Response of N-Fertilizer Rates and Timing of Application On Yield of Chipping Potatoes in Florida.

It is imperative to determine an optimal combination of nitrogen fertilizer rate and timing of application that maximizes potato production and quality. The objective of this study was to identify a suitable N-fertilizer rate for Atlantic chipping potato production in northeast Florida, and to evaluate its effect on plant growth, yield and quality of tubers. This study was conducted with grower collaboration on three farms for two consecutive years. This study focused on the effects of four levels of nitrogen at plant emergence (EMN: 0, 56, 112, 168 kg ha^-1) combined with two levels of sidedress nitrogen applied at the 15-20 cm growth stage (SDN: 56, 112 kg ha^-1) in a factorial design. Total N-fertilizer applied ranged from 112 to 336 kg ha^-1. Treatments were arranged in a randomized complete block design within each farm and repeated measurements of soil and plant tissue were taken at specified stages to monitor changes over the course of the growing season. The effects of EMN and SDN on soil nitrogen levels, plant biomass, plant nitrogen content, and potato yield were quantified. Analysis of tissue data showed that higher N-rates of EMN or SDN did not increase plant N content. The average total yield ranged from 34.6 to 36 Mg ha^-1. Mineral N content of the soil was measured throughout the season and reflected EMN and SDN treatments (p<0.0001). At harvest, residual soil nitrogen ranged from 5 to 40 mg kg^-1 with respect to increasing N application. As increased concentration of nitrogen in the soil was associated with higher N-treatments however was not correlated to an increase in potato yield; this suggests that under the conditions of this experiment there was no N-limitation for even the lowest N-rate.