Abstract

Drought and low concentration of soil nitrogen (N) limit crop growth and production in arid and semi-arid regions. Improving the efficient use of these limited resources is an important challenge. We tested one-year-old trees of three apple cultivars (Malus domestica cv. ‘Golden Delicious’, ‘Naganofuji No. 2’, and ‘Pink Lady’) grafted on M. hupehensis to determine how water and N supplies influence growth, biomass production, and water-use efficiency (WUE). Two watering regimes (80 and 50% field water capacity) and three N supplies (N0: 0, NL: 75, and NH: 150 mg N kg⁻¹ soil) were used. Drought dramatically diminished plant height (PH), basal diameter (BD), biomass production, total leaf area (LA), specific leaf area (SLA), leaf relative water content (RWC), photosynthetic rate (P_n), stomatal conductance (g_s), and WUE, but increased root/shoot ratio. NL significantly increased PH, BD, LA, SLA, RWC, P_n, g_s, and WUE, but NH reduced or had little influence on these parameters. P_n, g_s, LA, and root biomass significantly and positively correlated with WUE. Our results suggest that water and N are co-related, and NL enhance drought tolerance and WUE through increased photosynthetic capacity and water uptake. Thus, an appropriately low N supply would be recommended under dry condition, but excess N supply should be avoided.

Key words: Biomass production, drought, growth, Malus domestica, nitrogen, water-use efficiency.