Yield response to plant population for corn in Indiana
Recognize that percent stand establishment also influences the calculation of economic optimum seeding rates. If percent stand in your fields is historically lower than desired, then you either need to figure out how to improve the success of stand establishment or you need to use a higher seeding rate just to achieve the desired economically optimum final stand and, therefore, incur even more seeding cost.
Results from 58 field-scale trials around Indiana since 2001 suggest that optimum plant populations for corn grown under typical yield levels and growing conditions are in the neighborhood of 31,400 ppa or seeding rates of about 33,000 spa. The results further suggest that corn grown under severely stressful conditions may perform best at plant populations no higher than 25,500 ppa and perhaps as low as 21,000 ppa under truly severe growing conditions (actual drought, non-irrigated center pivot corners, non-irrigated sandy fields with minimal rainfall, etc.). Economic optimum plant populations are several thousand ppa less than agronomic optimum plant populations, the magnitude of the difference being dependent on grain price and seed cost.
There is limited evidence from these trials that hybrids characterized as “more” responsive to population respond any differently to seeding rate than hybrids characterized as being “less” responsive to population. There is also no evidence from these trials that N fertility level influences yield response to seeding rate.
On-Farm Field-Scale Seeding Rate Trials: We Need Your Help!
The 58 field-scale trials that are summarized in this report were scattered throughout the state and represent a wide range of growing conditions. However, there is a need for even more such trials to better “capture” the effects of different growing conditions, hybrids, and N fertilization on yield responses to plant population. Field-scale on-farm seeding rate trials are simple to conduct if your planter is equipped with GPS-enabled variable rate controls because we can create a “prescription” file for the trial that “tells” the VR controller where to automatically change seeding rates during planting. With a bit more effort, on-farm seeding rate trials can also be conducted without variable rate controls.
We encourage you to consider collaborating with us to conduct field-scale seeding rate trials on your farm. These trials can be customized to include two or more nitrogen fertilizer rates or multiple hybrids. Such trials will help you better identify the “ballpark” optimum plant populations for your conditions and can also be used to evaluate yield response to plant population in different areas or “zones” within fields to help address the question about the relative merits of variable rate seeding.
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