Application of the RothC model to the results of long-term experiments on typical upland soils in northern China L. Guo 1 , P. Falloon 2 , K. Coleman 3 , B. Zhou 4 , Y. Li 1 , E. Lin 1 & F. Zhang 5 1 Institute of Agro-Environment and Sustainable Development, Chinese Academy of Agricultural Sciences, Beijing 100081, China, 2 Meteorological Office – Hadley Centre for Climate Prediction and Research, Fitzroy Road, Exeter Devon EX1 3PB, UK, 3 Agricul- ture & Environment Division, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK, 4 Heilongjiang Academy of Agricultural Sci- ences, Haerbin 150000, China, and 5 Department of Plant Nutrition, China Agricultural University, Beijing 100094, China Abstract Arable land can be either a source or a sink for atmospheric carbon dioxide depending on its manage- ment. It is important to assess changes in soil organic carbon (SOC) under future climate change sce- narios using models at regional or global scales. This paper aims to calibrate the RothC model on non-waterlogged soils in northern China to obtain the necessary model input parameters for later use in large-scale studies. Data sets from three long-term experiments in northern China were used to evaluate the performance of the RothC soil carbon turnover model. The plant carbon input rate, an important model input parameter, was calibrated using experimental data under typical rotation sys- tems with different fertilization. The results showed that RothC accurately simulated the changes in SOC across a wide area of northern China (northeast, north, and northwest China. The modelling error expressed as root mean square error for four treatments (nil, manure, fertilizer, fertil- izer + manure) at three sites were less than 20.2%, and less than 7.8% if occasional extreme measured values were omitted. The simulation biases expressed as M (i.e. relative error) for all treatments at the three sites were non-significant. Observed trends in SOC included a decrease for the nil (no fertilizer or manure) treatment and an increase for the treatments which received both manure and fertilizers. The experiments also indicated that manures applied at an appropriate rate were more effective in increasing or maintaining SOC than fertilizers which were more effective in increasing crop yields. Keywords: RothC model, model performance, soil organic carbon, long-term experiment, northern China Introduction The content of soil organic carbon (SOC) is one of the most important indices of soil productivity. Depending on man- agement, soil can either emit CO 2 or sequester carbon. Appropriate soil management can both improve soil produc- tivity and reduce the decomposition of SOC, thus reducing emissions of CO 2 to the atmosphere. Soil organic matter (SOM) turnover models are being used to assess the regional or global dynamics of SOC (Jenkinson et al., 1991; Parton et al., 1993; Falloon et al., 1998b, 2002; Falloon & Smith, 2002). It is therefore important to test these models using data sets from long-term experiments covering the soil types, climate and land uses of the region under study. The current version of RothC (RothC 26.3; Coleman & Jenkinson, 1996) is one of the most widely used SOM turnover models. RothC was developed using data from the Rothamsted long-term experiments in England (Jenkinson & Rayner, 1977; Jenkin- son et al., 1987), and has been extended for application to other environments including various cropland, grassland and forest soils (Jenkinson et al., 1992, 1999; Coleman et al., 1997; Smith et al., 1997). The RothC model has been cali- brated in Australia (Skjemstad et al., 2004), America, Europe (Smith et al., 1997; Falloon & Smith, 2002), New Zealand (Parshotam et al., 1995), and Japan (Shirato & Taniyama, 2003). A number of other SOM models such as Century (Parton et al., 1987), DAISY (Hansen et al., 1991; Mueller et al., 1996), Candy (Franko et al., 1995), DNDC (Li et al., 1992), NCSoil (Molina et al., 1983; Nicolardot et al., 1994), QSoil (Bosatta & Agren, 1985), VVV (Verberne, 1992), etc. have Correspondence: L. Guo. E-mail: lpg_mail@yahoo.com Received April 2006; accepted after revision August 2006 Soil Use and Management, March 2007, 23, 63–70 doi: 10.1111/j.1475-2743.2006.00056.x ª 2006 The Authors. Journal compilation ª 2006 British Society of Soil Science 63