Abstract
1) With a view to illustrate the yield of various food crops obtained by the Japanese agricultural technique, at its highest level, the author collected the yield records of them from all the Prefectural Agricultural Experiment Stations in Japan. Fluctuation curves of the yield from unit area of many crops, such as; paddy rice, upland rice, barley, naked barley, wheat, barley for brewing, sweet potato, white potato, corn, foxtail millet, barnyard millet, proso millet, buckwheat, soybean, azuki bean, peanut, repereed and sesame, were studied. 2) By comparing the fluctuation in the yield of each crop by variety tests at every Prefectural Agricultural Experiment Station, the author considers that he call illustrate the sum of ycarly fluctuation, local fluctuation and varietal fluctuation of the crop concerned. 3) Every crop has its own fluctuation curve, which is a normal monomodal symmetric one. 4) From his point of view of Japanese agriculture as an occupation work the author illustrates the per-tan yield in calories, and from his point of viwew of Japanese agriculture as an enterprise work he illustrates the per-tan yield as monetary income, and also in protein, in starch or in oil and fat products. 5) By illustrating the per-tan-calory yield of sweet potato and that of paddy rice in the records of varietal yield tests at every Prefectural Agricultural Experiment Station and those in the governmental statistics, the author demonstrated the fact that the superiority of the sweet potato as a heavy yielder crop may only be local. We must submit after all to the conviction that the best is the fittest
