Nitrogen Management and Seeding Rates for Twin-Row and Single-Row Corn Production.

Twin-row (TR) planting continues to increase for both soybean and corn production systems in the mid-south region of the US.  Twin rows (20-25 cm apart) sown on 96-102 cm beds have been shown to increase grain yield for soybean and corn when compared to single-row (SR) production systems.  Early research with TR corn production was designed to evaluate comparisons of seeding rates and nitrogen (N) rates in producer fields.  In more recent research, comparisons of N rates (157, 202, 246, and 291 kg ha^-1) and seeding rates (61,750, 74,100, 86,450, and 98,800 seeds ha^-1) have been made for both SR and TR planting systems grown on 102-cm beds.  The research was designed to ascertain whether TR production leads to higher yields and more profitable production as compared to the traditional SR planting system in the wider row configuration.  When averaged across N rates in 2009, TR production was 2.0 to 4.8% higher yielding compared to SR production with the greatest advantage at the 86,450 seed ha^-1 rate.  When averaged across both N rates and planting systems, 86,450 seed ha^-1 produced significantly higher yields than the other seeding rates.  These results differ from previous research in producer fields that showed significant increases with seeding rates up to 98,800 seeds ha^-1.  Cultivars vary in their response to seeding rates and thus are the basis for on-farm studies to examine the cultivar effect in TR production systems.  Increasing N rates produced no increase in grain yield above 202 kg N ha^-1 when yields were averaged across seeding rates and planting patterns.  The research was continued in 2010 in an adjacent field of the same soil type and again following soybean.  Grain harvest will be completed in August with the data to be summarized immediately following harvest.