Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu
Since wheat seed sizes can vary, planting rates should be based on the number of seeds planted and not in lbs/acre. Different wheat varieties have been observed to range from 9,900 to 21,400 seeds per lb. Between 2018-2020 at the Carvel Research and Education Center in Georgetown, we observed that seeding rates from 1.5 to 2.0 million seeds per acre had the highest average yields, while yields slightly dropped at 2.2 million seeds per acre (Figure 1). Planting 1.2 million seeds or less produced the lowest yields.
Lower planting rates will attempt to make up with additional tillering, but according to drone imagery in this study, most of this growth occurs in February and March. The higher planting rates (>1.5 million seeds) had greater plant biomass in the fall, while rates <1.5 million attempted (but failed) to catch up in the early spring. Therefore, it is important to plant the right rate in soils with adequate moisture and fertility to achieve good tillering before winter vernalization.
When planting into corn fields, be aware of how residue may affect emergence and soil nitrogen availability. Irrigated fields with high yields may have low fall nitrogen, while some of our rainfed fields that suffered from drought may have plenty of residual soil nitrogen left for small grains. The best way to find out is a soil test.
Figure 1: Yields from the different seeding rates as a graph example.