University of Tasmania, Australia

Degradable polymer film effects on soil water and solute dynamics

Clear, degradable polymer films (DPF) are being developed for a range of agricultural applications. The films are laid either in conjunction with or following sowing with the same machines used to lay conventional low density polyethylene (LDPE) film. The film acts like a glasshouse to ‘recycle’ water that is evaporated from soil or leaf surfaces back into the soil, to be used again. Furthermore, any rain that does fall, will runoff into the inter-row spaces approximately doubling the effective rainfall there. Measurements also show that the warm, humid conditions under the film increase decomposition of organic matter and the CO₂ released is trapped under the cover, elevating it to concentrations which are no longer limiting to plant growth. The films also increase temperatures, which could have a range of both positive (e.g. lessening frost risk) and negative (e.g. heat stress) effects. The impacts of the film, to recycle evapotranspirative losses and concentrate/divert rainfall across a paddock, constitute a fundamental transformation of the hydrological cycle and are likely to affect soil water dynamics in a number of ways. These hydrological responses will in turn have profound effects on a wide range of crop and soil management practices.

The objectives of this study are to:

1. Understand and quantify the effect of DPF on the spatial distribution and movement of soil water and (selected) solutes under a range of climate x crop x soil x polymer configuration combinations;
2. Incorporate the findings from 1) into existing process-based farming system simulation models.

The project is a partnership between CSIRO, CRC Polymers, Rural Development Services and the University of Tasmania, and will involve controlled environment studies and field trials in commercial crops in collaboration with industry partners.

Supervisors: Dr Tina Acuna, Dr Shane Broad, Dr Shaun Lisson (CSIRO)