Figures (8)  Tables (3)

    • Figure 1. 

      Effect of different treatments on soil pH, electrical conductivity (EC), and soil water content (SWC). The different letters indicate significant differences (p < 0.05) between different treatments. The treatments are biochar (B0 and B1), nitrogen fertilizer (N0, N1, and N2) and irrigation (W and D).

    • Figure 2. 

      Effects of different treatments on photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs) and photochemical efficiency (Fv/Fm) in perennial ryegrass. The different letters indicate significant differences (p < 0.05). The treatments are biochar (B0 and B1), nitrogen fertilizer (N0, N1, and N2) and irrigation (W and D).

    • Figure 3. 

      Effects of different treatments on perennial ryegrass leaf peroxidase (POD) activity. (a) Photosynthetic rate, (b) superoxide dismutase (SOD) activity, (c) malondialdehid (MDA) content, and (d) abscisic acid (ABA) content. The different letters indicate significant differences (p < 0.05). The treatments are biochar (B0 and B1), nitrogen fertilizer (N0, N1, and N2) and irrigation (W and D).

    • Figure 4. 

      Effects of different treatments on plant water use (PWU), plant water use efficiency (WUEp), instantaneous water use efficiency (WUEins) and total dry biomass (DW). The different letters indicate significant differences (p < 0.05). The treatments are biochar (B0 and B1), nitrogen fertilizer (N0, N1, and N2) and irrigation (W and D).

    • Figure 5. 

      Effect of different treatments on total chlorophyll content, total nitrogen (TN), total phosphorus (TP) and total potassium (TK) in perennial ryegrass leaves. The different letters indicate significant differences (p < 0.05). The treatments are biochar (B0 and B1), nitrogen fertilizer (N0, N1, and N2) and irrigation (W and D).

    • Figure 6. 

      Effect of different treatments on nitrogen agronomic efficiency (NAE) of perennial ryegrass. The different letters indicate significant differences (p < 0.05). The treatments are biochar (B0 and B1), nitrogen fertilizer (N1 and N2) and irrigation (W and D).

    • Figure 7. 

      Heatmap of Pearson's correlation coefficients between soil and plant system under well-watered (W) or deficit irrigation (D) with nitrogen fertilizer (N0, N1, and N2) supply and with biochar (B0 and B1). * stands for significant at the level of p < 0.05. Increases and decreases in abundance are indicated by bars of color, in red and blue, respectively. Photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs), photochemical efficiency (Fv/Fm), plan water use (PWU), plant water use efficiency (WUEp), instantaneous water use efficiency (WUEins), total dry biomass (DW), total N (TN), total P (TP), total K (TK), peroxidase (POD) activity, Superoxide dismutase (SOD) activity, malondialdehid (MDA) content and abscisic acid (ABA) content, total N (STN), total P (STP), total K (STK), soil water content (SWC), electrical conductivity (EC), ${\text{NH}^+_4} $-N, ${\text{NO}^-_3} $-N and pH.

    • Figure 8. 

      Principal component analysis (PCA) of plant and soil parameters under well-watered (W) or deficit irrigation (D) with nitrogen fertilizer (N0, N1, and N2) supply and with biochar (B0 and B1). Photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs), photochemical efficiency (Fv/Fm), plan water use (PWU), plant water use efficiency (WUEp), instantaneous water use efficiency (WUEins), total dry biomass (DW), total N (TN), total P (TP), total K (TK), peroxidase (POD) activity, Superoxide dismutase (SOD) activity, malondialdehid (MDA) content and abscisic acid (ABA) content, total N (STN), total P (STP), total K (STK), soil water content (SWC), electrical conductivity (EC), ${\text{NH}^+_4} $-N, ${\text{NO}^-_3} $-N and pH.

    • MaterialpHEC
      (μS·cm−1)      		Total N
      (g·kg−1)      		Total P
      (g·kg−1)      		Total K
      (g·kg−1)      		Available N
      (mg·kg−1)      		Available P
      (mg·kg−1)      		Available K
      (mg·kg−1)
      Soil6.61152.631.190.813.2530.5818.2150.85
      Biochar8.32−−−−85.36316.59653.86
      Note: '−' represents no data; EC, electrical conductivity.

      Table 1. 

      Physicochemical parameters of experiment materials.

