Accumulated base: 50 F degree days and departure from normal--May 1 through July 1, 2007.
July dawns with some corn starting to tassel. Corn is a dioecious plant; that is, the male and female flowers are borne in separate structures with the male flowers in the tassel and female flowers in the ears. This process
increases the chances that the plants will crossbreed. Pollen (male) is shed to the wind, landing on silks
(female) to achieve pollination. The separation of the flowers, and also in timing—the tassels generally shed pollen one to a few days before the female silks are receptive—increases the chances of natural interbreeding. However, in many modern hybrids, male and female flowering is closer and tassels and ears emerge close to the same time.
Conversely, soybeans are mostly self-pollinated. In fact, the only cross pollination that occurs with most soybeans is if insect feeding (or a soybean breeder) physically rips open the anther (where the pollen is borne) and transfers pollen to a receptive flower on another plant.
We are still ahead of long-term averages for growing season degree-day accumulations throughout the state, and that has contributed to the rapid growth to flowering for both corn and soybean.
Rich Pope is an extension program specialist working with the Iowa State University Corn and Soybean Initiative.
This article originally appeared on page 214 of the IC-498(17) -- July 2, 2007 issue.