Nitrogen Uptake Patterns of Potatoes with High‐Frequency Sprinkler‐Applied N Fertilizer1

Abstract

AbstractIn order to understand utilization of N by Russet Burbank, a commonly grown indeterminate potato (Solanum tuberosum L.) cultivar, it is necessary to determine the partitioning of N in the plant. Fertilizer N efficiency is closely related to the latter. The objective of this research was to examine differences in N uptake patterns of Russet Burbank potatoes with N applied at excessive, adequate, and deficient levels in daily sprinkler irrigation. The N levels were selected on the basis of statistical significance of yield response to N fertilization. Experiments in 1980 and 1981 were done on a Quincy sand to loamy sand (mixed, mesic, Xeric Torripsamments) typical of coarse‐textured soils used for potato production in the Western United States. Daily mid‐season applications of a urea‐NH4NO3 solution were made for about 10 weeks through solid set sprinklers. Samples of vines and tubers were collected weekly and analyzed for total N. To show partitioning and time changes of vine and tuber N, regression curves were fitted to data for N uptake with time after emergence. Rate of N uptake functions were derived and used to determine N sink dominance by vines or tubers. At fertilizer rates greater than adequate for optimum tuber yield, the excess N showed up as increased N in vines and tubers with vines as the dominant N sink. At adequate and deficient N levels tubers were dominant N sinks, however, the deficient plants did not have a sufficient N supply for optimum yield. A desirable N uptake pattern is associated with the following: (i) A fertilizer N level that is adequate such that tuber yield and economic return on fertilizer investment are optimized which is about 340 kg N/ha for these experiments and (ii) The tubers express N uptake dominance (highest rate) from the start of rapid tuber development causing peak quantity of vine N uptake in the first one‐third to one‐half of the post‐emergent growth period.