Root-derived respiration and nitrous oxide production as affected by crop phenology and nitrogen fertilization

Abstract

In annual crops, the partitioning of photosynthates to support root growth, respiration and rhizodeposition should be greater during early development than in later reproductive stages due to source/ sink relationships in the plant. Therefore, seasonal fluctuations in carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) production from roots and root-associated soil may be related to resource partitioning by the crop. Greenhouse studies used 13 C and 15 N stable isotopes to evaluate the carbon (C) partitioning and nitrogen (N) uptake by corn and soybean. We also measured the CO 2 and N 2 O production from planted pots as affected by crop phenology and N fertilization. Specific root-derived respiration was related to the 13 C allocated to roots and was greatest during early vegetative growth. Root-derived respiration and rhizodeposition were greater for corn than soybean. The 15 N uptake by corn increased between vegetative growth, tasseling and milk stages, but the 15 N content in soybean was not affected by phenology. A peak in N 2 O production was observed with corn at the milk stage, suggesting that the corn rhizosphere supported microbial communities that produced N 2 O. Most of the 15 N-NO 3 applied to soybean was not taken up by the plant and negative N 2 O production during vegetative growth and floral initiation stages suggests that soybean roots supported the reduction of N 2 O to dinitrogen (N 2 ). We conclude that crop phenology and soil N availability exert important controls on rhizosphere processes, leading to temporal variation in CO 2 and N 2 O production.

Soil type overrides plant effect on genetic and enzymatic N2O production potential in arable soils

“…Potential denitrification and N 2 O production in soil, as well as the genetic potential for denitrification and N 2 O reduction in both root-associated and soil borne microorganisms, were determined by soil type rather than crop (Table 2). A range of studies showed that N 2 O emissions are higher in cropped soils when compared to bulk soils, thus indicating a significant influence of plants (Ding et al, 2007;H enault et al, 1998;Højberg et al, 1996;Klemedtsson et al, 1987;Ni et al, 2012;Sey et al, 2010;Verma et al, 2006). We observed a similar trend for the potential N 2 O production in soil, although this was not significant (Fig.…”

Root-Derived Contributions to Soil Respiration as Influenced by Agricultural Management Systems

“…Second, soil respiration rates (reflecting all heterotrophic and autotrophic respiration) were two to eight times greater than rates of root-derived (heterotrophic) respiration. Rhizosphere respiration (live root plus associated heterotrophic respiration) can contribute substantially to total soil respiration; soybean rhizosphere respiration contributed 40 to 95% of the C respired in a greenhouse study (Sey et al, 2010). Rates of rhizosphere respiration have been shown to increase through the flowering stage of plant development (Fu et al, 2002).…”

Responses of temporal and spatial variation in soil respiration to biotic and abiotic factors in a desert shrubland in northwest China

“…Root biomass depends also on the topographic heterogeneity in R s over the sand dune in phase II. However, from phase II to phase III, additional liable fresh litterfall and suppressed shrub photosynthesis (as declined photosynthetic pigments) results in larger contribution of heterotrophic respiration to total R s (Fu et al, 2002;Sey et al, 2010;Mauritz and Lipson, 2013). Also soil nitrogen content contributes strongly to the litterfall decomposition process (Yan et al, 2010;Sayer et al, 2011).…”