3.1. Gas Exchange
The studied factors, including fertilization sources (mineral and organic) and conduction systems, interacted significantly (based on the p-value less than the chosen significance level) and influenced the physiology of the fig trees. There were significant interactions for water use efficiency (WUE), transpiration (E), stomatal conductance (gs), leaf temperature (LT) (p < 0.01), internal CO2 concentration (Ci) (p < 0.01), instantaneous carboxylation efficiency (AN/Ci) (p < 0.01), net photosynthesis (AN) (p < 0.01), and maximum quantum efficiency of PSII (Fv/Fm) (p < 0.05). Due to these significant interaction effects, the combined means were analyzed using the Tukey test (p < 0.05) to compare treatment combinations and interpret the results.
Plants that received mineral fertilization showed higher water use efficiency (WUE) in the 2B, 3B, and 4B systems (7.14, 8.19, and 6.84 (µmol m
−2 s
−1) (mol H
2O m
−2 s
−1)
−1), respectively. Only in the espalier system did fertilization (OC) have a WUE of 5.35 µmol m
−2 s
−1 (mol H
2O m
−2 s
−1)
−1, similar to mineral fertilization of 5.72 µmol m
−2 s
−1 (mol H
2O m
−2 s
−1)
−1. Notably, the highest WUE with fertilization (M) was obtained in the systems with fewer branches, 2B and 3B, emphasizing the 3B system of 8.19 µmol m
−2 s
−1 (mol H
2O m
−2 s
−1)
−1, which was statistically superior to the other systems (
Table 4).
OC, CM, and CL presented median and similar values among the organic sources. Only SM resulted in lower
WUE for the conduction systems 2B (2.12 (µmol m
−2 s
−1) (mol H
2O m
−2 s
−1)
−1), 3B (3.17 (µmol m
−2 s
−1) (mol H
2O m
−2 s
−1)
−1), 4B (3.91 (µmol m
−2 s
−1) (mol H
2O m
−2 s
−1)
−1), and espalier (3.76 (µmol m
−2 s
−1) (mol H
2O m
−2 s
−1)
−1. Reductions in
WUE of around 70.31%, 61.39%, 42.84%, and 34.27% were recorded, respectively (
Table 4).
The lowest
E was obtained with mineral fertilization in the 2B, 3B, and 4B systems, presenting transpiration rates of 5.02, 4.56, and 4.97 mmol H
2O m
−2 s
−1, respectively. The highest
E value was observed in the 2B system, using SM and CL of 9.22 mmol H
2O m
−2 s
−1 and 8.32 mmol H
2O m
−2 s
−1, respectively, and in the 3B system, using SM and CL of 8.28 mmol H
2O m
−2 s
−1 and 8.17 mmol H
2O m
−2 s
−1, with no statistically significant difference. With 4B, the organic fertilizers did not differ statistically from each other and had higher
E than the mineral fertilizers. In the espalier system, the lowest
E was obtained with CM and M of 6.17 and 6.34 mmol H
2O m
−2 s
−1, respectively, and the highest
E was obtained using CL of 7.99 mmol H
2O m
−2 s
−1 (
Table 4).
The stomatal conductance (
gs) of plants subjected to the 2B and 3B systems was similar, with the lowest
gs observed with the M (0.41 and 0.47 mol (H
2O) m
−2 s
−1), CM (0.41 and 0.50 mol (H
2O) m
−2 s
−1), and OC (0.43 and 0.48 mol (H
2O) m
−2 s
−1) fertilizations, respectively, which did not differ statistically among them. As in
E, the highest
gs values were verified using SM (0.77 and 0.53 mol (H
2O) m
−2 s
−1) and CL (0.76 and 0.65 mol (H
2O) m
−2 s
−1) in the 2B and 3B systems. In the espalier system, the highest
gs values were obtained using a CL of 0.62 mol (H
2O) m
−2 s
−1. Only the 4B system did not differ statistically between the sources studied (
Table 4).
Plants fertilized with SM presented the highest
Ci in the 2B, 3B, and espalier systems of 280, 218, and 200.33 µmol mol
−1, respectively, which may indicate internal CO
2 accumulation. In the system with 4B, there was a more significant accumulation of
Ci with mineral fertilization, with 205.33 µmol mol
−1. With 3B, the M and CM sources presented the lowest
Ci of 155.67 and 169.00 µmol mol
−1. In turn, 4B had the lowest
Ci with CL (146.00 µmol mol
−1), and, in the espalier system, lower values were verified using OC and CM of 140.33 and 158.33 µmol mol
−1, respectively (
Table 5).
