Richard Taylor, Extension Agronomist; rtaylor@udel.edu
This past winter at a Kent County Crops Masters program on irrigation a number of growers talked about their experiences with irrigating wheat. In addition, I’ve talked recently with others who were able to estimate the value of irrigation on the sandier soils in southern Delaware. It seems that many of the growers irrigating wheat on sandy loam soil types in Kent County found yield responses on the order of 3 to 5 bu/acre this past year. On the loamy sands and sands in southern Delaware, growers report a larger response in the range of 20 to 30 bu/acre during 2006. This year’s very dry spring in many parts of the state suggests that once again we will find responses to irrigation. It’s still my contention that your best response to irrigation on wheat will be when you apply a lot of water early (before heads emerge) in an attempt to bring soil water levels to field capacity in both the top soil and the subsoil horizons. Once heads emerge, you should not irrigate while the wheat head is in flower since this can lead to the development of head scab. In our limited research on irrigated wheat, we also found small decreases in yield when irrigation was applied after heading. For that reason, unless the soil becomes excessively dry, I would suggest heavy early irrigation to charge up the soil water supply, no irrigation during heading and initial seed fill, and limit the number of irrigations after the seeds begin to fill to the minimum number possible that will keep the wheat growing up to maturity.
Other than the lower than ideal rainfall totals across the region at this point, the growing season has generally been very favorable for wheat development with cool nights and moderate daytime temperatures. Temperatures have been nearly ideal for wheat. Limited rainfall and cool weather also means that very little of the nitrogen fertilizer applied to wheat has been lost so yield potential from the fertility viewpoint should be high.