The impact of crop growth sub-model choice on simulated water and nitrogen balances

It is the aim of this study to analyse how different crop growth model routines affect the simulation of water flow and nitrogen transport of a crop rotation in agricultural fields. The model system Expert-N is briefly described and used to test the crop growth sub-models against data of a six-year field experiment on sandy soils. Expert-N is a modular soil-plant-atmosphere model system, which comprises different sub-models to simulate one-dimensional vertical transport of water, solute and heat in the unsaturated zone. It includes several sub-models to describe organic matter turnover and has three generic crop growth sub-models. The latter are derived from the crop models CERES, SPASS and SUCROS. Simulations were performed using the different sub-models for each of the cereal crops in the sugar beet, winter wheat, winter barley, winter rye crop rotation. Results show the impact of crop model choice on simulated water balances and turnover of C and N. It is concluded that the simulation of root growth and plant residue mineralisation needs some improvement.