Function describing exponential decline from a defined starting value, with a decreasing rate constant.

## Arguments

- t
Time.

- parent_0
Starting value for the response variable at time zero.

- alpha
Shape parameter determined by coefficient of variation of rate constant values.

- beta
Location parameter.

## Details

The form given here differs slightly from the original reference by
Gustafson and Holden (1990). The parameter `beta`

corresponds to 1/beta
in the original equation.

## Note

The solution of the FOMC kinetic model reduces to the
`SFO.solution`

for large values of `alpha`

and `beta`

with \(k = \frac{\beta}{\alpha}\).

## References

FOCUS (2006) “Guidance Document on Estimating Persistence and Degradation Kinetics from Environmental Fate Studies on Pesticides in EU Registration” Report of the FOCUS Work Group on Degradation Kinetics, EC Document Reference Sanco/10058/2005 version 2.0, 434 pp, http://esdac.jrc.ec.europa.eu/projects/degradation-kinetics

FOCUS (2014) “Generic guidance for Estimating Persistence and Degradation Kinetics from Environmental Fate Studies on Pesticides in EU Registration” Report of the FOCUS Work Group on Degradation Kinetics, Version 1.1, 18 December 2014 http://esdac.jrc.ec.europa.eu/projects/degradation-kinetics

Gustafson DI and Holden LR (1990) Nonlinear pesticide dissipation in soil:
A new model based on spatial variability. *Environmental Science and
Technology* **24**, 1032-1038

## See also

Other parent solutions:
`DFOP.solution()`

,
`HS.solution()`

,
`IORE.solution()`

,
`SFO.solution()`

,
`SFORB.solution()`

,
`logistic.solution()`