New Zealand Journal of Crop and Horticultural Science abstracts
Climatic risk for sweet corn production in Canterbury, New Zealand
D. R. WILSON
New Zealand Institute for Crop & Food
Research Limited
Private Bag 4704
Christchurch, New Zealand
M. J. SALINGER
National Institute of Water and Atmospheric
Research Limited
P.O. Box 3047
Wellington, New Zealand
Abstract The risk of sweet corn (
Zea mays L.) crops
failing to reach harvest maturity as a result of climatic variability among
seasons was quantified for four locations on the east coast of New Zealand's
South Island. Results of field experiments in the region showed that three
representative cultivars had thermal time requirements from planting to
maturity ranging from 1215 to 1320 deg.C days above a base temperature of
6deg.C. In simulations, crop success or failure was estimated for combinations
of five hypothetical cultivar maturities and four planting dates spanning the
ranges likely to be used in the region. Calculations used temperature records
that ranged from 17 to 25 seasons depending on location. A crop was judged to
fail if either its thermal time requirement was not met by 30 April or it was
frosted before the requirement was met. Allowance was made for the fact that
some "failed" crops were sufficiently close to maturity to be harvested
successfully. Risk was negligible at Blenheim, the most northerly location,
where seasonal mean temperature between 15 October and 30 April was 15.8deg.C
and the first autumn frost occurred late. Timaru, the most southern location,
had earlier frosts and a 13.7deg.C mean temperature, and risk of failure was
high except for early plantings of early-maturing cultivars. Lincoln,
representing the intermediate area of central Canterbury, had a mean
temperature of 14.6deg.C and a high risk of failure for late plantings of
late-maturing cultivars. This location is probably at the climatic limit for
commercial sweet corn production with an acceptable level of risk, using
currently available cultivars. A warming trend since 1928 has resulted in a
substantial decrease in risk over the period. The analysis highlighted the
marginal nature of the Canterbury climate, the effect on risk of the
sensitivity of the crop's development rate to temperature, and indicated the
potential benefit of any further climatic warming.
Keywords sweet corn; Zea mays L.; temperature; thermal
time; phenology; climatic risk
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