Climatic risk for sweet corn production in Canterbury, 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 °C days above a base temperature of 6°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 15.8°C and the first autumn frost occurred late. Timaru, the most southern location, had earlier frosts and a 13.7°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 14.6°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