Published at the Chat 'n Chew Cafe, July 2000

Take the Time to Wander Crop Variety Plots

R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-1150
Email address:

County fairs, field days, vacations and other activities are taking their toll on the number of patrons down at the Wander Inn. Hopefully, some of those ‘other’ activities include wandering through crop variety plots.

Crop variety test plots offer all sorts of information to growers, only part of which is reflected in the yield results book that is handed out at the conclusion of the growing season. Wandering plots now gives you an opportunity to look over other variety characteristics important to your variety selection decisions.

Any signed crop variety test plot is fair game. The fact that the seed company took the time and effort to put up variety signs tells you that they encourage visitors. Take along a notepad to take notes on. If you have a copy of the company's current variety description brochure, bring it along too.

Compare the relative heights (both plant and ear) among corn hybrids. High ear placement increases the risk of stalk lodging later because of the higher center of gravity.

Compare the relative stalk size among corn hybrids. Thicker stalks are generally correlated with better standability later on. Split a few stalks and check the thickness of the rind. Again, thicker stalk rinds are generally correlated with better standability later on.

If you walk variety test plots closer to harvest, you can also make comparative notes among hybrids for their relative stalk health and integrity. By late August or so, you can pinch lower stalk internodes and check for stalk rot development. Hybrid differences for stalk rot development often reflect differences for tolerance to stresses in general.

Compare the relative leaf health among corn hybrids. This year in particular has been conducive for the development for a number of leaf diseases, most notably common rust. In notill test plots, pay particular attention for hybrid differences for gray leaf spot infestation. If you find a disease you are not familiar with, ask a local Extension educator, crop consultant, or industry agronomist to identify the causal organism for you.

Another facet of leaf health is the so-called 'stay green' characteristic that reflects a hybrid's ability to simply remain viable longer than others. Generally speaking, 'stay green' hybrids have a higher tolerance to stress factors than others. If little leaf disease is visible, yet some hybrids' leaves are 'shutting down' while those of comparable hybrid maturities are remaining green, the latter are likely 'stay green' hybrids.

Shuck a few ears and compare the relative ear size among corn hybrids. Kernel row number is strongly determined by a hybrid's genetics. Number of kernels per row (ear length) is more influenced by 'environmental' factors and can indicate a hybrid's tolerance to various stress factors. Obviously, we would all like to shell 30,000 ears with 22 kernel rows each and 40 kernels long. Genetically, kernel row number may vary from as few as 12 to as many as 22. Numbers of kernels per row may vary from the low 20's to the mid-40's, some of which is genetically determined, some of which reflects a hybrid's response to growing conditions.

Later on as ears fill out more completely, compare the relative 'tightness' of the husk leaves. Fewer husk leaves, thinner husk leaves and looser husk leaves are all conducive to faster grain moisture loss during field drydown.

Compare the relative uniformity of plant appearance among corn hybrids. Given some of the early season stresses this year on initial stand establishment in many corn fields, hybrids in a test plot whose plants appear more uniform one to another may indicate better early season vigor than hybrids exhibiting a mixture of healthy and runty plants.

Happy Wandering!

Corn Growers GuidebookFor other information about corn, take a look at the Corn Growers Guidebook on the World Wide Web at

It is the policy of the Purdue Agronomy Department that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex, religion, national origin, age, or disability. Purdue University is an Affirmative Action employer. This material may be available in alternative formats.
© 2000, Purdue University
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