BETTY VALLE GEGG-NAEGER
MidAmerica Farmer Grower

PORTAGEVILLE, MO.
   Research on corn plant populations and several other issues was discussed recently by Dr. Gene Stevens, agronomist at the University of Missouri Fisher Research Center. Nitrogen and hybrid selection of corn rounded out the presentation.
   “We started field-scale experiments in 2013 using a precision planter which can vary seeding rates on the go,” he said. “The research began at the Marsh Farm, near the main Delta Center office, under center pivot irrigation and dryland fields; and we expanded the study in 2016 to include furrow irrigated fields at the MU Lee farm.”
   Before the 1940’s, farmers grew open pollinating corn varieties. The seeding rate then was normally 13,000 plants per acre.  When hybrids became available, they increased seeding rates up to around 20,000 plants.
   “For the past decade, corn seed companies have increased yields in new hybrids not so much by producing larger ears, but by breeding corn plants that can tolerate denser plant populations,” Stevens said.  “New hybrids have a more erect leaf angle than the old varieties. Because of their ability to grow in thicker stands, over time, recommended seeding rates for most hybrids have increased to around 30,000 seeds per acre range or higher. Ear sizes are sometimes smaller. But because more ears per acre are produced, yields have gone up.”
   However, not all soils produce optimum yields with high plant populations. A single field often has several soil types. Planting a high seeding rate on a soil with low available water holding capacity is risky.  Sands are the worse. When you don’t have adequate moisture either by rain or irrigation on droughty soils, you actually hurt yields with high plant populations.
   “So we’re doing research to determine what the optimum plant population should be,” Stevens continued. “With precision planters, the unit can be set to variably dispense seed as you’re driving through the field. With the right programming, it will automatically change the seeding rate to optimize populations for each soil,” he explained.
   “Most of the research we’ve done so far with irrigation and average soil conditions shows optimal yields in plant populations around 34,000 to 35,000. In our experiments we’re pushing seeding rates up to 48,000 to see what happens. One concern is that more lodging will occur from weaker stalks.
   “The study is funded by Climate Corporation, based in St Louis. Throughout the season, we collect soil N and corn tissue samples to expand a database used in FieldView N-Advisor which tracks corn nitrogen uptake and losses from leaching, volatilization, denitrification, and immobilization (www.climate.com).”
   “The trials include irrigated and non-irrigated corn and soybean fields. To schedule irrigations, we use the new MU extension Crop Water Use app (www. cropwater.org).  One of the great things about irrigation is farmers usually have more consistent yields from year to year,” Stevens stated. “You can’t control the price of the commodity, but at least you’re not at the mercy of rainfall. Precision planting is starting to be adopted in our region. I hope our research will help farmers decide how to manage plant populations on different soils in a field.
   “An exciting development in planter design is the ability to not only adjust seeding rates but switch hybrids on the go,” he said.  “In our soybean irrigation tests, we are matching varieties with soils.
   “We’ve been doing this research for several years.  Our goal is to test new technologies before farmers adopt them, so we can provide information to save growers money and help them avoid pitfalls,” he summed. ∆
   BETTY VALLE GEGG-NAEGER: Senior Staff Writer, MidAmerica Farmer Grower