Investment in science and industry development key to profitable agrifood sector 2

HIGHLIGHTS

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  Findings are likely to promote clay spreading and delving to manage water repellent soils.
  
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  We aim to analyse the cost-effectiveness of combinations of clay rates and different incorporation methods.
  
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  The project will also evaluate clay spreading on water-repellent gravel sands and clay delving on texture-contrast soils.
  

Funding and collaborators

GRDC, West Midlands Group, SEPWA.

Image 1

DAFWA Research Officer Giacomo Betti collects subsoil clay samples to determine the rates of clay spreading.

Image 2

Clay spreader in action at the Moora trial.

Coating technology - water repellence and soil fertility

Science Team: Dr Geoff Anderson (project leader), Christian Valentine

New coating technology for seeds and fertiliser granules is being explored to protect seeds from adverse field conditions and environmental stress.

The research is evaluating the dual concepts of coating seeds with a surfactant and water-absorbing polymer to overcome water repellence, and applying an elemental sulphur coating to phosphate fertilisers for overcoming sulphur deficiency.

The advantage of coating technology is that the amendments in the coatings are situated close to the growing seedlings, which can improve efficiencies and reduce application costs.

We are evaluating two seed-coating substances –– a commercial water-absorbing polymer and a soil surfactant. These seed coatings are being tested to improve crop establishment on repellent soils. Crops grown on repellent soils can suffer from patchy establishment, delayed emergence, low competitiveness with weeds and poor nutrient uptake.

A seed-coating technique for the water-absorbing polymer has been developed. It is hypothesised the polymer will draw water to the seed via soil humidity to aid germination and seedling survival on water repellent soils.

A surfactant coating, sourced from the Botanic Gardens and Parks Authority (BGPA) and UWA, has been used to help replant native flora after bushfires on water-repellent soils. When it rains, the surfactant leaches off to create a wetter and more favourable soil environment around the germinating seed.
Experimental evaluation of the seed coatings is assessing the impact on plant germination rates under a range of soil water conditions in glasshouse studies and evaluation of the yield benefits in the field. In these experiments, seed coating allows very low rates of the surfactant to be used.

The project is also studying the efficacy of an elemental sulphur coating on monoammonium phosphate (MAP) and diammonium phosphate (DAP) fertilisers to increase the sulphur content of these fertilisers.

Sulphur deficiency is a constraint to crop production across the grainbelt, due to sulphur deficient soils, the use of low sulphur fertilisers and sulphur leaching during high rainfall events from May to July.

The sulphur content of fertiliser can be increased by coating fertiliser granules with elemental sulphur. Elemental sulphur has the advantage over other sulphur sources because it can act as a slow-release fertiliser without affecting the efficacy of other fertiliser elements. When the elemental sulphur is coated onto fertiliser granules it has minimal impact on the influence of the N and phosphorus contents of these fertilisers.

We are testing mono-ammonium phosphate (MAP) that contains 10, 15 and 20% of coated elemental sulphur in this research. This approach will reduce fertiliser handling costs while increasing sulphur fertiliser application, reducing the risk of deficiency.

To enable this research, DAFWA has purchased a seed-coating machine from Canada, which has the capacity to coat up to 2kg of seed or fertiliser. This machine is available to other parties to build the capacity of the grains industry to test other seed and fertiliser coatings.

HIGHLIGHTS

DAFWA is evaluating two seed-coating substances –– a commercial water-absorbing polymer and a soil surfactant to improve crop establishment on water-repellent soils.

Elemental sulphur-coated fertiliser granules may provide an efficient approach for overcoming sulphur deficiency.

Funders and collaborators

GRDC, DRD Royalties for Regions, BGPA, UWA

Image 1

DAFWA is evaluating the use of seed coating to mitigate the impact of water repellent soils and fertiliser coating to overcome crop sulphur deficiency.

Green light for blue soil

Science team: Dr Steve Davies (project leader), Dr Craig Scanlan, Dr Gavin Sarre, Damien Priest.

Growers adopt inversion tillage to renovate problem soils, and usually to correct one or more constraints such as water repellence or herbicide resistant weeds, for example.

The use of inversion tillage equipment (mouldboard ploughs, rotary spaders, offset discs and disc ploughs) to correct water-repellent soils and reduce high weed burdens is relatively well understood. But less is known about how this equipment mixes soils.

Soil mixing is an important factor that determines how ameliorants such as lime and clay are distributed through the soil. A better understanding of soil mixing will improve our capacity to treat more than one soil constraint at a time.

We have designed a new method for quantifying soil mixing in field experiments. To identify soil fragments, we placed green or blue-coloured soil in narrow trenches in field plots and then passed different tillage implements through the coloured soil.

Soil pits were excavated near the trenches and the pit face was advanced in 5 cm increments so we could photograph the redistribution of the soil. We then used digital image analysis to create a 3-D reconstruction of the soil profile.

Our experiments showed that the mouldboard plough, rotary spader, offset discs and disc plough fragmented the soil in a similar way, despite having different mechanical actions. We also measured the redistribution of soil from different depths, giving us a better capacity to predict how inversion tillage will modify a stratified soil.

We are working on the data with soil scientists at the UniSA, who are developing computer models of the movement of soil particles by tillage.

Our future work on soil mixing will focus on a rapid method for excavating, imaging and visualising coloured soil used as a tracer in tillage experiments.

This work is in collaboration with the Royalties for Regions project, ‘New approaches to quantifying the properties of gravel soils and for sampling inverted soils to improve crop management’.