Unlike you and me, when a corn plant is in a difficult or uncomfortable situation, it can't just walk away. For this reason, the ability to sense and respond to situations of both feast and famine is very important to survival and every plant's ultimate goal, maximum seed production. This ability to "go with the flow" is really important to producers when selecting corn hybrids. Corn plants achieve this flexibility by manipulating yield components, which are ear number, kernel number, and kernel size.
FLEX is a buzz word thrown around a lot when we're talking about corn response to plant population, which is a main part of what I'm focusing on with this tiller project. But what is "flex"?
Flex is one measure of a corn plant's ability to adapt to its given environment. When we're talking about ear flex, the main focus is on ear size (specifically number of rows), which impacts kernel number. Hybrids producing ears of similar sizes regardless of environment are "fixed".
Different from flex, if a corn hybrid is prolific, this means the plant has the ability to adapt ear number. Non-prolific hybrids only put on one ear, semi-prolific hybrids are able to put on more than one ear, and prolific hybrids will put on a second ear if possible.
Why do flex and prolificacy matter?
FIXED hybrids are preferred in predictable environments where optimum plant populations can be estimated pretty reliably based on previous season experiences and growing condition expectations. In these cases, the general strategy is to pack as many plants into an area as possible, because if resources are not limited, then plant number is.
In cases where growing seasons are not as predictable, and the "packed plant population" strategy is too risky, FLEX hybrids are a really valuable tool. In these cases, plants can adjust ear sizes and even ear numbers (PROLIFICACY) on-the-go based on the resources they have available. Plants can compensate if 1) resources outweigh plant population (bigger ears and/or more ears), and also if 2) plant population outweighs resources (smaller ears and/or fewer ears). Because plant density decisions in these environments usually come with risk, flex hybrids with prolific potential provide some welcome wiggle room.
For a hypothetical example, given the same plant population of 20,000 per acre:
Non-limiting environment (favorable season with no soil nutrient limitations)...
Semi-prolific FIXED hybrid - 18-row ears with 2 ears/plant
Semi-prolific FLEX hybrid - 18-row ears with 2 ears/plant
Limiting environment (dry season with no soil nutrient limitations)...
Semi-prolific FIXED hybrid - 18-row ears with 1 ear/plant (kernel size probably suffers)
Semi-prolific FLEX hybrid - 14-row ears with 1 ear/plant
The real question is, what's the limit? How far can these prolific flex hybrids be docked in plant density and still have the ability to compensate?
Our team is looking into this from the viewpoint of tillering. The desired result when tillers are present in low-density corn fields is an increase in ear number beyond the two ears that a main stalk could produce on its own. This is especially the case in scenarios where there's more resources than plants to use them (ex: plant density too low). Our initial results have found that while tillers are capable of producing more ears, changes in other yield components might counteract these changes.