What was it all about?

This project involved three streams of research, carried out over four years from 2012 to 2015 to research cherry yield and quality.   

Plant bioregulators for optimal crop load management

Fruit set affects both yield and fruit quality, hence is a core issue of profitability for growers. Inadequate fruit set leads to low yields and a high incidence of fruit cracking, while excessive fruit set leads to over-cropping and undersized, soft fruit. This study investigated both of these problems.

Researchers looked at the effects of bioregulators, including Retain, on fruit set, and made a comparison of two rootstocks, Gisela and Colt.

Key findings included…

• Retain was consistent in improving fruit set in both cultivars, up to 65 per cent in Kordia and 48 per cent in Regina
  
   
• In wet seasons, Retain reduced the incidence of fruit cracking in Kordia by up to 44 per cent
  
   
• Both ethephon and ammonium thiosulphate were effective thinners
  
   
• Fruit set was found to be 52 per cent higher on Gisela than Colt rootstocks.

Girdling and floral biology for prevention of fruitlet drop and improved fruit quality

Fruitlet drop is an issue impacting the profitability of the cherry industry, with particular varieties showing enhanced susceptibility.

This component of the project examined the role of carbohydrate availability in fruitlet drop and post-harvest fruit quality in Kordia and Lapins sweet cherry varieties.

Starch and soluble sugar concentrations in branch, trunk and root tissue were measured regularly throughout the growing seasons of 2012/13, 2013/14 and 2014/15.

Normal transport of carbohydrates was disrupted five weeks after full-bloom by applying trunk girdling and limb defoliation treatments, and the rate of flower and fruitlet drop was monitored.

Researchers found that girdling significantly reduced root starch reserves, and while it reduced fruit drop in Lapins, it had no effect in Kordia. Girdling in Kordia resulted in firmer, sweeter and larger fruit that had better post-harvest shelf life.

Fertigation for fruit quality

Nutrient management is a critical component of commercial sweet cherry orchard production, as each nutrient plays an important role in the development and quality of sweet cherry fruit.

Whilst fertigation is commonly practised by cherry growers in Australia, research into optimal nutrient supply to meet tree demands is limited and the effects of oversupply of pre-harvest nutrition on fruit quality are virtually unknown.

Even less is known about the influence of micro-element nutrition on sweet cherry fruit quality and which is the best method of application.

This component of the project investigated the role of nitrogen and potassium fertigation on sweet cherry fruit quality and post-harvest shelf-life whilst at the same time shed light on the role of pre-harvest micro-element nutrition on fruit quality. This project included data from five separate trials conducted over four seasons.

Findings were complex but high-level results included…

• Obtaining the ideal balance of nitrogen supply to meet tree demand is a challenge for growers. 
  
   
• Higher rates of irrigation resulted in bigger cherries
  
   
• Foliar micro-element (manganese, zinc and calcium carboxylate) and potassium sulphate sprays were more effective for fruit and leaf uptake than delivery via fertigation 
  
   
• Manganese, zinc and calcium carboxylate sprays had no measureable impact on fruit quality.
  
   
• Potassium application increased fruit firmness at harvest.

ACT NOW

Download these fact sheets based on the research findings:

• Cherry shedding under the microscope
• Understanding flowering, fruit set and crop load in cherries
• Manipulating nutrition for fruit quality and shelf life
• Fruitlet abscission in sweet cherry