Assessment of soil organic carbon dynamics under long-term rice cultivation in Thailand

Transcription

1 Assessment of soil organic carbon dynamics under long-term rice cultivation in Thailand Nittaya Cha-un,,3, Amnat Chidthaisong,,3, Sirintornthep Towprayoon,,3,* The Joint Graduate School of Energy and Environment (JGSEE), King Mongkut s University of Technology Thonburi, Bangkok, Thailand, Prachauthit Rd, Bangmod, Tungkru, Bangkok, Thailand Center of Excellence on Energy Technology and Environment, PERDO, Ministry of Education, Bangkok, Thailand 3 Earth System Science Research and Development Center (ESS), King Mongkut s University of Technology Thonburi, Bangkok, Thailand, Prachauthit Rd, Bangmod, Tungkru, Bangkok, Thailand Abstract: Thailand is an agriculture-based country with almost % of arable land is used for rice cultivation. Soil organic carbon (SOC) is the one of the most important parameters to support healthy soil and rice productivity. This study aims to simulate long-term SOC variation ( years) under the different groups of major trade rice varieties in Thailand using DNDC model. The groups and rice varieties include ) Jasmine rice (Khao Dawk Mali ()), ) Fragrant rice (Patum Thani ()), 3) White rice (Suphan Buri (SPR )), ) Glutinous rice (Kao Khao ()), and ) Parboiled rice (Chainat (CNT )). The data sets of daily climate, soil properties, and rice management practices were input in the model. The simulation results showed that the changes in the SOC contents with time simulated -year spinup (99-) agreed well with the observation year () in sites from rice varieties. In long-term -year continuous simulation (99- ), the double irrigated rice cropping (PTT, SRP and CNT) in Central region show more SOC sequestration potentials than single rain-fed rice cropping ( and ) in Northeast region. Double crop cultivation practice in Northeast region may be the one of rice management options in order to maintain and increase SOC sequestration in the long-term. Keywords: Soil organic carbon; SOC dynamic; Soil carbon sequestration; Rice cultivation; Thai rice variety, DNDC model * Corresponding author. Tel.: :, Fax: address: sirin@jgsee.kmutt.ac.th. Introduction Rice is the main food crop for half of the world s population, and about 9% of the world s rice is produced in Asia (GRiSP, 3). Thailand is an agriculture-based country, where about 9% of farm land is used for rice cultivation. In Thailand, rice is the most important crop grown, and a major export crop in the world market (TREA, ). The different management practices in rice field such as water flooding/drainage, fertilizer application and other crop rotation are known to be the important factor for soil carbon sequestration and greenhouse gas emissions (Cai et al., 997; Cha-un et al., 7; Towprayoon et al., ). Foreseen future climate change associated with rising air temperature due to increasing atmospheric carbon dioxide (CO) are expected to increase methane (CH) emission and rice production (Van Groenige et al., 3). In addition, future climate change also affects the dynamic of soil organic carbon (SOC) which is an important factor in controlling rice productivity (Lal, ; Yan et al., ). The DNDC model is a computer simulation based on biogeochemical processes that has been developed for predicting carbon and nitrogen cycling in agro-ecosystems (Li et al., 99). This model is usually used for estimating SOC storage. Tang et al. () successfully estimated SOC storage and identified its changing trends under current cropping systems in Chinese cropland. DNDC model is also used to simulate long-term SOC dynamics under different management conditions in rice field (Mu et al., ; Shirato, ; Wang et al., ), but only a few have studied from Thai rice cultivation under different rice varieties. In these study we therefore have tried to simulate SOC in paddy field soil grown with different varieties, as it is known that field management of each rice variety may be different and thus this would affect SOC.

