Assessment of selenium mineralization and availability from catch crops

Selenium (Se) release from four plant species (Indian mustard, fodder radish, Italian ryegrass and hairy vetch) was measured under controlled leaching conditions and in a pot incubation experiment as part of a study of the potential for using these plant species as Se catch crops. Catch crops may reduce Se leaching and, by subsequent release of Se from the plant material, increase the available Se for succeeding crops. Plants grown both without and with Se addition (250 g Se/ha) were tested. In the leaching experiment, frozen plant material was incorporated into soil columns and incubated at room temperature for up to 19 weeks. The results showed that Se concentrations in the leachate were higher when Se‐enriched plant material was incorporated in the soil, indicating Se mineralization. When non‐enriched plant material was added to the soil, Se concentrations in the leachate were generally lower than that in the control, indicating Se immobilization. In the pot incubation experiment, the results were consistent with those from the leaching experiment. The addition of enriched plant material increased Se concentration in Indian mustard plants compared with unamended soil. However, the addition of plant materials grown without Se significantly decreased Se concentrations in plant dry matter, again indicating Se immobilization. Fertilizer application with inorganic Se as selenate did not affect Se concentrations either in the leachates or in the plants grown in the pot incubation. Thus, the results show the potential of catch crops to increase Se mineralization and uptake in succeeding crops.