Coupled effect of irrigation and nitrogen management strategies on spring potato (Solanum tuberosum L.) productivity, quality, and nitrogen use efficiency under sprinkler irrigation

Potato ( Solanum tuberosum L.) production on sandy soils requires coordinated irrigation and nitrogen (N) management because the low water- and nutrient-holding capacity of these soils increases the risk of crop water stress and nitrate-nitrogen (NO₃–N) movement below the root zone. In Florida, previous potato studies have largely focused on seepage-irrigated hill-and-furrow systems, while limited information is available on the combined effects of irrigation and N management for potatoes grown on flat, wide-bed systems under sprinkler irrigation. Therefore, a two-year field study evaluated the effects of full irrigation (FIT), deficit irrigation (75%FIT), and N application rates ranging from 112 to 392 kg N ha⁻¹ , along with a rainfed zero-N control, on potato growth, biomass accumulation, yield, quality, N uptake, and soil NO₃–N. Leaf area index (LAI), tuber biomass, and total biomass were responsive to N application rate, while total crop N uptake was similar between FIT and 75%FIT. Increasing N application beyond 224 kg N ha⁻¹ did not further increase total crop N uptake. Strong positive associations among biomass accumulation, N uptake, and tuber biomass further suggest that greater crop growth was accompanied by greater N acquisition and tuber development Soil NO₃–N concentrations varied between years and generally increased with N application rate, with greater concentrations in deeper soil layers at higher N rates, suggesting greater potential for N movement below the primary root zone. Tuber yield responded positively to N application, with the numerically highest yields obtained under FIT with 336 kg N ha⁻¹ in 2022 and FIT with 392 kg N ha⁻¹ in 2023. However, these higher N inputs did not produce corresponding increases in crop N uptake and were associated with greater residual soil NO₃–N. Despite differences in crop responses between years, 75%FIT produced growth, N uptake, and tuber yield responses generally comparable to FIT under the environmental and management conditions evaluated in this study. Across N treatments, rates of 224–280 kg N ha⁻¹ provided a favorable balance between crop productivity and N uptake, whereas further increases in N provided limited additional benefits and resulted in greater soil NO₃–N accumulation. Multi-location and multi-year evaluations are needed to determine the broader applicability of these management responses across Florida potato production systems.