Grain yield depends on good pollination of maize
It’s hard to believe that July is almost over. The corn has grown and the cob leaf is starting to stick out its head. With this in mind, Peter Thomison, OSU Extension Corn Specialist, provides the following explanation of the corn pollination process.
The pollination period, the flowering phase of corn, is the most critical period in the development of a corn plant from the standpoint of determining grain yield. Here are some key steps in the corn pollination process.
Most corn hybrids produce tassels and silks at about the same time, although there is some variability between hybrids and environments. On a typical midsummer day, the peak of pollen shedding occurs in the morning between 9 a.m. and 11 a.m., followed by a second round of pollen shedding in the late afternoon.
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Pollen release begins in the middle of the central spike of the panicle and later spreads across the entire panicle, with the lower branches being the last to release pollen. Pollen grains are borne by anthers, each containing a large number of pollen grains. The anthers open and the pollen grains shed early to mid-morning after the dew has dried on the acorns. Pollen is light and is often carried considerable distances by the wind. However, most of them settle within 20 to 50 feet.
Pollen release is not a continuous process. It stops when the glans is too wet or too dry and starts again when the temperature conditions are favourable. Little or no pollen is released when the acorn is wet, so there is little chance of pollen washing off the silks during a rainstorm. In addition, the bristles are covered with fine, sticky hairs, which serve to catch and anchor pollen grains.
Under favorable conditions, the pollen grain remains viable for only 18 to 24 hours. However, the pollen grain begins pollen tube growth in the silk canal a few minutes after its contact with a silk and the pollen tube grows down the length of the silk and enters the female flower (ovule) in 12 to 28 hours.
A well-developed ear shoot should have 750 to 1,000 ovules (potential seeds) each producing one silk. The bristles near the base of the ear emerge first and those at the tip emerge last. Under the right conditions, all silks will emerge and be ready for pollination within three to five days. This usually gives enough time to pollinate all the silks before pollen shedding stops.
The pollen of a given plant rarely fertilizes all the silks of the same plant. Under field conditions, 97% or more of the grain produced by each plant is pollinated by other plants in the field. Each tassel contains up to 2 million or more pollen grains, which translates to at least 2,000 pollen grains produced for each ear shoot bristle. Pollen shortages are a problem in extreme heat and drought conditions; they can also occur in fields characterized by uneven emergence in plants that emerge later.
Poor grain formation is more often associated with poor timing of pollen shed and silking – silks emerging after pollen has been shed. However, modern hybrids rarely exhibit this problem unless they are under extreme drought stress.
Minimize the ash content of forage
Forage harvesting practices increase the external component of forage ash content. There are some management practices that growers can use to minimize the increase in ash percentage. The following list comes from a paper written by Dan Undersander, extension forage specialist at the University of Wisconsin:
Raise the cutter bar of a disc mower: The lower the cut, the more likely it is to bring soil into the forage. Consider an alfalfa cutting height of 3 inches and 4 inches for alfalfa-grass mixtures.
Use flat knives on the disc mower. The angled cutters create some suction and while they help pick up lodged forage, they also pick up more soil.
Keep the windrow off the ground. Placing a wide windrow on higher stubble will decrease the amount of soil that can accumulate at the bottom of a windrow.
Prevent the rake tines from touching the ground. Raising a cloud of dust when raking probably adds 1-2% ash to the hay.
Use a windrow merge. Since the hay is not rolled on the ground, there can be 1-2% less ash in the forage.
I am also bittersweet in reporting that this is my last week with the OSU Extension Office in Wayne County. I have been so blessed to serve this community and to build the lasting relationships I have with you. I am grateful to have had these opportunities. Take care and happy farming.
Haley Zynda is an OSU Agriculture and Natural Resources Educator and can be reached at 330-264-8722 or [email protected]