Location
Luancheng Station is located in Luancheng county of Hebei province (37°53' N, 114°41'E and elevation at 50.1 m), represents the typical high production area in the northern part of the North China Plain. The rapid declining groundwater table has become the main problem that threatens the sustainable agricultural development in this area.
Climatic
Located in the eastasian monsoon region, Luancheng station has a semi-humid and warm temperate climate. The mean annual temperate is 12.3 ℃, the mean annual precipitation is 530.8 mm. The annual total sunshine radiation quantity and length reach 543.3 KJ/cm2 and 2608 hours, respectively. The sunlight percentage is 59.1%. The accumulated temperature of equal to or more than 0 ℃ is 4710 ℃, and the frost free period is about 200 days. The light and heat resources are abundant, rain and heat occurs in the corresponding period, it greatly benefit to agriculture production.
Vegetation and soil
This area represents the typical high production area in the North China Plain and is at the piedmont of the Taihang Mountains. The dominant cropping system in the region is winter wheat (Triticum aestivum L.) – summer maize (Zea mays L.) double cropping rotation (two crops harvested in a single year) without fallow. The soil is classified as silt loam Haplic Cambisol.
Observation system
Luancheng semi-humid dry farming flux observation site is located in the warm temperate zone. Two layer conventional weather observation system and an open-path eddy covariance system were installed. At the same time, soil and plant carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are observed with static-chamber method.
Principal Investigator
Yuying Wang
E-mail: wangyuying@sjziam.ac.cn
Station director
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Assistant station director
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Members
Yuying Wang Assoc,Professor
Xiaoxin Li Assoc,Professor
Wenxu Dong Assoc,Professor
NNSFC
1.The study of the carbon isotope fractionation during respiration process in a winter-wheat and summer-maize double cropping rotation in Huabei Plain. (Yuying Wang 2015-2018)
2.The stable isotope studies of dynamic water consumption structure and transpiration efficiency at canopy scales in irrigated farmland. (Yucui Zhang 2015-2017)
3.The influence mechanisms of agriculture land use change on evapotranspiration and groundwater depletion in Huabei Plain. (Yanjun Shen 2015-2018)
1. we report on the responses of crop yield, N2O emission and yield-scaled N2O emission (N2O emission per unit N uptake by grain and aboveground biomass) to different N fertilizer rates in a winter wheat-summer corn double-cropping system in the North China Plain. Soil N2O emission measurements were carried out for two years in a long-term field experiment, under semi-arid conditions with four flood irrigations events per year. Our results indicated that N2O emissions were linear functions and yield-scaled N2O emissions were cubic functions of N fertilizer application rate. Yield-scaled N2O emissions were lowest at application rates of 136 kg N ha-1 yr-1. Using a quadratic plateau model, it was found that maximal crop yields were achieved at an application rate of 317 kg N ha-1 yr-1, which is 20% less than current practice. This level is suggested to be a compromise between achieving food security and mitigation N2O emissions.
2. we report on concentrations of CO2, CH4 and N2O in air of 300 cm deep soil profiles, at resolutions of 30–50 cm, over a full year. Gas samples were taken weekly in a long-term field experiment with an irrigated winter wheat–summer maize double cropping system, and four fertilizer N application rates (0, 200, 400 and 600 kg N ha−1 year−1). The concentrations of CO2 in soil air increased with soil depth and showed a seasonal pattern with relatively high concentrations in the warm and moist maize growing season and relatively low concentrations in the winter-wheat growing season. CH4 concentrations decreased with depth, and did not show a distinct seasonal cycle. Urea application did not have a large effect on CH4 or CO2 concentrations, neither in the topsoil nor the subsoil. Concentrations of N2O responded to N fertilizer application and irrigation. Application of fertilizer strongly increased grain and straw yields of both winter wheat and summer maize, relatively to the control, but differences in yield between the treatments N200, N400 and N600 were not statistically significant. However, it significantly increased mean N2O concentrations peaks at basically all soil depths. Interestingly, concentrations of N2O increased almost instantaneously in the whole soil profile, which indicates that the soil had a relatively high diffusivity, despite compacted subsoil layers. In conclusion, the frequent measurements, at high depth resolutions, of concentrations of CH4, CO2 and N2O in soil air under a winter wheat–summer maize double crop rotation provide detailed insight into the production, consumption and transport of these gases in the soil.
3. we quantified the GHG production and consumption at seven depths (0–30, 30–60, 60–90, 90–150, 150–200, 200–250 and 250–300 cm) in a long-term field experiment with a winter wheat-summer maize rotation system, and four N application rates (0; 200; 400 and 600 kg N ha-1 year-1) in the North China Plain. The gas samples were taken twice a week and analyzed by gas chromatography. GHG production and consumption in soil layers were inferred using Fick’s law. Results showed nitrogen application significantly increased N2O fluxes in soil down to 90 cm but did not affect CH4 and CO2 fluxes. The top 0–60 cm of soil was a sink of atmospheric CH4, and a source of both CO2 and N2O, more than 90% of the annual cumulative GHG fluxes originated at depths shallower than 90 cm; the subsoil (>90 cm) was not a major source or sink of GHG, rather it acted as a ‘reservoir’. This study provides quantitative evidence for the production and consumption of CH4, CO2 and N2O in the soil profile.