220 



TALKS OX MANURES. 



These explanations are no doubt good as far as they go, but 

 experience furnishes many facts which cannot be explained by any 

 one, or all, of these suppositions. Lime, we all know, does much" 

 good on soils abounding in organic matter, and so it frequently 

 does on soils almost destitute of it. It may liberate potash, soda, 

 silica, etc., from clay soils, but the application of potash, soda, and 

 silica has little beneficial effect on the soil, and therefore we can- 

 not account for the action of lime on the supposition that it ren- 

 ders the potash, soda, etc., of the soil available to plants. Further- 

 more, lime effects great good on soils abounding in salts of lime, 

 and therefore it cannot be that it operates as a source of lime for 

 the structure of the plant. 



None of the existing theories, therefore, satisfactorily account 

 for the action of lime. Prof. Way's views are most consistent with 

 the facts of practical experience ; but they are confessedly hypo- 

 thetical ; and his more recent investigations do not confirm the 

 idea that lime acts beneficially by converting the soda silicate into 

 the lime silicate. 



Thus, six soils were treated with lime water until they had ab- 

 sorbed from one and a half to two per cent of their weight of lime. 

 This, supposing the soil to be six inches deep, would be at the rate 

 of about 300 bushels of lime per acre. The amount of ammonia in 

 the soil was determined before liming, after liming, and then after 

 being exposed to the fumes of carbonate ammonia until it had ab- 

 sorbed as much as it would. The following table exhibits the results: 



No. 1. Surface soil of London clay. 



No. 2. Same soil from 1^ to 2 feet below the surface. 



No. 3. Same soil $ feet below the surface. 



No. 4. Loam of tertiary drift 4 feet below the surface. 



No. 5. Gau'tclay surface soil. 



No. 6. Graltclay 4 feet below the surface. 



It is evident that lime neither assisted nor interfered with the 

 absorption of ammonia, and hence the beneficial effect of liming 

 on such soils must be accounted for on some other supposition. 

 This negative result, however, docs not disprove the truth of Prof. 

 "Way's hypothesis, for it may be that the silicate salt in the natural 

 soils was that of lime and not that of soda. . Indeed, the extent to 