    • TreatmentsTotal N
      (g·kg−1)      		Total P
      (g·kg−1)      		Total K
      (g·kg−1)      		Available K
      (mg·kg−1)      		Available P
      (mg·kg−1)      		${\text{NH}^+_4} $-N
      (mg·kg−1)      		${\text{NO}^-_3} $-N
      (mg·kg−1)
      WN0B01.21 ± 0.06c0.80 ± 0.03b3.23 ± 0.06b17.99 ± 0.30f51.67 ± 2.76b3.52 ± 0.11ef15.57 ± 0.71h
      WN1B01.26 ± 0.04bc0.82 ± 0.04b3.20 ± 0.04b18.61 ± 0.99ef52.22 ± 3.18b6.90 ± 0.52c44.17 ± 0.91e
      WN2B01.41 ± 0.05bc0.82 ± 0.02b3.26 ± 0.05b18.96 ± 0.80ef52.92 ± 4.88b8.66 ± 1.10b50.71 ± 1.14b
      WN0B11.78 ± 0.07a1.16 ± 0.03a4.21 ± 0.05a27.27 ± 1.68d121.99 ± 2.30a3.68 ± 0.07e18.51 ± 0.63g
      WN1B11.73 ± 0.19a1.16 ± 0.06a4.26 ± 0.17a28.22 ± 0.75cd124.40 ± 3.28a6.97 ± 0.19c47.64 ± 0.80c
      WN2B11.76 ± 0.21a1.17 ± 0.05a4.25 ± 0.09a30.12 ± 0.99ab124.56 ± 10.67a9.21 ± 0.15a55.98 ± 1.15a
      DN0B01.31 ± 0.04bc0.81 ± 0.04b3.15 ± 0.04b18.29 ± 0.38ef53.77 ± 2.40b3.09 ± 0.18f14.04 ± 1.43h
      DN1B01.23 ± 0.06c0.82 ± 0.02b3.22 ± 0.09b18.90 ± 0.10ef52.91 ± 2.59b6.16 ± 0.05d40.49 ± 1.77f
      DN2B01.27 ± 0.10bc0.85 ± 0.06b3.24 ± 0.06b19.44 ± 0.46e54.54 ± 2.86b8.26 ± 0.07b44.69 ± 1.48de
      DN0B11.76 ± 0.11a1.18 ± 0.05a4.25 ± 0.10a28.86 ± 0.55bc124.92 ± 5.95a3.46 ± 0.11ef14.85 ± 1.36h
      DN1B11.78 ± 0.12a1.17 ± 0.04a4.31 ± 0.14a29.32 ± 1.09bc126.06 ± 4.51a6.50 ± 0.05cd44.63 ± 1.10de
      DN2B11.80 ± 0.13a1.17 ± 0.05a4.32 ± 0.12a31.16 ± 0.90a125.79 ± 4.32a8.50 ± 0.20b46.36 ± 0.81cd
      ANOVA
      Insnsns***ns******
      Nnsnsns***ns******
      B********************
      I * Nnsnsnsnsnsns***
      I * Bnsnsnsnsnsns*
      N * Bnsnsns*nsnsns
      I * N * Bnsnsnsnsnsns*
      Each value is the average (± SE) of four biological replicates. Different letters in the table represent significant differences between treatments at the level of p < 0.05. *, **, and *** indicate significant levels at p < 0.05, p < 0.01, and p < 0.001, respectively; ns denotes no significance. The treatments are biochar (B0 and B1), nitrogen fertilizer (N0, N1, and N2) and irrigation (W and D).

      Table 2. 

      Analysis of variance table and means of biochar (B), irrigation (I), and N fertilizer (N) treatments on soil physicochemical parameters. The meaning of treatments are different biochar (B0 and B1), nitrogen fertilization (N1 and N2) and irrigation (W and D).

    • FactorsPnTrgsFv/FmPWUWUEpWUEinsDWTNTPTKPODSODMDAABA
      I*********ns******************ns************
      N******************************ns************
      B********************************************
      I * N***************************nsns***ns******
      I * B***ns**nsns************nsns**********
      N * B************ns***ns***nsnsns***********
      I * N * B***ns***nsns*******nsnsns************
      Photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs), photochemical efficiency (Fv/Fm), plan water use (PWU), plant water use efficiency (WUEp), instantaneous water use efficiency (WUEins), total dry biomass (DW), total N (TN), total P (TP), total K (TK), peroxidase (POD) activity, Superoxide dismutase (SOD) activity, malondialdehid (MDA) content, and abscisic acid (ABA) content. The outputs of the three-way ANOVA are shown where *, **, and *** indicate significant levels at p < 0.05, p < 0.01 and p < 0.001, respectively; ns denotes no significance. The treatments are biochar (B0 and B1), nitrogen fertilizer (N0, N1, and N2) and irrigation (W and D).

      Table 3. 

      Analysis of variance table and means of biochar (B), irrigation (I), and N fertilizer (N) treatments on plant physiological parameters. The meaning of treatments are different biochar (B0 and B1), nitrogen fertilization (N1 and N2) and irrigation (W and D).