On-Farm variable rate nitrogen management in irrigated potato

Abstract Purpose Variable Rate Nitrogen (VRN) fertilization can improve yields, quality and/or N use efficiency (NUE) of several crops. The objective of this study was to evaluate how pre-emergence VRN zones vs. uniform N management impacts potato (Solanum tuberosum L.) yield, quality and NUE. Methods Low, average and high N zones were created and evaluated for 10 site-years at fields near Grace, Idaho, United States of America (USA), with rates based upon yield goals, soil, irrigation and previous crop information. Uniform N rate strips were placed through all zones as a positive Grower Standard Practice (GSP) control to represent traditional N management. Results On average, VRN in high yield potential zones resulted in increases of 4.6, 4.6 and 4.8 Mg ha-1 for total, marketable and US No. 1 yields, respectively. There were no yield decreases with lower N rates in the low yield potential zones. Six fields had significant increases in tuber size with VRN in high yield potential zones resulting in average increases of 10, 8, and 11 g tuber-1 for total, marketable, and US No. 1 tubers, respectively. As expected, NUE was inversely correlated with N rates, but average NUE was 25 kg ha-1 greater across fields for VRN than traditional N management. Conclusion Higher N rates generally increased potato productivity in areas with high yield potential and lower N rates were able to maintain similar productivity with less N in areas with low yield potential. Thus, VRN applied to potato in this manner can improve yields and quality while increasing N efficiency.