Accumulated temperature and maize development in England

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Abstract
Summary: Information is given on dates of sowing and mid-silk for Inra 200 in 40 experiments (two each year at Oxford, 1962–75, and at Cambridge, 1970–5), together with cumulative temperatures between these dates. Two methods of defining effective temperature for maize development have been considered, namely the method advocated by U.K. Meteorological Office with 10 °C as the base temperature (the Ag. Met. method) and that defined in Ontario units. The regression relation between accumulated temperature and dry-matter content of the grain during ripening has also been calculated, from data obtained in the years 1966–74, and assessments made of cumulative totals in Ag. Met. day °C and in Ontario units from the date of silking until the grain D.M. content is 40%, when the crop is considered suitable for ensiling, and from silking until grain D.M. content is 60%, when the crop may be considered ripe.Cumulative temperature totals were significantly more stable over experiments than time expressed in calendar days. Totals of Ontario units were less variable than totals of Ag. Met. day °C. Estimated requirements for Inra 200 were 405 day °C or 1380 Ontario units from sowing to mid-silk, 255 day °C or 800 Ontario units from silking to 40% D.M. in the grain (for silage crops), and 380 day °C or 1235 Ontario units from silking to 60% D.M. in the grain.