Modelling approaches of soil organic matter turnover within the CANDY system

Abstract

The development of the CANDY system (CArbon and Nitrogen DYnamics) has been based on experience of organic matter turnover and nitrogen dynamics gained over a long period, a major part of the scientific work in Bad Lauchstädt. The main objective in developing the model was to give farmers a tool for calculating short term dynamics of nitrogen transformations and long term changes in the carbon content of the soil. For this reason the system consists of a database interface and several model components. The main component is the CANDY module, written in TURBO - PASCAL which calculates daily changes of water, temperature, carbon and nitrogen for a 2 m deep soil profile. Alongside this daily-timestep nitrogen simulation, there is a long term carbon module that calculates the amount of decomposable carbon in steady state for a given crop rotation. The calculation is specific to the site and management practices and is based on averaged turnover conditions, yields and inputs of organic material.