Importance of Early-Season Nitrogen Rate and Placement to Russet Burbank Potatoes

Early-season nitrogen (N) is necessary for optimal potato vegetative growth and creating an optimal growing condition for high yields; however, on sandy soils it also increases the risk of losing fertilizer N through leaching. This 3-year field experiment evaluated whether a smaller amount of N placed near the plant roots could provide the benefits associated with higher rates of early N applications that were less well placed. Two rates of N applied at emergence (40 or 80 kg N ha⁻¹) were spot-placed (5 to 7 cm around each plant), banded along the row, or broadcast applied, and compared to no N or where all of the in-season N was applied at tuberization. All plots except the zero N controls received a total of 170 kg ha⁻¹ of in-season N. Where emergence N was spot-applied in some years, tuber numbers were reduced compared to where the N was broadcast, and in these situations, resulted in increased tuber size and higher yields of prime-sized tubers (U.S. No. 1, 170 to 370 g). Where differences existed, results from banded treatments were intermediate between those from the spot and broadcast treatments. However, in spite of apparent N placement effects likely associated with having a higher concentration of N near the plant roots early in the season, no differences were evident between the two rates of emergence N within a given placement. In this experiment, total yields were not affected by rate or placement of emergence N. Overall, this experiment provides support for the concept of placing early-season N near the plant roots, and band applications along the row may be a grower-manageable alternative for achieving this goal.