Phillip Sylvester, Extension Agriculture Agent, Kent County; phillip@udel.edu; Cory Whaley, Extension Agriculture Agent, Sussex County; whaley@udel.edu; James Adkins, Associate Scientist-Irrigation Engineering; adkins@udel.edu; Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu
Wheat has quickly reached heading and is flowering in some parts of the state. This is an important time for Fusarium head blight management, which was discussed in the April 27 issue: click here http://extension.udel.edu/weeklycropupdate/?p=11688
It is also important to pay attention to soil moisture during this critical time. Relatively warm temperatures and lack of recent rainfall may have depleted soil moisture levels. Although the forecast calls for thunderstorms, growers with the ability to irrigate should consider doing so, with the goal of keeping available water content >50%. There are a number of tools available to the grower for measuring soil moisture, ranging from electronic soil moisture sensors to a soil probe. It is probably too late to setup sensors in the field, but you can still estimate soil moisture by feel and appearance. Here is a helpful factsheet: click here https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_051845.pdf
Essentially, you use a soil probe to determine your soil moisture level within the depth of the root zone. If you determine soil moisture to be less the 50%, consider irrigating.
From 2013 to 2016, we conducted research at the UD Warrington Irrigation Research Farm to evaluate the impact of various irrigation strategies on yield and to determine the optimal strategy to maximize yield (sponsored by the Delaware Crop Improvement Association). We’ll skip right to the results – irrigation resulted in significantly higher yields in three of four years compared to a non-irrigated check. On average, yields were 7-14% higher compared to the non-irrigated check. There were only slight differences between the various irrigation strategies. However, we discovered a significant trend; adequate soil moisture levels must be maintained before flower and at levels high enough to support the crop through flowering and early grain fill. Our take home message is to consider irrigating during periods of dry, warm weather a couple of weeks before and after flowering. Growers should adopt an irrigation strategy that monitors soil moisture levels early on and that provides enough water to carry the plant through flowering and early grain fill. Given the extended period of dry weather and variable soils throughout the state, plan to check your own fields now. Continue to monitor your soil moisture level after each irrigation to ensure adequate water is available within the root zone. It may take multiple passes with the irrigation to fully recharge the soil profile. Finally, there is a concern that irrigating wheat during flower may increase the risk of Fusarium head blight. This is another reason growers should fill the profile before flower and resume irrigation after flower. However, if you need to irrigate during flower to protect yield, do so during the day, allowing enough time for the heads to dry before dusk.