WHAT TO CONSIDER
Most cell expansion occurs at the base of internodes and is affected by light/shade interactions, daylength, and temperatures. Stalk elongation begins at the V5 growth stage. Taller corn typically develops from later planting dates because plant height increases due to elongated internodes during longer days. Early planting dates lead corn to reach the V5 growth stage of elongation during early, cool spring weather when daylengths were shorter. Auxin, a plant growth regulator, encourages expansion of internodes, and shade increases auxin levels. The effect of shading may be noticed in corn fields with high populations.1 In contradiction, intense solar radiation can reduce auxin levels, limiting internode elongation.
It is not uncommon for corn with early planting dates to have shorter stature 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 prone to compaction from equipment traffic and can inhibit root and shoot development during spring. Consequently, short corn may be interspersed throughout the field and noticed in rows adjacent to equipment 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.
When taller corn plants are interspersed throughout the field, there are 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 plants should not affect total field yield.4
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.
Vegetative growth of plants with normal root development can also be inhibited by dry weather. Cell expansion depends on water uptake, and less internode elongation indicates plants are limited on moisture. Drought can cause short plants with reduced leaf area and shorter distance between leaves. Plants shortened by drought may have 1) leaves stacked closely together or 2) reduced flexibility of leaf movement.3
Short plant height is not expected to negatively affect yield. Reduced canopies can mean a reduction in harvested sunlight. 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. Weather conditions can still allow fields with plants appearing short or non-uniform to 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.