Small Grains Specialist, University of Minnesota
Wheat, barley, and oat are cool season annuals and are most productive when they grow and develop during cool weather. The yield potential of a crop is largely determined by the 6 leaf stage. Cool temperatures during this period are particularly important for the development of a high yield potential. For example, the number of
tillers that ultimately produce grain at harvest declines as planting is delayed (Figure 1). The number of spikelets per spike is determined during the 4 to 5.5 leaf stage (Figure 2). Spikelet numbers are negatively correlated with temperature; spikelet numbers are greater when temperatures during the 4-5.5 leaf stages are cool.