574 



Journal of Agriculture. 



[lo Sept.. 1910. 



The following is a table of the results obtained from the sprayed 

 plots : — 



Artificial Manure. — A plot of six rows was put in at each farm for 

 the purpose of trying six different manures, not .so much for their yielding 

 capacity, but to test the theory that Scab is caused by strong alkalies or 

 acids in the soil. 



For this purpose several specially strong manures were prepared and 

 sown alongside those of normal strength. Thus, a potato manure con- 

 taining a double quantity of potash was prepared and used alongside a 

 row receiving a normal potato manure. This was done, as it has been 

 contended that where rubbish had been burned the extra supply of potash 

 conferred on the adjacent .soil a power of producing Scab. Likewise, 

 an extra acid superphosphate was prepared and sown alongside a row 

 receiving a normal superphosphate to test the theory that where a stack 

 had decayed and left the soil acid. Scab was more strongly marked. The 

 other two rows were manured with nitro-superphosphate and iron sulphate 

 respectively. All the manures were applied as heavy dressings, namely, 

 4 cwt., except in the case of iron sulphate, which was applied at the rate 

 of 1 1 cwt. per acre. 



Taking the following table and comparing the results, it would appear 

 that the extra-strong manures lose little, if anything, by the comparison, 

 and certainly do not uphold the theory of the causation of Scab by strong 

 alkalies or acids in the .soil. It is true that a slightly alkaline medium is 

 favourable to the growth of low forms of life since it neutralises the aci<:ls 

 which they produce as waste products of their life processes. These 

 acids, if allowed to accumulate, would tend to the destruction of 

 the organi.sm; but in a slightly alkaline medium, such as calcareous soil, 

 the acid is neutralised almost as soon as formed and the organisms have a 

 better chance of increasing. It is in this way that the increase of Seal) 

 in limey soils, and in patches where wood ashes have been spread, is 

 accounted for, and it is not due to the action of lime on the skin of the 

 potato. 



