Tuesday, November 14, 2006 - 9:00 AM

Effects of Seed Treatments on Various Soybean Plant Populations.

Palle Pedersen, Iowa State Univ, Dept. of Agronomy, 2104 Agronomy Hall, Ames, IA 50011 and Jodee Roland, Iowa State University, 2104 Agronomy Hall, Ames, IA 50011.

Just five years ago, optimum planting date for soybean [(Glycine max L.) Merrill] in Iowa was May 20. Today, optimum planting date is the last week of April through the first week of May. Significant yield increases have been observed all over Iowa when planting that early. However, there is a risk associated with this. Other than late spring frost, soils are cool and wet which will slow seedling growth and make them vulnerable to soil-borne pathogens that may reduce plant stand. Limited information exists in the literature on the use of soybean seed treatment as a way to improve grower’s profitability. Seed prices will continue to increase in the future and growers will not be able to afford to use current seeding rates to stay competitive. A lower seeding rate does not always mean a lower yield since the soybean plant is able to compensate for space. However, the risk of a lower yield is increased because of the lower stand. A soybean seed treatment may be able to minimize this risk. The objective of this study is to identify the optimum plant population for soybean using various seed treatments. Research was conducted on 5 locations in Iowa from 2005 to 2006. The experiment was a randomized complete block in a split-split plot arrangement with four replications. Main plots were two row spacing (38 and 76 cm), sub-plots were 4 seed treatments (control, ApronMaxx, CruiserMaxx Pak, and an experimental), and sub-sub plots were six plant populations (180 000, 240 000, 300 000, 360 000, 420 000, and 480 000 seeds per ha). Data will be presented from 2005 and 2006.