北海道大学 大学院農学院 修士論文発表会，2017 年 2 月 7 日

Effect of Renovation on Greenhouse Gas Emissions in a ManagedGrassland
環境資源学専攻 地域環境学講座

土壌学 Vecky D Kuswandora

1. Introduction
Renovation practices effect on greenhouse gas (GHG) emissions need to be evaluated forsustainable land management and protecting the environmental quality. Soil disturbance during
renovation and tillage incorporation with residue may increase GHG emissions (Prior et al.,
2000; Reicosky and Lindstrom, 1993). Since the state of tillage method and residue
management can be considered to be different depending on the different renovation method,
therefore this study were to investigate the effects of renovation practices on soil GHG
emissions in a managed grassland, to evaluate the effects of renovation practices related toenvironment factors to soil GHG emissions, and to assess the greenhouse gas intensity (GHGI)
expressed as Global Warming Potential (GWP) per unit crop yield in order to provide data that
could contribute to decision-making for sustainable agricultural practices.
2. Materials and Methods
The study was conducted in a managed grassland with Timothy grass (Phleum pretense L.) as
main species at Shizunai Experimental Livestock Farm of the Field Science center for theNorthern Biosphere, Hokkaido University, Japan. Six different tillage treatments under splitplot design with three replications were established on 1 September 2015: No tillage plot (NT),strip-tillage (ST), shallow tillage-15 cm depth with residue (T15+) and without residue (T15-),
deep tillage-30 cm depth with residue (T30+) and without residue (T30-). All plots were
sprayed by herbicide on 25 August 2015 and seeded on 3 September 2015. The amount ofresidue input was 1.14 Mg C ha-1. CO2, CH4 and N2O fluxes were measured by closed chamber
method. CO2 emissions from bare plot and planting plot in each treatment were defined as
microbial respiration (Rh) and soil respiration (Rs), respectively.
3. Results and discussion
Rs from all treatment plots were relatively high in early period immediately after tillage
operations. The Rs rate ranged from -0.88 to 424.36 mg C m-2 h-1. Both the lowest and highest
Rs rates were observed at NT. The lowest flux was recorded in February, coinciding with thelowest soil temperatures, while the highest Rs occurred on 15 August 2016. A significantcorrelation (P<0.01) was observed between Rs and soil temperature. Rs and Rh showed similarseasonal patterns. Rh rate ranged from -0.88 to 405.78 mg C m-2 h-1. Annual cumulative carbon
among the tillage methods did not differ from Rs but significantly different from Rh. Annual
Rh was T15+> T30+> NR > ST= NT (p <0.01). CH4 fluxes ranged from -421.22 to 370.89 µg
C m-2 h-1. Tillage method significantly enhanced annual CH4 uptake (p<0.05). The amount ofannual CH4 uptake was T30+ = T15+ = NR = ST > NT. N2O fluxes ranged from -166.46 to2416.62 µg N m-2 h-1. The peak of N2O fluxes were observed in all renovation plots immediately
after renovation operations, and in all treatments within 9 days after fertilization. Annual N2Oemissions were not significantly different among the treatments, but there was a tendency of
NR> T15+> T15–> NT> ST> T30–> T30+. The GWP tended to be higher at T15–, T30–, T15+
and T30+ than NR and lower at ST and NT. The difference in total gas emissions was due tothe difference in CO2 emissions. Total yield biomass was highest in NR (8.20 Mg ha-1 yr-1)
followed by T15+ (5.78 Mg ha-1 yr-1) and lowest in NT (4.77 Mg ha-1 yr-1).
4. Conclusions
Even though T15+ tended to have high GWP, T15+ was also produce significantly high totalyield, so that resulted in low value of GHGI. This results suggest that adopted T15+ forgrassland renovation could be expected to produce high yield and reduce GHG emissions.