Optimizing nitrogen fertilizer rates and time of application for potatoes under seepage irrigation

• Published in: Field crops research 2018-01, Vol.215, p.49-58
• Main Authors: Rens, Libby R., Zotarelli, Lincoln, Rowland, Diane L., Morgan, Kelly T.
• Format: Article
• Language: English
• Subjects: Florida; N uptake; Plant biomass; Sandy soil; Soil ammonium; Soil nitrate; Subirrigation; Tuber yield
• ISSN: 0378-4290; 1872-6852
• DOI: 10.1016/j.fcr.2017.10.004

•N fertilizer applied well in advance of planting can still contributed to the nutrition of a potato crop.•N fertilizer applied well in advance of planting is prone to leaching, especially in years with heavy rain events.•N application at plant emergence had a large impact on tuber yield.•Highest tuber yield was achieved with N rates 114–138kgha−1 of N at emergence. Splitting N fertilizer application is recommended to increase crop N use efficiency by reducing risk of leaching. The objective of this study was to optimize the timing and rate of split N fertilizer applications to maximize tuber yield and quality of chipping potatoes grown using seepage irrigation in Florida. A two-year study was conducted on two commercial farms using cultivars Atlantic and FL1867. A factorial of two N rates applied at pre-plant (Npre-pl) 0 or 56kgha−1 30days before planting followed by four N rates applied at plant emergence (Nemerg) 0, 56, 112, or 168kgha−1 were randomized in a complete block design with four replicates. At tuber initiation, all treatments received an additional 56kgha−1 of N. All applications of N were of granular ammonium nitrate banded. Total N applied for the various treatments ranged from 56 to 280kgha−1 of N. Soil N was monitored in the 0–20cm soil depth layer throughout the season. Whole plant biomass peaked at 8.5–8.7Mgha−1 with Nemerg rates between 112–143kgha−1. Plant N uptake range from 66 to 157kgha−1. N uptake use efficiency decreased with increasing N rates. Potato yield ranged from 25 to 42Mg ha−1 in both years. In 2013, application of 56kgha−1 of Npre-pl produced 2.5–5.1Mgha−1 higher yield than treatments receiving 0N. In 2014, there was an interaction between Npre-pl and Nemerg on yield. The higher 56kgha−1 Npre-pl resulted in higher yield only when Nemerg was at or below 56kgha−1. For cv. Atlantic when no Npre-pl was supplied, yield increased linearly in response to Nemerg rates, while with 56kgha−1 of Npre-pl, yield responded quadratically to Nemerg reaching a maximum at 114kgha−1. For cv. FL1867 yield increased quadratically to Nemerg peaking at 138 and 126kgha−1 of when 0 or 56kgha−1 of Npre-pl was applied, respectively. The study shows that while the risk of Npre-pl loss is high, Npre-pl can result in higher yield, especially when subsequent N rates are low. Application of Npre-pl was particularly effective in a dry year. By contrast, when soil mineral N from Npre-pl was largely lost to leaching in a high rainfall year, yield was incr