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Trials and Demonstrations Update

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Sustainable Agriculture

Improving soil health and carbon sequestration of degraded soils when sown to mixed perennial shrubs

The aims of the project are to identify and quantify the soil health benefits of stabilising degraded land on established forage shrub sites of various ages; attempt to identify the time after planting that soil benefits will be realised; and analyse the micro climate in and around shrubs for correlations between soil health, plant cover, and plant diversity.

The trial is being run by Dr Sarita Bennett and Dr Sue Low of Curtin University, with four sites at Jennacubine set up to monitor the micro-climate, soils and understorey vegetation under various aged forage shrub sites. Weather stations monitoring the microclimate within and between the shrub rows have also been installed.  

Image: Sampling soils 

Preliminary results

Ambient Temperatures and the benefits of shade

Initial results from the trial have found that maximum daily temperatures were consistently greater in the more exposed inter-rows compared to under the shrubs. The newer forage shrub site with a high diversity of shrub and tree species reduced the ambient temperature more than the older monoculture saltbush site.

Dr Sarita Bennett and Dr Sue Low presented the results at a Greening Australia event in October 2016 and emphasised that shade can be vital in Western Australia’s hot summers. Sheep joining commonly occurs over summer however, heat stress can impact on sheep fertility, conception rates and lamb birth weights.  Conversely, shelter during winter lambing can reduce wind chill and increase the micro-climate temperature, improve lambing rates, lamb growth rates and wool growth by reducing cold stress.

Image: Sheep grazing amongst saltbush

Understorey Growth

2016 had an early break of season and consistent rainfall over the winter and spring months. As a consequence the understorey vegetation had a much greater proportion of legumes than seen in 2015 (2000kg DM grasses in 2015 to 4000kg DM of legumes in 2016) and the amount of feed available was significant. Sarita and Sue believed the 2016 understorey growth had the potential for two grazing opportunities and still allowed for seed set for 2017.

The project will continue until December 2017.