Corn Roots Water and Risks

So, as is my want, I was watching “variety news” a couple of days back. In this case, the RFDTV Rural Farm TV (RFD is the abbreviation for Rural Free Delivery that was the program where the US Postal Service would actually deliver mail to farms instead of holding it at the Post Office for pick-up…)

I like it sometimes as it reminds me of my Farm Town roots, and, frankly, it is refreshingly grounded in reality. Farmers are like that. Crops don’t care what you think. They grow, or not, based on reality of events. As an amusing example, on general TV you will substantially NEVER see a pregnant woman doing the news, weather reports, or in major series (unless the plot involves it and the ‘baby’ is a pillow for a few scenes… though in a couple of series they did work a real pregnancy into the plot line; even if rarely.) On RFDTV right now the ‘weather lady’ is significantly pregnant. Not a big deal. Everyone knows it. It’s a real part of life. Just like in the Real World where a friend gets pregnant and everyone just keeps on with work. Remarkably refreshing reality as she does a wonderful job on the weather report, and doesn’t mind “showing”. Farmers are used to births…

The sports report has Rodeo in it. The weather covers crop impacts. The financial report is about crop prices and futures.

This particular weather report they were talking about the very heavy rain totals in places from Indiana to Mississippi and a few States each side. The Corn Belt. They brought up a point I’d not thought about. Roots.

I knew that standing water too long rots seeds, and can rot roots. I knew that plants only grow the roots they need. I’d not thought it through. They did. (Farmers are like that…)

See, corn only grows roots at one stage of development. (This, I knew. But knowing isn’t thinking.) As the corn develops, if the ground is very wet, why make a lot of roots? Make just enough and move on. The problem comes later. If, as they pointed out, the water stays ‘too much’ through a few more weeks, the corn will all have made small root structures. It is NOT just about flooded corn areas, but also WET corn areas. Then, if August is dry (or even just normally dry), the corn will have small roots. Not enough to support normal production on normal August rains. Oops.

So some amount of time was spent worrying this point. What could be done, if anything, to mitigate it. When would be the critical time period when root growth halts. Would August stay ‘above normal rains’ so normal crop, or become “normal” or even dry, so reduced crop yields?

And that’s the kind of thing I like at the Rural Farm News with the pregnant Weather Lady. Reminds me of life back in my old Farm Town. Real, honest, and not paying a lot of attention to the Global Warming BS. Just looking at the things that really matter and living a grounded life. And knowing far more about corn root development, water effects, and the likely impact on corn futures; than just about everyone else…

So when wondering about likely impacts on crops, remember that it isn’t just “warm good, cold bad”. Nor is it just “wet good, drought bad”. It is far, far more complex. And, in particular, if a tiny bit of cooling is accompanied by a lot more rain and wind, then the “blowdown” crop losses from the wind and the “tiny roots” losses of yield, are likely to matter a great deal more than 2/10ths degrees of cooler.

Given that the Little Ice Age was accompanied by just those sorts of ‘more wind’ and ‘more rain’ effects, and that wheat losses in Europe were quite high then; it is more important to look at the precipitation and wind patterns when trying to predict what our present Solar Funk will do to world economic life and grain supplies.

Oh, and something similar happens to soybeans. They didn’t spend as much time on that as the corn, mostly just mentioning that it mattered, since corn was more important right now. Soybeans often planted after corn in some regions.

With that, a few links.

https://www.agry.purdue.edu/ext/corn/news/timeless/PondingYoungCorn.html

Effects of Flooding or Ponding on Corn Prior to Tasseling

R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address: rnielsen at purdue.edu

Recent intense rainfall events (technically referred to as “toad stranglers” or “goose drownders”) have caused flooding of low-lying corn fields or ponding (standing water) in poorly drained swales within fields. Other areas within fields, while not technically flooded or ponded, may remain saturated for lengthy periods of time.

What are the prospects for recently submerged corn fields or plants simply enduring days and days of saturated soils? The flippant answer is that such suffering crops will survive until they die.

What I mean to say is that no one can tell you with certainty the day after the storm whether a ponded area of a corn field will survive or whether there will be long-term yield consequences until enough time has gone by such that you can assess the actual recovery of the damaged plants. We can, however, talk about the factors that increase or decrease the risks of severe damage or death to flooded soils.
[…]
Extended periods of saturated soils AFTER the surface water subsides will take their toll on the overall vigor of the crop.

Some root death will occur and new root growth will be stunted until the soil dries to acceptable moisture contents. As a result, plants may be subject to greater injury during a subsequently dry summer due to their restricted root systems.

Nutrients like nitrogen are rapidly remobilized from lower leaves to upper, newer leaves; resulting in a rapid development of orange or yellow lower leaves.

Because root function in saturated soils deteriorates, less photosynthate is utilized by the root system and more accumulates in the upper plant parts. The higher concentration of photosynthate in the stems and leaves often results in dramatic purpling of those above-ground plant parts (Nielsen, 2012).

Damage to the root system today will predispose the crop to the development of root and stalk rots later by virtue of the photosynthetic stress imposed by the limited root system during the important grain filling period following pollination. Monitor affected fields later in August and early September for the possible development of stalk rots and modify harvest-timing strategies accordingly.

Concomitant (I found a new word in the dictionary!) with the direct stress of saturated soils on a corn crop, flooding and ponding can cause significant losses of soil nitrogen due to denitrification and leaching of nitrate N.

