Sang Yoon Kim 1) , Jessie Gutierrez 1) , and Pil Joo Kim 1,2)*

1. Increase of CH4 emission in No-tillage Paddy Soil during Rice Cultivation Sang Yoon Kim1), Jessie Gutierrez1), and Pil Joo Kim1,2)* 1Division of Applied Life Science (BK 21 program), Graduate School, Gyeongsang National University, Jinju, 660-701, South Korea, soilmethane@gmail.com 2Institute of Agriculture and Life Sciences, Gyeongsang National University , Jinju, 660-701, South Korea, pjkim@gnu.ac.kr Research background Results and Discussions Recently, no-till systems (NT) have been used in paddy field in some eastern Asian countries and several studies were carried out to investigate the relationship between methane emission and tillage management. Most of previous studies reported that seasonal CH4 fluxes were decreased by more than 50% due to reduced mineralization of organic matter in NT soils. However, long-term NT might stimulate more CH4 emission during rice cultivation due to increased accumulation of total organic carbon in paddy soil. Fig. 1. Changes of CH4 emission patterns in paddy soil during rice cultivation as influenced by conventional tillage and no-tillage in different tillage year. Objectives Table 1. Physical and chemical properties of paddy soil in conventional tillage(CT) and no tillage (NT) cultivation systems at rice harvest in 2nd and 5th in, respectively The objective of this study was to determine the effect of two different tillage systems : conventional tillage (CT) and no-tillage (NT) on CH4 emissions in paddy soil during rice cultivation. Materials and Methods Experimental site description 1. Investigation site • GNU Ricefield Experimental Plot , Jinju City, Korea 2. Rice cultivation and fertilization background • Cultivar: Dongjinbyeo (Oryza sativa L. Japonica) • Fertilization : N-P2O5-K2O = 90-45-58 kg ha -1 3. CH4 gas sampling and analysis • Gas sampling : Closed chamber method at 10:30 AM for 30 minutes twice in a week • Gas chromatography (Shimadzu, GC2010 with FID) 4. Methanogenic activity • Soil sampling: 35DAT and 70DAT soil sample • Total DNA extraction by Fast DNA SPIN Kit (MP Bio) • Real time PCR condition for mcrA gene analysis - Methanogens: 95oC for 5 min, 40 cycles at 94oC for 45 sec, 55oC for 45 sec and 72oC for 45 sec - Primer selection • Methanogens (ML-F/ML-R) 5. Soil chemical properties and plant growth characteristics • Soil sampling: harvesting stage • Soil physical and chemical properties - Bulk density, porosity, total C, hot H2O-extractable C • Plant growth and yield characteristics - Plant height, tiller number, straw yield and rice yield Fig. 2. Total CH4 flux during rice cultivation as influenced by conventional tillage and no-tillage in different tillage year. Fig. 3. Changes of total and hot water-extractable C concentrations during rice cultivation in soil in the 5th year after installation. Fig. 4. Changes of mcrA gene copy number at different rice growing stage in the 2nd and 5th year after installation. Conclusions ML-F: GGT GGT GTM GGA TTC ACA CAR TAY GCW ACA GC • Conventional tillage system could significantly affect CH4 emission. In contrast, no-tillage reduced CH4 emission during rice cultivation only in a short term period. • Aside from the improvement of soil physical properties, continued no-tillage practice was more effective than conventional tillage to accumulate more organic matter in soil. • Increased accumulation of soil organic carbon may had provided more methanogenic substrates as hot water extractable C that enhanced more methanogenic activity during rice cultivation and increased CH4 emission. • Long-term no-tillage investigations are needed to firmly establish the other factors for the occurrence of higher CH4 emissions with no-tillage practices in paddy soils. ML-R: TTC ATT GCR TAG TTW GGR TAG TT