Effects of nitrogen content on growth and hydraulic characteristics of peach (Prunus persica L.) seedlings under different soil moisture conditions

A pot experiment was conducted to investigate the effects of nitrogen content [N-1 (no fertilizer), N-2 (0.15 g.kg(-1)), and N-3 (0.3 g.kg(-1))] on the growth and the hydraulic characteristics of peach seedlings under different soil moisture conditions (W-1, W-2 and W-3, in which the soil water content was 45% to 55%, 60% to 70%, and 75% to 80% of the field water capacity, respectively) by using a specialized high pressure flow meter with a root chamber and a coupling, which was connected to plant organs. Leaf area and leaf hydraulic conductivity (K-L) increased significantly in the seedlings because of increased soil moisture and N content. K-L increased with leaf area. A linear correlation was documented between K-L and leaf area. K-L was higher in the morning and began to decline sharply after 16:00, at which K-L declined after an initial increase. Soil moisture and N content enhanced shoot (K-s) and root (K-r) hydraulic conductivities, thereby improving the low soil moisture condition to a large extent. Ks and Kr of the seedlings were reduced by 32% and 27% respectively in N-1, and by 14.7% and 9.4%, respectively in N-2, and both in W-1, compared with the control treatment. N-3 had no significant effect on Ks and Kr under similar conditions. Linear negative correlations were observed between Kr and the excised root diameter as well as between Ks and the shoot stem diameter. The shoot-to-root ratio increased with increase in N content. The shoot-to-root ratio in N-3 was increased by 14.37%, compared with N-1 in W-1 as well as by 12% and 4.39% in W-2 and W-3, respectively. Knowledge of the effects of soil moisture and N fertilizer on hydraulic characteristics and growth is important. Our results provide basic guidelines for the implementation of water-saving irrigation and fertilization management of nursery stock.