2 . Material and methods. Investigation of trade rice varieties In this study, rice varieties and study sites were selected from the annual crop data from Rice Department (RD) and Department of Agricultural Extension in. The groups of rice varieties in this study were based on the amount consumed and exported. These included; (Fig. ); ) Jasmine rice (Hom Mali rice): Khao Dawk Mali () ) Fragrant rice (Hom Pathum): Patum Thani () 3) White rice: Suphan Buri (SPR ) ) Glutinous rice: Kao Khao () ) Parboiled rice: Chainat (CNT ) Lower North & Central Hom Pathum rice Upper Northeast Glutinous rice Lower North & Central White rice SPR, CNT Lower Northeast Hom Mali rice Fig. The groups of rice varieties in different rice sub-ecosystem in Thailand. Site locations The selected provinces for this study were considered from the accumulative cultivation area which is more than % for each rice variety cultivation area. The lists of five rice varieties and study sites are listed in follows;. ) ( provinces): Ubon Ratchathani, Nakhon Ratchasima, Srisaket, Roi-et, Buriram, Surin, Yasothon and Amnat Charoen ) ( provinces): Khon Kaen, Sakon Nakhon, Udon Thani, Kalasin and Maha Sarakham 3) ( provinces): Uttaradit, Chai Nat, Suphan Buri and Ang Thong ) SPR ( provinces): Nakhon Sawan, Ratchaburi, Saraburi and Kanchanaburi ) CNT (3 provinces): Phetchabun, Nakhon Sawan and Chai Nat.3 DNDC model.3. Data collection and simulation This study implemented the DNDC model, version 9 in site mode (open source, downloaded from for long-term simulation of SOC dynamic. The model requires climate data such as daily maximum and minimum air temperatures, and rainfall. This study performed a - year spin-up from 99 to and a -year projection from to for each site using the adjusted model and the generated continuous -year daily weather data. Daily weather data were obtained from the Thailand Meteorological Department (TMD) station nearest to each site (< km)

3 for the previous and observation years. As for the future projection (7-), the daily climate data were obtained from PRECIS regional climate model, ECHAM SRES B. The locations of study site and weather station from TMD are shown in Fig.. Fig. Locations of study site and TMD weather station site The soil properties were compiled from Land Develop Department (LDD), which included soil texture, clay fraction, bulk density, ph and soil organic carbon. The crop calendar and field management practices for each site were compiled from the government published reports, supplemented data from Rice Department (RD), Office of Agricultural Economics (OAE) and Department of Agricultural Extension (DOAE). Bases on this information, and are photosensitive rice varieties, farmers therefore grow single rice cropping even in the wet season. While,, SRP and CNT are non-photosensitive rice varieties, there are adopted for double rice cropping system..3. Data analysis For multi-site simulation, simulated SOC contents at the target year () were compared with the observed data at each site. The R and the normalized root mean square error (NRMSE) were used in order to evaluate the goodness of fit and model performance (Katayanagi et al., 3). 3. Results and discussion 3. Model performance for multi-site simulation The spin-up was performed for a period of years from 99 to with continuous climate and weather observation data, and fixed crop calendar and crop management practices. At the target year (), simulated SOC contents were not significantly different from the observed values at all sites (Fig. 3). The relationship between observed SOC contents and simulated ones were significantly positive correlation. Moreover, simulated SOC contents in single rain-fed rice of and (R =.9, NRMSE=.; Fig. 3a) were better agreed with observation than those in double irrigation rice of, SPR and CNT (R =., NRMSE=.7; Fig. 3b). This results can be explained by the different soil properties (texture, clay fraction and initial SOC contents) and conventional practices of rice management and water regime for each location, which had influence on SOC dynamics (Shirato, ). 3

4 Observed and Simulated SOC contents and at year Observed Simulated Observed vs simulated SOC contents Simulated SOC content (g C kg-) SOC (g C kg-) Sim =.93 Obs P <. R =.9 NRMSE =. Observed SOC content (g C kg-) (a) and Observed and Simulated SOC contents PTT, SPR and CNT at year Observed vs simulated SOC contents Observed Simulated Simulated SOC content (g C kg-) SOC (g C kg-) Sim =. Obs P <. R =. NRMSE =.7 Observed SOC content (g C kg-) (b) PTT, SRP and CNT Fig. 3 Comparison and relationship between obsereved and simulation values at observed year for (a) and, and (b) PTT, SRP and CNT rice varieties. The broken line indicates the result of linear regression with a y-intercept of zero. 3. Long-term simulation under the different rice verities The effect of conventional practices of single rain-fed rice ( and ) and double irrigated rice (, SRP and CNT ) on the simulated SOC stock was consistent throughout the -year simulation (Fig. ). The simulated SOC stock gradually increased during the simulation period. This long-term simulated results clearly indicate that double irrigated rice practices of, SRP and CNT were high in SOC sequestration potential. On the other hand, single rain-fed rice practices ( and ) are not only losing SOC sequestration in long-term. stock for CNT SRP SOC stock ( tonc ha-) SOC stock ( tonc ha-) Fig. Annual variation of SOC the SRP CNT SRP CNT SRP the fiverice varieties under conventional practices from 99 to simulation period SOC stock ( tonc ha-) SOC stock ( tonc ha-) SOC stock ( tonc ha-) SOC stock ( tonc ha-) CNT SRP during

