roOCT.. igi2.] Rchitniii "j l.inu to Soil h\rtilit\. 623 



Tn the absence of iime, the production of ninmonia is hampered by 

 iicidity. The e\il will be most marked (jn stiff soils which are badly 

 aerated, and on peatv soils rich in organic matter. These classes of 

 soils, therefore, require heaxier a])i)lic;ations of lime than sandy soils poor 

 in organic mattrr or humus. 



Second Stage of Nitrification. 



The second stage in the production of soil nitrates, \iz.. tlie change 

 from ammonia to nitrate, is also helped by limi\ J'"ig. 2 shows the relative 

 amounts of nitrate produced from ammonia in a soil during 21 days. Th^y 

 experiments from which the.se results are abstracted were conducted in the 

 laboratory of the Department, and are fully de.scribed in the July i.ssue 

 •of the Journal of Agriculture. No. i shows the nitrate formed where 

 hot lime was added to the soil. No. 2 with no addition made to the soil. 

 \(). 3 with gypsum added, and ^so. 4 with carlKmate of linif. In the 

 te.sts free or combined lime was used in equivalent amounts. 



On contrasting the cylinders, the different compounds of lime are se^n 

 to act in different wavs. Gypsum was of but little help to nitrification, 

 ■carbonate of lime increased it fourfold, while hot lime stopped nitrification 

 .altogether. Corroborative results w-ere obtain;^fl in a second series of tests 

 la.sting 51 days. 



The first .and second stages of nitrification are alike due to bacteria 

 both of them tend to produce acid, and in both the production of acid 

 inhibits the organisms. The effects of lime upon the second stage may 

 therefore be discu.ssed with reference to the whole process of nitrate pro- 

 ■fluction from the organic matter of the soil. 



The Best Form of Lime for Nitrification. 



The most effective form of lime is the carl)onate. The .soil organi.sms 

 •cannot endure acid, but neither can they enrlure free alkali or soluble base 

 as this is present in hot lime. It is tho.se facts which explain the results. 

 Carbonate of lime removes any acid which mav be produced, but it is not 

 alkaline in reaction. Gypsum is not alkaline in reaction, but it is unable 

 to neutralize acid substances produced bv the germs. Hot lime can 

 neutralize the acids all right, but it is too strongly alkaline to allow the 

 bacteria to work. 



In Great Britain the old usage in applying lime was to spread 4 or 5 

 tons of hot lime to the acre. It was a matter of common knowledge that 

 such applications tended to diminish the yield for the first one or two 

 years. The chief reason was that the land was rendered too alkaline for 

 nitrification to proceed. During the fir.st years the heavy dressing was 

 gradually converted into carbonate of lime by the carbonic acid of the air 

 and .soil, and the lime then began to be of benefit. 



Such heavy dressings of hot lime are now seldom employed in agricul- 

 ture, about I ton being a usual amount. Comparatively light dressings are 

 quickly converted to carbonate, and in such cases a benefit is expected 

 (luring the first vear. Even light dressings, however, should not l)e applied 

 with the seed of any crop, but are better put on several months l)efore, 

 in order that the hot lime mav be converted into carbonate. 



Direct applications of carbonate, as in ground limestone or marl, may 

 Tk? given at any time without danger to nitrification, and. practically speak- 

 ing, to any amount. 



Gypsum has no important action in stimulating the production of 

 jiitrates. 



