Group: Tillage (G 01)

Many tillage operations perform several physical processes as they modify the soil and surface condition (e.g., loosening the soil, mixing soil properties within the tillage zone, burial of residue, etc.). All of these physical processes require some information that is common among them. These "shared" parameter values, like tillage depth, surface area disturbed, etc., have been grouped together into a single "group" line so that they don’t have to be specified repeatedly as parameters for each individual process that needs them. This allows one to conveniently make a single change to a shared parameter listed in a "group" line and have it impact all the succeeding processes that require it. But it also requires ensuring that any "process" line that requires a shared parameter has the appropriate "group" line specified before that "process" line in the definition file of that operation. Often, a tillage operation may contain multiple tillage tool components on a single implement (e.g., disk gang, followed by a row of chisel shanks) or consist of a several individual implements, one behind the other (e.g., a springtooth harrow with a straight tine drag harrow behind it). These types of tillage operations/implements can be represented as a single operation in WEPS by specifying the physical processes each tillage tool component performs on the soil/surface/vegetation. Often, this is done by specifying a Tillage "group" line, followed by the appropriate "process" lines to represent the tillage/residue burial effects of the individual tillage tool components. Thus, multiple "Tillage group" lines, followed immediately by several "process" lines, will be used to represent multi-tool and multi-implement tillage operations in WEPS. The parameters are:

Actual Depth
Actual tillage depth.

Intensity
Tillage intensity value (bounded between 0 and 1.0). A zero represents no soil disturbance and 1 represents maximum soil disturbance. This parameter value impacts the soil layer "mixing" process simulated within WEPS, as well as "soil loosening".

Area Affected
Surface are affected (bounded between 0 and 1.0). A 0 would represent no surface are disturbed. A 1 would mean that the tillage processes occured across the entire width of the implement. Somewhere between 0 and 1 would indicate only a fraction of the soil below would be disturbed.

Standard Depth
Depth at which some of the physical processes have coefficients specified. In WEPS, many of these coefficients are then interally adjusted based upon actual tillage depth, as well as other parameters.

Minimum Depth
Minimum tillage depth. This depth value is used to determine the lower limit at which WEPS will adjust certain process-specific parameters which are influenced by tillage depth.

Maximum Depth
Maximum tillage depth. This depth value is used to determine the upper limit at which WEPS will adjust certain process-specific parameters which are influenced by tillage depth.