1906.] LIMING SOILS AND PLANTS. 97 



The third plat received no hme. All three of the plats were 

 seeded to timothy in the early autumn in an identical manner. 



At the right, where the lime was worked into the soil before 

 seeding, the stand of timothy was good. Only a very small 

 stand of timothy was secured where the lime was used as a 

 top-dressing. Where lime was omitted altogether timothy 

 was wholly absent. In all but the first instance the product 

 was chiefly weeds mixed with a small amount of such grasses 

 as could thrive upon acid soil. The material from the top- 

 dressed plat is shown in the middle and that from the unlimed 

 plat at the left. 



THE INFLUENCE OF LIMING UPON THE HUMUS. 



It was found, -after a lapse of several years, that under con- 

 tinuous culture with hoed crops the amount of humus in the 

 soil became somewhat reduced upon the limed plats. At the 

 same time the percentage of nitrogen contained in the humus 

 became greater. It might be inferred, therefore, from the in- 

 vestigations conducted by Hilgard that on this account the effi- 

 ciency of the nitrogen in the humus may have been increased. 

 Under a system of cropping, which includes the occasional 

 turning under of a grass sod, there need be no' fear of injury to 

 the soil from a depletion of the humus by liming, so long as 

 proper attention is paid to the kind of soil and the amount and 

 kind of lime applied. To illustrate, a sandy soil should sel- 

 dom, if ever, receive more than from half a ton to one ton of 

 lime per acre at a single application, and for such soils the 

 carbonate of lime is usually preferable to either slacked or plain 

 burned lime. 



In this connection a word ought to be said about " humus '"' 

 in a general way. Some of the dictionaries define humus as 

 essentially a brown substance produced by the action of the air 

 upon vegetable and animal matter. Many writers also refer 

 to the entire mass of the organic matter in soils as '' humus." 

 Grandeau applied the name Matiere noire (black matter) to 

 that part of the organic matter which could be extracted from 

 the soil by means of ammonia water after the preliminary re- 

 moval of the lime and magnesia. Much is said in the agricul- 

 tural press about the need of humus in the soil, yet usually 

 without reference to whether the term humus as used applies 



Agr. — 7 



