Evaluating the Century C model using two long-term fertilizer trials representing humid and semi-arid sites from India

Two long-term fertilizer experiments (LTFE) datasets were used to evaluate the performance of the Century ecosystem model in contrasting regions of India viz Mohanpur (humid) and Akola (semi-arid) with mean annual rainfall of 1619 mm and 793 mm, respectively. Mohanpur grew rice and wheat in rotation for 19 years since 1986. Akola grew sorghum and wheat in rotation for 9 years since 1988. Both these experiments involved treatments with different doses of inorganic (fertilizer) and organic (farm yard manure, paddy straw, and green manure) inputs. The model closely resembled measured SOC level for all the treatments in Mohanpur LTFE. For Akola, it tended to overestimate treatment effects at the end of the experimental period. At the humid site (Mohanpur) modelled data simulated measured data reasonably well for all treatments, with control and treatments with fertilizer alone and in combination with organic inputs showing the best agreement (RMSE 1–3). At the semi-arid site Century performed well for the early years, but lower during the end of the experiment. The comparison between measured and modelled yields for the three crops (rice, wheat and sorghum) showed a reasonably good correlation (r = 0.8).

Research highlights▶ Century C model was evaluated in the two long-term fertilizer experimental sites which represent typical soils with special reference to high clay shrink-swell soils (Vertisols) ▶ To suit the requirements of the model the crop files were modified for the Indo-Gangetic Plains (IGP) and the Black Soil Region (BSR) ▶ At the Semi-arid site (Vertisols, BSR) Century performed well for the early years, as compared to the result during the end of the experiment. ▶ The model closely resembled measured SOC level for all the treatments in the IGP site. ▶ For high clay soil site (BSR), the model tended to overestimate treatment effects. ▶ More datasets will be necessary on soil-clay moisture relation vis-a-vis the availability of moisture in the Vertisols for requirement of model simulations.