Source: A. J. Bussan, Department of Horticulture, U. W. Madison
Later this week the weather is to turn incredibly hot. For many parts of the state from the Illinois border all the way to Hwy 29 we have seen little precipitation unlike our fellow residents from the far Northern reaches of the state. ET at Hancock and Arlington has averaged 0.2” per day over the past week.
Air temperatures > 90 F and sunny days will lead to ET typically 0.25 to 0.27” per day. These hot air temperatures will increase energy demand across the state and may limit the time that irrigation systems will be allowed to operate.
Try to irrigate to near field capacity for all crops to prepare for the oncoming warm temperatures, especially potatoes, snap beans within days of flowering or with pin beans, and peas where you are trying to finish the crop. Deep rooted crops such as corn, sweet corn, soybean, or alfalfa may have to rely on soil moisture reserves during the heat stress so irrigation water can be applied to shallow rooted crops with higher sensitivity to heat and drought stress depending on how you have split fields under your pivots. Also remember that irrigation efficiency can be improved when irrigating outside the heat of the day.
Fresh market farmers and gardeners in Southern and Central parts of the state need to irrigate fields and gardens as well. Multiple vegetables from lettuce to tomatoes will benefit a great deal from irrigation at the current time. Soil moisture has been depleted even on the best soils and the heat will cause substantial stress in the coming days. Prioritize irrigation on higher value vegetable crops. Sweet corn will benefit from irrigation, but not as much as other crops. Winter squash and pumpkin do not need irrigation as much as other vegetable either and can be watered when the conditions are less stressful or soil moisture status is in good shape for other crops. Make sure to monitor how much irrigation water has been applied so you do not apply to much water. Also remember, the best time of day to sprinkler irrigate is in the morning so the canopy is wet at the same time as dew would normally occur. This way the sun can dry the canopy and prevent a number of foliar diseases.
Make sure to keep yourself and your staff hydrated as well and stay safe.