SURF 2023

Caption: Compare CO₂ and CH₄ levels under different fertilizer and crop rotations. (by Mingjie Chen)

Description: This is an overview of the data, taking the flux average of the three measurements calculated.

• Different colors signify different fertilizers: traditional fertilizer, bio-fertilizer1 (enzyme1) and bio-fertilizer2 (enzyme2) respectively.
• The X-axis crop represents the four different crop rotations, and the Y-axis represents the flux of gases carbon dioxide on the left and methane on the right.
• The range represented by the error line is the mean plus minus the standard variance of the flux (mean±sd).
• Biochemical fertilizer 2 may have effect on carbon dioxide emission of rice as inferred preliminarily from the graph.

1. Among the three fertilizers, biological enzyme fertilizer 2 was able to significantly affect carbon dioxide emission by lowering it, suggesting that photosynthesis was enhanced in rice, while the other two fertilizers did not show significant differences. This may be because biological enzyme fertilizer 2 was inoculated with photosynthetic bacteria. Meanwhile, the three fertilizers did not significantly affect methane emission.

2.  Previous studies [1,2] have shown that crop rotation affects carbon emissions. However, the four crop rotation plants selected in this project had no significant effect on carbon dioxide and methane emissions from the rice field. Further research may be warranted to explore the potential reasons behind the observed lack of impact.

3. The application of biological colonies has gradually matured in the agricultural field, and more and more invention patents have emerged. It is foreseeable that circular agriculture is the future development of China's agriculture, combined with the research of biological strains, to further improve agricultural ecology, reduce air pollution, and develop green economy agriculture.

4. There are limitations in the experimental design caused by lack of detailed field inspection and communication prior to the design of experiments.

• Rice was planted too densely, so operators had to set aside the plants to conduct sampling when they grow up later, which is a big disturbance to the environment.
• The height of the chamber and the water surface are poorly adapted. When the plants grow up later and their height exceeds the chamber, the leaves would block the sunlight as well as the air insulation will be weakened by being submerged in the water, which would result in inconvenient operation and systematic errors when measuring.

5.Data bias during single measurements may occur due to instability in the field environment and operational errors.

• Sometimes the water level inside the base was not high enough for good liquid sealing, leading to the mingling of internal gases with the atmosphere and an overall decrease in the concentration of internal gases.
• Sometimes the operator blocked the sunlight, resulting in the weakening of photosynthesis intensity, such that the carbon dioxide concentration inside the chambers concentration increased instead.
• Sometimes the measurement was not started immediately after the chamber was covered, which led to insufficient reliability of the data for flux calculation. What we would like to fit is the situation of greenhouse gases produced by rice plants when the chamber was not covered. Therefore, the further forward in time the data are measured, the more reliable the calculations and fits might be.

6.Field measurements rather than laboratory operations make it difficult to control the stability of the experimental environment and make precise measurements [3]. Nevertheless, the farm gives a more primitively ecological environment of a real rice paddy [4], which is more relevant to the topic of our research, and therefore more generalizable.

[1] Bandyopadhyay, T.K., Goyal, P. and Singh, M.P. (1996) ‘Generation of methane from paddy fields and cattle in India, and its reduction at source’, Atmospheric Environment, 30(14), pp. 2569–2574.

[2] Li, C. et al. (2005) ‘Modeling impacts of farming management alternatives on CO2, CH4, and N2O emissions: A case study for water management of rice agriculture of China’, Global Biogeochemical Cycles, 19(3).

[3] Metrology Lab (2023) https://agriculture.vermont.gov/weights-measures/metrology-lab (21 August 2023).

[4] Moritsuka, N. et al. (2021) ‘Laboratory and field measurement of magnetic susceptibility of Japanese agricultural soils for rapid soil assessment’, Geoderma, 393(115013). doi: 10.1016/j.geoderma.2021.115013.

Experimental site

The study site is situated in the experimental farm of the Tianchun organic farm, SuZhou (31°24′N, 120°25′E).

• Climate: subtropical monsoon Marine climate.
• Mean annual precipitation: approximately 1000 mm.
• Soil type: Aeric Endoaquept with sandy clay loam texture.
• Water and heat conditions have an obvious transition.

Experimental instruments

1.  Weather station HOBO U30
   Meteorological data collection (Air Temperature, Soil Temperature, Humidity, etc.) by Automatic weather station (HOBO U30)
   

2. Chamber technique
   

   The chamber is divided into two parts: the cylinder box (red part A in Figure1.) and the base (black part B in Figure1.). The material is transparent acrylic plate which is convenient to quantify the contribution of ground vegetation (Pavelka, et al., 2018).

   The box close at the top and open at the bottom. On the inner wall, two fans are installed at 1/3 and 2/3 height and are powered by dry batteries. Flux box height 500mm, bottom diameter 500mm, which is suitable for rice growth.

   The base is a transparent cylinder with a height of 100mm, the top has a ring of grooves (red lines in Figure1.) with a depth of 10mm. The grooves are slightly wider than the wall thickness of the box, and will be filled with water to act as a seal. The bottom is at an angle of about 25 degrees to ease the base into the soil.
   
   

   Data from the chamber comes from the LI-7810 CH₄/CO₂ Trace Gas Analyzer, based on the OF-CEAS (Optical Feedback-Cavity Enhanced Absorption Spectroscopy) .

   The instrument increases the laser drive current so that the laser scans the wavelength range across the absorption characteristics of the gas. It is a basic open system, where air is supplied to the gas analyzer by an external pump (Figure2.). Air inlet and outlet are connected to the chamber. LI-7810 can make a local wireless network to transmit data when Wi-Fi is enabled. CO2 measurements range from 0 to 10,000 ppm and H2O measurements range from 0 to 60,000 ppm.