One thing yield king Kip Cullers preaches is adequate plant population — high enough to maximize yield.
“Today, we'll talk to you about Kip's environment and some of the background works Pioneer has done over the years to optimize genetics to perform in an environment like Kip's,” said Scott Nelson, Pioneer agronomy research manager, at the recent field day on Cullers' Stark City, Mo., farm. “Kip's place is unique and he'll have record yields like he usually does. He'll squeeze as much out of our genetics as anyone can.”
Farmers must provide the environment to allow expression of genetics in high plant populations.
“For example, Kip is using a lot of the twin-row systems you see here. That's one way of getting higher densities while still (achieving) more equidistant spacing to intercept light aboveground.”
In the past, Pioneer has done much work looking at grain yield response over densities.
“Trust me, we know it's different on everyone's farm. In central Iowa and Illinois, our max yields might be on 36,000 to 40,000 plants per acre. In west Texas or dryland Nebraska, planting 36,000 plants will be trouble — that means (dealing with) limiting factors like water.” However, under good growing conditions, most Pioneer hybrid genetics “will maximize yields around 36,000 plants per acre.”
Cullers' environment is fairly unique, said Nelson.
“We haven't run the study here. His max yield might be closer to 60,000 to 70,000 plants per acre. That shows the interaction between environment and genetics.”
The importance of plant populations can be further demonstrated, said Nelson, by looking at hybrids released in the 1930s through the 1950s.
“For different densities — say, from 10,000 plants to 80,000 plants per acre — the response will actually begin going backwards. The older hybrids couldn't handle higher plant populations. They lodge, fall over and can't compete.”
However, newer hybrids like higher densities and that's reflected in yield.
“They can keep standing, keep yielding, and keep putting ears out even when close together. We've kind of desensitized them to competition. That's a trait we've built in over time and it'll help with drought tolerance.”
Some might wonder where the extra yield is coming from. “Obviously, there's the number of ears per acre, the number of kernel rows and number of kernels per row. Those are the three things.
“Under high densities, your kernel row number doesn't change a lot. Basically, that's a genetic component the breeders have built in.
“The adjustment that means a good year over a bad one is the number of kernels per row. That's a big factor. Under optimum conditions, Kip will have over 50 kernels per row. In a stressful environment, that drops down dramatically and some ears will be scatter-brained.”
The other factor the Pioneer researchers look for when screening and breeding is silk longevity. How good are the silks, especially under drought stress?
“Under drought, the tassels will usually still develop and come out. But the silks will be delayed. One thing we've been able to breed into our corn is silk that'll come out even under tough conditions.
“If you just pollinate a bunch of ears after the silks first emerge, they'll usually remain viable for five to seven days. Then, they lose viability and can't wait for pollen any more.”
The tassels usually aren't the limiting issue.
“Only when temperatures reach 104 or 105 degrees will pollen viability be an issue.”