STIR {SoilManageR} | R Documentation |
Calculate STIR value
Description
The function calculates the soil tillage intensity rating (STIR) value
of tillage and sowing operations.
By default, the STIR()
function of SoilManageR
operates on SI units (cm and km/h) and not in imperial units (inch, mph)
as the original STIR equation (USDA-NRCS 2023).
However, the user can specifiy that the input is in imperial units.
The function can process custom input, if no such input is provided
it assumes default values from the STIR_value_LUT
.
Usage
STIR(
device = NA,
speed = NA,
speed_unit = "km/h",
type_modifier = NA,
depth = NA,
depth_unit = "cm",
area_disturbed = NA,
original.STIR.value = FALSE
)
Arguments
device |
tillage or sowing implement or operation, must match predefined list, or all necessary inputs (speed, type modidifier, depth, area_disturbed) must be provided |
speed |
speed of the operation (km/h or mph) |
speed_unit |
unit of the speed input, must be either NA, "km/h" or "mph". Default value is "km/h" |
type_modifier |
tillage operation type modifier, must be a value between 0 and 1 |
depth |
depth of the soil that is affected by the operation (cm or inch) |
depth_unit |
unit of the depth input, must be either NA, "cm" or "inch". Default value is "cm" |
area_disturbed |
share of the surfave that is disturbed by the operation (0 to 1) |
original.STIR.value |
logical value, if TRUE, the original STIR value of
the operation in the |
Details
The concept of the STIR value was developed within the RUSLE2 framework by the USDA-NRCS (2023). The STIR equation is defined as
STIR = (0.5 * speed) * (3.25 * type_{modifier}) * depth * area_{disturbed}
where speed
and depth
are provided in mph and inches(!).
For the purpose of this function we assume that 1 inch = 2.54 cm
and 1 mph = 1.609 km/h
.
The tillage type_{modifier}
is defined to be:
-
1.00
for inversion operation -
0.80
for mixing and some inversion operations -
0.70
for mixing operations -
0.40
for lifting and fracturing operations -
0.15
for compression operations
In the STIR_value_LUT
there are more than 400 operations,
incl. the original operations from the RUSLE2 software (as of 2023-02-24)
and operations defined by the SoilX project.
For further details on the STIR please consider the RUSLE2 website (https://fargo.nserl.purdue.edu/rusle2_dataweb/RUSLE2_Index.htm) or the description of the SoilManageR package
Value
STIR value of the operation
References
USDA-NRCS (2023). “Revised Universal Soil Loss Equation, Version 2 (RUSLE2), Official NRCS RUSLE2 Program and Database (V 2023-02-24).” USDA-NCRS. https://fargo.nserl.purdue.edu/rusle2_dataweb/RUSLE2_Index.htm.
See Also
-
tillage_intensity()
to calculate STIR values for management_df -
STIR_values_LUT()
for the reference data used by theSTIR()
function
Examples
#example without additional information
STIR("plough")
#example with additional information
STIR("rotary_harrow", depth = 15)
#custom example
STIR(speed = 10, type_modifier = 0.8, depth = 15, area_disturbed = 0.45)
#example that returns orginial STIR value
STIR("plough", original.STIR.value = TRUE)
#example that uses imperial units
STIR("plough", depth = 5, depth_unit = "inch", speed = 8, speed_unit = "mph")