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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: Abstract Only
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: Management of nitrogen in corn production systems is critical to the improvement of production efficiency and environmental quality. Observations of nitrogen response have typically been conducted at plot scale and the results transferred to field situations. There is a need for within field studies to increase the confidence of producers in the experimental results so that adoption of the improved management systems can occur more rapidly. We designed a study to evaluate the response of corn production to nitrogen rates across multiple fields and years in Iowa. The study was designed to compare various nitrogen rates that ranged from a base rate of 50 kg ha-1 to 200 kg ha-1 with three or four rates within each field. Fields were selected in different locations to provide a range of different soil types and also potential rainfall differences during the growing season. Soil samples for soil nitrate content were collected after planting and the application of the starter rate of N fertilizer (50 kg ha-1). Leaf chlorophyll readings were collected at multiple times during the growing season along with aircraft overflights of reflectance at planting, mid-vegetative growth, maximum vegetative growth at the onset of grain-fill, and mid-grain fill. Yield was collected with combine yield monitors in each strip which was designed to be a minimum of 50 m wide through the length of the field. Temporal patterns of reflectance within fields revealed that the early season patterns were dominated by soil patterns within the field with a disappearance of spatial patterns in the mid-season and beginning grain fill period, with a reappearance of spatial patterns during grain-fill. Detection of nitrogen stress on crops was most evident during grain-fill because of the interaction of the spatial patterns with soil water availability.