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Estimation of field soil nitrogen mineralization and nitrification rates using soil N transformation parameters obtained through laboratory incubation

Urakawa, Rieko, Ohte, Nobuhito, Shibata, Hideaki, Tateno, Ryunosuke, Inagaki, Yoshiyuki, Oda, Tomoki, Toda, Hiroto, Fukuzawa, Karibu, Watanabe, Tsunehiro, Hishi, Takuo, Oyanagi, Nobuhiro, Nakata, Makoto, Fukushima, Keitaro, Nakanishi, Asami
Ecological research 2017 v.32 no.2 pp. 279-285
mineralization, nitrification, nitrogen, prediction, soil temperature
We tested the potential of estimating in-field (in situ) nitrogen (N) transformation rates based on soil temperature data and N transformation parameters (Q₁₀ and N transformation rates at standard temperature) obtained through laboratory incubations at three constant temperatures for 4 weeks. This test was conducted based on a comparison between in situ measurements and estimates using soils from 16 sites across 9 regions within the Japanese archipelago. The actual in situ N mineralization and nitrification rates measured using the buried-bag method at 0–50-cm-soil depth were 111 ± 34 and 106 ± 45 kg N ha⁻¹ year⁻¹, respectively, and estimates of both the rate and the amount were largely accurate. For rate alone, estimates were accurate in the 0–10-cm soil layer for annual and seasonal averages (except for spring–summer) whereas for amount alone, estimates were accurate to depths of 50 and 30 cm for N mineralization and nitrification, respectively. Thus, estimates of the rates and amounts were approximately equal to the actual in situ rate/amount, given the wide range of prediction intervals of the field measurement data. The differences between the estimates of N transformation rates derived from hourly measured and monthly average soil temperatures were negligible. Therefore, in situ soil N transformations, which are laborious to measure in the field, have the potential to be estimated from a combination of monthly average soil temperatures and N transformation parameters, which are relatively straightforward to obtain through laboratory incubation.