James Adkins, Irrigation Engineer, adkins@udel.edu
Field Corn
While Wednesday (6/26/24) night’s rain provided temporary relief for most of the state (my condolences to central Kent County), last week’s weather pattern was the highest water demand period I have seen since 2012. Unfortunately for most, the rainfall merely allowed for a brief catch-up for the many fields that were severely behind. Evapotranspiration (ET) for April 15 planted corn averaged 0.3” per day for the past week while corn planted May 12 was modeled to have used an average of 0.24” per day. Most of Delaware’s irrigation systems struggle to meet the 0.3” demand without supplemental rainfall.
Looking forward to the next 5 days, ET is expected to be lower with early corn predicted to average 0.25” of daily demand and later corn in the 0.2” per day range. Systems that are unable to meet these daily demands should be run at maximum capacity to maintain soil moisture while anticipating yields to be somewhat limited. In deficit irrigation scenarios, avoid the temptation to run the systems fast applying very little water frequently. Applications in the 0.4” – 0.7” range provide the best opportunity for beneficial crop water use and minimize evaporative losses.
Soybean
In normal years I do not recommend irrigation of full-season beans until they reach the R1 or flowering stage. Unfortunately, some irrigation is going to be necessary simply to keep the crop alive this year. If your beans have not flowered a weekly application of 0.5”- 0.75” should be sufficient to keep them going but any fields that are in flower are predicted to use 0.25” per day in the week ahead. Keep in mind that soybeans tend to draw water from a shallower soil profile than corn so multiple small applications are ideal. If your beans have recently started flowering, you haven’t been irrigating, and didn’t get substantial rainfall, you are going to need to replenish the 1.5” of soil moisture deficit before adopting a 0.25” per day approach. Double crop beans should be managed to maximize vegetative growth to obtain canopy ASAP and will require irrigation from the start and likely before planting. Recently emerged beans are forecasted to use 0.5” per day in the coming week.
General
The Delaware Irrigation Management System (DIMS) has been revamped to be mobile-friendly. This system automatically tracks your crop water usage using data from the DEOS weather station network and provides a forecast and prediction model to plan for the upcoming 5 days. To use this free system to schedule irrigation visit https://dims.cema.udel.edu/
Irrigation wells occasionally fail. There is an emergency well replacement process through DNREC however if you do not have a water allocation in place, your replacement will be held up for the mandatory 2-week advertising period. For more information on water allocations contact Patty Murray of the DNREC division of water at patricia.murray@delaware.gov or 302-739-9948
24-hour Rainfall values for 6/26 – 6/27/2024