Modern corn hybrid fields are most productive if the field has a consistent ‘stand’ of plants, evenly spaced and equally developed. Lots of factors are involved is a successful establishment of this uniform growth. Field conditions, germination environment conditions, seed uniform vitality and genetics are the main interacting contributors to uniformity of seedling emergence. Some of these are controllable by the corn grower and the seed producer, some are measurable prior to planting, but temperatures and rain variables are always part of the unknowns at the start of a corn season.
Determining the vitality of seed at the time of planting is not always as accurate as it might seem to everyone. Each individual seed has had its own experience from initial pollination in the seed production field, stresses during seed maturation, exposure to potential pathogens, roughness during shelling, moisture addition during seed treatment, shipment to farm and finally placement in field.
Multiple attempts to evaluate the percentage of individuals within a seed lot that are likely to not emerge in the field is made by germination tests. Attempts are made to standardize the tests among labs, but referee samples in which multiple labs germinate sister samples drawn from the same commercial seed bag show slightly differing results with warm tests and greater differences among cold tests. These lab to lab differences become greater as the average quality of a seed lot is lower, with some labs having percent germination meeting most company standards and others determined as failing.
Added to the difficulties of determining acceptable seed quality of a seed lot, each individual seed is at a different stage of losing its cellular integrity - they are all aging but potentially at varying rates. Seed producers have the very difficult task of determining what is the rate of deterioration within a seed lot. When do they stop testing and start shipping? Multiple tests can be done to determine germination quality of a seed lot but there still can remain those that fail to germinate adequately in the field for optimum hybrid performance. Sometimes this becomes a major reasons that the grower decides the hybrid yield capacity is poor, blaming the genetics of yield instead of the seed quality. It is complicated!!
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About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.