Improving fruit quality and consistency in cherries through maximized nutrient availability (CY12002)

What was it all about?

Running from 2012 to early 2018, this project looked at improving soil health to boost cherry crop yields and fruit quality.

The work involved trials on two commercial orchards in Tasmania – one in the Derwent Valley and one in the Huon Valley – where the impact of different nutrient management strategies was observed on fruit quality at harvest, soil health, and the longer-term diversity of soil microbes and beneficial invertebrates.

The treatments included a conventional nutrient regimen using applications of the synthetic fertiliser traditionally used at the orchard sites, as well as a herbicide, and for comparison, an alternative nutrient management regimen using a humate soil conditioner or compost, blended with targeted minerals. The alternative program was dynamic, changing in response to regular soil testing and aiming to rebalance available soil minerals and promote soil biology, with the long-term aim of reducing nitrogen inputs.

There were further treatments involving the addition of ‘effective microbes’ (a mix of about 80 different species of beneficial microorganisms) to both the conventional and alternative programs.

The researchers reported that the project “successfully demonstrated that it is feasible to achieve high-quality fruit with alternative nutrition regimes, rather than conventional fertilisers and herbicide use.”

The project team reported the following results…

• The alternative regimen resulted in a higher fruit set than the conventional in most years of the trials, though the addition of effective microbes appeared to have no effect here.
  
  
• The alternative regimen led to a higher percentage of A-grade fruit in most years. Here, effective microbe application led to a significant increase in A-grade fruit in years two, three and four of the trials.
  
  
• Lapin cherries were the more responsive to the alternative approach and the application of effective microbes – though this may be due to site factors and soil type. Sweetheart fruit diameter, however, was 1-2mm smaller in the alternative regimen in most years.
  
  
• There was significantly less fruit cracking in the alternative regimen in years three and four, while effective microbe application reduced the incidence of cracking in every season.
  
  
• Monthly application of effective microbes was effective at reducing the incidence of fruit cracking under both alternative and conventional regimes. Cracking incidence was very high in the 2016/17 season, which had high rainfall leading up to harvest – more than 50 per cent of fruit in the conventional regimen was affected, but the alternative regimen reduced cracking by 37 per cent.
  
  
• In regard to other fruit quality attributes, the researchers report variation between the trial years, with firmness and sugar content increased in some years, but not others. They report that “it is worth noting that, in the alternative regimen, fruit quality attributes of firmness, TSS and stem retention force met Australian ‘export finest’ standards, with a higher percentage of A-grade fruit. This means that results from this study have demonstrated that humate-based nutrition programs are capable of yielding high quality fruit with good pack-outs with no loss of quality.”
  
  
• In regard to soil health, healthier soils were achieved using the alternative treatments, with reduced soil compaction, improved water infiltration and a higher abundance of mycorrhizal fungi. The presence of fungal species was significantly affected by fertiliser treatment, but not by effective microbe application. The researchers report that “the majority of the bacterial and fungal species in the effective microbe inoculum were not found in the soil, and those that were detected were at extremely low levels – however application of effective microbes had a beneficial effect on fruit quality, perhaps through stimulation of other organisms. Further work is needed to clarify this response.”

ACT NOW

Download fact sheets produced during the course of the project, including…

• Cherry soil health, how does this affect fruit quality? (produced early in the project)
• Can improved soil biology increase nutrient availability?
• Cherry soil health