(1) The present series of experiments were carried out with 9 species of Crotalaria (including 9 varieties of C. juncea) which are cultivated for economic use in respect to their general characters. growth and yields, resistance to diseases, etc. The purpose of the experiments was to select such as would be suited for cultivation in warm parts of Japan.
(2) The proper temperature for the germination of Crotalaria was found to be about 30°C. Most varieties of C. juncea, especially the one introduced from Ceylon-as all species of Crotalaria generally do-produced hard seed.
(3) Those seeded on June 1 gave heavier yields than those seeded on June 15. It may be inferred that, in case seeding is done later than the middle of June, yields will considerably decrease. It was C. juncea that gave the largest yields compared with other species.
(4) C. spectabillis, being of the earliest type, was short, and had leaves of large leaf area, covering a wide area of ground. These characteristics may recommend this species as a cover-crop in hill-side farms. C. juncea was the tallest, standing 2.5 to 3 meters.
(5) The result of the short-day treatment was that C. juncea showed little or no susceptibility_ to it, C. mucronata a little, and C. intermedia comparatively much.
(6) Though generally C. juncea was little productive of seed, the one brought from Ceylon gave heavy seed yields, and proved itself an excellent variety. C. spectabilis was the one most productive of seed of all the species.
(7) With regard to the resistance to cold weather, C. spectabilis was the foremost, followed by C. juncea; C. intermedia seemed rather intolerant of cold.
(8) It may be suggested that C. intermedia and C. mucronata, which are generally used for feeding domestic animals, should be used for silage if they are to be of any economic importance in the future, since the animals do not much like them for good.
(9) The extent of harm done by diseases and insects varied considerably, depending on the individual variety. When there was much rain during the early part of the germination period, the plant was usually affected by the fungus Rhizoctonic solani, and was vulnerable to attack by harmful insects of various kinds after the flowering period. Especially noticeable was the injury to the pod by the insect Lampides boeticus, which reduced seed production to a considerable extent. It was found that C. spectabilis and C. intermedia were comparatively susceptible to the fungi Botrytis cinerea and Corticium centrifugum respectively. Some varieties of C. spectabilis and C. intermedia were found affected by viruses, and the latter was also often affected by the fungus Corticium cinerea.
(10) Though further studies are necessary to decide how to combine Crotalaria with other crops in rotation, inter-cropping or mixed cropping in Japan, it has become clear that, of those now in experimental planting, some, such as C. spectabilis, might immediately be put into practical use.

View full abstract

[in Japanese]

View full abstract