Soil Temperature Effects on Winter Wheat and Winter Barley Emergence in the Field

In the Pacific Northwest, potential yield and erosion control are affected by time of stand establishment of winter cereals. The objectives of this study were: 1) to investigate the effect of soil temperature on the rate of first and 70% emergence of winter wheat (Triticum aestivum L.) and winter barley (Hordeum vulgare L.) in the field; and, 2) develop a means of predicting the average effect of planting date on emergence at one location in eastern Oregon. Two depths of soil mulch on stubble- and bare-fallowed field plots were used to investigate the effect they have on soil temperature and on rates of first and 70% emergence. The soil was a Walla Walla silt loam (mixed, mesic Typic Haploxeroll). McDermid wheat was planted at biweekly intervals from August to November 1976 and 1977. Hudson barley was planted at similar intervals in the fall of 1976. Seeds were placed in moist soil with a deep furrow drill. Average soil temperatures were 0.5-2.0 C higher at 10 cm under the bare-fallow than under the stubble-fallow treatments, but tillage did not affect emergence rate. Regression equations of emergence rate and average 10-cm soil temperature at a nearby U.S. Weather Bureau shelter were highly significant. The equations indicated that wheat required 149 and 210 degree days above a minimum of 0.7 and 0.4 C to obtain first and 70% emergence, respectively. Barley required 92 and 159 degree days above a minimum of 6.1 and 3.5 C for first and 70% emergence, respectively. A graph of 15-year average daily 10-cm temperature from 1 August through 30 November at Moro, Ore., was used with the equation to predict: 1) the average last date of planting to obtain emergence within a specified time period; and 2) the average length of time needed for emergence when the crops are planted on a given date. The average latest time to plant and obtain 70% emergence within 14 days is the last week of September.