Tuesday, 8 November 2005
6

Nitrogen Release Characteristics of a Polymer Coated Urea Used for Potato Production.

Carl Rosen and Matthew McNearney. University of Minnesota, Department of Soil, Water, and Climate, 1991 Upper Buford Circle, St. Paul, MN 55108

Field experiments were conducted on a Hubbard loamy sand soil at the Sand Plain Research Farm in Becker, Minnesota to evaluate N release characteristics of a polymer-coated urea fertilizer (ESN, Agrium, Inc. Canada) and effects of the fertilizer on yield and quality of Russet Burbank potato. The coated fertilizer applied at 45, 135, 225, and 315 kg N/ha was compared with equivalent rates of urea. An additional 45 kg N/ha was applied as diammonium phosphate to all treatments except a zero N control. All coated urea was applied as a band at planting except for one additional treatment at the 225 kg N/ha rate where the application was split between planting and emergence. All urea was split-applied between emergence and hilling. In addition, two post-hilling urea-ammonium nitrate treatments were included to simulate fertigation. Tuber yields increased with increasing N rates for both N sources. Yields tended to be higher with coated urea compared with conventional urea at the two lower N rates and the same as urea at the higher N rates. Tuber size tended to be larger when fertilized with coated urea compared with conventional urea. Tuber quality was not affected by N source or rate. To determine N release from the fertilizer, coated urea was buried in plastic mesh bags in the fertilizer band at planting and removed at periodic intervals. Approximately 40% of the N from the coated urea was released by 40 days after planting, which preceded peak N demand by potato. About 90% of the N was released by 110 days after planting.

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