James Adkins, Extension Engineer, adkins@udel.edu
Established small grains are burning through 0.02-0.03 inches of water per day if not tilled and 0.04-0.05 inches under conventional tillage. Since the roots are shallow, irrigation should be applied in small (0.2-0.35 inch) increments at a high frequency of every 4-8 days. Try to take advantage of this unusually warm weather to get the crop established by ensuring adequate soil moisture. If in doubt on whether irrigation is needed, use the hand-feel method to estimate soil moisture from a 0-4” soil sample and start irrigation whenever the soil is below 50% available water. https://nrcspad.sc.egov.usda.gov/distributioncenter/pdf.aspx?productID=199
Cover crops will also need similar amounts of irrigation to establish a good stand and encourage root growth. Early planted stands of radish and other species may be using as much as 0.1 inches per day if fully canopied. While it pains me to recommend irrigation on cover crops in a low margin year, the cost of application ($4-$6 per acre inch) is relatively insignificant compared to the cumulative seed and planting costs already incurred to establish cover.