Silage and grain growers aim for a balance in quantity and quality when it comes to corn production, and it all starts with establishing proper planting practices. It's important to understand the relationship between planting rates and outcomes when planning for the crop year ahead, so let's delve a bit deeper into this concept.
Figure 1. A chart displaying the top factors that can affect corn yield. Plant population has the possibility to effect yield by 8%, or 20 bushels per acre on a field averaging 260 bushels per acre.
Your specific farming environment may sometimes call for a more unique and personalized planting approach, but there do exist general rate ranges that act as broader suggestions. The perfect rate for you may be different than your neighbor's since it depends somewhat on soil quality, seed germination rate, topography, land size, budgets, water availability, and production goals. This also explains why identical planting practices implemented year after year can still result in yield and quality variances.
So how much should you plant? It depends on your ultimate goal and quality of your land. It makes sense that planting at higher densities will result in higher volume yields, but this also slightly decreases the size of the ears, which is why for grain purposes it's recommended to have 2,000 to 4,000 fewer plants per acre than with silage corn. Whether it's for grain or silage purposes, more productive soil and ideal growing conditions will better support a greater number of plants in general. Yield doesn't infinitely increase with higher planting rates however; there is a point where the cost to purchase more seed exceeds the extra harvest potential, since too much density creates additional competition for nutrients, light, and space, which ultimately results in poorer quality feed and poor growth.
Many studies have been done to determine this level of optimal benefit. Up to a certain point, yield values will increase proportionately with seed population. However, it was found by Iowa State University that yield values start declining around 40,000 plants per acre from too much competition.
Figure 2. A visual representation of the population/yield association, looking at 30 and 20 inch spaced rows.
The majority of today's farmers plant between 30,000 and 38,000 seeds per acre. This number has increased steadily over the last couple decades as improved hybrid seeds are continually released on the market. It appears that this trend may continue as varieties become better adapted to higher populations and more efficient at nutrient usage. Where you fall within this range is totally dependent on the quality of your land and seed (higher germination rates have a better chance of successful stand and can handle a more conservative planting rate). Having a professional assessment of your field completed can help determine your production capabilities and if variable rate-seeding (VRS) is beneficial for your opperation (VRS adjusts optimal planting populations to the specific soil and topographical changes within a field).
Figure 3. Trends over the past century, including future estimations, showing an almost linear increase in corn populations and yields.
Regardless of where you fall within the range, remember that more is not always better. In an effort to maximize yield, planting too heavy can actually reduce the relative feed value of your crop and make it less valuable. There is an economical balance. Planting good quality seed at the right population for that specific environment allows the plant the best chance of growing into high quality feed, essentially producing a greater return on your investment in the end.
Figure 4. Economic maximum returns on seed costs are shown by the colored dots at the various yield levels. For example, the financial return on seed investment at 240 bu/acre is greatest when 39,000 seeds per acre were planted. Increasing the rate to 40,000 and above actually decreases the proportion of return.
Ready to get started? Let us know where you and your field stand when it comes time to order seed. Contact us for corn seed orders and questions here.
Table of Figures
Figure 1: "The Seven Wonders of the Corn Yield World", Dr. Fred Bellow, Crop Physiology Laboratory, http://cropphysiology.cropsci.illinois.edu/research/seven_wonders.html.
Figure 2: "Think carefully about corn plant populations to maximize profits", Jeff Coultier, University of Minnesota Extension, https://www.extension.umn.edu/agriculture/corn/planting/optimum-plant-population-for-corn-in-minnesota/
Figure 3: NASS Query (11/2/2012) and D. Duvick: Heterosis: feeding people and protecting natural resources P 19-29.
Figure 4: "Putting variable rate seeding to work on your farm", Pioneer, https://www.pioneer.com/home/site/us/agronomy/library/variable-rate-seeding/?elqTrackId=6a19725f9b5b4859b5288b394c465d49&elq=849a48fd4da44a2a9653910bde3a2a35&elqaid=2582&elqat=1&elqCampaignId=3053