Using different versions of the Rothamsted Carbon model to simulate soil carbon in long-term experimental plots subjected to paddy–upland rotation in Japan

Abstract

We validated the Rothamsted Carbon (RothC) model against 14 experimental plots subjected to different paddy-upland rotation patterns, including continuous paddy rice cropping and different periods (short, medium, and long term) of upland conversion, in Akita prefecture, northern Japan. We ran the model using the original version of the RothC model, the paddy-soil version of the RothC model (which uses a reduced carbon decomposition rate), and alternating the use of the original and the paddy-soil versions for years with summer upland cropping and paddy rice cropping, respectively. The best simulation pattern was provided by the alternate use of the two versions. In comparison with the original RothC model, alternate use of the two versions showed a smaller root mean square error in all experimental plots and a smaller absolute value of the mean difference in 10 plots with continuous paddy rice cropping and short-and medium-term upland conversion. Alternate use of the two versions had a lower root mean square error and lower absolute value of the mean difference in long-term upland conversion plots compared to the values for the paddy-soil version and showed better performance than the paddy-soil version when straw was applied. The model performance from alternating use of the two versions compared well with the performance reported in previous studies. Alternating the use of the two model versions provides a good technique for simulating changes in soil organic carbon with time, even with a paddy-upland rotation pattern. In addition, this technique will enable a more accurate inventory of Japanese greenhouse gases and help land managers better manage soil fertility in a paddy-upland rotation system.

Effect of the long-term application of organic matter on soil carbon accumulation and GHG emissions from a rice paddy field in a cool-temperate region, Japan-II. Effect of different compost applications-

“…Accumulation of organic matter (i.e., carbon and nitrogen) in paddy soils is important from the perspective of responding to climate change and maintaining crop productivity (details are described in Takakai et al 2019, in this issue). Long-term application of organic matter to paddy fields increases carbon storage in the soil (e.g., Cheng et al 2016;Shirato, Yagasaki, and Nishida 2011;Sumida, Kato, and Nishida 2005;Yokozawa et al 2010). In order to quantitatively evaluate the effects of long-term application of organic matter on soil carbon storage, it is effective to use fields with long-term experiments on continuous cropping that have been conducted in various parts of Japan (Kanamori 2000).…”

Assessment on the rates and potentials of soil organic carbon sequestration in agricultural lands in Japan using a process-based model and spatially explicit land-use change inventories – Part 2: Future potentials

“…Furthermore, predictive power of RothC_p application for paddy fields needs further validation and refinement, as this subversion of RothC model, employing additional parameters to adjust SOC decomposition rate under submerged and drained yet rather moist soil conditions by simple tuning, has been tested with data from only a limited numbers of longterm field experiments at this stage (Shirato and Yokozawa, 2005;Shirato et al, 2011). As paddy fields have been holding one of the largest area is among all land-use types in agricultural lands in Japan, even relatively small changes in prediction on the rate of SOC stock change per unit area basis in this land-use category may exert large impact on overall figure of country level estimation of SOC stock change.…”

“…In order to support the decision making of policy makers at local or central governmental level and implementation of SOC sequestration on agricultural lands, it is essential to develop measures that enable them to provide a reliable estimation on future potential of SOC sequestration at large spatial scale. So far, previous studies have demonstrated that application of currently available process-based models of SOC turn-over is an effective approach to estimate temporal changes in SOC stock over several decades or centuries (Jenkinson et al, 1990;Kelly et al, 1997;McGill, 1996;Shirato and Yokozawa, 2005;Shirato et al, 2004;Skjemstad et al, 2004). In many of those studies, validation of the model was conducted based on observed changes in SOC stock in long-term field experiments, in which the rate of organic matter application to soils or soil initial conditions, key parameters determining SOC stock change, have had been known or well identified.…”

Decline in Fertility of Paddy Soils Induced by Paddy Rice and Upland Soybean Rotation, and Measures against the Decline

“…For instance, the effects of poultry manure compost and swine manure compost on soil N fertility in paddy-upland rotation have yet to be elucidated. It was reported that different versions of the Rothamsted Carbon model could simulate soil carbon dynamics in paddyupland rotations (Shirato et al 2011). The development of a dynamic model of available soil N in paddy-upland rotation would greatly improve the understanding and management of soil N fertility.…”