IX.] 



ACTION OF LIME 



259 



micro-fungi are favoured by an acid reaction in the 

 soil, consequently we find that various fungoid diseases 

 of plants are specially prevalent on soils devoid of 

 calcium carbonate, a notable example being the slime 

 fungus, Plasmodiophora bmssiar, which causes " finger- 

 and-toe," "club root," or "anbury" in turnips, cabbages, 



Tabi.k LXXX.— Effect ok Lime upon Rothamsted Grass Plots 

 (Unlimed = ioo). 



and similar plants. This disease docs not occur on cal- 

 careous soils and can be obviated on soils where it does 

 prevail by a thorough liming, best applied both after 

 the removal of one turnip crop and again immediately 

 before another is sown. As long an interval as possible 

 should elapse between the two cruciferous crops to 

 enable the spores of the disease to die off in the 

 soil, now rendered faintly alkaline. The finger-and- 

 toe fungus is not the only one thus affected by lime, 

 but it is the one known on the widest scale ; speaking 

 generally, calcareous sc'ls are always the healthiest for 

 crops. 



But the nitrogenous conipounds in the soil are not 

 the only ones rendered more available by the presence 

 of carbonate of lime ; both phosphoric acid and potash 

 are thereby kept or brought into a more soluble form. 

 When soluble phosphates are applied to the land they 

 are precipitated either as di-calcium phosphate, ferric 



