Abstract
Nitrogen (N) fertilization has a considerable effect on food production and carbon cycling in agro-ecosystems. However, the impacts of N fertilization rates on the temperature sensitivity of soil respiration (Q10) were controversial. Five N rates (N0, N45, N90, N135, and N180) were applied to a continuous winter wheat (Triticum aestivum L.) crop on the semi-arid Loess Plateau, and the in situ soil respiration was monitored during five consecutive years from 2008 to 2013. During the growing season, the mean soil respiration rates increased with increasing N fertilization rates, peaking at 1.53 μmol m−2s−1 in the N135 treatment. A similar dynamic pattern was observed during the non-growing season, yet on average with 7.3% greater soil respiration rates than the growing season. In general for all the N fertilization treatments, the mean Q10 value during the non-growing season was significantly greater than that during the growing season. As N fertilization rates increased, the Q10 values did not change significantly in the growing season but significantly decreased in the non-growing season. Overall, N fertilization markedly influenced soil respirations and Q10 values, in particular posing distinct effects on the Q10 values between the growing and non-growing seasons.
Highlights
Temperature sensitivity is an essential index to quantify and evaluate the carbon (C) cycle and the future global C balance [1,2,3]
The grain yield significantly was increased after N fertilization (p < 0.05), yet no significant differences were observed among the N90, N135, and N180 treatments (Fig 2)
Compared with the unfertilized treatment (1.07 μmol m−2 s−1), the soil respiration rate significantly increased under the fertilized treatments (N45-N180) (p < 0.05) (Fig 3a)
Summary
Temperature sensitivity (i.e., the Q10 value, which represents variations in the soil respiration rate over a temperature shift of 10 ̊C) is an essential index to quantify and evaluate the carbon (C) cycle and the future global C balance [1,2,3]. It is of particular relevance to predict the potential carbon dioxide (CO2) efflux feedback between terrestrial ecosystems and future global warming scenarios [4]. In specific for agro-ecosystems, variations in Q10 values are influenced by agronomic management practices as well as natural environment. N fertilization is a common field practice to improve soil fertility and crop growth, and sustain food production [5,6,7]. In China, arable soils are intensively cultivated through high N fertilizer inputs (23 million Mg in 2011), which.
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