抄録
In the eastern half of Hokkaido, it is usual to till the pasture for crop rotation either early in spring or late in autumn after harvesting of hay. A trial trilling was made in the middle of August, followed by immediate seeding of winter rye which was to be ploughed in as green manure. Potato was planted on this trial field ploughed in next spring, giving an yield of 474.8 kan per tan, while it was only 344.8 kan per tan on a field where potato was raised for several successive years and 587.3 kan on the control area of pasture which was ploughed early in spring as usual in the same year. It is conclusive, therefore, that the trial field had a better harvest than the field of successive potato cultivation, but a poorer harvest than the pasture ploughed early in spring.
