Agrotextiles
The film has to outlast the crop and then vanish. Six degrees of soil temperature moves that balance further than any change to the polymer.
— days
Time to lose half the film mass under actual soil conditions
First-order kinetics assume degradation proceeds at a constant proportional rate, which biodegradation does not: there is usually an induction lag while the surface is colonised, then a faster phase, and the single rate constant here averages over both. The thickness correction is linear, appropriate for surface-driven attack and wrong once the film fragments and its surface area jumps. Degradation also effectively stops below about 10 °C, which a Q10 extrapolation will not show you. Compliance with EN 17033 or a comparable standard rests on soil burial testing, not on a projection.
Biodegradable Mulch Film Half-Life in Soil — free, with the formula and a worked example, at Textile School.