Corn plant height is influenced by the environment and determined by the end of pollination. Specific factors that affect height include water intake, temperature, and amount of solar radiation on top leaves during growth.
Early-season cold temperatures can increase internode rigidity and limit cell expansion and internode elongation.
Yield is not necessarily influenced by plant height.
CAUSES OF INTERNODAL GROWTH
Stalk elongation begins at the V5 growth stage. Most cell expansion occurs at the base of internodes and is affected by light/shade interactions, daylength, and temperatures. Taller corn typically develops from later planting dates because plant height increases due to elongated internodes during longer days. Auxin, a plant growth regulator, encourages expansion of internodes, and shade increases auxin levels. This ‘shading effect’ may be noticed in corn fields with high populations.1
In contrast, intense solar radiation can reduce auxin levels, leading to less internode elongation. Cell wall expansion is limited by cold temperatures, and internodes may become rigid if there was a cool period during vegetative growth. Early planting dates lead corn to reach the V5 growth stage of elongation during early, cool spring weather when daylengths were shorter.
ENVIRONMENTAL EFFECTS ON PLANT HEIGHT
Corn with early planting dates are typically shorter compared to those with later planting dates. Early planted corn has more vegetative growth occurring when days are shorter, soils and air temperatures are cooler, and soils can be saturated. Saturated soil is unfavorable for root and shoot development and is prone to compaction when driven on during spring field work. Compacted soil from equipment can lead to shorter corn in rows adjacent to the tracks.2
Early root development that is inhibited from these early-season conditions can limit moisture and nutrient uptake during the rapid growth stage of corn.
Vegetative growth of plants with normal root development can also be inhibited by dry weather. Cell expansion depends on water uptake, and shorter internode elongation indicates plants are limited on water. Drought can cause short plants with reduced leaf area and shorter distance between leaves. In combination with short stalks, leaves stacked closely together have less interaction with neighboring plants and reduced flexibility of leaf movement.3
Where moisture is adequate, uneven corn plants have differences in leaf height. Light penetration is limited to the upper six to seven leaves. Uneven plants allow greater light penetration, and an increased opportunity for more leaves to intercept sunlight. Taller plants could produce more grain than shorter plants; however, this differential competition among plant should not affect total field yield.4
POLLINATION OF SHORT CORN
Most plants reach full height by the end of pollination. Corn heights may appear to even out as all tassels completely emerge. Successful pollination of shorter corn is still expected; however, full canopies are needed to reach yield potential.
Short plant height is not expected to negatively affect yield. A reduced canopy can mean a reduction in sunlight harvested. Yield potential should stay on track for shorter plants if plants are not dramatically short (as in the case of significant drought), pollination is successful, and there are normal grain fill conditions. Early planted fields with short plants interspersed among tall plants can have greater yield potential compared to later planted, fields with uniform tall plants. Even when plants appear to be short or non-uniform, growing season conditions can still mean the field will have similar or greater yield potential compared to later planted fields with taller plants.4
1Nielsen, R. L. 2001. Short corn at tasseling. Purdue University.
2Larson, E. 2016. Will short corn limit your yield potential? Mississippi State University.
3Nafziger, E. 2012. Short corn, short yields? University of Illinois.
4Hicks, D. R. 2004. Corn comments: uneven plant height. University of Minnesota.