Submitted to: Annals Of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 15, 2001
Publication Date: June 1, 2001
Interpretive Summary: Understanding of root development is an important challenge for crop simulation. Soil factors affecting root development have to be quantified to provide a reliable basis for soil management to improve crop production. A hypothesis has been proposed which treats root proliferation as a resultant of convective and dispersive processes. The dispersive process is driven by gradients in root density whereas the convective process is caused by the geotropism. Both processes may be enhanced or mitigated by the availability of soil water, soil density, nutrient concentrations. This hypothesis results in a model of root redistribution in soils that is mathematically similar to models of water and solute transport in soil. A greenhouse experiment was performed to test this hypothesis, and the model was used to simulate the root development in this experiment. The model explained approximately 75 percent of the variation in root concentration measured in the experiments. Root diffusivity depended on root density. The geotropic root development was not observed. Root growth rates did not depend on root density. The convective-dispersive model of two-dimensional root growth and proliferation models is a promising component for crop simulators which will lead to the increase in reliability of crop modeling for decision support in production agriculture.
Soil, water, solute, heat, and gas transport processes are often simulated with convective-dispersive or diffusion-type equations. These models must be coupled with a root activity model to simulate plant development. To make such coupling easier, a generic convective-dispersive model of root growth and proliferation is proposed. The sub models of root growth rate and root convective and dispersive propagation rates are built so that statistical hypothesis testing could be used to reject a hypothesis on dependence of the rates on root and soil variables. The objective of this work is to test this model with corn plants grown in pots where walls and a bottom provided mechanical restrictions to the root growth. Treatments included ordinary and doubled fertilization and irrigation amounts. Plant development was monitored weekly by destructive sampling for 45 days after emergence. Root concentrations were determined in 24 sections of the pots along with the shoot parameters. The modular soil and root process simulator 2DSOIL was used to simulate root development. The model explained 73 to 77 percent of the variation in the value of the logarithm of the root concentration measured in the experiments. The hypothesis that root diffusivity does not depend on root concentration could be rejected, whereas, the hypotheses about the absence of the geotropic root development and decrease of the root growth rate with the growth of root concentration could not be rejected.