Jacob P. Vossenkemper Department of Plant and Soil Sciences Oklahoma State University

Problems  (Booth, 2009) estimated that each spring 391 million dollars in nitrogen fertilizer is flushed down the Mississippi River  Additionally (Malakoff 1998) estimated 700 million dollars annually  Currently NUE is 33% for cereal grain production worldwide (Raun and Johnson, 1999)  Nitrogen fertilizer is one of the most costly inputs in agriculture production today

Solutions Rotations Forage production systems Genetically modified hybrids Foliar applied nitrogen Precision agriculture approaches (application resolution)

Precision Agriculture Approaches  Traditionally midseason fertilizer applications in corn (Zea maize L.) are placed down the center of 76 (cm) rows  Advent of precision agriculture technologies allows producers to place midseason nitrogen closer to the plant RTK ( Real Time Kinematics) correction signal Auto track Auto steer

Objectives  To evaluate midseason (V8 to V10) variable liquid UAN (Urea Ammonium Nitrate) rates (45, 90, and 134 kg/ha) applied at different distances (0, 10, 20, and 30 cm) from the center of the row  Currently evaluating planting distances (10, 20, and 30 cm) away from preplant UAN applied in continuous bands

76.2 (cm) Row 0 (cm) Directly on the brace roots

10 (cm) From the Row 76.2 (cm) Row

20 (cm) From the Row 76.2 (cm) Row

30 (cm) From the Row 76.2 (cm) Row

Application Methodology UAN applied in a continuous stream

Application Methodology

Previous Work  A three year study by Vyn and West (2008) from Purdue University found that planting corn using RTK guidance systems 12.7 (cm) (five inches) from the preplant N band using UAN generally improved corn yields  An ongoing collaborative project at Oklahoma State University involving Bio-systems and Agricultural Engineering, has shown that planting corn using RTK guidance systems (cm) (six inches) from the pre-plant band of UAN generally improved corn yields in a dry-land production system.

Previous Work  Shoup and Janssen in 2009 found that in extremely wet conditions planting closer to nitrogen bands may be beneficial.  However, planting closer to pre-plant nitrogen in normal conditions proved to have little effect on grain yield (Shoup and Janssen, 2009: Agronomy e- update 191, Kansas State Ext Pub)  In a study conducted at Oklahoma State University midseason applications of nitrogen (V8 to V10) were applied to every other row. Rows that did not have midseason applications (V8 to V10) had lower yields (Edmonds, 2007).

Previous Work  This study provides evidence that mass flow of nitrate in semi-arid to arid climates may not be substantial enough to move midseason N great distances in a single growing season on a micro-scale (0 to 76 cm).

LCB Irrigated Treatment Structure 2008  Randomized Block Design  Plots six (m) by four rows  Harvested middle two rows  Port silt-loam TRT Pre-Plant N (kg/ha) Midseason N (kg/ha) Distance from plant (cm)

LCB Irrigated Treatment Structure 2009 TRT Pre-Plant N (kg/ha) Midseason N (kg/ha) Distance from plant (cm) on stalk Mid row Added three high rate (224 kg/ha) treatments Randomized Block Design Plots six (m) by four rows Harvested middle two rows Port silt-loam

76.2 (cm) Row 13 (cm) Directly on stalk of plant

76.2 (cm) Row 0 (cm) Directly on the brace roots

38 (cm) Down the Center of the Row 76.2 (cm) Row

45 kg N/ha applied preplant, excluding check SED =

LCB Irrigated Added Treatments 2009

Haskell Dry-land Treatment Structure 2008 TRT Pre-Plant N (kg/ha) Midseason N (kg/ha) Distance from plant (cm) No data as of yet Trial still in the field

Conclusions Research suggests that under irrigated conditions in a silt-loam soil Midseason N rates of 45 (kg/ha) applied at the base of the plant 0 (cm) were better than middle of the row Closer applied midseason N rates ranging from 90 to 224 (kg/ha) may or may not be beneficial N applied at the base at high rates showed no evidence of being detrimental to yield