Corn Pollination Quick Facts
Corn Pollination Quick Facts
The pollination and reproductive process in a corn plant are critical to final yield, and there are several things that can happen to the corn plant during that two week period that can significantly reduce yield.
When we have pollination issues due to stress, we generally think of high temperatures and drought conditions, but extended periods of rain and wet weather can interfere with pollination. Insect feeding and herbicide injury can also disrupt this process, and can cause differing levels of yield loss depending on the severity.
The following information includes many quick facts to use as a reference and help understand the reproductive process of a corn plant.
Silk Emergence:
Tassels generally emerge first followed by the silks 2-3 days later, but the two can emerge at the same time.
Silks grow from the base of the ear first and initial growth can be up to 1.5 inches per day. Later in the season the growth will likely slow to around 1/2 inch per day.
Complete silk emergence from the ear will occur over a 4-8 day span.
Silks will continue to lengthen or grow for up to 10 days or until pollination occurs.
Clipped silks (from insect feeding) will continue to re-grow until a pollen grain lands on them.
The silks will remain receptive to pollen for up to 10 days after they emerge from the husks.
Silks are primarily comprised of water and severe droughty conditions can cause the silks to become unreceptive or collapse, preventing pollination.
Droughty conditions can delay silk emergence while heat can speed up the pollen shed process, with the combination of these two conditions making the pollination window small.
Pollen shed:
Individual tassels produce approximately 6,000 anthers, which contain the grains of pollen that are shed through pores at the ends of the anthers.
The central spike is first to shed pollen with the bottom lateral branches last.
In as little as 3 minutes, all of the pollen from one anther can be shed but a tassel can shed pollen for 5-6 days.
Field variability generally results in 10-14 days of pollen shed which typically takes place in the morning or late afternoon since temperatures above 86⁰ greatly slow pollen shed.
If the anther is covered by dew, the pollen cannot be expelled.
A pollen grain is one of the largest particulates found in the air and falls at a rate of 1 foot per second; in a 15 MPH wind, a pollen grain can travel up to one-half mile in just minutes.
Most pollen will fall within 40-50 feet of the plant from which it was shed · In a field setting, the majority of pollination (estimated at 97%) is done by neighboring plants rather than self-pollination.
In typical field conditions, an individual pollen grain will remain viable for 1-2 hours but high temperatures will rapidly degrade pollen.
An individual pollen grain is roughly 60% water by weight and its viability greatly decreases if its moisture content falls below 40%.
Fertilization:
Fertilization can occur from a pollen grain landing anywhere on the silk.
Silks have small sticky hairs that trap or capture the pollen grains.
Pollen does not get washed off silks.
In mere minutes from landing on the silk, the pollen grain will germinate.
After germination, a pollen tube will grow down the silk channel to reach the ovule (eventual kernel).
The pollen tube contains the male genetic material and then fertilizes the female ovule.
There can be up to 1,000 ovules per ear, even though we will only harvest around 400-600 kernels per ear.
Typically it takes 24 hours from the time the pollen grain lands on the silk for fertilization to take place.
Within 24 hours of fertilization, the silk will become detached from the ovule and fall off signaling successful fertilization.