Diversity the key to soil health

Diversity was the key word when thinking of the biological health of our soils at a series of soil field days run by Agriculture Victoria and the Surf Coast Inland Plains Network recently. Soil Microbial Ecologist, Dr. Helen Hayden, who has spent the past 10 years researching soil biology, discussed with local farmers, researchers and extension staff, how a diversity in food sources was required to feed a diverse range of soil “bugs”.

Dr. Hayden described how the macrofauna and mesofauna (those bugs big enough to see with the naked eye, such as earthworms, beetles and mites) break down plant material, roots and stubble into particles small enough for the microfauna and microflora, such as protazoa, nematodes and fungi to digest. These “microscopic bugs” are the ones responsible for nutrient cycling, soil structural stability and other critical functions in a healthy soil. The different bugs have specialised mouth parts, specific to a food source. A diverse range of food sources was needed to maintain a diverse range of soil biology.

The more diverse the range of soil biology, the more resilient the soil is. If climatic conditions or the use of an agricultural chemical did not suit a particular species, another type would be available to take over the role. Increasing the organic matter in the soil allowed for greater water holding capacity and improved structure.

This was demonstrated at Evan and Suzanne Lewis’s sheep and cropping property at Werneth, in south west Victoria. In 2014, Evan and Suzanne volunteered the worst paddock on their farm to trial “cover cropping” as part of the Corangamite CMA Land
Health Program.

Since that time, 4 different summer and winter cover crops have been planted using a zero till disc seeder, all containing a number of different plant species. The aim was to use plants to encourage soil biological activity, to improve the structure and fertility of a waterlogged, sodic clay soil. Although the region has just experienced the wettest winter for many years, the trial paddock suffered from no waterlogging, and those in attendance were impressed by the barley/clover combination thriving in it. One local farmer who had inspected the paddock two years ago at the start of the trial was amazed at the improvement in such a short time.

Dr. Hayden demonstrated the simple methods producers can use to monitor the biology in their soils, identifying a number of bugs with the naked eye, including the interestingly patterned Land Planarium, or terrestrial flat worm (with racing stripes!), at the Maude field day. Modern lab based techniques to measure and monitor soil biology were discussed, along with the importance of taking multiple samples from across a paddock, as soil biology was highly variable within a paddock,
described by Dr. Hayden as “hot spots and not spots.”

The variability of topsoil depth was demonstrated at Peter Stray’s grazing property at Maude, where two soil pits were dug 15m apart, with topsoil depth varying from 10cm to over 30cm. The workshops were funded by Corangamite CMA as part of the Australian Government’s National Landcare Program.

For more information read the latest edition of the Corangamite FARM TALK magazine.