Bill gave an overview of the influence of management on soil carbon. While temperature and moisture (rainfall) are the biggest factors influencing soil carbon management does also have a strong influence. Bill showed some results from long term (150 year!) trials at Rotham in England which demonstrated that cropping does deplete soil carbon (compared to pasture). It also showed that soil carbon can be increased by adding organic amendments (such as manures) however these additions must be continued to maintain soil carbon. Bill also showed a ranking of management practices and their influence on soil carbon. Bare fallows are the worst thing that you can do for soil carbon - growing pasture is one of the best. Tillage has its place and doesn't appear to be as bad as we have thought. Following on from Bill, we had a series of short presentations by farmers and agronomists on specific management activities that they have had experience in. Peter Aird (Serve-Ag) gave an overview of drainage and the importance that this has for encouraging good plant growth and healthy soils. Bill Chilvers (Oakdene) spoke about his experiences with a long term (5 year) Southern Farming Systems stubble trial, where they found that retaining stubble significantly reduced compaction (and increased infiltration) of soils. Stubble also had positive effects on critters both good and bad (earthworms and slugs). Bill concluded that effectively managing stubble requires a long term view and good attention to detail - and there is a place for burning in some situations. Wheat stubble was highlighted as being one of the more difficult to manage (both in terms of amount of material and slowness in breaking down). Rob Bradley (Woollen Park) gave an overview of his Nuffield scholarship, in which he was interested in researching the sustinability of our cropping systems, where has has found inputs and efforts are on an upwards trend to keep producing the same yields. As he travelled the world, Rob found that integrated livestock and cropping systems (like ours in Tassie) are actually quite rare and "old fashioned”. Instead, the trend of overseas commercial farms is increasingly to separate livestock and cropping as the system intensifies. He ventured into the organic sphere where integration is still practised and an important part of the nutrient cycle. Rob concluded that livestock (and pastures) are a critical component of ensuring the sustainability of his cropping program. The morning wrapped up with a presentation by Ian Smith (Crystal Brook) on his recent experiences with compost teas. Ian runs a vegi farm and is running a trial this year to look at the effects of compost tea on onions. Results so far are very encouraging, with much better root development and lower weed pressure on the area treated with compost tea (interestingly the onions on this side were innoculated with micorrhizal fungi and were not drilled with any fertiliser - other than that they have been treated exactly the same). Ian gave us a lot of information on the practicalities of preparing compost tea, and on the importance of using good quality compost (composts ain't composts!).
After lunch Bill, Darrel Wise (manager at Kinburn) and Peter Aird took us on a tour of the farm, where we looked at four paddocks with similar soil types but very different management histories. Bill demonstrated the use of his rating system for soil structure (where 10 is excellent structure and 1 is very poor) - the variation in soil structure across the paddocks was very clear.
The afternoon was broken up by the running of the Melbourne Cup where John Rees (having Dunaden in the sweep) was the winner of the soil testing prize (valued at $278) donated by AgVita Analytical. We then broke into small groups for the final test of the day - matching 4 different soils with their paddock histories. This allowed the groups to put into practice a lot fot he theory that had been covered throughout the day - and they got to do a "bucket chemistry" labile (active) carbon analysis of the soils using potassium permanganate. All groups did an excellent job of working out which soil belonged where and the prize had to be settled by random draw.
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