Response of Corn Density and Nitrogen Rate in Corn Border Rows On Strip-Intercropped Corn and Soybean.

Strip intercropping of corn (Zea Mays L.) and soybean [Glycine max (L.) Merr.] has been extensively researched as a cropping system to improve land use efficiency.  With strip intercropping in the Midwest, corn yield has increased while that of soybean has decreased when compared to monoculture equivalents.  Most of this production difference is attributed to increased yield in corn border rows and decreased yield in soybean border rows.  While many studies have focused on corn plant density and strip size, there has been little research focused on altering corn density from row to row within intercropped strips.  The objective of our research was to determine the optimal corn planting density for corn border rows as to maximize corn plot yield and land use efficiency.  The response of supplemental N at high corn densities was also evaluated.  In this experiment, alternating 8-row corn and soybean strip plots planted in the east-west direction were established on May 2009 at Urbana, IL.  Treatments, which are based on preliminary data collected in 2008, consisted of four corn seeding rates (79,000 99,000 119,000 and 139,000 seeds ha^-1) and the presence or absence of 56 kg ha^-1 of additional N applied as 28% urea-ammonium nitrate solution.  Treatments were applied to the outside two corn rows on each side of the 8-row plots, while the inside 4 rows were planted at a constant 79,000 seeds ha^-1 and received a standard field N fertilizer rate (179 kg N ha^-1).  Soybean was planted at a constant density of 333,000 seeds ha^-1.  Preliminary data from 2008, along with in-season corn and soybean plant measurements and yield component data will be presented.