Replant corn – How to decide.

This year we had some fields that were planted early and then went thorugh a very wet, cold period and now the emergence is less than desirable in some areas of the field. Do I replant the poor sections, or the whole field (with the price of corn this would be a very costly option), do I leave it alone, these are all very good questions.

Corn replant decisions are difficult. The following table can be utilized as a guideline when assessing yield potential at various planting dates and populations. In general it doesn’t pay to replant corn where populations of healthy plants are greater than 18,000 plants per acre
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First we need to establish the population that has emerged. You can do this by counting the number of plants in 1/1000 of an acre (see chart). Do this a number of times in the field. Also, assess the cause of reduced emergence using the following checklist.

 Rotted seed or seedlings
 Sprout twisted or leaves expanded underground
 Seeds hollowed out (insect damage)
 Check seed intactness (firmness)
 If seed is watery or “yellowy pus” it is not going to emerge
 Do not worry about crooks or turns of the coleoptile (shoot) as it may be responding to the seed orientation (corn seed does have an up and down side); also, cold soil will often disorient coleoptile growth.

As this is a very difficult decision please contact your NK field representative or seed dealer if you have any questions.

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Does Corn have an expiry date?

Many of us would not drink milk past the expiry date, maybe on a dare but even then many of you are probably a little uneasy with just the thought of this. As corn harvest is slowed down due to weather or full elevators I get that same uneasy feeling I get thinking of drinking spoiled milk. In 2010 we planted our corn early and had great heat and rains throughout the summer in much of the corn producing areas of Ontario and Quebec and yet we are somewhat surprised that the standability is starting to weaken. Could it be that we have went past the expiry date on corn stalks and roots?
I would say yes. Current moisture levels are below 20% and the corn was fully mature (black layer) over a month ago, so the plant has been dead for a while. Dead plant material rots. If you add moisture (heavy dews, frequent rains even frost) it rots faster, plain and simple. Add high winds and rotting stalks break. One of the main differences I see in traveling from a Western corn area (mid west US) to an Eastern corn area is the higher level of moisture and therefore rot organisms that the corn plant must survive. In the East our expiry date is less than the West. Also, how the plants partitions its energy resources (sugars) – yield or plant health affects the expiry date of corn. If every plant only has one 2 gallon pail of energy to use where is it going to use it (ex. 1/2 gallon for stalks, 1/2 gallon for roots and 1 gallon for grain) each hybrid is different on how it partitions its 2 gallon bucket. Generally, the very high yielding genetics put more of its bucket into grain and the stalks and roots may run out as we go later into the season (shorter expiry date). Average yield with consistent standability may use more of its 2 gallon bucket for stalks and roots and therefore stand longer but yield less (long expiry date).

So what do I do as a grower? Harvest your short expiry date hybrids early to maximize the yield of those hybrids. This fall select a portfolio corn genetics that have long and short expiry dates.

Have a safe harvest.

Frost on small emerged corn

Contributed by Robert Moloney, NK Brand Seeds

The last few nights have been downright chilly across the province.  Fortunately even though the temps have dipped below freezing and there has been widespread ground frost, the small emerged corn out there at this point should come through it OK.  We’ll likely lose some emerged leaves, but they’re not critical to the plant at this point.

With the low temperatures the last few nights we will definitely be seeing some leaves burned off.  These leaves aren’t critical to the plant long term, so this isn’t a huge concern.  The good news is that the growing point of the plant is still well insulated underground at this stage and as long as it is still alive the plant will likely be fine.  A bonus right now is that we good soil moisture which will help keep the soil temperatures warmer, even when air temperatures drop below zero.  To have a significant number of plants killed we would need to freeze the ground deep enough to kill the growing point or have frost penetrate a poorly closed seed slot and kill it.  With the good planting conditions this spring and current soil moisture this shouldn’t be much of an issue.

When assessing frosted corn you should wait for up to 48 hours to see what’s happening.  Although the damage is already done, it may take a day or two to show up.  Low lying fields and fields with a lot of trash are going to have the most injury.  Burnt off leaves can generally be ignored unless they are preventing emergence of new healthy leaves.  The important determinant of the plant health at this point is the health of the growing point of the plants.  Determining if the growing point is healthy is pretty simple.  First slice the plant in half vertically.  Then look at the inside of the plant near the base and make sure that the tissue there is white and firm.  That’s a healthy growing point.  If it is off colour, browned or watery then the growing point is likely injured and it would be a good idea to get a professional assessment.

2 other points: DO NOT spray anything on emerged corn for at least 3 to 4 days after frost/cold temperatures.  The plants are under stress and not as capable of metabolizing chemicals at this time.  BE CAREFUL STAGING PLANTS later in the season.  Since we are likely to lose at least a few leaves, the plant may be more mature than the number of leaves suggest.  If the first leaf you are counting doesn’t have a ROUNDED TIP you are missing at least one, but possibly more, leaves from the plant.  Although these leaves aren’t there anymore, they still count toward the staging for safe herbicide application.

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