In the past, high transport costs have largely limited the use of bulky, low value manure products to regions with intensive animal units. The widespread adoption of minimum till cropping systems resulted in these products now often left on the soil surface, where their effectiveness in enhancing soil properties and delivering plant nutrients is greatly diminished. It may well be that most of the beneficial effects that are attributed to using manures and other organic soil amendments, such as improved soil properties and nutrient supply, are not being delivered in minimum/zero till cropping systems.

Granulated compost as game changer

Pelletised animal manures have been available for a long time, but these products supplied primarily niche markets and were too expensive for use in broadacre farming operations. The development and large-scale production of granulated compost products, which resemble granular fertiliser (size, shape, density, flowability), is a game changer for broadacre farming. The granular compost products, which can contain additional plant nutrients or soil ameliorants (e.g. gypsum) and be blended with mineral fertiliser, provides minimum-till farmers for the first time ever, with an opportunity to apply organic based fertilisers with existing air-seeding or strip-tilling equipment.

Research Needs and Opportunities

As the production and use of granulated compost and organo-mineral fertiliser products is a brand new development, there are many open questions from manufacturers and farmers that need answering. The use of granulated compost and blended organo-mineral fertiliser products in minimum till farming enterprises has not yet been assessed and evaluated systematically. Therefore, aspects such as the following need to be investigated:

  • Chemical, physical and biological product characteristics
  • Product quality requirements (to prevent negative plant growth response)
  • Appropriate application rates
  • Fertiliser replacement capacity
  • Capacity to improve soil properties and soil health
  • Effects on plant growth and crop yield
  • Economic viability

We are collaborating with Grassdale Fertilisers to answer some of the above questions. It is this context that allows us to invite Honours and Master of Agricultural Science students to work with us in assessing the agronomic and economic viability of using granulated compost and organo-mineral fertiliser products in minimum till farming systems on the Darling Downs.

At the beginning of this research program we will assess the agronomic viability of standard and blended compost granules and their capacity to replace commercial base fertiliser products. These assessments will be done in both glasshouse and field trials, as outlined below.

  1. Glasshouse trials

A series of glasshouse trials will be conducted in Gatton, utilising
(i) 1m flower boxes that allow mimicking joint application in a row of seeds and compost granules / mineral fertiliser with an air seeder,
(ii) three different soil types, two from Grassdale Farm, plus a sand-based low nutrient growing medium)
(iii) three types of plants, i.e. silage corn or forage sorghum, wheat or other grain, and cotton

  1. Increasing application rates
    Plant growth (fresh / dry weight)  and chlorophyll levels (SPAD - as proxy for nitrogen supply) will be assessed with increasing rates of standard and blended compost granules in comparison to mineral base fertiliser (e.g. MAP, Cotton Sustain) applied at similar nutrient loads in order to develop and compare response curves
  2. Potential for replacing mineral base fertiliser
    Plant growth (fresh / dry weight) and chlorophyll levels (SPAD - as proxy for nitrogen supply) with standard rates of mineral base fertiliser will be compared with using standard and blended compost granules on their own or in combination with mineral base fertiliser, with all treatments at similar nutrient loads. This glasshouse trial will mirror the field trial.
  1. Field trial

A field trial will be carried out at Grassdale Farm near Dalby in which the use of mineral base fertiliser (Cotton Sustain, 350 kg/ha) will be compared with the use of blended (50:50) compost granules on their own, and in combination with standard mineral base fertiliser for production of silage corn on a paddock with a newly installed lateral irrigation system. All treatments, except for the zero treatment, will supply similar N, P, K nutrient loads.

The trial will be carried out in collaboration with Cotton Grower Services, which will assist not only with agronomic advice, but also with soil and leaf sampling and testing.

Details of all trials will be defined collaboratively with our commercial partners.

Gatton, December 2020

Project members

Primary Supervisor

Dr Alwyn Williams

Senior Lecturer in Agronomy
School of Agriculture and Food Sciences

Associate Supervisor

Mr Johannes Biala

Research Centre Manager
School of Agriculture and Food Sciences