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Planting corn into bone-dry soils?

After a relatively dry fall and the same conditions through much of winter so far, there's some concern about dry conditions once corn-planting time rolls around in the Corn Belt this spring. So, if you think you might find yourself in these shoes once spring rolls around, what can you do to prepare?

So, what are the chances you'll lose yield potential because of how dry it's been so far this winter? In the state of Iowa, at least, it depends. In the northern areas where soils retain moisture better, dry conditions at planting don't mean a lot; according to Iowa State University Extension agronomist  Roger Elmore, from central Iowa north, yield potential only slips 1% in the northeast area while farmers in northwest and central Iowa don't lose any yield potential. That's if the topsoil and subsoil have less than 50% the normal moisture.

On the other hand, Elmore's research shows corn planted in dry soil loses 36% and 30% of yield potential in southwest and southeast Iowa, respectively.

"Another way to think about yield potentials is to look at probabilities of experiencing a year that would provide yield reductions with dry soils at planting," Elmore says. "A median year at NW, SW and SE would result in sizable yield reductions if soils were dry at planting. A 25 percentile year would reduce yields at NE if soils were dry at planting, and only the worst year since 1986 would reduce yields at the Central location."

Find the right hybrid

So, if you're in those areas most susceptible to yield loss because of dry soil at planting, one way to keep that from happening is to plant the right corn hybrid. Look at your soil moisture levels, how well your soil retains that water and what type of hybrid maturity you plant. In 4 out of 5 locations around Iowa, the yield of full-season hybrids wound up higher than early-season hybrids regardless of whether the soil was at half or 100% of its soil moisture capacity.

"It is interesting to note though that in the years where full-season hybrids yielded more than early-season hybrids, the yield advantage was much greater than in the years where early-season hybrids yielded more than the full-season hybrids. This was true at all locations and with both soil moisture scenarios," Elmore says. "Interestingly, yield estimates for early- and full-season hybrids were consistent across both planting situations, whether soils were relatively moist or dry. The probabilities of either of the hybrids performing well were similar whether soils were moist or dry at planting."

Plant populations

One more variable to consider is plant population. If it's dry when you run your planter, should you trim plant populations so those seeds going into the ground can have a greater share of the scarce moisture present? In general, Elmore says his research shows a diminishing return to higher plant populations under dry conditions. In other words, yield potential hits a wall when the soil's dry, regardless of the number of seeds planted.

"At the SE research farm near Crawfordsville, [Iowa], with dry soils at planting 32,000 plants per acre (PPA) increased yields over those of 37,000 ppa one-third of the time. With wet soils at planting, in all but one year (1997) 37,000 PPA increased simulated yields over 32,000 PPA. Lower plant populations in NW and SE Iowa have a greater probability of resulting in greater yields that higher plant populations if soils at planting are dry than in other parts of the state," Elmore says. "The modeled yields show that higher plant populations improve the chances for higher yields in high-yielding years (see figures linked in the endnote). In lower-yielding years, yields resulting from different plant populations are similar; thus, seed costs associated with higher populations may not be offset by yield increases in lower yielding years. But the probabilities of greater returns from higher seeding rates in better years would seem to counterbalance those concerns."

But, even if you're planning on dry conditions at planting as of right now, be careful to keep up with your soil moisture between now and planting, as any change can alter how your fields respond.

"We all know that many things can happen between now and planting. If soil moisture conditions do not improve -- that is soils are dry at planting -- what I’ve tried to explain here is that planting to achieve high plant populations is a good approach, as it is every year," Elmore says. "Meanwhile, as before, let’s hope for complete recharge of our soil before planting!"

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