|Hart, Galen - HART & ASSOCIATES|
Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 28, 2004
Publication Date: July 28, 2004
Citation: Hatfield, J.L., Engelhardt, B.E., Oesterreich, W., Swalla, A.A., Hart, G.F. 2004. Spatial variation of yield and reflectance patterns in corn fields induced by soil and nitrogen management [CD-ROM]. International Conference on Precision Agriculture Abstracts & Proceedings. St. Paul, Minnesota. Technical Abstract: Management of nitrogen (N) to increase production efficiency and decrease the environmental impact has proven to be a difficult task because of the variability in response among fields and years. Demonstration of the effect of reduced N rates across fields has been documented in several studies. This study has been conducted across production fields in central Iowa in 2002 on fields ranging in size from 35 to 75 ha with the objective to quantify the spatial patterns of yield in response to N rates and the interactions of soil types and soil properties with rates. The general design has been to place N rates in wide (50m) strips across fields with treatments replicated as many as three times. The amount of N applied has ranged from 0 to 230 kg N ha**-1 using a full range or normal practice application methods. Field measurements have included topography, electrical conductivity, leaf chlorophyll, leaf N status, stalk nitrate, hand-harvested yield, and grain quality all captured with differential GPS location. Field/strip yields were obtained with GPS integrated yield monitors. Reflectance data were obtained with an aircraft mounted hyperspectral scanner with 24 wavebands. Differences in grain yield were not evident with changing in N rates; however, there were interactions of N rate with soil type, topography and electrical conductivity. As expected, spatial patterns of reflectance decreased in variability from bare soil to early grain fill and then began to increase in variability in the grain-fill period but variation is influenced by N application rates. Quantifying the spatial patterns in yield across fields with spectral measurement, soil properties and topography in response to N rates provides insights into the inconsistencies in corn yield response to N rates. This information is assisting producers and N suppliers with information on field-scale N management.