Economic response of potato to nitrogen rate, timing of nitrogen application, cultivar, and irrigation

Three multiyear studies were conducted in Manitoba, Canada to evaluate the effect of nitrogen (N) fertilizer rate (ranging from 0 to 225 or 0 to 240 kg N ha −1 ) and its interactions with timing of N application (preplant, split application), cultivar (Russet Burbank (RB), Glacier Fryer (GF), Umatilla Russet (UR)), and moisture regime (irrigated, nonirrigated) on the yield and net revenue (NR) of potato ( Solanum tuberosum L.). Based on soil test N, all sites were expected to be N-responsive, with soil test N at most sites ranging from 24 to 45 kg NO 3 -N ha −1 to 60 cm and measuring 70 and 117 kg NO 3 -N ha −1 to 60 cm at the remaining two sites. Linear and quadratic coefficients of N and irrigation were significant for yield and NR. However, the NR curves for N inputs were relatively flat, and the NRs were only slightly less than the optimal NR within the vicinity of the optimum. Split N applications performed similarly to preplant N, and GF performed better than RB or UR; however, GF optimal economic N rates were about 55% higher than the optimal economic N rates of RB and UR cultivars. Optimal economic N rate for the best potato practices ranged from 157 to 216 kg N ha −1 , depending on the studies; or averaging at about 188 kg N ha −1 . Adoption of these best N management practices will improve profitability and N use efficiency in potato production and reduce negative environmental impacts.