Corn heat unit variability and potential of corn (Zea mays L.) production in a cool climate ecosystem

Abstract

Recent interest in corn (Zea mays L.) production among forage producers in Newfoundland, Canada, raises questions of risk, scale and impact of seasonal heat accumulation for attaining maturity. The objectives of this paper were to present the results of corn performance in a short-term trial at three selected sites (St. John’s, Deer Lake and Stephenville), calculate corn heat unit (CHU) probability levels of these sites to assess the long-term risks, and determine CHU values of locations across Newfoundland to describe their suitability for corn production. Daily values of CHU were accumulated from the conversion of daily maximum (Tmax) and minimum (Tmin) air temperature for each location using the last day of 3 consecutive days in the spring with mean daily air temperatures (Tmean) ≥ 12.8°C as the starting date and the first date of a killing frost in the autumn (Tmin ≤ -2°C) or 30 September, whichever was earlier, as the ending date. Corn grown for silage at the three selected sites was within the desired level of 250–350 g kg-1 DM at 50% kernel milk line (R5.5) stage. Corn reached harvesting stage (R5.5) before the occurrence of a killing frost at Deer Lake and Stephenville. To protect seedlings against killing frost, mulching with transparent polyethylene film is recommended at St. John ’s. There was considerable year-to-year variability in CHU at each of the three sites. Differences in seasonal CHU for St. John’s were identified over two periods: from 1945–1989 and 1990–2001. The most recent period (1990–2001) has generally been warmer than the earlier period. A warming trend, as indicated by the CHU trends at the three sites, holds the prospect of some significant longer-term benefits for Newfoundland agriculture. Across Newfoundland, average (1956–1990) seasonal CHU accumulations (CHUave) based on STARTave and ENDend) ranged from 1686 at St. Lawrence to 2695 at Gander. Using the 80% probability (START80% and END80%) dates, the CHU80% ranged from 1486 at Port aux Basques to 2382 at Gander. The CHU values would help producers select what corn hybrid(s) to grow in their area. Overall, these analyses underline the potential for successful corn production in Newfoundland. Key words: Corn (Zea mays L.) maturity, corn heat units, cool climate region, 50% kernel milk line (R5.5), temperature