Nutrient Management Research Database
General Information
Research Title
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Summary/Abstract from Original Source
Results from the first two years of this study support the concept of variable rate N application in potato production,especially when based on Imagery zonal management. This method showed significant increases in total yield, as well as U.S. No. 1 tubers. The recognized increase in yield and quality more than compensated for the increased cost of this method of variable rate N fertilization. Using EC added another layer of information but did not further improve yield and net returns, but more research regarding interpretation of this data in Idaho soils is needed before conclusions are drawn. Grid sampling alone does not seem to be an effective method for variable rate N fertilizer application, most likely due to the fact that spatial differences in yield potential are not being considered with this method. It is reasonable to assume that the results for the grid method would improve if a variable yield goal and/or added layers of information (such as imagery) were added. The cost of making yield goal adjustments is minimal and, as such, is a recommended addition for this method. This was not included in this trial because an evaluation of grid mapping as it is currently practiced in industry was desired for comparison with the other methods. Adding imagery to the already high cost of grid sampling may be cost prohibitive,but the added layer of information would be expected to improve the results. These combinations were not evaluated in this study and, therefore, are only surmised. Further evaluation of these methods for variable rate N application is planned
Research Highlights
Design and Methods
This study investigated the potential benefits of variable rate pre-season fertilization.
Four methods of fertilization were applied:
- Traditional (i.e. non-variable rate)
- Grid Mapping
- Bare Soil Imagery
- Bare Soil Imagery + EC mapping
Traditional rate was determined based on a single yield goal with a single composite test for soil nitrate.
Grid mapping determined N application rates based on testing from a 1.25 acre grid map.
Bare soil imagery is used to identify areas of potential difference and sampling each of those areas to determine applciation rates.
Bare soil + EC mapping used the bare soil approach along with a map of electrical conductivity.
Potato yield and quality were assessed.
Results
In the first year, all three variable rates approaches increased yields, though no differences were determined between the three. The average yield increase was 17 cwt per acre.
In the second year, an average increase of 20 cwt per acre was found when using the variable rate techniques.
In the third year, only the bare soil imagery approach increased yields at a rate of 28 cwt per acre.