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Prediction of micronutrient deficiency normally involves soil extraction tests and correlations between soil extractable micronutrients and their concentration in plant tissues. The present study reports that the inclusion of soil properties in addition to soil extraction data represents a powerful tool for improving models for a simple determination of phytoavailable Zn and Cu. Soil and plant samples were collected in spring 2000 from 19 cereal fields in Central and Southeast Norway at sites with known micronutrient deficiency. Based on the sample information, the model approach used stepwise regression, applying actual plant Zn and Cu concentration as the response, and soil extractable Zn/Cu and physico-chemical properties of the soil as model predictors. A model involving citric acid extractable Zn coupled with selected soil properties could predict the concentration of Zn in plant tissues of barley and oats grown under field conditions with a significantly high precision (R2=0·96, P<0·001). The soil parameters included in the model, and their importance for phytoavailability of Zn, were in the order: citric acid extractable Zn>clay content>total Zn>pH>total C>total N. Inclusion of DTPA extractable Zn in the model, rather than citric acid, resulted in a slightly lower precision in the prediction of phytoavailable Zn (R2=0·86, P<0·001). A corresponding model for phytoavailable Cu, determined by DTPA and soil parameters, gave less precise prediction (R2=0·59, P<0·01). DTPA was more suitable for predicting phytoavailable Cu than citric acid. Plant Mn concentration could not be correlated to any of the extracting agents.

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Biofortification of forage crops has an important role in improving the quality of plants used for animal nutrition. The field experiments were conducted in three consecutive years in Subotica, Serbia, in order to investigate the effect of Se, Zn, and Cu foliar fertilization on the yield, Se and Zn contents and nutrient efficiency, as well as on other mineral compositions of alfalfa hay. The treatments were as follows: i) control without fertilization, ii) 5 g Se ha-1 , iii) 10 g Se ha-1 , iv) 0.5 kg Zn ha-1 , v) 1 kg Zn ha-1 , vi) the combination of these two elements (0.5 kg Zn ha-1 and Se 10 g ha-1) and vii) 2% Cu solution. The application of Se, Zn, and Cu had no effect on dry yield or on crude protein, P, K, Ca, Mg, Fe, Mn, Mo, and Co contents in alfalfa hay. However, Se, Zn, and Cu fertilization significantly increased the contents of Se, Zn, and Cu in alfalfa hay. The results showed that Se and Zn contents in plant biomass were significantly correlated with the applied doses of Se (r=0.99) and Zn (r=0.99). The production years of alfalfa and the weather conditions proved to be significant factors in fertilization efficiency.

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