Southeast Europe is Europe's major production area of soybean of maturity groups (MG) 0, I and II, but genotype by environment interaction (GEI) for soybean traits in this region is still not characterized. The objective of this study was to characterize GEI in soybean grown in Croatia for seed yield, protein and oil content. Fourteen soybean cultivars of MG 0 and I were evaluated at 15 environments. In the combined ANOVA, genotypes, environments and GEI were significant. All three seed traits were more affected by year than by location and seed yield and protein content were more sensitive to environmental changes than oil content. Genotype by environment interaction is generally of less importance than effects of genotypes and years, especially for oil content. High-yielding genotypes had values of regression coefficient (b) close to 1, indicating that they were not responsive to extreme environments, either positive or negative. Means and b values were not correlated for yield and negatively correlated for protein and oil content, probably because of low-input practice in the region. The absence of recognizable differences in means, b values and principal component scores of AMMI analysis between two MGs for all traits indicated that soybean cultivars of MG 0 may be recommended for growing in the region because they responded similarly to environmental changes as do fullseason genotypes of MG I.

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The influence of foliar magnesium (Mg) application before flowering on chloroplast pigment indices was investigated in a 2-year field experiment with five soybean cultivars. Acetone extraction of pigments (chlorophyll a and b, total chlorophylls, and carotenoids as well as their ratios) was compared to chlorophyll meter (SPAD-502) readings. The untreated plants showed significant influence of cultivar on pigment concentrations, and pigment ratios were year-dependant. Foliar fertilization with Mg influenced chlorophyll concentration mostly in the year 2004, and carotenoids were not altered by Mg treatment. Cultivar differences prevailed in the next year when Mg treatment was less effective. The interactions among year, cultivar, and Mg application were showed to be significant for a particular parameter. The SPAD-502 readings significantly correlated with pigment concentrations only in the untreated plants in 2005. However, the foliar treatment influenced significantly SPAD readings in 2004, through the interaction with cultivar in once-treated plants and as a single factor in twice-treated plants. Grain yield was under significant positive influence of leaf Mg concentration in both years, and one treatment with Epsom salt was enough for significant grain yield increase.

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