40 



crops. When bullocks have been fed Swedes affected with "club-root" 

 and the uneaten fragments of the roots have been thrown among the litter, 

 the spores of the disease have been found to live unharmed through the 

 making and rotting of the manure, so that fresh land may thus become 

 infected when the dung is carried on to it. 



Club-root. — On many soils, particularly those of a sandy nature, the 

 turnip crop is often almost wholly destroyed by the disease known as ' ' club- 

 root. " Cabbages and other cruciferous crops are equally attacked; so much 

 so that in gardens which have become infected it is practically impossible to 

 raise crops of this nature. The disease is caused by an organism, Plasmo- 

 diophora brassicae, belonging to the slime fungi and forming spores which 

 may remain dormant in the soil for some time, certainly for two or three 

 years. It has long been known that the best remedy against club-root con- 

 sists in the application of lime, and as far back as 1859, Voelcker showed 

 that soils on which this disease is prevalent are deficient in lime, and in 

 many cases in potash also. Later researches have only served to emphasize 

 the fact that the disease is associated with soils of an acid reaction, in 

 which calcium carbonate is wanting, or present in very small proportions. 

 The fungus, as is generally the case with fungi, refuses to grow in a 

 neutral or slightly alkaline medium, and the only way to get rid of the 

 infection in the land is to restore its neutrality by repeated dressings of 

 lime. At the same time, the land should be rested as long as possible from 

 cruciferous crops ; uneaten fragments of diseased turnips, etc., should not 

 be allowed to go into the dung, or if they do, the dung should be used on 

 the grass land. Manures, again, which remove calcium carbonate from the 

 soil, like sulphate of ammonia, or acid manures like superphosphate, should 

 not be employed ; neutral or basic phosphates, with sulphate of potash on 

 sandy soils, should be employed instead. 



The following figures show the amount of lime dissolved by hydro- 

 chloric acid from soils affected with "finger-and-toe," as compared with 

 spots in the same field where the disease was not in evidence : — 



