Composting at Scale for Soil Health - Lawn Solutions Australia

Composting at Scale for Soil Health

All Turf Solutions have had a passion for improved soil health since the start of our turf production operation. Our production facility at Rathdowney QLD is fairly new with our first paddocks planted just prior to Cyclone Debbie washing them away in 2017. We moved a considerable amount of soil around and attempted to salvage the topsoil where economically viable but even then, we found the disturbance of the topsoil layer resulted in poor soil health. Certainly, more could have been done in the early days with setting up the paddocks, but the money just wasn’t there.

After a couple of years of turf production, we started to see disease pressure in some of our paddocks that had areas of next to no topsoil in the profile. A downward spiral of reliance on fungicides was beginning to appear and at that point, we reached out to BioHub Solutions for assistance with strategies to improve our soil health. A year down the track with applications of carbon, worm juice, seaweed, and inoculations with biology developed by Griffith University we reduced our reliance on fungicides. With applications of fresh chicken litter, this was our only source of dry organic material.

We were accumulating turf scraps, so we had some of the ingredients already on the farm to produce compost. Compost based on turf scraps alone wasn’t going to work due to the high soil content. This must be balanced out with the addition of green waste or straw and also the addition of animal manure to achieve a favourable carbon-nitrogen ratio.

The Composting Process

Composting is a method of speeding up the decomposition of organic materials. The ingredients are made into a heap or in our situation windrows (elongated mounds) to facilitate the composting process. Heat given off by microorganisms inside the heap is trapped there by the insulation provided by the outer few centimetres of the windrow. Inside temperature rises and so does the rate of decomposition. Composting is most rapid when the heap is made with the right ingredients and turned frequently.

soil compost

Key Requirements

If provided with the right conditions, microorganisms will do the work.

  • Plenty of organic matter for energy
  • Enough nutrient elements, especially nitrogen
  • Oxygen – those microorganisms that are best at decomposing plant materials need plenty of oxygen
  • Moisture – not too much and not too little
  • A source of cations, especially calcium to stabilise the compost

soil compost

Decomposer microorganisms

The main microorganism species responsible for decomposing organic material are bacteria, fungi and actinomycetes (branching bacteria).

Organic materials and nutrients

Any organic material that is of plant or animal origin can be composted, with several factors that will dictate the quality of the product produced.

  • The size of the material will determine the length of time for break down.
  • An adequate level of nutrients C: N ratio minimum of 5:1 is a large factor for composting.
  • A moisture level of 55% to 65%
  • Oxygen – At least 50% of the heap should be air for maximising oxygen for the microbes.
  • Calcium level – added as gypsum or lime depending on the pH

Depending on air temperatures and the size of the heap, finished compost should be available in 6-12 months.

Manure from grain-fed animals (eg poultry) will supply phosphorus used at around 7kg per cubic meter. Poultry manure and litter will also supply nitrogen though it should be tested as nitrogen content can vary widely.

Turned compost heaps should be no more than 1.5-2.5m high and 2-3m wide. Larger quantities should be in the form of windrows. 

compost material

Volume change

Of the carbon in each bite from the materials from microbes, about 60% is converted to CO2, about 33% is made into microbial cells, and the rest is discarded as soil wastes. When these microbes are used by others as food about 60% of their carbon is converted to CO2, and so on. The heap gets smaller. Loss of carbon means that the concentrations of other elements in the remaining material increase meaning a richer source of elements.

Temperature and pasteurisation

The temperature inside composting heaps can range from 45 deg C to 75 deg C, decomposition is most rapid in a range of 45-50 deg C. Eventually the amount of undecomposed material decreases, so microbial numbers and the temperature of the heap fall.

The moist, hot, oxygenated conditions in an active compost heap are just right for killing plant and animal pathogens and parasites. At 65 deg C most plant parasitic bacteria, viruses and insects are eliminated.

Our first batch consisted of approximately 60% turf scraps, 30% Green waste (scarifying material from a paddock we needed to renovate) and the rest included chicken litter and Ag lime.

Subsequent batches have included the addition of gypsum and or calcium silicate. We further inoculated the rows with “BioForce, MicroLife Rapid Compost”. The opportunity to have waste from a paddock stripped with a Field Topmaker was ideal as this increased the nitrogen ration required to help activate the rows. Once turned and water added the rows heated up within a day and maintained at 70 degrees for a little over a week. We turned the rows daily adding more water as needed. I think the soil component of the rows shortens the time the rows will remain at temperature. While the textbooks indicate an aerated composting process should be around four weeks to ensure good compost production and weed seed control, we haven’t found any weed seed germination and no turf grass survival or germination. We have a couple of resilient turf grass strains that have their own rows to minimise any contamination possibilities.

We had our first batch tested by Southern Cross University in Lismore and were suitably surprised by the results.

See below the results from our compost and nutrient calculator based on 5 tonnes per hectare;

This is our third year of compost production, and we are still perfecting our procedures and learning from our mistakes. In our second year, we had some failures primarily due to not having the nitrogen ratio high enough to keep the temperatures high enough for any longer than 3 days. This resulted in rebuilding the rows and starting them off again. The addition of fresh grass clipping has given us our best results to date.

Due to the size of our operation, we prefer to get everything in place to carry out our turning once per year as this allows time to accumulate waste and materials and set aside the time to run the turner. Moving forward we would like to grow a green manure crop we can harvest and add to the rows at the time of turning. This would lift the nitrogen ratio required to compost the turf scraps.

The compost produced can then be used throughout the following year for amending soils now with the inclusion of our trace elements, lime, gypsum etc. We have been regularly checking stockpiles for weed germination and apart from a few broadleaf weeds, we have seen no evidence of grasses germinating.

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