Category Archives: Corn

Irrigation Termination Decisions for Corn and Soybean

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As we approach the end of July, much of our corn and some of our soybean acres are in the latter portion of their respective reproductive growth stages. As we progress toward physiological maturity, lets revisit irrigation termination decisions for these two crops.

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Irrigation timing: Corn & soybean

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Photo credit: University of Tennessee Institute of Agriculture (UTIA), Shekoofa’s lab

Irrigation timing: Corn & soybean

As we head into the second week of June, many growers are understandably concerned about potential yield loss due to drought stress.  In this blog post our Extension Corn and Soybean Specialist, Dr. Jake McNeal and I have discussed irrigation strategies for both corn and soybean.

Understanding the relationship between crops and their environment is critical for effective irrigation management. Crop water use and demand varies as a function of growth stage and weather conditions.  Furthermore, the capacity of a soil to hold and deliver water to plant roots (soil water–holding capacity) varies widely across different soil textures.

Also, we want to emphasis that there is a distinct physiological difference between heat stress and drought stress, especially in corn. Even in the presence of adequate soil water, corn leaves will often curl inward from the leaf margins during extended periods of high temperatures. Many refer to this as “pineapple leaves” or a “pineapple crop”. Furthermore, it is very difficult to discern between the two without utilizing a soil water sensor in your crop.

Corn-The Mid-South region of the U.S. receives sufficient annual rainfall to grow corn without irrigation in most years. However, irrigation is common in corn production because rainfall is not always distributed adequately throughout the growing season for the crop, especially during critical reproductive periods. Therefore, not all rainfall can be considered effective. Continue reading

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Crunch Time for Weed Control

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Picture 1. Goosegrass escaping multiple glyphosate applications. Tipton County. Mid-June 2022

As the calendar turns to June weed management concerns change from ryegrass and horseweed to the summer annuals goosegrass, junglerice and Palmer amaranth.

Tennessee growers are in a real crunch time to control these three summer annual weeds. Big percentages of the corn, soybean and cotton crops all need some kind of POST application right now. The planter technology that can plant three different crops across large acreages very quickly has one drawback. The sprayers often cannot keep up to most every acre needing to be sprayed just as quickly. Continue reading

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Herbicide Stewardship

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It is crunch time for weed control in our row crops.  When every minute counts to get herbicide applied it is tempting to cut corners on herbicide stewardship.  The forecast would suggest that Tennessee will be entering a bit of a dry spell.  Herbicide drift is even harder for crops to recover from when drought stressed so please take time to use best management practices applying all herbicides but particularly products that contain dicamba and 2,4-D. Continue reading

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Corn Herbicide Maturity Cut-Offs

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How large can corn be before glyphosate could potentially cause injury? The glyphosate label states it can be applied up through the V8 corn growth stage. My experience has been if glyphosate is applied to corn larger than that it can at times cause ears to be barren.  This phenomenon is difficult to predict ahead of time as it can vary due to maturity of the corn at application, hybrid and weather.

Crop stage and/or crop height is used to determine the cutoffs for a given herbicide.  Often the label states the limits at whichever (crop stage or crop height) comes first.  Crop stage can easily be done by counting the number of leaf collars that are fully exposed (ex.  4 collars = 4 leaf) (Picture below).

4 leaf (collar) corn – V4 stage

Postemergence Corn Herbicides Crop Height Cutoff Crop Stage Cutoff
Accent 20 inches 6 leaf
Atrazine (Bicep, Degree Xtra, Acuron, etc.) 12 inches
Buctril 8 leaf
Callisto* 30 inches (without atrazine)
Capreno* 20 inches 7 leaf (without atrazine)
Corvus 2 leaf
Dicamba (Banvel, Clarity) 8 inches (1 pt/A) or
36 inches (1/2 pt/A)
5 leaf

Distinct 24 inches
Glyphosate – RR corn only 30 inches 8 leaf
Halex GT 30 inches 8 leaf
Hornet 24 inches
Armezon/Impact 8 leaf
Laudis 8 leaf
Liberty (Ignite) – LL corn only 24 inches 7 leaf
Diflexx 36 inches 6 leaf
Realm Q 20 inches 7 leaf
Resource 10 leaf
Resolve Q 20 inches 7 leaf
Roundup PM – RR corn only 8 leaf
Status 36 inches 10 leaf
Steadfast Q 20 inches 7 leaf
2,4-D 8 inches

*Note that if atrazine is added to herbicides such as Callisto or Capreno for example, the cutoff would be reduced to 12 inches.

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Corn and Soybean Tolerance to Flooding and Submergence

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Excessive rainfall over the weekend (5/12 and 5/13) in the North Western river counties has resulted in several calls this week concerning flooding and standing water in corn and to a lesser extent in soybean. Crop response will depend on the length of time the crop remains submerged and varies between corn and soybean. With rain still in the forecast for the next few days, here are a few agronomic considerations to be aware of. Continue reading

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