1906.] LIMING SOILS AND PLANTS. 95 



In this final view of potatoes the results with calcium acetate 

 are at the left and those with unleached wood ashes are at the 

 right. In both lots every tuber was scabbed and in the former 

 case 97.5 per cent, of the lot was rendered unfit for market. 

 In the case where the wood ashes were used the yield was good 

 but not a single smooth marketable tuber resulted. 



In the light of these results the question which naturally 

 suggests itself is : Why did not Professer Thaxter find 

 that wood ashes favor scab in the same manner as the mortar 

 and cement? The answer seems to be that either the tubers 

 which were planted where wood ashes were used were free 

 from the fungus, as well as the soil itself, or else Professor 

 Thaxter in his zeal used more wood ashes than would be likely 

 to be employed per acre in agricultural practice, thus rendering 

 the soil about the tubers so alkaline that the fungus could not 

 grow. This seems probable for the reason that the mortar 

 and cement would render the soil less alkaline than the same 

 weight of wood ashes, and possibly on this account they pro- 

 duced a condition which was especially favorable to the de- 

 velopment of the scab fungus. 



Too great alkalinity like too great acidity should lessen the 

 scab judging by Professor Thaxter's experiments upon the 

 pure cultures of the fungus. 



The practical suggestions growing out of the Rhode Island 

 experiments are the following: 



First. Avoid using scabbed tubers in planting, if possible. 



Second. If scabbed tubers or such as are not positively 

 known to be free from the fungus are used, wash them 

 thoroughly with water and then treat them with corrosive sub- 

 limate solution or with fresh formalin, as recommended by 

 Bolley and others. (For directions see Farmers' Bulletin 

 No. JJ, U. S. Department of Agriculture. ) 



Third. Avoid as direct manures for the potato crop wood 

 ashes, lime, stable manures, basic slag meal, carbonate of 

 potash and any and all other substances which are alkaline in 

 their reaction. 



Fourth. If for other reasons these alkaline substances 

 should be added to the soil, apply them from two to four years 

 before potatoes are to be grown and always treat the " seed " 

 tubers as recommended under (2). In this wav the 

 Rhode Island Station has for more than ten vears avoided scab 



