Many surrounding states have recently conducted research into optimum corn plant populations with goals of updating older research. Much of that research has come to the similar conclusion that recommendations from the 80’s-90’s haven’t changed much. From 2012 to the present, the Carrington Research Extension Center has conducted plant population x hybrid maturity research in dryland and irrigated environments. The results presented here are specifically for dryland corn. The goal of the study was not only to find the population that resulted in maximum yield, but also to identify economically optimum populations. For simplicity, we grouped maturity as either short maturity (RM 83-85) or long maturity (RM 87-90). Plant populations are established plants/a.

Here are a few of the important findings:

1. If you have a shorter maturing hybrid (RM in the low 80s), more plants were needed to reach maximum and economically optimum yields than later maturing hybrids (upper 80 RM). Economically, you needed roughly 3000 more plants/a for shorter maturity hybrids.
2. Over the three years of the dryland study, the short maturing hybrids had an average yield of 153 bu/a and the longer maturing hybrids had an average yield of 163.5 lb/a
3. For maximizing yield, the shorter maturity hybrids needed a population of just over 37,000 plants/a though a population of 32,500 provided a yield within 1% of maximum. The longer maturing hybrids reached maximum yield at 34,300 plants/a but a population of 29,500 provided a yield within 1% of maximum.
4. Table 1 and Table 2 provide a breakdown of the economically optimum plant populations based on seed cost and grain price combinations for short and long maturing varieties.
5. See this previous Center Points  for information on how hybrid maturity affects yield.

Table 1. The plant population that gives maximum economic return based on seed cost / unit (80,000 seeds) and grain price for corn varieties ranging from RM83-RM85. 95% stand establishment is assumed.

Table 2. The plant population that gives maximum economic return based on seed cost / unit (80,000 seeds) and grain price for corn varieties ranging from RM87-RM90. 95% stand establishment is assumed.

Mike Ostlie, Ph. D.
mike.ostlie@ndsu.edu
Research Agronomist