The Effect of Limestone Applications on Soil Composition, Potato-Scab Development and Yields of Potatoes, Barley and Clover1

In a field experiment begun in 1931 at Charlottetown, Prince Edward Island, ground limestone, at rates of 500, 1000, 1500, 2000 and 3000 lb. per acre, was applied periodically for a 3-year rotation of potatoes, barley and clover hay. The analysis of soil samples, representative of the 0-6 inch depth, showed that by 1948 there was a close relationship between the rates of limestone used and the pH values, exchangeable calcium content and per cent base saturation. The analysis of subsoil samples showed that, by 1951, the effect of the limestone treatments was negligible at the 6-12 inch depth. During the years 1940 and 1948, inclusive, there was evidence of increasing potato scab—a disease caused by Streptomyces scabies (Thaxter), Waksman and Henrici—particularly in plots receiving the higher rates of limestone. Consideration of crop yields for the same period showed that application of limestone had no effect on potato yields but resulted in significant increases in the case of barley and clover.