Differential Effects of Soil Water Content and Temperature on Nitrification and Aeration

Abstract

Environmental concerns have stimulated increased interest in NO−3 accumulation in soils. The aeration status of the soil, which is mainly governed by the water content and temperature, is a central factor. The biological process responsible for NO−3 accumulation, nitrification, was measured to estimate the combined effects of water content and temperature and determine their joint effect on soil aeration. The effects of temperatures of 15, 20, 25, 30, and 35°C and water contents equivalent to 0.35, 0.42, 0.50, 0.52, 0.57, and 0.60 relative water content (volumetric water content/total porosity) on the nitrification activity of soil samples containing 2‐mm sieved soils taken at 0 to 20 or 20 to 40‐cm depth were determined by measuring NO−3 accumulation for 17 h. A descriptive model including three biological parameters, maximum nitrification rate (Nrmax), optimal relative water content (Θopt), and temperature, was developed. Maximum Nrmax occurred at 25.5°C in 0‐ to 20‐cm soil and at 20°C in 20‐ to 40‐cm soil, suggesting an adaptation of soil nitrifying populations to the temperature regime of the soil. The Nrmax value was negatively related to Θopt, and Θopt was dependent on temperature (T). This Θopt (T) relationship was parabolic in nature, with Θopt being at a minimum between 20 and 25°C. It could be simulated using O2 diffusion and respiration rates, inferring that these processes influenced Θopt and T correlation. The ranges of O2 concentrations favorable to maximum nitrification within an aggregate volume fraction were estimated for different temperatures. Nitrification was generally maximum when the intraaggregate pore spaces were saturated with water, with no water in the interaggregate pore space (i.e., 0.44 relative water content at 25°C and 0.36 at 20°C at 0‐ to 20‐ and 20‐ to 40‐cm depths).

Microbial mediation of biogeochemical cycles revealed by simulation of global changes with soil transplant and cropping

“…In addition, soil CO 2 efflux, another process comprising autotrophic and heterotrophic respiration, was nearly doubled at the transplanted sites. Consistently, it has been well documented that soil nitrification and CO 2 efflux are strongly affected by climate changes (Grundmann et al, 1995;Davidson et al, 1998).…”

“…Similar to the observation with the CO 2 efflux, our results showed that nitrification capacity was increased (Table 1). As soil nitrification is well known to be microbemediated (Grundmann et al, 1995;Lodhi et al, 2009), we examined the correlation between N gene abundance and nitrification in all of the soil samples. A strong positive correlation (r ¼ 0.70, Po0.001) was observed (Figure 4), suggesting that the increase of N cycle gene abundance in soils may partially explain the increase of the nitrification capacity in this study.…”

Emissions of Nitrous Oxide (N2O) and Di-Nitrogen (N2) from the Agricultural Landscapes, Sources, Sinks, and Factors Affecting N2O and N2 Ratios

“…Production of N 2 O via heterotrophic nitrification is poorly understood because autotrophic and heterotrophic nitrification can occur simultaneously in a given soil and it is difficult to separate the end products of these two processes without using 15 N tracers (Matheson et al, 2003). Sufficient soil O 2 levels [(optimum at water filled pore space (WFPS) of 60%)], adequate NH 4 + concentrations, a favorable soil temperature above 5 o C (optimum 25 to 35 o C), and soil pH above 5 (optimum 7 to 9) are among the known soil and environmental conditions which control the rate of autotrophic nitrification (Linn & Doran 1984;Grundmann et al, 1995;Whitehead, 1995;Zaman et al, 1999a;Šimek., 2000;Zaman & Chang, 2004;Zaman et al, 2007;Saggar et al, 2009;Zaman et al, 2009;Zaman & Nguyen, 2010). Among these factors, NH 4 + and O 2 concentrations are considered the most critical factors affecting autotrophic nitrification (Zaman et al, 2007).…”

Effects of a clear-cut on the in situ nitrogen mineralisation and the nitrogen cycle in a 67-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantation

“…III) due to suppression of water uptake by roots. This higher soil moisture may have led to overestimating production and uptake rates [29]. However, Sierra [73] did not find a high response of mineralisation to an increase in soil moisture inside incubated cylinders of soil, and nor did Jussy [40] find such a response in laboratory incubations of this specific soil.…”