Submitted to: Proceedings of Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/15/2000
Publication Date: 3/5/2000
Citation: Franzen, D.W., Halvorson, A.D., Hofman, V.L. 2000. Spatial nutrient relationships and profitability of variable-rate fertilizer application in a wheat and sunflower rotation. Proceedings of Great Plains Soil Fertility Conference. 8:88-93.
Interpretive Summary: The use of variable-rate fertilizer technology in the semi-arid northern Great Plains production systems needs to be evaluated. Soil sampling on a one-acre grid intensity is not practical for dryland production systems. This study tested various soil sampling strategies and evaluated whether variable-rate nitrogen application would provide a positive economic return nto growers. The results show that NO3-N, P, S, and Cl levels in the soil were often related to topography. This reduced the number of soil samples needed to make meaningful nutrient management decisions. Application of a variable-rate of nitrogen fertilizer appeared to be profitable in sunflower when the range in soil NO3-N was large enough to make a meaningful change in N rate across the field.
Technical Abstract: A variable-rate fertilizer study was conducted near Mandan, ND in a winter wheat, sunflower, spring wheat rotation. Grid soil sampling from these fields revealed that fertility patterns were related to topography. The nutrients included in this relationship were NO3-N, P, S, and Cl. By zone soil sampling based on topography, the number of soil samples required to describe the field was reduced while maintaining a high or higher level of information than the next best grid size sampling estimate. Variable-rate application of fertilizer was profitable in sunflower when the range of NO3-N values was sufficient to provide for meaningful change in N rate and when the range was in a category where changes of N rate were possible.