fertility if the cake and the ashes from the stems are returned to the fields, the carbon, hydrogen and oxygen of which the oil is almost wholly composed coming from the atmosphere rather than from the soil.
In Japan rape is grown as a second crop on both the upland and paddy fields, and in 1906 she produced more than 5,547,000 bushels of the seed; $1,845,000 worth of rape seed cake, importing enough more to equal a total value of $2,575,000, all of which was used as a fertilizer, the oil being exported. The yield of seed per acre in Japan ranges between thirteen and sixteen bushels, and the farmer whose field was photographed estimated that his returns from the crop would be at the rate of 640 pounds of seed per acre, worth $6.19, and 8,000 pounds of stems worth as fuel $5.16 per acre.
