MAPPING ZINC FERTILITY OF SOILS USING INDICATOR PLANTS AND SOIL ANALYSES (SEED, GEOSTATISTICS, HAWAII, COLORADO)

This investigation examined whether or not plant composition data, especially Zn contents of grains could be used to evaluate the Zn status of soils and crops and produce soil fertility maps. A possible role of Zn deficiency in Maui sugarcane growth failure was also investigated.;Zinc contents of all grains, especially wheat, were sensitive to the soil Zn status. The range of Zn concentration (mg Zn/kg) in grains were: corn, 17 to 45; sorghum, 6 to 28; millet, 13 to 51; rice, 12 to 44; wheat, 14 to 71; soybean, 23 to 68; and cowpea, 16 to 54. Critical levels of Zn in seedlings, foliar tissues, and grains were estimated. Grains of cereals and legumes proved to be a good indicator tissue for evaluating the Zn status of soils and crops. This sensitivity was verified in a field study in Colorado where wheat grains contained 12 to 60 mg Zn/kg and a good correlation existed between grain Zn and soil Zn. Zinc status of Colorado soils and wheat grain was mapped using geostatistical analysis procedures. The data suggest that grain and foliar analysis provide a valid basis for evaluating and mapping the Zn status of soils and crops. A level of Zn that was adequate for every crop produced wheat grain that contained 43 mg Zn/kh and sugarcane leaf blades with 22 mg Zn/kg.;Zind deficient plants of sugarcane developed symptoms similar to those of Maui growth failure. Application of Na and K salts depressed plant Zn and sugarcane growth and aggravated the symptoms. Applications of Zn increased foliar Zn, aleviated symptoms and improved plant growth.;Isarithmic maps were prepared of the Zn status of two sugarcane plantations on the Island of Maui, Hawaii. Zinc contents of leaf tissues coincided with soil Zn. Fields of sugarcane that were affected by Maui growth failure in the past years were lower in soil and plant Zn than other fields.;In greenhouse studies using two Zn deficient soils of Hawaii, the order of increasing crop responsiveness to Zn application was: wheat (Triticum aestivum), sugarcane (Saccharum officinarum), sorghum (Sorghum bicolor), rice (Oryza sativa), millet (Pennisetum americanum), soybean (Glycine max), cowpea (Vigna unguiculata), and corn (Zea mays).