Thursday, 10 November 2005 - 10:00 AM
307-6

Variable Rate Nitrogen in Potato Production.

Bryan G. Hopkins, Jason W. Ellsworth, Thomas R. Bowen, Aaron G. Cook, and Ralph A. Oborn. University of Idaho, Idaho Falls R&E Center, 1776 Science Center Dr Ste 205, Idaho Falls, ID 83402-1575

Potatoes (Solanum tuberosum) are particularly sensitive to nitrogen (N) nutrition. The fertilizer N needed is related to both residual soil N and yield potential and, as such, is hypothesized to have significant spatial variability. Three methods of variable-rate N fertilization using geospatial technologies were compared to the traditional method of uniform application in five potato fields in Eastern Idaho. The methods used to divide the fields into application zones included: 1) grid sampling, 2) bare soil imagery with intensive soil sampling, and 3) electrical conductivity mapping with bare soil imagery and intensive sampling. On average, the variable rate N resulted in better total (1.9 M ha-1) and US No. 1 (2.7 M ha-1) yields over traditional fertilization. All three methods showed an increase in net return over the traditional scenario with grid at $135 ha-1, imagery $376 ha-1, and imagery + conductivity at $319 ha-1; although only the latter two methods were statistically significant. Incidence of hollow heart was also reduced with the variable rate N application. Combining the conductivity technology with bare soil imagery did not result in further improvements in yield and grade, although it should be noted that this method performed better than the others in one of the five fields evaluated. Although further work is needed to support these findings, it appears that using geospatial technologies for variable rate N management in potatoes is economically viable. It is also probable that this technology will improve N use efficiency, which will likely have positive environmental benefits. Current year results will also be presented.

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