Wheat, 25 bushels, 

 Barley, 38 bushels, 

 Oats, 50 bushels, . 

 Turnips, 25 tons, . 

 Potatoes, 9 tons, . 

 Red clover, 2 tons. 

 Rye grass, 2 tons, 



ACTS CHIEFLY UPON TOE ORGANIC MATTER OF THE SOIL. 401 



But the different crops which we grow contain lime in unlike propor- 

 tions. Thus the average produce of an acre of land under the follow- 

 ing crops contains of hme — 



' I rain or roots. Straw or tops. Total. 



1-5 7-2 8-7 lbs. 



2-1 12-9 15-0 lbs. 



2-5 5-7 8-2 lbs. 



45-8 93-0 138-8 lbs. 



6-6 259-4 266-0 lbs. 



— 126-0 126-0 lbs. 



— 33-0 33-0 lbs. 

 'These quantities are not constant, and wheat especially contains 



much more lime than is above stated, when it is grown upon land to 

 which lime has been copiously applied. But the very different quanti- 

 ties contained in the several crops, as above exhibited, shew that one 

 reason why lime favours the growth of some crops more than others is, 

 that some actually take up a larger quantity of lime as food. These 

 crops, therefore, require the presence of lime in greater proportion in the 

 soil, in order that they may be able to obtain it so readily that no delay 

 may occur in the performance of those functions or in the growth of those 

 parts to which lime is indispensable. 



§ 23. The chemical action of lime is exerted chiefly upon the organic 

 matter of the soil. 



There are four circumstances of great practical importance in regard 

 to the action of lime, which cannot be too carefully considered in refe- 

 rence also to the theory of its operation. These are — 



1°. That lime has little or no effect upon soils in which organic mat- 

 ter is deficient. 



2^. That its apparent effect is inconsiderable during the first year 

 afler its application, compared with that which it produces in the second 

 and third years. 



3°. That its effect is most sensible when it is kept near the surface of 

 the soil, and gradually becomes less as it sinks towards the subsoil. 

 And, 



4°. That under the influence of lime the organic matter of the soil 

 disappears more rapidly than it otherwise would do, and that after it 

 has thus disappeared fresh additions of lime produce no further good 

 effect. 



It is obvious from these facts, that in general the main beneficial pur- 

 pose served by lime is to be sought for in the nature of its chemical ac- 

 tion upon the organic matter of the soil — an action which takes place 

 slowly, which is hastened by the access of air, and which causes the 

 organic matter itself ultimately to disappear. 



§ 24. Of the forms in which organic matter usually exists in the soil, 

 and circum.stances under which its decomposition may take place. 



I. — The organic matter which lime thus causes to disappear is pre- 

 sented to it in one or other of five different forms : 



1°. In that of recent often grom moist, and ufcdecomposed roots, 

 leaves, and stems. of plants. 



