Showing papers by "Arvin R. Mosier published in 1990"

Evolution of dinitrogen and nitrous oxide from the soil to the atmosphere through rice plants

Abstract: It is commonly assumed that a large fraction of fertilizer N applied to a rice (Oryza sativa L.) field is lost from the soil-water-plant system as a result of denitrification. Direct evidence to support this view, however, is limited. The few direct field, denitrification gas measurements that have been made indicate less N loss than that determined by 15N balance after the growing season. One explanation for this discrepancy is that the N2 produced during denitrification in a flooded soil remains trapped in the soil system and does not evolve to the atmosphere until the soil dries or is otherwise disturbed. It seems likely, however, that N2 produced in the soil uses the rice plants as a conduit to the atmosphere, as does methane. Methane evolution from a rice field has been demonstrated to occur almost exclusively through the rice plants themselves. A field study in Cuttack, India, and a greenhouse study in Fort Collins, Colorado, were conducted to determine the influence of rice plants on the transport of N2 and N2O from the soil to the atmosphere. In these studies, plots were fertilized with 75 or 99 atom % 15N-urea and 15N techniques were used to monitor the daily evolution of N2 and N2O. At weekly intervals the amount of N2+N2O trapped in the flooded soil and the total-N and fertilized-N content of the soil and plants were measured in the greenhouse plots. Direct measurement of N2+N2O emission from field and greenhouse plots indicated that the young rice plant facilitates the efflux of N2 and N2O from the soil to the atmosphere. Little N gas was trapped in the rice-planted soils while large quantities were trapped in the unplanted soils. N losses due to denitrification accounted for only up to 10% of the loss of added N in planted soils in the field or greenhouse. The major losses of fertilizer N from both the field and greenhouse soils appear to have been the result of NH3 volatilization.

The Use of Acetylene for the Quantification of N2 and N2O Production from Biological Processes in Soil

Abstract: Losses of nitrogen from soil have many adverse environmental effects. Supplies of potable water may be contaminated by NO 3 − leached from agricultural soils, and since the 1970s there has also been concern about the effects of gaseous N-compounds produced from NH 4 + and NO 3 − by micro- organisms. The rate of degradation of the Earth’s protective ozone screen is enhanced by N2O (Crutzen, 1983), and N2O also has a significant effect on the Earth’s thermal balance via the greenhouse effect (Lacis et al., 1981). N2 is not harmful to the environment, but the losses of fertilizer nitrogen via denitrification to N2 are economically undesirable. Consequently, it is essential to develop methods for quantitative studies of the nitrogen cycle in soil in order to find ways of minimizing N losses in agriculture and forest management.

Rhizosphere Denitrification; A Minor Process but Indicator of Decomposition Activity

Abstract: The primary inputs of organic matter driving heterotrophic processes in soil are of plant origin. Microbial activity increases more than an order of magnitude when moving from the bulk soil through the rhizosphere towards the root surface (Brown, 1975; Helal and Sauerbeck, 1986). The composition of the soil microbial population (Rouatt et. al., 1960) and its denitrifying capability (Smith and Tiedje, 1979) show dramatic changes over this small distance in soil. Decomposition of recalcitrant soil organic matter can be stimulated in the rhizosphere (Helal and Sauerbeck, 1986) and grazing on soil microbes by soil animals is greatly increased in this environment (Clarholm, 1985). As members of the rhizosphere microbial community, the activity of denitrifying bacteria is expected to be dramatically affected by the presence of plants. Since the comprehensive work by Woldendorp (1963), several investigations in arable soil have shown a substantial influence of plants on denitrification (Bakken, 1988, Christensen 1985, Klemendtsson et. al., 1987, Von Rheinhaben and Troldenier, 1984 are more recent examples). Plants in waterlogged soil (Broadbent and Tusnem, 1971; Garcia, 1975; Reddy and Patrick, 1986) and algae in marine sediments (Andersen et. al., 1984) can also have a marked influence on denitrification. Some studies found no or weak influence of plants on denitrification (Haider et al., 1985; 1987).