Uniform and vigorous stands of corn are absolutely required for achieving optimum yields. Uneven plant spacing or emergence reduces yield potential from Day One. Yield losses can easily approach 7 to 15 bushels per acre due to uneven stands. Subsequent uneven growth of the crop can result in further yield losses.
Secrets for Successful Germination and Emergence. Quick, uniform germination and emergence of corn is promoted by four factors. Anything you can do to ensure the presence of these four factors will greatly increase the odds of successful stand establishment.
First of all, soil temperatures at the seed depth should be consistently greater than 50 degrees F to encourage rapid corn germination and emergence within seven days after planting. Secondly, soil moisture at the seed depth needs to be uniformly adequate, not too wet or too dry. Excessively wet soils limit oxygen supply to the embryo, while excessively dry soils cannot provide enough moisture to initiate the germination process. Thirdly, seed-to-soil contact needs to be uniform to ensure rapid uptake of moisture by the kernel. Finally, successful germination and emergence require pest-free conditions.
Secrets for Successful Seedling Growth. Even if germination and emergence occur satisfactorily, subsequent seedling growth that is uneven or less than vigorous can still limit yields. Two criteria are necessary for uniform seedling growth after emergence is complete.
First of all, the seedling must be able to tap into the energy reserves of the kernel until the permanent (nodal) roots are established. For this to happen, the kernel, seed roots, and mesocotyl (connecting 'pipeline' between kernel and seedling crown) must be remain healthy until about the four or five leaf collar stage of development. Secondly, the permanent (nodal) root system itself must successfully develop during the first two to three weeks after planting to ensure a uniform stand of corn.
Thus, the period from emergence to about knee-high is critical for establishing a uniform stand of corn. Damage to the kernel or mesocotyl prior to the establishment of the permanent (nodal) root system will stunt or kill the seedling. Damage or stress to the first few sets of nodal roots can also severely stunt the young corn plant.
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The Corn Growers Guidebook , a WWW resource for corn management systems in Indiana and the eastern CornBelt.
Purdue University Agronomy Extension WWW Home Page.
Purdue Agronomy On-Line! , Purdue's Agronomy Department WWW Home Page.