Prolonging profitability and longevity following soil amelioration

Page last updated: Monday, 25 March 2024 - 10:54am

The aim of this project is to help more growers with ameliorated soils in the medium and high rainfall zones adopt new farming systems techniques to maintain the benefits of soil amelioration, as well as reduce the risks of poor crop establishment, soil erosion and reversal of soil constraints.

State date: 01/01/2019
Finish date: 01/06/2024

Description:

The uptake of soil amelioration in WA is on the rise, with more than half of growers (52 per cent) in WA’s grainbelt having undertaken some form of mechanical soil amelioration in 2019. A further 23 per cent have undertaken soil amelioration by non-mechanical methods, such as spreading lime, gypsum or clay-rich soil.

According to a GRDC report, 38 per cent of farms applied lime nationally in 2021, with more farms in WA using the technique than any other State. WA also recorded a higher percentage of soil testing compared to other states.

However, it has been found that often once that initial work has been undertaken, certain on-farm practices limit the longevity or value of the soil amelioration.

For example, without the introduction of controlled traffic farming (CTF) post-amelioration, growers run the risk of re-compacting the soil they have just spent thousands of dollars fixing. In fact, up to 60 per cent of soil re-compaction happens in the first pass. Biotic constraints such as weeds or soilborne pests and disease can also increase on ameliorated soils and reduce the benefits if not managed.

As a result, this project identified management changes to preserve the benefits of soil amelioration and maximise profitability. It included research into crop rotations, species choice, seedbed preparation, crop establishment, herbicide use, managing weeds and soilborne pests and disease and minimising wind erosion.

This project involved research and case study sites in the Geraldton, Esperance, Albany and Kwinana West port zones. 

Research undertaken provides the following answers and increased confidence to grower decision making:

  1. Strategic deep tillage can lower soilborne disease and pest pressure, but the effects are often short-lived and break crops such as canola and pulses are critical for the continued suppression of these soilborne pathogens, thereby preserving the yield gains and profitability of soil amelioration. Similarly, weed densities can increase rapidly after soil amelioration and growers should select diverse post-soil amelioration rotations that maximise weed control. Shifting the timing of soil amelioration to a period between May and the first two weeks of June maximises productivity in periods of lower wind erosion risk. Yields on ameliorated soil in this period are equivalent to or better than those achieved on earlier sown non-ameliorated soil.
  2. Single pass, combined, seeding / amelioration systems maximise crop establishment and groundcover, minimising wind erosion risks while maximising productivity.
  3. Pre-emergent herbicides on recently ameliorated soils, that now contain reduced organic carbon, are far more active and damaging to emerging crops.
  4. Strategic deep tillage changes the location of pathogens throughout the soil profile, shifting them from the surface 10 cm to deeper in the profile, previously free of the disease. The initial burial of pathogen did not influence the yield gains from deep tillage. Four years after deep tillage,  the influence of deep tillage on pathogens had waned with most treatments having inoculum levels similar to the no-till treatment.
  5. In a trial to determine whether intercropping can provide rapid groundcover, increase biomass inputs and boost productivity following soil amelioration, canola-pea, wheat-canola, wheat-lupin and wheat-pea intercrops had lower or the same biomass and yield productivity as the monoculture wheat. The implementation of intercropping has practical challenges and a significant biological, yield or economic benefit, over monocultures, is required to justify its use following soil amelioration.   

Funding partner:

GRDC

Project code:

DAW1901-006RT