium nitrate does not stimulate the nitrifying organisms in any of 

 the concentrations, whereas potassium in the lowest concentration does. 

 Otherwise these two compounds are very similar in action. Both in low 

 concentrations depress the accumulation of nitric nitrogen in the soil, 

 but at a higher concentration this toxicity disappears. When the quan- 

 tity of nitrates added to the soil exceeds 310.4 p. p. m., the nitric nitrogen 

 rapidly disappears from the soil. At the highest concentrations tested the 

 added nitric nitrogen was rapidly disappearing. 



Calcium and magnesium nitrate in the lower concentrations are quite 

 similar in action, but at 38.8 p. p. m. of nitric nitrogen in the fonn of 

 magnesium nitrate is more active as a soil stimulant than the calcium 

 in any of the concentrations tested. At the higher concentrations the 

 nitric nitrogen disappeared from the soil more rapidly where the mag- 

 nesium salt was added than where the calcium salt was added. 



Manganous nitrate is the strongest nitrate stimulant tested, at one 

 concentration increasing the nitric-nitrogen content of the soil one- 



