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Title: Spatial patterns of nitrogen response within corn production fields

item Hatfield, Jerry

Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/23/2008
Publication Date: 7/23/2008
Citation: Hatfield, J.L. 2008. Spatial patterns of nitrogen response within corn production fields [CD-ROM]. In: International Conference on Precision Agriculture Abstracts & Proceedings, July 20-23, 2008, Denver, CO.

Interpretive Summary:

Technical Abstract: Corn (Zea mays L.) yield response to nitrogen (N) application is critical to being able to develop management practices that reduce N application or improve N use efficiency. Nitrogen rate studies have been conducted within small plots; however, there have been few field scale evaluations. This study was designed to evaluate N response across 14 corn fields in central Iowa using different rates of N applied in strips across fields. These fields ranged in size from 15 to 130 ha with N rates that typically ranged from 50 to 150 kg ha-1. Some fields had three rates of N while others had four rates that included a 200 kg ha-1 application rate. Within each field strips were randomized and treated as replicates and were a minimum of 50 m wide. Observations were made of the soil type, topography obtained with GPS units, leaf chlorophyll readings at three times during the season for 30 leaves from each strip, hyperspectral data obtained with aircraft scanners with a pixel size of 2 m at four times, and crop yield with the combine yield monitor. All data were georeferenced for each field and subjected to a number of statistical and spatial analyses. There was a nonsignificant relationship between yield and N application rate in this study because yield to N response varied among fields. There was a significant relationship with soil type across the study because of the effect of soil water availability during the late grain-fill period. Crop yield showed the same general frequency distribution for different N rates within a field; however, the lower N rates had a greater dispersion than the higher N rates. Higher N rates did not make the field more uniform. A similar response was found for the normalized difference vegetative index (NDVI), nir/red, and red/green ratios in which the NDVI showed little variation at any of the N rates and didn’t change during the season. The red/green ratio was the most responsive to different times during the season and showed a significant correlation to yield. The spatial patterns of these vegetative indices showed that during the mid-season there was little variation. The spatial patterns within a field reveal information about the potential response of a field to management.