New Zealand Journal of Crop and Horticultural Science
abstracts
Effect of environment and time of planting on the production and quality of
yacon (Smallanthus sonchifolius) storage roots
J. A. Douglas
J. M. Follett*
New Zealand Institute for Crop and Food Research Limited
Private Bag 3123
Hamilton, New Zealand
email: douglasj@crop.cri.nz
M. H. Douglas
New Zealand Institute for Crop and Food Research Limited
Private Bag 50 034
Mosgiel, New Zealand
B. Deo
New Zealand Institute for Crop and Food Research Limited
Private Bag 4704
Christchurch, New Zealand
J. J. C. Scheffer
New Zealand Institute for Crop and Food Research Limited
Cronin Rd., RD1
Pukekohe, New Zealand
R. A. Littler
Department of Statistics
The University of Waikato
Private Bag 3105
Hamilton, New Zealand
M. Manley-Harris
Department of Chemistry
The University of Waikato
Private Bag 3105
Hamilton, New Zealand
Abstract The tuberous root yields of yacon (Smallanthus
sonchifolius) were compared from field trials planted in September, October,
and November at four sites (Pukekohe, Hamilton, Lincoln, Mosgiel) across New
Zealand. The September plantings gave the highest yields at all sites, with
the October plantings giving 17% less yield and the November plantings 61%
less. The September planting at Hamilton produced the highest yield of 90
t/ha, Pukekohe 64 t/ha, Lincoln 22 t/ha, and Mosgiel 15 t/ha. Regression
analysis established a strong positive relationship between dry root yield
and accumulated growing degree days (GDD) below 10°C calculated for base temperatures 0, 6, and 8°C
(R2 = 0.87–0.88). Regression analysis R2 values declined
above 10°C. Dry root yields were high where heat accumulation was at least
1800 GDD8 for the growing season with c. 1 t/ha of dried roots being produced
for every additional 100 GDD8 above 1200 degree days. This relationship helps
to identify suitable production environments for yacon. Best root production
also needs an undefined level of cool temperatures as at the warmest site crown
production was favoured. Total fructo-oligosaccharide (FOS) content of the
yacon roots varied from 48.2% to 67.5%. November yacon had the lowest FOS content
and conversely the highest content of non-FOS carbohydrates.
Keywords yacon;
Smallanthus sonchifolius; time of planting;
root yield; fructo-oligosaccharides; growing degree days
New Zealand Journal of Crop and Horticultural Science, 2007, Vol. 35:
107–116
0014–0671/07/3501–0107 © The Royal
Society of New Zealand 2007
*Deceased.
H06086; Online publication date 20 March 2007. Received 12
September 2006; accepted 9 February 2007
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