Jul 24Corn Pollination
The flowering period of corn is one of the most critical periods in grain yield determination. Stress during pollination such as drought, high temperatures, hail damage and insect feeding can have an irreversible impact on yield.
The process: Pollen shed occurs mid-morning and begins in the middle of the main spike, continuing both up and downwards, finishing with the lower branches. The process begins approximately 2-3 days before silk emergence and continues for 5-8 days, with peak shed on day 3. Pollen shed is not continuous; if it is too wet or dry, it stops and begins again when conditions are favourable. There are 750-1000 potential kernels producing a silk on a well-developed ear shoot. Silks from the base emerge first and finish with silks from the tip. If conditions are favourable, all the silks will emerge and be ready for pollination within 3-5 days.
Stressors: Poor kernel set is seldom caused by lack of pollen. Each tassel has 2-5 million pollen grains, which provides a high ratio of pollen to silks. Drought stress can delay silking, which increases the ASI (anthesis-silking interval) and some silks may not get pollinated. This causes poorly filled tips. Drought stress after pollination can also cause kernel abortion through reduced photosynthesis and carbohydrate availability. Extended heat stress of 38°C plus can cause a reduction in pollen production and viability. Lastly, insect clipping of silks can result in reduced seed set.
Want to evaluate pollination? Do the shake test! 1-3 days after a silk is pollinated and fertilization of the ovule is successful, the silk will detach from the kernel. Any unfertilized ovules will still have a silk attached. Unwrap the husk and gently shake the ear, this can give you an idea of your pollination progress.
Laura Johnston, CCA-ON, Maizex Seeds Yield Specialist, West Elgin County