Objectives Nitrogen nutrition and soil moisture are important factors affecting the growth and quality of lily (Liliumspp.) cut-flowers. Different nitrogen fertilizers and irrigation volumes were tested in order to provide scientific basis for water and nitrogen management of lily cut-flowers.

Methods Taking Liliumspp. cv. Sorbonne as plant material, a pot experiment had been designed with five nitrogen fertilizer treatments:only ammonium-nitrogen, only urea, only nitrate-nitrogen, both ammonium and nitrate nitrogen (50%:50%) and both urea and nitrate-nitrogen (50%:50%) under the same N amount, and two watering levels, normal irrigation (soil water content was kept at 60%-70% θ_fduring the seedling stage and 70%-80% θ_fafter the squaring stage, θ_fis field capacity, W1) and deficit irrigation (soil water content was kept at 50%-60% θ_fduring the seedling stage and 60%-70% θ_fafter the squaring stage, W2). Plant height and stem diameter after lily growth stopping, flower number, flower diameter, vase life, and the contents of soluble sugar, soluble protein and malondialdehyde (MDA) in leaves and tapels at 7 and 14 days after the flowering were respectively determined.

Results The combined application of ammonium- and nitrate-nitrogen fertilizers had higher plant height, larger flower numbers, longer vase span of cut-flowers and higher contents of soluble sugar and soluble protein in leaves and tapels, and less accumulation of MDA at 7 and 14 days after the flowering. Compared to the normal irrigation, the effects of the deficit irrigation on plant height, flower number and diameter, vase span of cut-flowers and the contents of soluble sugar, soluble protein and MDA in leaves and tapels after the flowering varied with different nitrogen treatments. In addition, different water and nitrogen treatments had different cut-flower periods. Under the two watering levels, the cut-flower periods were 100 d in applying only urea, 90 d in the combined application of urea and nitrate-nitrogen fertilizer and 85-86 d in the combined application of ammonium- and nitrate-nitrogen fertilizers. Under the normal irrigation, the cut-flower periods were 85-86 d in applying only ammonium- or nitrate-nitrogen fertilizers. But under the deficit irrigation, the cut-flower periods were 91 d in applying only nitrate-nitrogen fertilizer and 87.5 d in applying only ammonium-nitrogen fertilizer.

Conclusions Under the condition of this study, the combined application of ammonium- and nitrate-nitrogen fertilizers is favorable to high plant height and flower numbers, shorten the cut-flower period and prolong the vase span of cut flowers, thus improve the quality of cut-flowers. The effects of the deficit irrigation on the quality of cut-flowers depends on nitrogen fertilizer form.