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JenREES 8-30-20

Grateful Nebraska held our State Fair this year! Seeing the youth competing, showcasing 4-H projects, and the excitement, smiles, and friends reconnecting from across the State this past weekend was heartwarming!

Received many calls about end of season irrigation this past week. Would encourage our farmers to finish the season well! You’ve been through much in another trying year and the past few weeks have been extra hard keeping up with irrigation, cleaning out bins, and getting combines ready in the heat. It can be tempting to just stop but would encourage you not to quit irrigating too soon, particularly on soybeans. Soybean maturity (R7) is defined when 50% (or all) of the field plants possess one mature pod (when the interior white membrane no longer clings to the seed). In most years, most leaves and pods will have changed color (from green to yellow-green or yellow) by this plant-based R7 date.

The heat has pushed crops along, but we’ve also had a great deal of humidity. Corn is moving the starch line slower in irrigated fields. That’s a good thing for fill and a harder thing regarding labor, time, and money. A lot of corn in this area is 1/3 milk and I just saw a few fields at ½ milk over the weekend. 

  • Corn at ¼ milk needs 3.75” (approximately 19 days to maturity)
  • Corn at ½ milk needs 2.25” (approximately 13 days to maturity)
  • Corn at ¾ milk needs 1” (approximately 7 days to maturity)
  • Soybean at full seed (R6) needs 3.5” (approx. 18 days to maturity)
  • Soybean with leaves beginning to yellow and pod membrane still attached to seeds (R6.5) needs 1.9” (approx. 10 days to maturity)

So, we’re potentially looking at one to two more irrigations yet for some of this corn and soybeans depending on the current status of your soil moisture profile, development of the crops in your particular fields, and any rain. It is recommended to allow that soil moisture profile to dry out to 50-60% depletion towards the end of the season to capture moisture in the off-season. So one way to consider this is a step-wise approach. If you typically irrigate at 35% soil moisture depletion and have around 2” left, the next week you could wait till a trigger of 40% depletion with the following week’s trigger around 50%. Again, this depends on your individual field’s soil moisture status and crop development after a taxing August.

Upon physiological maturity, corn ears begin drooping down. However throughout the area, corn ears are doing this that aren’t at ½ starch yet. These ears will black layer prematurely at the cost of yield. Dr. Bob Nielsen from Purdue shares that yield penalty can be as much as 40% at denting when there’s essentially no milk line visible and around 12% at half milk. So what causes this? The ear shank can collapse when there’s a lack of turgor pressure due to stress from the inability to keep up with crop water demand. August has been abnormally dry with warmer than average temperatures the past few weeks. Sometimes the ear shank also cannibalizes itself, similar to what can happen in stalks. Perhaps part of this can be from poor root development or lack of root development into deeper layers? In areas that have received less rain, perhaps deeper soil layers are drier in spite of having moisture in the top soil layer from irrigation? For those with conventional hybrids, European corn borer tunneling can also cause this type of collapse. There’s also some hybrids that I notice this happening more than others; perhaps genetics also plays a roll? That shank is the source for feeding the ear, so when it collapses, it weakens it. Keep an eye on ears in these fields as we approach harvest and consider getting at them sooner if possible.

Drooping corn ears in this irrigated field with green plant tissue above ears. This corn was getting close to 1/2 milk.
Photo by Dr. Jim Specht showing end of season soybean development stages. Notice the white membrane still attached to the seed in R6 stage and how it disconnects at R7 (maturity). Not all pods on the plant may be at R7 at the same time. R7 for all the plants in the field is considered when 50% (or all) of the field plants possess one mature pod (when the interior white membrane no longer clings to the seed). In most years, most leaves and pods will have changed color (from green to yellow-green or yellow) by this plant-based R7 date.
Sudden Death Syndrome (SDS) has been observed for the past several weeks in fields. Thankfully it’s been minor this year compared to last year. It’s wise to take a soil sample for soybean cyst nematode (SCN) in these areas of the field to determine if you also have a nematode problem. The combination of the diseases has a synergistic impact on yield.

JenREES 8-16-20

Crop Updates: For the past week, crops used around 0.22” per day in the York area, around 0.20” as one goes east towards Ithaca and closer to 0.25” per day going south towards Harvard and Guide Rock (based on High Plains Regional Climate Center data posted on CropWatch).

