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Bruising costs potato growers £26 million a year

11 August 2011

 

With dry weather exacerbating the risk of bruising potatoes at harvest, AHDB Potatoes has called on growers to take a proactive stance and make quality assessments at all stages of harvesting, from lifting to store loading.
 
“In addition to costing growers an estimated £26 million per year, bruising does untold damage to consumer confidence.” says AHDB Potatoes technical executive Gary Collins. “Undamaged potatoes are the first thing shoppers look for.
 
 “Growers shouldn’t adopt the ‘one size fits all’ approach to harvester setup; the harvester settings should be altered for each crop in accordance with soil conditions,” he urges.
 
Scottish Agronomy senior agronomist Eric Anderson says: “Ideally, field samples should be taken in advance of harvest and put through a system such as a bruise barrel to test bruise susceptibility. These samples should then be hot-boxed and assessed for bruising and damage. This will highlight the crops most at risk from harvesting and grading damage, allowing a grower to choose to harvest fields with the lowest risk first. 
 
“Alternatively, open up a field with the harvester and take representative tuber samples a day or so before committing to lifting the whole field. Bruising can vary between fields, so sometimes it is well worth leaving one area and returning to it at a later date.”
 
Monitoring is vital to ensuring the least possible damage to tubers and ensure maximum saleable yield. The minimum action taken should be to monitor tubers from five to six loads per day at the final handling point i.e. end of the harvester elevator or grader and look for excess bruising and damage.
 
“If this is high, more samples should be taken throughout the system to pinpoint the issues, which could be as simple as leaving agitation on when it is not needed,” continues Mr Anderson.
 
“All loads delivered to stores should be monitored on arrival,” he advises. ”Furthermore, during harvesting, the operator should also conduct a visual check of the harvester and compared it with AHDB Potatoes harvester guidelines.” 
 
With bruising normally taking up to three days to show, a hot-box useful tool that helps identify bruising issues earlier.
 
“If a grower doesn’t have a hot box, crop can go into store without bruise and damage levels being monitored. This can prove costly as there may be downgrading or rejections of tubers later on. A hot-box can be a commercially bought piece of equipment, or made on-farm. It is important to remember that the tubers need fresh air to avoid breakdown or the development of ketones which can look like bruising. The setup should be 34-36oc, with 95-98% relative humidity for 15 to 24 hours. Samples should be manually peeled and assessed as soon as they are removed from the hotbox.
 
“Our understanding of bruising susceptibility has moved on in recent years – we now know more about a crop’s pre-disposition to damage, although this only becomes evident when you put the harvester through. A good on-farm risk assessment system will help pinpoint where bruising occurs and help growers avoid costly rejections.
 
“Bruising is a significant factor affecting the whole of the GB potato industry and it is estimated that each grower is losing £200/ha as a result of bruising,” says Mr Anderson. “Many people think that bruising is influenced solely by the dry matter. However, bruising sensitivity depends on variety, tuber size and shape, age, nutrition, soil type and temperature, in addition to tuber firmness (turgor).”
 
Further AHDB Potatoes-sponsored research work is ongoing at University of Leeds and Cambridge University Farm to increase the understanding of the relationship between bruise susceptibility, tuber cell wall properties and tuber mechanical properties.
 
“In another season, good planning prior to planting will help minimise risks. Growers should check areas such as separation, clod and stone removal, correct machinery set-up and tractor wheel size and track width.”
 
For more detailed information go to www.potato.org.uk/growing/bruising  
For a H&S DVD that covers harvesting email potatoes.publications@ahdb.org.uk
 
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