Foliar selenium (Se) treatment of garlic at concentrations of 10, 50, and 100 μg of Se/mL was carried out in open field conditions in 2008 and 2009 in Estonia. Bulb weight and yield structure, content of total Se, S, N, P, K, Ca, and Mg, ascorbic acid content (AAC), pungency, total phenolics, and total antioxidant capacity (TAC) were determined. The highest level of Se decreased total S, K, and Ca in both years; no negative impact on bulb weight was observed. In 2009 Se10 treatment had significantly more bulbs with the largest diameter compared to the other treatments. In 2008, the AAC was decreased by Se50 and the content of total phenolics by all Se treatments; however, TAC was increased. Foliar Se fertilization of garlic at rates of 10-50 μg of Se/mL can be recommended to increase the number of large bulbs and increase bulb antioxidant capacity.

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Chemical Composition and Quality of Cultivated and Natural Blueberry Fruit in Estonia Nutrition studies suggest that blueberries help keep us healthy and these possible health benefits may be due to the antioxidant capacity as well as other natural compounds in blueberry fruit. Different taxa of Vaccinium species (Bilberry - Vaccinium myrtillus L.; lowbush blueberry - Vaccinium angustifolium Ait.; half-highbush blueberry - Vaccinium corymbosum x Vaccinium angustifolium ‘Northblue’ and ‘Northcountry’) were analyzed for surface color, size, sugars, titratable acidity, soluble solids, fat, protein, vitamins and anthocyanin content. The blueberry fruit were harvested from three commercial blueberry plantations and from one natural habitat in 2003. The fruit of V. angustifolium were collected from two different areas: one plantation was located on mineral soil and the other on peat soil (abandoned peat pits). The anthocyanin content ranged from 125 to 405 mg·100 g-1 of fresh berry in different species and cultivars. Half-highbush blueberry ‘Northblue’ had the largest berry size but ascorbic acid and anthocyanin contents were low. V. myrtillus had the lowest total energy value, but the highest anthocyanin content. Glucose and fructose content was higher in fruit of V. angustifolium compared with the other species. The soil type (mineral or peat soil) did not affect anthocyanin and ascorbic acid content of V. angustifolium fruit but titratable acids and moisture content was higher in fruit of V. angustifolium grown on peat soil, compared with mineral soil.

The decomposition of fresh crop residues added to soil for agricultural purposes is complex. This is due to different factors that influence the decomposition process. In field conditions, the incorporation of crop residues into soil does not always have a positive effect on aggregate stability. The aim of this study was to investigate the decomposition effects of residues from two different cover crops (Brassica napus var. oleifera and Secale cereale) and one main crop (wheat straw) on soil aggregate stability. A 105-day incubation experiment was conducted in which crop residues were mixed with sandy loam soil at a rate of 6 g C kg−1 of soil. During the incubation, there were five water additions. The decomposition effects of organic matter on soil conditions during incubation were evaluated by determining the soil functional groups; carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions; soil microbial biomass carbon (MBC); and water-stable aggregates (WSA). The functional groups of the plant residues and the soil were analyzed using Fourier transform infrared spectroscopy (FTIR) and a double exponential model was used to estimate the decomposition rates. The results show that the decomposition rate of fresh organic materials was correlated with the soil functional groups and the C/N ratio. Oilseed rape and rye, with lower C/N ratios than wheat straw residues, had faster decomposition rates and higher CO2 and N2O emissions than wheat straw. The CO2 and N2O flush at the start of the experiment corresponded to a decrease of soil aggregate stability (from Day 3 to Day 10 for CO2 and from Day 19 to Day 28 for N2O emissions), which was linked to higher decomposition rates of the labile fraction. The lower decomposition rates contributed to higher remaining C (carbon) and higher soil aggregate stability. The results also show that changes in the soil functional groups due to crop residue incorporation did not significantly influence aggregate stability. Soil moisture (SM) negatively influenced the aggregate stability and greenhouse gas emissions (GHG) in all treatments (oilseed rape, rye, wheat straw, and control). Irrespective of the water addition procedure, rye and wheat straw residues had a positive effect on water-stable aggregates more frequently than oilseed rape during the incubation period. The results presented here may contribute to a better understanding of decomposition processes after the incorporation of fresh crop residues from cover crops. A future field study investigating the influence of incorporation rates of different crop residues on soil aggregate stability would be of great interest.

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