Table 6.

The influence of Ca(NO3)2, Ca(NO3)2H3BO3, and N:P:K (24:7:7) fertilization on the salt tolerance of spring foliage of evergreen oak and holly. Newly emerged leaves were detached at month 8 post-fertilization from trees growing under field conditions and subjected to 8% salt (NaCl) exposure under laboratory conditions. Improvements in tolerance were measured by chlorophyll fluorescence (Fo, Fv/Fm) and leaf chlorophyll content (SPAD).

Species/fertilizerFoFv/FmSPAD
Evergreen oak
Control148.7 (32.13)0.236 (0.050)17.8 (4.66)
Ca(NO3)2 (20 g/m2)139.7ns (28.24)0.253ns (0.038)18.5ns (3.98)
Ca(NO3)2 (40 g/m2)112.8* (30.11)0.292* (0.045)22.1ns (4.44)
Ca(NO3)2 (80 g/m2)136.3ns (25.67)0.219ns (0.038)17.4ns (3.88)
Ca(NO3)2H3BO3 (20 g/m2)122.7* (30.17)0.265* (0.042)21.4ns (5.21)
Ca(NO3)2H3BO3 (40 g/m2)115.9* (31.98)0.280* (0.040)21.3ns (5.07)
Ca(NO3)2H3BO3 (80 g/m2)127.9* (27.60)0.256ns (0.058)18.3ns (3.45)
N:P:K (24:7:7) (20 g/m2)131.5ns (39.04)0.234ns (0.059)21.7ns (4.28)
N:P:K (24:7:7) (40 g/m2)136.2ns (39.41)0.238ns (0.043)22.9ns (6.65)
LSD20.610.02775.03
Holly
Control193.1 (36.78)0.184 (0.039)13.7 (4.90)
Ca(NO3)2 (20 g/m2)181.4ns (39.44)0.197ns (0.041)14.2ns (5.09)
Ca(NO3)2 (40 g/m2)146.5* (38.90)0.227* (0.044)17.0* (5.38)
Ca(NO3)2 (80 g/m2)177.0ns (37.88)0.171ns (0.039)13.4ns (4.00)
Ca(NO3)2H3BO3 (20 g/m2)159.2* (30.25)0.207ns (0.051)16.5ns (3.72)
Ca(NO3)2H3BO3 (40 g/m2)150.4* (34.56)0.219* (0.045)16.4ns (4.21)
Ca(NO3)2H3BO3 (80 g/m2)166.2ns (32.30)0.199ns (0.048)13.5ns (6.28)
N:P:K (24:7:7) (20 g/m2)170.6ns (36.74)0.182ns (0.037)16.8ns (5.13)
N:P:K (24:7:7) (40 g/m2)176.9ns (40.29)0.185ns (0.040)17.0* (2.89)
LSD30.660.03293.22

  • All values mean of 15 trees, 2 leaves per tree.

  • ↵* = significantly different at P < 0.05, ns = not significantly different from control value.

  • Values in parentheses represent the standard error of the mean.