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Ongoing project

Investigation of skin hardening and splitting disorders in sweetpotatoes (PW18001)

Key research provider: The Queensland Department of Agriculture and Fisheries

What’s it all about?

Beginning in April 2019, this investment represents a collaboration between Australian and US researchers to better understand the causes behind splitting and skinning in sweetpotato crops, and how they can be reduced.

Splitting can occur during storage, but in cooler weather the main nematode-resistant sweetpotato cultivar grown in Australia is prone to splitting on-farm at harvest, with reported losses as high as 30 per cent. Meanwhile, other cultivars are susceptible to skinning damage during harvest and post-harvest operations, leading to sunken, darkened areas on the skin surface.

Initial research in the US has drawn a link between cultivar, crop nutrition and skin hardening, which this investment delving deeper into. Specifically, the researchers are looking at the effect of nutrients and whether their manipulation can influence skin hardening in different varieties, in turn influencing the rates of splitting and skinning in sweetpotato.

Controlled glass house trials have been conducted in Queensland and Louisiana in the USA, to investigate ways to reduce skin hardening and splitting in sweet potato cultivars.


The Louisiana trials have been conducted at the Louisiana State University (LSU) AgCenter, to investigate the role of potassium, phosphorus and two different forms of nitrogen on skin hardening and root splitting in sweet potato tubers. Initial results were to be presented to industry in early 2020 along with Prof. Villordon from LSU, however this has been rescheduled to November-2020 in response to COVID-19 travel restrictions.


Two further experiments were established in Queensland to look at possible links between calcium (Ca) and boron (B) on skinning, skin hardening and root splitting in four sweet potato cultivars (Beauregard, Bienville, Bellevue, and Murasaki). Both experiments ran for 140 days, with assessment dates at 50 days after planting (DAP) and again at 140 (DAP). Experiments were staggered with the first beginning (planted) in December-2019 and the second in February-2020.

Plants received one of the three nutrient treatments from days 51 to 140:

  • Hoagland’s solution
  • Hoagland’s solution minus Calcium
  • Hoagland’s solution minus Boron.

Elements such as skinning, splitting and periderm (skin) thickness were actively being monitored through the trials with activities such as water pressure testing on skinning rates and microscope analysis on thickness measurements undertaken. The final harvest (140 DAP) has been completed for both trials and data is currently undergoing analysis.

Importantly, alternative delivery methods of group workshops to keep growers updated on trial outcomes are being explored due to current COVID-19 travel restrictions.

Related levy funds

This project is a strategic levy investment in the Hort Innovation Sweetpotato Fund