ZusammenfassungUreaform (UF) is a condensation product between urea and formaldehyde consisting of short chains from methylene-diurea to tevamethylenepenlama. The rate of nitrogen release is mainly related to chain solubility. The mineralization of UF is governed by microbial activity. A wide spectrum of organisms is known to be involved. The degradation is mainly influenced by the biological fertility of the soil, temperature and to a limited degree by moisture, whereas pH and panicle size have no pronounced effect. The imponance of the activity index (A.I.) as a unit to evaluate the quality of an UF product and the versatility of the UF system in general are discussed. More recent uial results with UF products show the beneficial effects of the particular kind of slow release nitrogen fertilizer in meeting needs for improved fertility management and reduced pollution of drainage waters. K.W., 1.C. Thomas, and R.L. Duble (1982): Nitrogen source effect on nitrate and ammonium leaching and runoff losses from greens. Agronomy Journal 7 4 947-950.
Brown,
708-709.
Foliar fertilization, or the application of nutrient solutions to the foliage of plants, has become a very important tool as a supplement to traditional soil fertilization. So far, knowledge about the real mechanisms of foliar nutrient uptake is still limited. In this study different manganese (Mn) and zinc (Zn) carriers differing in their solubility and chemical characteristics (chelated or non-chelated, with or without the presence of a surfactant-penetrant) were compared with regard to their penetration characteristics through enzymatically-isolated cuticles. The experiments were explicitly conducted under high humidity conditions in order not to penalize compounds with a higher deliquescent point. The results show that Mn penetrates more rapidly through the cuticle than Zn ions for unknown reasons. The addition of a surfactant-penetrant enhances the penetration rate in the case of Mn ions. This trend is much less pronounced for zinc ions. Formulations based on insoluble carriers, such as carbonate or oxide, only poorly penetrate through the cuticle. In order to rapidly control micronutrient deficiency problems, only fully water soluble micronutrient carriers should be used.
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