DuPont Pioneer agronomy research discovers trends in optimum plant density and yield gains

Analysis of 30 years of corn plant population responses shows that as agronomic optimum plant density increased, the range for maximizing corn yields also widened. This means modern hybrids benefit from increased plant populations without the previous instability that resulted from higher populations.

DuPont Pioneer has collected data on corn plant population responses and yield gains to provide better information on hybrids. From 1987 to 2015, nearly 200,000 yield and plant population data points were collected from more than 40 locations throughout North America. In collaboration with Pioneer, the data was analyzed by Ignacio Ciampitti, an associate professor in crop production and cropping systems at Kansas State University. Recently, the study was published in Scientific Reports and recognized for its discovery of trends in optimum plant density and yield gains.

“It used to be that we were primarily achieving yield gains by improving the plant density tolerance, but there is evidence from this and other recent studies that we are seeing yield per plant increasing,” said Paul Carter, DuPont Pioneer agronomy manager.

Key findings

The average agronomic optimum plant density across environments and hybrids increased from 30,500 plants per acre from 1987 to 1991 to 37,900 plants per acre from 2012 to 2016. During the first five years, the range of optimal agronomic plant density was very narrow but this increased over time.

“This indicates that modern hybrids not only need more plants in order to push for higher yields, but also they are showing a stability that the old hybrids did not. For farmers, that means they have some leverage,” Ciampitti said. “It’s really unique to have this amount of data, from multiple sites, across that many years in order to track plant density and its relationship to corn yields.”

Over the duration of the study, average corn yield over all locations at the agronomic optimum plant density increased from 135 bu/A in 1987 to 188 bu/A in 2015, representing an overall yield gain of 53 bu/A. As the agronomic optimum plant density increased, the range for maximizing corn yields also widened.

New elite hybrids are credited for these increases in yield per plant.

“This data shows that yield gains might be due to increased planting density, but also that yield per plant might have increased,” said Stephen Smith, affiliate professor of agronomy, Iowa State University and retired research fellow at Pioneer. “If this is the case, then breeders will have found a level and class of genetic response that has mostly remained hidden. Additional studies will be needed to determine if there are additional genetic mechanisms at work contributing to yield. Hopefully there are breeders who will be able to identify at least some of those and further increase that genetic contribution to yield gains.”

Agronomic Optimum Plant Density (averaged over all Pioneer hybrids) ranged from 30,500 pl/acre for 1987 to 1991 to 37,900 pl/acre for 2012 to 2016, with average yields moving from 135 to 195 bu/acre. Plant density contributed 9 to 18 percent of the corn yield gain during the last 30 years of crop improvement.

As new hybrids are developed, Pioneer will continue looking at research from on-farm and GrowingPoint® Agronomy trials to see how findings are influenced at the local level.

“This is important because it helps us understand our hybrids better and the information can help us improve yields,” Carter said. “For the grower, we can provide better information on how to manage the hybrids we sell. That is even more important now as more growers are looking at careful management of their inputs using variable-rate seeding prescriptions. If growers are using Encirca® STAND services variable-rate seeding, whether by themselves or with their Pioneer sales representative or Encirca certified services agent, they are using that same data to decide what seeding rates will work best based on productivity levels across the field.”

Pioneer also offers growers a free Planting Rate Estimator, which utilizes these concepts as a starting point to help growers make important operational decisions. Growers can work with their local Pioneer representative to fine tune seeding rate decisions based on hybrid agronomic characteristics, such as stalk and root strength, harvest timing logistics, and economic adjustments for grain and seed price.


This study results were published in Scientific Reports in March 2018. It is available online at www.nature.com/articles/s41598-018-23362-x. Others involved in the study were Yared Assefa, post-doctoral research; Dr. Ciampitti’s lab with Kansas State University; and Mark Hinds, Steve Paszkiewicz, Gaurav Bhalla, March Jeschke, and Ryan Schon with DuPont Pioneer.