Regional Investigation on Interaction of Nitrogen Management, Hybrid Selection, and Population on Corn Production

Making sound recommendations for N fertilizer rate and timing for optimal corn yield and minimal N loss can be complex and challenging, especially considering seasonal and locational variability. Splitting N applications between pre-plant and in-season allows room for adjustment to specific seasonal conditions. Tools such as crop sensors and the Maize N model have been developed to help fine-tune corn N management. The general objective of this study, initiated in 2012, is to evaluate these two approaches for determining in-season N rates for corn over a three state region (Nebraska, North Dakota, Missouri). Other factors such as plant population, hybrid drought score, and soil productivity were also evaluated. Two experimental sites per state were selected, making a total of six sites. Sites within states were in close proximity, each state having a high and a lower soil productivity site. At each site a high and moderate plant population were evaluated for both a low and a high drought score hybrid. Four basic N treatments were used: unfertilized check, N-rich strip (preplant), sensor-based approach and model-based approach. The two latter treatments involved in-season application. Sensor-based treatments were determined by canopy reflectance using a Handheld Crop Sensor. Pre-plant, at-planting and in-season N application method and source varied by state.

Weather conditions affected study sites in 2012. Water stress masked N treatment effects at some sites that were not fully irrigated. The Nebraska sites experienced a large amount of soil N mineralization, particularly in March, which resulted in all treatments (including control) having high available N. Additionally, leaf curling due to drought stress and low populations due to soil crusting likely impacted the sensor readings in North Dakota. For all sites, the in-season N application rate for the model-recommended treatments exceeded that of sensor-recommended treatments. The sensor treatment appears to have higher N use efficiency as seen by partial factor productivity (yield/total N fertilizer); however, the agronomic efficiency (fertilized-control yield/total N fertilizer) was not correlated to N strategy for many of the sites. This is the first year of a large and complex study that was unfortunately impacted by drought. It is planned to continue in 2013. IPNI-47