Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. IX. Simulation of soil carbon and nitrogen pools using CENTURY model

Abstract

Cultivation and cropping of soils results in a decline in soil organic carbon and soil nitrogen, and can lead to reduced crop yields. The CENTURY model was used to simulate the effects of continuous cultivation and cereal cropping on total soil organic matter (C and N), carbon pools, nitrogen mineralisation, and crop yield from 6 locations in southern Queensland. The model was calibrated for each replicate from the original datasets, allowing comparisons for each replicate rather than site averages. The CENTURY model was able to satisfactorily predict the impact of long-term cultivation and cereal cropping on total organic carbon, but was less successful in simulating the different fractions and nitrogen mineralisation. The model firstly over-predicted the initial (pre-cropping) soil carbon and nitrogen concentration of the sites. To account for the unique shrinking and swelling characteristics of the Vertosol soils, the default annual decomposition rates of the slow and passive carbon pools were doubled, and then the model accurately predicted initial conditions. The ability of the model to predict carbon pool fractions varied, demonstrating the difficulty inherent in predicting the size of these conceptual pools. The strength of the model lies in the ability to closely predict the starting soil organic matter conditions, and the ability to predict the impact of clearing, cultivation, fertiliser application, and continuous cropping on total soil carbon and nitrogen.

Modeling nitrous oxide emissions from irrigated agriculture: testing DayCent with high‐frequency measurements

“…However, at this study site, the soil is a self-mulching vertisol, which shrinks and swells considerably during wetting and drying phases, resulting in significant pedoturbation and increased soil carbon and nitrogen turnover rates. These shrinking and swelling soils are thus an exception to the widely observed relationship between organic C and clay content and annual decomposition rates are significantly higher than those of non-vertisol soils with similar clay content (Chilcott et al 2007). Accordingly, we increased the inherent decay rate of the passive soil organic matter pool by a factor of three in order to realistically represent the observed low C values in this soil (;1.55%).…”

Soil carbon change and its responses to agricultural practices in Australian agro-ecosystems: A review and synthesis

“…In Australia, the CENTURY model was used to model continuous cultivation and cereal cropping systems (Carter et al, 1993;Chilcott et al, 2007) and was found to satisfactorily predict the impact of long-term cultivation and cereal cropping on total organic C as well as other related attributes. Models have been used to assess soil C dynamics under future climate change, such as CO 2 increase, warming, rainfall variability and their combination elsewhere.…”

Adding ecosystem function to agent-based land use models

“…The model has been used to simulate ecosystem dynamics for over 40 long-term experiment stations (Paustian et al 1992, 1996; Parton and Rasmussen 1994; Probert et al 1995; Kelly et al 1997; Cerri et al 2004; Chilcott, Dalal, Parton, Carter, and King 2007) in both tropical and temperate systems. These sites typically have extensive data sets on the cropping rotations, cultivation practices, organic and inorganic inputs, and harvest practices during the experimental periods.…”