IX.] 



ACTION OF LIME 



263 



applying lime to an old hop garden at Farnham, 

 Surrey, where the soil consisted of an alluvial loam, 

 very deficient in carbonate of lime, and heavily dressed 

 with organic manures for many years previously. The 

 plots chosen for comparison received a complete artificial 

 manure with or without 1 ton of lime per acre; the 

 figures for the crops in the following table have been 

 reduced to percentages to eliminate the great fluctua- 

 tions due to season. 



Of course, as lime itself supplies no food to the 

 plant, but only sets in action the dormant residues 

 already present in the soil, the forcing of crops by the 

 aid of lime alone soon results in the exhaustion of the 

 land. Hence the old saw : — 



" Lime, and lime without manure, 

 Will make both land and farmer poor." 



The exact effect of lime in promoting fertility 

 depends upon the plant food in question. We have 

 already seen that all the decay processes which result 

 in the oxidation of the humus are promoted by the 

 presence of a base to combine with the organic acids 

 produced by the decay, and, in particular, that the 

 presence of an easily attacked base is necessary for 

 nitrification. As a nett result, the oxidation of the 

 humus and the formation of nitrates is much increased 



