The mixing and making of potting mixes is covered under “Potting Mixes” and “Compost & elements for growing” in detail and will not be covered again here. At this level I will discuss the importance of Carbon in the potting mixes in both the control of diseases, nutrient sponges and the need for good aeration. Organic growers will be delighted at our results and the results of others in the use of vermicasts, manures and what some farmers consider to be trash or waste. This includes baggass, grain hulls and sawdust. In the above files there are complete breakdowns of their chemical ratios and content so I will be more focused on nutritional values for our plants here.
The importance compost and even small amounts of animal manure in potting mixes cannot be overestimated.
The following experiment was commenced with the department of Primary industries in Queensland. On that day back in 1983 I had problems with some ferns which were developing black veins on the fronds. We called the department and they sent out a qualified botanist who reported back a week later that we had Zinc toxicity in the fronds of the plants supplied and in the mix. After this we examined our procedures carefully and realized the zinc was probably coming from a 10,000 litre holding tank on site. While we were talking Keith asked me whether we were having any fungal problems especially Phytophthora cinnamomi? I answered quickly no and don’t want to either. It turned out that most nurseries and farmers growing Rhumora adiantiformis were having problems.
We gathered 2 cartons of the ferns together. Keith departed to inoculate half the plants with Phytophthora cinnamomi and used the other half as control agents. After a few weeks the plants were again inoculated with the Phytophthora cinnamomi fungus as there was no sign of any uptake or stress in the ferns. Two weeks later and the same results appeared, no symptoms nothing. A week later the mix was checked and our inputs collated. There were various strains of fungi in the mix but no Phytophthora cinnamomi. In fact our mix was a living time bomb. It was alive with hundreds if not thousands of different organisms.
We decided to examine the effects of fresh and composted animal manures on the development of Phytophthora cinnamomi and the results of various ferns exposed to the fungus. The ferns exposed to the fungus in soilless mixes without compost all succumbed over the perusing weeks where as those that were grown in our aged sawdust mix with added composts showed no visible signs of stress or the fungus in their tissues.
There is a lot of information on the web in relation to nutrients and plant growth and while our experiences show that there probably is a relationship between animal manures and the suppression of certain fungal diseases. It does not stand that all fungi will succumb to natural inputs like in our case. Plants that are grown in sterile mixes are probably more at risk of developing problems once a virus or fungus is introduced to a mix that has no variety of living organisms as its foundation.
There are also numerous experiments being done using vermicast or vermicompost which are all indicating that these potting medium have synergistic effects on growth and yields of the plants used in the experiments. (See our results in the above files where vermicast appears to eliminate certain seeds either by the worms eating the seeds or promotes the growth of others by not consuming them or they pass through the gut of the worms unaffected by the passage.)
Results using vermicast as a potting medium as was shown (“Potting Mixes” and “Compost & elements for growing”) indicate that the vermicompost prepared from cow dung had significant effects on the weed growth, suppression or elimination of weed seeds. Growth of citrus tree stock (Citrinus trifoloiata) compared to control plants was significantly better. While vermicompost mixes and vermicasts have shown potential in laboratory and controlled nursery situations there is no advanced work to date done on sustainable crop production. Further studies will be needed to determine the long term effects of vermicast applications under large field conditions but on potting mixes the results proved beyond doubt that vermicasts used as a top dressing or incorporated into the mix was highly beneficial in the growth of Citrinus trifoliata root stock.
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