Simulating Root Density Dynamics and Nitrogen Uptake – Can a Simple Approach be Sufficient?

The modeling of root growth in many plant–soil models is simple and with few possibilities to adapt simulated root proliferation and depth distribution to that actually found with different crop species. Here we propose a root model, developed to describe root growth, root density and nitrogen uptake. The model focuses on annual crops, and attempts to model root growth of different crop species and row crops and its significance for nitrogen uptake from different parts of the soil volume. The presented model was built on a simple approach, however with the capacity to simulate different root distribution patterns by changing only one parameter, namely a root form factor which controls the root density in different soil layers. Root density is calculated by a modification of the Gerwitz and Page (1974) equation for root length density, in their approach root density at the bottom of the root zone was set to a fixed value whereas the root form parameter changes during the growth season. We set a fixed value for the root form parameter for root density distribution and let the root density at rooting depth be variable. In Figure 1 the root model flexibility is illustrated. The figure shows a situation where all parameters are equal except the form factor value (az). By changing the form factor from 0 to