Optimising the benefits of vermiculture in commercial-scale vegetable farms

Everybody knows earthworms are good for your soil.  Horticulture Innovation Australia (HIA) – as the peak body for Horticulture in Australia – has invested in a three year project that aims to increase the numbers and activity and therefore the benefits of earthworms to commercial vegetable production.  The project commenced in Spring 2016. 

SESL Australia in conjunction with Blue Environment has established a total of 18 sites across the country in six states (Vic, NSW, Qld, Tas, Sth Aust. & W. Aust) – three sites per state.

Of the 18 sites, 2 sites were selected for research purposes – one in Maffra, Victoria, and one in Moriarty, Tasmania.  The remaining observation sites monitor business-as-usual practices on those farms to determine impacts on worm numbers.

Observation sites were selected based on current use of a beneficial soil conditioning management practice, which effectively means improved management of soil carbon. Representative blocks were selected on the observation farms and transects mapped for sampling.

Research sites were selected for the same reasons plus the businesses’ long-term commitment to their soils and the owners’ commitment to the research trials.  A randomised block design was developed for the research plots. 

The research blocks host a range of experimental treatments including green manure / cover crops, biofumigant crop, compost, and worm casts.

Benchmark data were gathered for soil properties (pH, EC, total N, total carbon, labile carbon, bulk density, moisture content and soil temperature), microbial biomass, worm numbers and worm genus.  Site histories are also being gathered and include crop rotations plus a broad range of management practices such as tillage and chemical use.  These data will assist our understanding of the conditions that favour worm populations.

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All sites are managed conventionally with the exception of an organic pumpkin grower in Queensland and a biodynamic grower in Western Australia.

All sites were sampled in Oct / Nov 2016, and are scheduled for repeat testing once each year in late winter.

Worm counts varied widely across soil types, climatic zones and management practices.  The highest worm count was found, not unexpectedly on one of our Tasmanian sites.  This farmer practices strip tilling, i.e. minimum tillage (disturbance) prior to sowing.  The result was over 2,500 worms per square metre of soil.  Incredibly, our lowest worm count was also in Tasmania on a long-term green manure trial site where all soil indicators promised high worm numbers.  We found zero worms per square metre!

These results raise more questions than answers at this stage.  However, we are confident that this project will improve our understanding of worm populations on vegetable farms and provide sound guidance to farmers to help lift numbers of these most willing workers.

Contact Declan McDonald, manager of this project, for more information or queries about how SESL Australia can help you in similar projects.