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Fluid Journal : Summer 2016
6 The Fluid Journal Summer 2016 Dr. Tindall is Senior Agronomist for the J.R. Simplot Company in Boise, Idaho, and is also a member of the FFF Board of Directors and its Fluid Journal Editorial Committee. Dr. Mooso is the Agronomy Manager for Simplot and member of the FFF R&E Committee. Figure 3. Fluid (6-24 -6) timing and placement applications to U.S. # 1 yield of Russet Burbank potatoes produced under irrigation at Aberdeen and Parma ID during 2014-15. expressed as to how potatoes would respond to rates and timings of nutrients, and in this case, low salt 50-50 poly/ ortho fertilizer blends to either furrow, furrow/foliar combinations or strictly foliar applications. Positive responses were observed over the UTC for all treatments, but it appears that the strongest response for total potato tuber yields came with a combination of furrow and foliar (data not shown). However, the most important information for potato processing a fresh market is the US #1 production (Figure 3). When applications are made across fertilizer rates it appears that the strongest contribution may actually come from foliar applications of low salt 6-24 -6 applications. Or certainly, a combination of in-furrow with a combination of foliar, depending on the phosphorus content of the plant as indicated by petiole P concentrations (data not shown). While U.S. #1 potato production is interesting to look at, it is also expressed in cwt/ac. Higher quality potatoes were increased over the UTC with applications of 6-24 -6 when applied either at furrow, furrow + foliar or simply applied as a foliar (Figure 4). When averaged across all treatments and in both locations over the two years, there was little difference between combining a furrow with foliar applications of 6-24 -6. Furrow applications alone were not enough to generate the highest U.S. #1 yields. From this study it appears that 3 gals/ ac were the maximum rate that should be applied directly to the seed piece. However, higher yields were observed with either foliar alone or a furrow + foliar and at the higher application rates. There may also be site variations with the 6-24 -6 applications between Parma and Aberdeen. Although the data were not shown, there was not as much suppression in potato yield with furrow applications in Parma as appeared in Aberdeen. This needs further evaluations. Summing up Although the complete study has not been finished, there are interesting observations that can be discussed from using low salt fluid fertilizers in irrigated potato production in the Pacific Northwest. The use of 6-24-6, which includes both N, P, and K in a formulation that would be classed as a low salt, can benefit both total and U.S. #1 yields. The greatest production increases may Figure 4. Timing, placement, and rates of low salt liquid 6-24 -6 applications to Russet Burbank potatoes applied at Aberdeen and Parma Idaho 2014-15. come from a combination of in-furrow + foliar or with foliar applications when higher rates are used. Rates of 6 or 9 gallons/ac appear to maximize production parameters and could be used as guidelines for growers to initiate similar applications on their production fields. The authors are not suggesting that these applications replace what has been a well-thought-out P nutritional program, but as an easy way to provide a high P fertilizer during times of high nutritional requirements. Additional information will be required to determine if higher yield environments make a difference as to optimum combinations of furrow and foliar 6-24 -6 applications. The authors would like to thank Dr. Jeff Stark and Dr. Mike Thornton and their staffs with the University of Idaho in conducting these studies in cooperation with the J.R. Simplot Company. The University of Idaho does not endorse this or any other products that might be discussed in this article.