ReachOut: Finishing Strong

ReachOut: Finishing Strong from United Farmers Cooperative on Vimeo.

Mike Zwingman

Mike Zwingman

Imagine had Columbus spied the first slivers of the American shore out yonder in the blue and said, “Mateys, let’s just turn around.”  Or that Armstrong and Aldrin peeped but their heads out of the Eagle and agreed that a look was quite enough.  Imagine had Janis Joplin asked not for a Mercedes-Benz, but a Pinto instead.

This article is about going all the way.

If you’ve been following this blog over the past few months, you well know that I am downright passionate about irrigation.  I’ve plied you with articles about when to begin irrigating, why, and how, and now that the time of year is upon us, I have a last one for you: how to stop.

If you’ve been following this blog over the past few months, you won’t be surprised to hear that the how and when of stopping aren’t set and pat.  The date and process of stoppage that is best and most profitable for your operation depends on the particular details of your situation, especially your planting date and your hybrid type.  The situation in your fields is complex and dynamic and your sensitivity to this complexity will help you both close out this growing season as successfully as possible and best ready your fields for next growing season.

By now, 90 percent of your expenses are spent.  You’ve been fueling and seeding, fertilizing, applying, and irrigating since May.  With harvest on the horizon, you are just about done with another season, and I’m certain that you’re a little pooped.  The last thing that you want to hear from me is another injunction to stop and think about the complexity of this process.  But you’re so close to the end and a strong final push will leave you dancing in the end zone, instead of hooked from behind at the five yard line and pounding the turf with your helmet.


Right now, your corn is likely at half milk or full dent.  Your plants will need just about 3 additional inches of water to achieve physiological maturity.  One common answer for delivering these final inches is to make two last passes of 1.5 inches each.  This answer has been prevalent for a few years now and it would suffice for “normal” water requirements and “average” conditions in “typical” fields.  But here’s what I say: in an era of more exact science and tighter profit margins, why settle for averages when we can use real numbers and actual conditions to guide our final irrigation passes and up our profit in the process?

To save y’all some math, check out the chart below.  Using your planting date and hybrid type, you can find a pretty darn specific number of days until your corn will reach black layer, which is the sign of full maturity in a corn plant, the sign that it’s cashed out.  This is the number of days that you have to lay down those final 3 inches of water.

UFC Reachout 9.2.13

Start now with a pass of ¾ to 1 inch, then watch.  Watch what the weather does.  Watch your soil conditions.  And when it appears that you need some more water, and Mother Nature won’t be providing a helping hand, make another pass of ¾ to 1 inch.  And watch again.Header1

Now, Mike, you might be saying.  I can do this in two passes, or I can do it in three.  So what?

Good question, and thanks for your honesty.  The so what is this: With a little extra care, you can finish your corn crop as profitably as possible and ensure that your fields are best positioned to accept and handle water until you plant again.  The ideal approach during this time of the season is to walk a thin line between providing your plants with enough water to maximize grain fill and working your soil down to dryness so that it can accept fall rain and winter melt and minimize runoff.  Working to minimize runoff between growing seasons will reduce erosion in your fields, preserve top soil, and prevent other undesirable issues in other sectors of the world, like algae blooms and contaminated drinking water.  Dividing your final 3 inches over three passes instead of two will help you negotiate this thin line and provide the water your plants need while preventing the overwatering that will cost you precious top soil.

For those of you using cover crops this winter, carefully managing the stoppage of irrigation provides another bonus as correct water management will facilitate the quick and sturdy establishment of your cover crops before winter.

And that, friends, is my final word on irrigation for 2013.  Rest assured that I will pick up the topic with joy again in the spring.  Until then, we fortunately have much planning, calibration, and decision making, among other things, to discuss.

  • Kevin Medow


    Your water use required from 50% starch line till black layer is higher than any other number I have seen, what source are you using? Pioneer research says that 1.4″ of water is needed to reach maturity from this stage. From all the years of my use of Moisture sensors the amount of water use in these last weeks of development is over stated. We can also use a 60% moisture depletion threshold instead of 50% for determining the final irrigation which also helps. Kevin