Impact of Plant Populations on Irrigated Corn Yield in Arkansas.

Field trials evaluating the impact of plant population on corn yield and agronomics were conducted from 2015-2017 in Eastern Arkansas. Trials were conducted at Rohwer (38 inch row spacing), Marianna (38 inch row spacing) and Newport (30 inch row spacing) to evaluate response of commonly planted corn hybrids to varying plant populations. All trials were planted with vacuum planters to facilitate optimum seed spacing. Plots at Rohwer and Marianna were replicated four times and two times at Newport. Plot size ranged from 4 rows x 30 feet at Rohwer and Marianna to 4 rows x 240 feet at Newport. Target plant populations for each hybrid were 25, 30, 35, 40, and 45 thousand plants per acre. Trials at Marianna and Rohwer were furrow irrigated as needed, while Newport had limited irrigation. Fertilizer was applied according to soil test recommendations for yields of 200 bu/acre and greater.

Yield results from Rohwer from 2015-2017 indicate plant populations need to be 30,000 plants/acre or greater to maximize yield under high yield potential conditions. Many hybrids evaluated at Rohwer had maximum yields achieved near 40,000 plants/acre, but varied by hybrid. However net returns were greatest at a normal plant population of approximately 35,000 plants/acre. At Newport and Marianna where yield potential tended to be lower, the optimum plant population varied, depending on overall trial yield potential and hybrid, but optimum plant populations and economic plant population still tended to be 30,000 plants/acre or greater. Lodging was observed in one trial and increasing plant populations did increase late season plant lodging.