5 . Conclusion Overall, the SOC dynamics changes with time and the simulated results by DNDC model agreed well with the observation at all sites from rice varieties. We performed a long-term simulations using the DNDC model to test the future status of SOC storage in the field of major trade rice varieties in Thailand in order to find management option to improve SOC sequestration and soil fertility. In longterm -year continuous simulation (99- ), the double irrigated rice cropping (PTT, SRP and CNT) in Central region would have more SOC sequestration than single rain-fed rice cropping ( and ) in Northeast region. This result can be suggested that double crop cultivation practice in Northeast region is the one of rice management option in order to maintain and increase SOC sequestration in the long-term. Acknowledgement Funding in this study are partly supported by ESS-KMUTT, IRN-TRF and CTI-PERDO for financial support. We also would like to thanks Dr. Chitnucha Buddhaboon and Ms. Benjamas Rodsopha from Rice Department (RD) for their data support. References Cai, Z., Xing, G., Yan, X., Xu, H., Tsuruta, H., Yagi, K. and Minami, K Methane and nitrous oxide emissions from rice paddy fields as affected by nitrogen fertilisers and water management. Plant and Soil, 9, 7-. Cha-un, N., Chidthaisong, A., Yagi, K., Sudo, S. and Towprayoon, S. 7. Greenhouse gas emissions, soil carbon sequestration and crop yields in a rain-fed rice field with crop rotation management. Agriculture, Ecosystems & Environment, 37(), 9-. GRiSP. 3. Rice Almanac. Fourth ed. International Rice Research Institute. Los Baños, Philippines, 3 p. Katayanagi, N., Ono, K., Fumoto, T., Mano, M., Miyata, A. and Hayashi, K. 3. Validation of the DNDC-Rice model to discover problems in evaluating the nitrogen balance at a paddy field for single-cropping of rice. Nutrient Cycling in Agroecosystems, 9(), -. Lal, R.. Soil carbon sequestration impacts on global climate change and food security. Science 3, 3-7. Li, C., Frolking, S. and Harriss, R.99. Modeling carbon biogeochemistry in agricultural soils. Global Biogeochemical Cycles, (3), 37-. Mu, L., Liang, Y., Xue, Q., Chen, C. and Lin, X.. Using the DNDC model to compare soil organic carbon dynamics under different crop rotation and fertilizer strategies, Spanish. Journal of Agricultural Research, (), -7. Shirato, Y.. Testing the suitability of the DNDC Model for simulating Long-term soil organic carbon dynamics in Japanese paddy soils. Soil Science and Plant Nutrients, (), 3-9. Tang, H., Qiu, J., Ranst, E.V. and Li, C.. Estimations of soil organic carbon storage in cropland of China based on DNDC model. Geoderma, 3, -. Towprayoon, S., Smakgahn, K. and Poonkaew, S.. Mitigation of methane and nitrous oxide emissions from drained irrigated rice fields. Chemosphere, 9, 7-. TREA.. Thai rice situation and trend -. Thai rice exporters association (in Thai) [Online]. Available at: Van Groenigen, K.J., Van Kessel, C. and Hungate, B.A. 3. Increased greenhouse gas intensity of rice production under future atmospheric condition. Nat. Clim. Change, 3, -9. Wang, L., Qiu, J., Tang, H., Li, H., Li, C. and Ranst, E.V.. Modelling soil organic carbon dynamics in the major agricultural regions of China. Geoderma, 7, 7-. Yan, X., Yagi, K., Akiyama, H. and Akimoto, H.. Statistical analysis of the major variables controlling methane emission from rice fields. Glob. Change. Biol.,, 3-.