Overcoating: a strategy for the delivery and control of nutrient release in fertilizers.

Reference	Presenter	Authors (Institution)	Abstract
05-001	Fábio Plotegher	Plotegher, F.(Domínio Química - FAPESP); Santos, R.B.(Universidade de São Paulo); Junior, V.R.(Universidade de São Paulo); Majaron, R.F.(Universidade Federal de São Carlos); Majaron, V.F.(Universidade Federal de São Carlos); Polito, W.L.(Universidade de São Paulo); Ribeiro, C.(Universidade Federal de São Carlos/ Embrapa Instrumentação);	Brazil stands out worldwide as one of the largest producers in several crops of economic interest such as: soy, corn, sugar cane, coffee, citrus among others. One of the main factors that helped to leverage this productivity was a greater and better fertilization of the soils. However, as in the rest of South America, in Brazil most of the fertilizers used are models oriented to temperate soils, that is, they present high solubility, which causes great losses of the nutrients applied in the crops, as is the case of phosphate that ends up being immobilized in the soil due to the great concentration of iron and aluminum ions. One way around this problem is to use polymers from renewable resources to cover fertilizer granules, acting as a physical barrier, controlling the release of nutrients. Thus, this work proposed first, to use a zinc oxide suspension (ZnO) to cover granules of the commercial fertilizer monoammonium phosphate (MAP), so that each MAP granule can carry the micronutrient Zn to the soil, ensuring a better distribution of this element and secondly the use of a layer of zeins obtained from maize applied on the ZnO layer to act as a physical barrier and to control the release of both phosphate and ammonium from commercial fertilizer and from zinc. The results showed that there was adhesion between the deposited ZnO particles on the MAP granules and also the adhesion of the zeins on the whole system. The release tests on citric acid showed that there was delay in the release of both phosphate and ammonium as well as zinc. These results showed that it is possible that each fertilizer pellet carries a micronutrient with it facilitating the management of fertilization and that it is possible to use the zeins to control the release of nutrients in commercial fertilizers and this is an environmentally more correct option.
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