Effect of silicon on barley growth and N2O emission under flooding.

The global climate change is related with greenhouse gas emission from cultivated soils - carbon dioxide, methane and nitrous oxide. The emissions of N2O also have negative influence on ozone layer of our planet. The major source of the nitrous oxide is denitrification process in soil, which controlled by specific soil microbe society. The pot experiment with flooding to accelerate the denitrification process and the application of the monosilicic acid as a source of soluble form of Si was carried out with barley. Several forms of nitrous oxide emission (unlimited carbon denitrification and potential denitrification with or without ethylene application) were measured. The obtained data showed that the application of monosilicic acid to brown soil when growing barley under conditions of soil flooding has a significant effect on nitrogen emission and can change the N2O:N2 ratio. The application of the monosilicic acid reduced the uC-D N2O emission, while increased the PD N emission. Generally the application of the water soluble Si decreased the N2O:N2 ratio. We suggested that the presence of monosilicic acid in the system provides a more complete denitrification process with the formation of N2 in the NO3- → NO2- → NO→N2O → N2 reaction sequence, while the deficiency of bioactive Si mainly provides the formation and emission of N2O. Considering that N2 is not a greenhouse gas, we can conclude that application of monosilicic acid to the soil can reduce greenhouse gas emissions and reduce the impact of global climate change on agricultural activity.

Methane production and consumption in loess soil at different slope position.

Methane (CH(4)) production and consumption and soil respiration in loess soils collected from summit (Top), back slope (Middle), and slope bottom (Bottom) positions were assessed in laboratory incubations. The CH(4) production potential was determined under conditions which can occur in the field (relatively short-term flooding periods with initially ambient O(2) concentrations), and the CH(4) oxidation potential was estimated in wet soils enriched with CH(4). None of the soils tested in this study emitted a significant amount of CH(4). In fact, the Middle and Bottom soils, especially at the depth of 20-40 cm, were a consistent sink of methane. Soils collected at different slope positions significantly differed in their methanogenic, methanotrophic, and respiration activities. In comparison with the Top position (as reference soil), methane production and both CO(2) production and O(2) consumption under flooding were significantly stimulated in the soil from the Middle slope position (P < 0.001), while they were reduced in the Bottom soil (not significantly, by 6 to 57%). All upper soils (0-20 cm) completely oxidized the added methane (5 kPa) during 9-11 days of incubation. Soils collected from the 20-40 cm at the Middle and Bottom slope positions, however, consumed significantly more CH(4) than the Top soil (P < 0.001).