AbstractsBiology & Animal Science

Typescript. Thesis – University of Hawaii, 1964. Bibliography: leaves 105-113. xi, 113 leaves mounted ill. (part col.) tables The study of micro-nutrients in tropical soils has been receiving increasing attention in the past decade. There is an awareness that a great shortage of information exists today regarding the status and availability of micro-nutrients. Zinc is one of these trace elements that has been established as being in critical supply in many tropical countries. Because of the rapid disappearance of new lands, the heretofore common cropping practice of "shifting agriculture" will become a thing of the past in many tropical areas. It is expected that as land is intensively farmed year after year, the depletion of zinc, as well as other trace elements, will continue to grow. The very process of soil weathering in the tropics is a process of attrition of this element from the soil. It can also be expected that the use of modern concentrated, purified, inorganic fertilizers with resultant heavy crop removal from the soil will further contribute toward a shortage of this element. In Hawaii the problem of zinc deficiency was recognized in certain soils shortly before World War II. Lyman and Dean (45) reported zinc deficiency in pineapples and described symptoms which consisted of blistering and mottling of leaves and of curvature of the "heart" leaves. This "crookneck" symptom in pineapple has subsequently been recognized in Queensland, Australia (2). The Hawaiian pineapple industry has recognized the existence of zinc deficiency and has included zinc in their foliage spray program in many of their fields. Zinc deficiency in coffee has been recognized as being a widespread problem. Some of Hawaii's problems are akin to those of Brazil's in that zinc-deficient plants are in both cases usually located on hilly lands at high altitudes and with moderately high to high rainfall conditions. Zinc, when applied as a foliar spray, has been reported by Shoji and Ota (63) to be more successful in correcting zinc-deficiency in coffee than when added to the soil. Younge and Plucknett (85) have associated zinc-deficiency with coral limed-areas. The pH was found to have become excessively high in such areas. Observations and yield data were taken on corn and alfalfa. In his fertility study of humid Hawaiian pastures, Younge (84) showed that Kaimi clover-paspalum forage responded to zinc application. Clements (23) reported that neither phosphate nor coral stone significantly affected the zinc-index readings for sugar cane grown in a hydrol humic latosol, but a highly significant interaction between them was shown. The writer is not aware of any widespread zinc deficiency problem in the sugar cane industry in Hawaii today. Although much progress has been made in the recognition of zinc-deficiency, there yet remains to be found satisfactory explanations of the mechanisms and conditions that affect the availability of zinc in soils. As a result, whereas foliage spray of zinc has been generally effective in correcting…