As we think about water use the finish the year, the following come from the NebGuide Predicting the Last Irrigation of the Season found at: https://go.unl.edu/k74n:

  • Corn at Beginning Dent needs 5” of water (approximately 24 days to maturity)
  • Corn at ¼ milk needs 3.75” (approximately 19 days to maturity)
  • Corn at ½ milk (Full Dent) needs 2.25” (approximately 13 days to maturity)
  • Corn at ¾ milk needs 1” (approximately 7 days to maturity)
  • Soybean at beginning seed (R5) needs around 6.5” (approx. 29 days to maturity)
  • Soybean at full seed (R6) needs 3.5” (approx. 18 days to maturity)
  • Soybean with leaves beginning to yellow (R6.5) needs 1.9” (approx. 10 days to maturity)

Spent a lot of time last week looking at ear development in fields, particularly those impacted by the July 8th windstorm. Also appreciated a long conversation with John Mick with Pioneer on what he was seeing. For the most part, I’m seeing a lot of ‘normal’ ears that vary in the amount of tip back from lack of pollination and/or kernel abortion. Less commonly seen are ears with 3/4 husks. On plants that were pinched, continue to see messed up secondary and/or tertiary ears after the loss of the primary ear. On plants that bent and righted themselves, seeing a variety of things. Some are more ‘normal’ while other ears are much smaller that either didn’t pollinate well and/or had kernel abortion.

Last month, had mentioned a curious thing regarding how many hybrids are putting on multiple ears on the same ear shank, on the primary ear node. It’s far more than I’ve ever seen before. In sharing some observations with Dr.’s Tom Hoegemeyer and Bob Nielsen, they share it’s most likely a genetic X environmental response under excellent growing conditions or some other phenomena. As I continued to see these ears in fields and husk them back, for the most part, they don’t appear to be detrimental to the main ear, which is good. So it’s more of a curiosity than anything.

Many of us probably don’t examine ear shanks much in comparison to the ears. However, when one does look at ear shanks, one will observe they are similar to the corn stalks in that there are nodes and internodes. Each node also produces a leaf (in this case a husk leaf) instead of a collared leaf such as what happens on the main stalk. And each node (on stalk and on ear shank) has an axillary meristem which allows for ear development. Normally, there must be genetic or hormonal suppression so that only one main ear is formed on a shank at a stalk node. It’s not uncommon for us to observe an ear on different nodes of the stalk (ex. Nodes 12 and 13). What is more uncommon is to observe multiple ears on different nodes of the same ear shank, such as what is being observed this year.

Renovating Lawns: If your lawn is in need of repair, now through mid-September is a great time-perhaps the best time-to do so! This resource, Improving Turf in the Fall at https://go.unl.edu/rz9z is a great one to walk you through renovation depending on your situation. Some lawns can be easily improved by adding fertilizer this fall and/or overseeding. Some may need total renovation, which starts with a glyphosate (Roundup application) followed by waiting at least a week to then prepare the soil for planting.


Multiple ears on the same ear shank (with husk tissue on left and husked on right). Doesn’t appear to be impacting main ear in most fields I’ve seen these in. And, this is occurring on primary ear nodes and within fields (not just in endrows or in lower population areas).

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Pretty impressive brace root development on leeward side of plants that tried righting themselves.

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Ears from the plants with the brace roots from above photo. These are pretty decent with some tip back, but otherwise more ‘normal’. Other plants like this have ears that have poor kernel set.

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Seeing some ears with 3/4 husk.

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Bent plant that tried righting itself with a ‘zippered’ appearance to ear and poor pollination in addition to kernel abortion.

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Plant with loss of the primary ear showing multiple ears on the secondary and tertiary ear nodes.

More on Last #Irrigation

It’s been a long irrigation season thus far, but we are so thankful for irrigation in this part of the Country during this drought of 2012!  Questions continue to roll in regarding last irrigation for corn and soybeans.  Corn at 1/2 starch only needs 2.25″ to finish up so it’s important to know what your soil moisture status is.  For most irrigated producers, at 1/2 starch, you should be finished irrigating.  

For soybeans at R5 or beginning seed fill, you still need about 6.5″ to finish out the crop.  At R6 when the seeds are filling, that drops to 3.5″.  At R7 when you begin to see leaves yellowing, that is beginning maturity and you are finished irrigating.  They key is we don’t want to fill the profile going into the fall as we’d like to replenish the profile with fall and spring rains and winter snow.  However, with soybeans, it’s also critical not to stop irrigating too soon during seed fill.

Gary Zoubek, Extension Educator in York County sheds more light in the following video produced by UNL’s Market Journal.

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