Significant loss of soil N will cause nitrogen deficiencies and possible additional yield loss.
On the other hand, if the corn dies in the ponded areas it probably does not matter how much nitrogen you’ve lost.

I think you can see that Farming can be remarkably technical.

http://www.soilcropandmore.info/crops/Corn/How-Corn-Grows/

Covers the names given to the various stages of corn growth, and what you need to know to identify each stage. What the plant needs at each stage, and how to get them to grow the most by being as good a servant as possible to your corn crop… The stages are Vx for vegetative (i.e growth) and Rx for reproductive (i.e making corn). Don’t worry if you can’t follow this due to the jargon in it. I’m mostly putting it here so the non-Farmers can lose their ideas about Farmers not being well educated. I sat in on a Soils Science class in the Ag department at U.C. (I went to an Ag campus) and decided NOT to get an Ag Econ degree as that class was “way hard”. Physics, Geology, Chemistry, Biology and more all rolled up in one big ball. I took regular Econ instead ;-)

Vegetative Stages and Development

Germination and Emergence (VE)

Figure 5. Under adequate field conditions, the planted seed absorbs water and begins growth. The radicle is first to begin elongation, figure 5, from the swollen kernel, followed by the coleoptile with the enclosed plumule (embryonic plant), and then the three to four lateral seminal roots. VE (emergence) is finally attained by rapid mesocotyl elongation which pushes the growing coleoptile to the soil surface, white line in figure 5. Under warm, moist conditions, plant emergence will occur within 4 to 5 days after planting, but under cool or dry conditions, 2 weeks or longer may be required.

Upon emergence and exposure of the coleoptile tip to sunlight, coleoptile and mesocotyl elongation stops. At this time, the growing point (stem apex) of the plant is 2.5-3.8 cm (1-1′, inches) below the soil surface and is located just above the mesocotyl. The rapidly developing embryonic leaves then grow through the coleoptilar tip and development of the above-ground plant follows.

Because the radicle and lateral seminal roots (collectively termed the seminal root system) begin growth directly from the seed, the soil depth at which they initially develop depends upon seed planting depth. Growth of these roots, however, slows soon after VE and is virtually non-existent by the V3 stage. Although the seminal root system continues to function throughout most of the corn plant’s life, its most important contribution occurs before the nodal roots become well established .

Figure 6. The soil depth of the growing point at VE also marks the depth at which initial nodal root growth will begin. This depth (2.5-3.8 cm) is relatively constant over different planting depths due to mesocotyl elongation, see figure 6.

The nodal root system is initiated at about VE, and the first set (whorl) of nodal roots begins elongation from the first node during V1. From V1 to about R3 (after which there is very limited root growth), a set of nodal roots begins development at each progressively higher node on the stalk, up to 7 to 10 nodes total. The nodal root system becomes the major supplier of water and nutrients to the plant by the V6 stage.

All roots except the radicle, initially tend to grow at an angle of 25 to 30 degrees from horizontal. Initial radicle root growth, however, can be aimed in any direction (except up) by orienting the seed. Nodal root growth begins to turn more downward as temperatures increase and drying occurs in the upper soil layers.

The point here being that very wet soil during a specific period of time (VE to R3) gives a small root system that stays near the surface. IF during the later R stages of corn yield development, you get a dry spell (or even just normal rain) the roots are too small and too shallow to give normal yield. Oh Dear.

And that, my friends, is why the heavy rains matter even where they do not make a puddle or standing water, and why we want it to STAY a little wet through August in the corn belt. Either dry out soon (still in the V stages) or stay wet through the R stages to about R4, then dry as the corn dries. Anything else will have reduced yields.

That is also why I scoff at the Global Warming Theorists when they prattle on about Global Warming causing crop losses or Global Warming Drought causing crop losses. They are just so naive about what really is important to the corn. If it is a little dry, they grow deeper roots and more of them. If it is warmer, they grow faster and mature earlier in the season before the greatest summer heat. It’s cold damp roots at early growth, and dry later, that’s the problem now. Not cold. Not hot. Not wet or dry. But the pattern of wet and dry. That’s what matters now. That’s what Farmers know.

When in doubt, listen to the Farmers. They know a hell of a lot more than the Global Warming Theorists and their Chicken Little Useful Idiots.

If the informality of it all, or the folksy way of talkin’; makes you think maybe these are not the brightest folks around, just reread that part about corn growth and stages… But be sure to do it with a bit of The South in your tone, and with a pleasant song to your voice… then realize that these are just folks comfortable in their own skin, and with no need to show off. And if anyone ‘knows beans’ it’s them. AND corn, and sorghum, and sugar cane, and cotton and wheat, barley, rye, cows and chickens and pigs and peaches and…

Now I think I’m gonna go back t’ RFDTV and catch up on the weather reports in Farm Country. I’ll need to keep watching now for at least the next few months to keep up with the progress of the Weather Lady. It’s almost like they’re family now… and I don’t want to miss it if she brings the kid on for a round of “show and tell” after delivery. I’ve already learned a few things about how to get my corn to grow more consistently. Since soybeans are coming next, and I’ve just cleared a patch in the garden, I’m hoping to get some pointers on beans too. After all, it’s important that I know beans. Wouldn’t want folks to be sayin’ “He don’t know beans” ;-)

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