Temporal Patterns of N2O Fluxes From a Rainfed Maize Field in Northeast China

Abstract

Rainfed agriculture is one of the most common farming practices in the world and is vulnerable to global climate change. However, only limited studies have been conducted on rainfed agriculture, mainly using low-frequency manual techniques, which caused large uncertainties in estimating annual N2O emissions. In this study, we used a fully automated system to continuously measure soil N2O emissions for two years (April 2017 to March 2019) in a typical rainfed maize field in Northeast China. The annual N2O emissions were 2.8 kg N ha−1 in year 1 (April 2017 to March 2018) and 1.8 kg N ha−1 in year 2 (April 2018 to March 2019), accounting for 1.9 and 1.2% of the nitrogen fertilizer applied, respectively. The inter-annual variability was mainly due to different weather conditions encountered in years 1 and 2. A severe drought in year 1 reduced plant N uptake, leaving high mineral N in the soil, and the following moderate rainfalls promoted a large amount of N2O emissions. The seasonal pattern of N2O fluxes was mainly controlled by soil temperature and soil nitrate concentration. Both soil moisture and the molar ratio of NO/N2O indicate that N2O and NO were mainly derived from nitrification, resulting in a significant positive correlation between N2O and NO flux in the intra-rows (where nitrogen fertilizer was applied). Moreover, we observed that the N2O emissions during the freeze–thaw periods were negligible in this region for rainfed agriculture. Our long-term and high-resolution measurements of soil N2O emissions suggest that sampling between LST 9:00 and 10:00 is the best empirical sampling time for the intermittent manual measurements.

Process-based modeling of soil nitrous oxide emissions from United States corn fields under different management and climate scenarios coupled with evaluation using regional estimates

“…In addition, the reduction in N 2 O gs caused by wet conditions could also be attributed to p CENTURY using a monthly time-step, which could not capture rapid changes in water filled pore space and N 2 O emissions following rainfall events (Schmidt et al, 2000;Beheydt et al, 2007;Xia and Wander, 2022). Soil N 2 O changes can occur at a sub-daily time step so studies have attempted to capture high temporal resolution N 2 O dynamics (Laville et al, 2011;Lognoul et al, 2017;Su et al, 2021) using data collected with advanced techniques such as automated chamber and micrometeorological measurements (Hensen et al, 2013;Bréchet et al, 2021). However, such calibration data would be too expansive to collect at the broad scale for N 2 O modeling.…”

Mitigation of soil nitrous oxide emissions during maize production with basalt amendments

“…Run 2 also had a N 2 O peak period (29 days) that was consistent with average agricultural N 2 O peaks after fertilization. Additionally, all of Run 2′s containers had N 2 O fluxes (between 0.25 and 14 nmol N 2 O/m 2 s) within average expected agricultural ranges (1-50 nmol N 2 O/m 2 s) (Huang et al, 2014;Huddell et al, 2021;Su et al, 2021;Maier et al, 2022). These fluxes were slightly higher than N 2 O fluxes from Run 1, which we attribute to soil settling between iterations of the experiment given that we did not homogenize the top 10 cm of soil during this iteration of the experiment.…”

Large Seasonal Variation in Nitrogen Isotopic Abundances of Ammonia Volatilized from a Cropland Ecosystem and Implications for Regional NH3 Source Partitioning

“…An in situ experiment to investigate soil-volatilized NH 3 was performed in a maize field at the National Field Observation and Research Station of Shenyang Agro-ecosystems of the Chinese Academy of Sciences (41.52°N, 123.37°E), Liaoning Province, Northeast China (Figure a,b). The soil in this area is classified as Alfisols, and the soil texture is silt loam. , The cropping system is one crop per year in northeastern China, with rice and maize as the main crops. Planting and harvesting typically occur in May and October.…”

“…The soil in this area is classified as Alfisols, and the soil texture is silt loam. 44,45 The cropping system is one crop per year in northeastern China, with rice and maize as the main crops. Planting and harvesting typically occur in May and October.…”