Page:Report of the Puerto Rico Experiment Station (IA CAT31294391015).pdf/7

 on root yield and quality of Derris plants grown at two locales haying marked differences in rainfall. The 9 clones are to be maintained separately, thus making it possible to evaluate the merits of these clones when grown under different environmental conditions.

A shipment of nine varieties of Derris was received from the East African Agricultural Research Institute, Amani, Tanganyika Territory, through the courtesy of P. J. Greenway. None of the plants survived shipment, however.

A group of Derris plants that had been held at the Glenn Dale (Md.) station of the Bureau of Plant Industry, Soils, and Agricultural Engineering, Division of Plant Exploration and Introduction, for safekeeping during the war was transferred to this station.

R. H. Hageman and C. Pagan

Derris from two agronomic experiments was harvested, and chemical and biological evaluation of the roots were completed.

One of the most tedious and costly operations in the commercial production of Derris is the manual digging of the roots. Derris plants were grown on three types of replicated plots: (1) Level ground that served as a control, (2) ridges that were 8 inches high, and (3) 16 inches high, in an attempt to determine what effect ridging would have on root yield, insecticidal constituents, and ease of harvesting. The root yields were essentially equal for all three types of plots. The chemical and biological toxicity of the roots decreased as the height of the ridge increased. It required from one-half to two-thirds the time to manually harvest the roots of the plants grown on the ridges as compared with those grown on the ground. From this experiment the practice of growing Derris on ridges cannot be recommended as an economical agronomic practice. Harvesting by plow was from three to four times faster than digging manually even on the 25-foot experimental rows. Plowing to an 8-inch depth recovered only 75 percent of the roots. A mechanical device that would turn over a 14- or 16-inch furrow would probably yield a higher percentage of the roots.

Nine high-quality Changi clones were introduced by the station in 1940. These clones were identified as MG (Mayagüez-Goodyear) and numbered from 1 to 9 in order of decreasing rotenone percentage obtained in a preliminary evaluation. The plants of the second evaluation trial were harvested in January 1948, 31 months after planting to the field in a well-replicated experiment, and evaluated for yield and toxicity. No significant differences were found in yield of roots among the nine clones, but clone 9 was highest in root production. Clones 1, 2, 3, and 4 were consistently better than the remaining clones with regard to quality of root, based on percentage rotenone. The average yield of rotenone for the nine clones accounted for about one-half the total toxicity, as determined by bio-assay. The best clones in the group, based on the amount of insect control per plant or per acre, were clones 1 and 9.