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| I think there are more than one or two ways to maximize corn production. That there can be competing fine results with high populations and with low populations. Different corn plant characteristics for each. There are secondary effects from plant population on rate of canopy and so the effect of the canopy on weed suppression. A good canopy slows the weeds, but too much canopy cuts the solar input to the corn plants too. At the same time any sunlight that reaches the ground didn't grow corn, but it might grow weeds to compete with the corn for nutrients and water. That hurts production. Unfortunately we can't always control those nutrient and solar inputs. Those with irrigation can control the water, unless nature floods the fields. but we have no way to add growing degree days which really hurt last year.
In 2007 I planted Crows 4221R, a RR variety rated to grow well with reduced nutrition. E.g. to use the N efficiently. I put down N with the planter, after a bit a MAP was spread, and I side dressed with more 32% with the corn more than 3' tall. That corn set two ears per plant early but later absorbed that second ear filling the first. Population was 34,000. That corn didn't fire the lower leaves in August while all the neighboring corn fields had 3 or 4 brown leaves. This stuff just stayed green until the whole plant matured. It was harvested at 15.5% just before the stalks started falling over en masse. 173.2 bu / acre on 111 units of N. Really good N efficiency, though there have been better reports. For profit we need N efficiency, not corn numbers that demand huge amounts of N unless we have unlimited amounts of "free" manure to apply which we need to use up. An Ottlie number from 2005 looked as good, but a Dyna Grow number that I finished the patch with (total planted ground 23.3 acres) didn't like the plan and produced half filled ears. Stalk tests at the end of the summer showed that the Crows might have responded to a bit more nitrogen.
Speaking of response to N, over the winter while researching the answer to my tenant's question on N in the tilled strip at planting I read a recent ISU MS Thesis that tested unmentioned corn numbers on yield vs N using N rates of 50, 100, 150, and 200 pounds of N per acre. Not knowing anything about the corn variety the data is practically useless, but there wasn't near the response to the 50 pounds going from 100 to 150 as the previous 50 pounds of N and the last 50 pounds had almost no measured response. Besides not publishing the corn variety, I think the N increments were on the large side, which drastically reduces the value of that research.
Sure, its been shown that with copious amounts of heat units, nutrients (whether manure, or dry, or wet chemicals), and water, huge amounts of corn can be grown. Whether that's one or three ears per plant will be a future variable. Problem is when applying large amounts of P and N, some washes down stream, some leaches and gets into the streams and gets blamed for poor water quality at Des Moines water works (which really doesn't do nearly as much water processing as St. Louis does getting water from the Missouri River with all its silt) and the Gulf hypoxia. We need corn varieties bred for efficiency in use of N because we may be forced to reduce N rates (though much P and N surely comes from major city sewage plants dumping in to the rivers) and economics may also require that reduction in N application.
Some would like bigger ears. Then we need bigger stalks and ear stems to keep from dropping those ears on the ground. That's one way production has increased in recent years, the cob stems are fatter so the hole bored by corn borer don't wreck that structure so much. But you don't want to pick by hand! Bigger ears, more ears per plant, both can lead to greater production and greater nutrient efficiency. Thickly planted corn tends to have thinner stalks than over fertilized lightly planted corn. The thick stalks probably stand better but more of the nutrition went to those thick stalks, not the ear. There are many trade offs.
If one looks over a field looking at the heights of the ground (unless planed flat for flood irrigation) it has much natural variation in elevation. Humps and valleys. When one has the privilege of seeing the whole field at once, the single highest hump is easily found. But when one is out in the corn and can only see a few feet, its possible to find a local hump that isn't anywhere near the highest in the field, but going any way from that hump in any direction is down hill. Optimizing corn production is like that field. Its easy to find a local maximum, but until you can do every possible experiment its not possible to know if that local maximum is the global maximum. And with the many influences on corn production its not possible to predict that global maximum. Many of the corn numbers, population and fertilization rates we have today are on some local maximum. But different local maximums.
Gerald J. | |
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Seed corn genetics heading in the right direction ?
