Effects of Different Amounts of Humic Acid on the Content of Soil Available Selenium, the Forms of Selenium and the Selenium Absorption in Garlic

Selenium (Se) is a necessary trace element for human health. The land area deficient in Se is up to 70% in China. And also, in some Se-enriched areas, Se-rich agricultural products can't be produced, because the bioavailability of Se in soil is very low. In this paper, soil with higher Se content was collected from a Se-rich area in Fujian Province. The soil culture test and pot experiment were carried out, to study effects of different amounts of humic acid on the content of soil available Se, the distribution of soil Se forms, and its absorption characteristics in garlic. The results showed that, the soil available Se was improved significantly with the increase of humic acid amount (<i>P</i><0.01). Contents of soil available Se were followed by 20% OM (43.3~50.6 μg&#183;kg^-1) > 10% OM (37.6~48.8 μg&#183;kg^-1) > 5% OM (37.6~48.8 μg&#183;kg^-1) > CK (33.0~41.5 μg&#183;kg^-1). The organic matter content was also increased with the increase of humic acid amounts. The significant positive correlations between contents of organic matter and different forms of Se in soils were found. The correlation coefficients were 0.963, 0.962 and 0.906 in the water-soluble Se, exchangeble and bound to carbonates Se, and the bound to organic matter and sulfide Se, respectively. The highest correlation was found between the organic matter and water-soluble Se, with the correlation coefficient of 0.821 with grey correlation analysis method, following by bound to organic matter and sulfide Se (the correlation coefficient was 0.693), and the minimum value was existed in the bound to Fe-Mn oxides (0.482). Se contents in dry weight of different parts of garlic showed the order of root (0.167~0.653 mg&#183;kg^-1) > stem (0.114~0.326 mg&#183;kg^-1) > leaf (0.056~0.086 mg&#183;kg^-1). The fresh Se contents were reached the Se-rich food standards (HB 001/T-2013) in all treats, from 0.018 mg&#183;kg^-1 to 0.110 mg&#183;kg<sup>-1