Tuesday, November 14, 2006 - 8:00 AM

Effect of Delayed Emergence on Corn (Zea mays L.) Grain Yields.

Kyle Lawles1, Kyle Freeman1, Roger Teal1, Brian Arnall1, Brenda Tubana1, Olga Walsh1, Byungkyun Chung1, Starr Holtz1, and William Raun2. (1) Oklahoma State University, Ag Hall, Stillwater, OK 74078, (2) Oklahoma State Univ, 044 N Ag Hall,, Dept. of Plant & Soil Sciences, Stillwater, OK 74078-0507

Crops with uniform stands have the advantage of producing higher grain yields under good growing conditions and management systems than crops with poor stands.  Delayed emergence and complete failure of seed emergence are causes of uneven crop stands early in the season.  The objectives of this study were to determine corn (Zea mays L.) grain yield reduction as a function of interplant competition arising from delayed emergence and to evaluate yield levels associated with 3 plant sequences, with and without delayed emergence. These variables were investigated at two experimental sites established in the spring of 2005, near Stillwater, OK at the Lake Carl Blackwell Agronomy Research Farm under irrigation and at the Efaw Agronomy Research Farm in a rainfed environment. Pioneer (33B51) Bt corn hybrid was planted late March or early April at a seeding rate of 73779 plants ha-1. Each 2.7 m-row was planted by hand to maintain 18 cm-inter row spacing. A total of 15 plants within row were divided into five 3-plant subgroups. Each subgroup contained three plants, two plants planted on the same day and a delayed plant planted between the two plants.  The delayed plants were planted 2, 5, 8, and 12 days after initial planting (to simulate various delayed emergence scenarios).  At the irrigated site, grain yields decreased when the planting was delayed more then 2 days (6% 5-day, 15% 8-day, 30% 12-day).  At the rainfed site corn yields increased with increasing days delayed (8% 2-day, 10% 5-day, 23% 8-day) up to 12 days where yields were reduced (5%). This indicated that plant population was potentially too high for the rainfed site in 2005.  If plant population is desirable for the moisture regime, uneven plant emergence beyond a two days emergence delay results in grain yield loss.