When shape and size really does matter
The size and shape of sweetpotato roots significantly influence sprout production, according to new CQUniversity research.
PhD graduate Craig Henderson has spent the past few years researching how to improve the efficiency and quality of sweetpotato sprout production in Australia, with findings that are relevant globally.
“Australian growers rely on producing their own planting material to ensure high-yielding crops,” Dr Henderson explained.
“This process involves burying virus-free sweetpotato bedding roots (similar in size and shape to supermarket sweetpotatoes) in nursery plant beds on their farms. The sprouts that emerge are cut when they are about 30–40 cm long and used for planting. I studied how the size and shape of these bedding roots, along with their installation and management in nursery beds, affect the number and quality of sprouts. My research also examined how nitrogen fertiliser influences sprout growth.”
The study found that medium-sized roots (five to eight cm wide) were the most efficient, producing high-quality sprouts without wasting space or being unnecessarily costly.
“Cutting sprouts at the right time is crucial; harvesting too early in particular reduces both the quantity and quality of usable sprouts,” he explained.
“Nitrogen fertilisation of plant beds had less impact than expected. Possibly there is substantial nitrogen fixation by beneficial bacteria within the bedding roots, however this needs much more investigation.”
Dr Henderson said the study also found that fungal and bacterial diseases in nursery beds, especially during wet weather, were a major issue, and could significantly reduce sprout production.
Have the findings been adopted by industry yet?
“Some recommendations, such as the ideal size of sweetpotato roots for planting, the optimal timing for sprout cutting, and adjustments to plant bed installation and irrigation practices, are already being adopted by growers,” Dr Henderson explained.
“However, further research is needed to address disease management in nursery beds, which remains a significant challenge.”
Dr Henderson said in the meantime, through adopting the findings, producers can:
- Optimise their bedding root orders and nursery bed management to maximise high-quality sprout production per square meter, saving money and time
- Better estimate the area of nursery beds needed to produce sufficient planting material for their fields
- Reduce losses caused by disease, through improved plant bed construction and irrigation practices
“These improvements are expected to result in higher yields and lower production costs for sweetpotato farmers.”
