Tillage is an important procedure for modifying the soil environment to enhance crop growth and conserve soil and water resources.CSM simulates tillage and related field operations for single seasons or multiple years. The approach is based on procedures first developed by Dadoun (1993) as the CERES-Till model for maize and refined by Andales et al. (2000) for the CROPGRO-Soybean model.
The processes considered include effects of crop residues on the soil surface and on chemical and physical properties that vary with soil depth. Each event is described by date and implement used. The implement is characterized by its effects on soil properties, including mixing of soil layers and crop residues and changes in soil bulk density.
From a modeling viewpoint, a key issue was how to manage different spatial and time scales. The soil is simulated as varying only with depth but in reality, the thickness of the soil is affected by tillage. This poses challenges for ensuring that the masses for water, nutrients, residues and the soil per se are conserved as soil layers are mixed and the density of each layer is altered. The model runs on a daily time step, but events such as tillage, application of residue, and irrigation can all happen within a single day and the sequence/timing can influence simulations.
As an example, effects of four implements (moldboard plow, tandem disk, tine harrow, and planking were simulated for a field experiment where winter wheat was grown with different tillage and residue management practices (White et al., 2010).
Simulated effects of tillage are heavily dependent on the specified effects of an operation on soil mixing and bulk density. Another area where further research is needed is the estimation of kinetic energy of rainfall or sprinkler irrigation, which cause soil settling (increase bulk density).
Andales, A.A., Batchelor, W.D., Anderson, C.E., 2000. Incorporating tillage effects into a soybean model. Agricultural Systems 66, 69-98.
Dadoun FA (1993) Modeling tillage effects on soil physical properties and maize (Zea mays L.) development and growth. Unpublished Ph.D. thesis, Michigan State University, MI
White, J.W., Jones, J.W., Porter, C., McMaster, G.S., Sommer, R., 2010. Issues of spatial and temporal scale in modeling the effects of field operations on soil properties. Operational Research 10, 279-299.