Ohio corn growers have a pretty good looking corn crop to date. Growth and development has been fast and furious as the corn has had all the heat and moisture for excellent growth. Many areas of Ohio have had 17 to 19 inches of rainfall since April 1 and we have accumulated near 1,700 Growing Degree Days since May 1. Most of the corn crop was planted the first 10 days of May. Bottom line is, we are ahead of normal for heat unit accumulation and rainfall. Due to the excellent condition of corn, many of these acres have had a fungicide application to protect the genetic
potential of the corn crop.
Although it has been very hot and humid, pollination has progressed at a normal pace and kernel set looks good. Here are some facts about corn pollination that has taken place in your fields.
Pollination and fertilization of the embryos is one of the most important stages of corn crop development. Much of the yield potential of the corn plant, ear length and row number, has been established earlier in the season but successful pollination can help determine the extent to which yield potential is met. Unfortunately, pollination is also one of the least controllable aspects of corn production since its success or failure is primarily influenced by environmental conditions.
Corn has both male and female reproductive parts on each plant. Male and female flowers are separated on the corn plant by distance unlike a soybean flower. Given the separation of the ear and tassel on individual plants and the large amounts of pollen floating around in a production field, it is understandable why corn is cross-pollinated. Did you know that many of the embryos on the ear actually get pollinated from another plant?
The tassel is the male flower or inflorescence of the corn plant. This male inflorescence consists of many spikelets located along the main spike and lateral branches. The spikelets enclose two small flowers called florets. Each floret contains the male reproductive structures that hold the pollen. I like to refer to them as cannons that push the pollen out into the air. The tassel develops deep in the whorl of the plant beginning at approximately V5. Severe stress or chilling at tassel initiation can potentially reduce tassel branching and spikelet formation. Did you know that an individual plant may produce several million grains of pollen?
At V5-V6 growth stage potential ears are initiated at each node but typically only the uppermost ear fully develops. Depending on hybrid genetics and growing conditions, a secondary ear may develop at the next lower node. The female ovules that become kernels upon successful fertilization are located in paired rows along the surface of the ear. A primary ear may develop up to 1,000 ovules, of which only around 400 to 700 are usually harvested. Row number is determined shortly after ear initiation, but ear length is not completely set until just before tasselling. Therefore, severe stress from environmental conditions or herbicide injury can interfere with ear formation or row length beginning at around V5.
Pollen shed begins shortly after the corn tassel is fully emerged from the whorl called VT stage. Pollen shed may occur for up to two weeks, but usually lasts for five to eight days, with peak shed by about day three. Generally, pollen shed and pollen viability are minimally affected by environmental stresses. However, very hot, dry conditions may reduce pollen viability and decrease length of pollen shed. Did you know that most pollen shed takes place in the morning? Silks begin growing from the ovaries at the base of the ear first, then progressing toward the ear tip. Consequently, silks from the base are the first to emerge from the husk, usually a couple of days after pollen shed has begun. Silks can grow as much as 1 to 1.5 inches per day. Silks will continue to elongate to some extent until pollinated, or until they senesce. Silk longevity is around 10 days under typical growing conditions.
Pollen that lands on a silk is captured by small hairs on the surface of the silk. The pollen grain germinates immediately, producing a pollen tube that grows down the length of the silk, resulting in fertilization of the ovule within 12 to 28 hours. A mass of long, green silks is an indication that pollination has not occurred. Did you know that you could carefully peel off the husk leaves and give the ear a “shake” to determine successful pollination? The silks that freely fall from the ear have a pollinated kernel. Good luck to all of you as you conduct your ear size determinations.