Effect of different nitrogen and potassium levels on nitrogen efficiency and some nutrient contents of sweet fennel

To investigate the effects of different nitrogen and potassium fertilizer rates on nitrogen use efficiency (NUE), nitrogen uptake efficiency (NUPE), nitrogen utilization efficiency (NUTE) and N, K, P, Ca and Mg nutrient contents in sweet fennel, a factorial experiment was conducted based on randomized completely block design with three replications in University of Zanjan, Iran. The applied fertilizers included 50, 100, and 150 kg/ha of N and K from urea and potassium sulfate sources, respectively. N and K application had significant effect on NUE and N, P, Ca, P, and Mg contents. Increasing nitrogen application rate levels desreased NUE, NUPE, and NUTE. Increasing of K application rate caused increment of N efficiency. Application of N and K fertilizers increased N, K and P concenterations on bulb tissue. Increasing N application rates resulted in more Ca and Mg concentrations, but application of K decreased Ca and Mg contents in bulb tissue. Regarding short growing period of sweet fennel, lower rates of N fertilizer is recommended to improve NUE.