The instantaneous carboxylation efficiency (
AN/
Ci) was similar to the results of internal CO
2 concentration. The lower-efficiency plants (
AN/
Ci) were observed to be fertilized with SM in the 2B (0.07), 3B (0.12), and espalier systems (0.14). In the 4B system, lower
AN/
Ci values were also observed with M fertilization (0.17), although they did not differ statistically from those with SM (0.16). It is worth noting that lower
AN/
Ci values led to reductions in the photosynthetic rate (
Table 5).
The highest
AN/
Ci values varied among the studied conduction systems. In the 2B system, the highest
AN/
Ci was obtained with M (0.26), which did not differ statistically from OC (0.26) and CL (0.22). With 3B, the highest
AN/
Ci values were obtained with mineral fertilizer (0.24) and CM (0.20), which were statistically equal. In the 4B system, the organic fertilizers CL, CM, and OC presented efficiencies of 0.26, 0.22, and 0.20, respectively, which were statistically equal. In the espalier system, the highest efficiencies were obtained with OC (0.26), followed by CL (0.22) and M (0.22), which were statistically equal (
Table 5).
The 2B and espalier systems showed similar behavior regarding fertilizer sources. The highest
AN rates were obtained with the use of CL, with 38.53 and 36.71 µmol m
−2 s
−1, respectively, followed by M, with 35.65 and 36.26 µmol m
−2 s
−1, respectively, and OC, with 34.72 and 37.15 µmol m
−2 s
−1, respectively, statistically equal. It is also noteworthy that using the organic sources CL and OC, which are statistically equal, increased the
AN of fig trees by 2B to 49.23% and 43.66%, respectively. In the espalier system, the use of CL and OC fertilizers also increased the
AN of fig trees by 22.20% and 23.12%, respectively, compared to SM (
Table 5).
Plants submitted to the 3B system presented higher
AN, with means of 35.94 µmol m
−2 s
−1, 34.63 µmol m
−2 s
−1, and 33.45 µmol m
−2 s
−1, respectively, statistically equal. In this condition, using CL increased
AN by 24.11% compared to SM. The highest
AN was obtained in the 4B system, with a CL of 36.37 µmol m
−2 s
−1 and a CM of 36.29 µmol m
−2 s
−1, which were statistically equal. In this system, these organic sources represented increases of 19.11% and 18.93% in the
AN of fig trees compared to SM (
Table 5).
As in
WUE,
E,
gs,
Ci, and
AN/
Ci, it was observed that the
AN of plants fertilized with SM was impaired in all the conduction systems studied, causing a considerable reduction in the photosynthesis of the plants in each system. In 2B, this reduction was more pronounced than in the other systems used, representing a 49.23% decrease, which is among the highest photosynthetic rates obtained in this system. In the different systems, 3B, 4B, and espalier, reductions of 26.88%, 19.11%, and 22.20%, respectively, were observed (
Table 5).
The maximum quantum efficiency of PSII (
Fv/
Fm) varied according to the fertilizer sources and conductive systems used. There was no difference in the
Fv/
Fm values obtained in the 2B system for the fertilizer sources. The plants in the 3B system had higher
Fv/
Fm values, with an OC of 0.77, which did not differ statistically from CM and CL. The lowest
Fv/
Fm values were obtained in plants with M and SM of 0.70, which were statistically equal. With 4B, the organic sources had higher values, with CL fertilization of 0.76 standing out, and M fertilization provided the lowest value, 0.68. In the espalier system, the highest
Fv/
Fm values were obtained with OC, followed by SM, and the lowest values were obtained in CM, with a value of 0.68 (
Table 6). The conduction systems used differed statistically only in bovine fertilization, where plants with 3B had the highest
Fv/
Fm values, 0.76, and espalier promoted the lowest value, 0.68 (
Table 6).
3.2. Chlorophyll Content Index
The chlorophyll content index, composed of chlorophyll a, b, and total contents, was significantly influenced by the fertilizer sources (mineral and organic) and conduction systems at the level of (p < 0.01) for the fertilizer sources and conduction systems studied. Due to these significant interaction effects, the combined means were analyzed using the Tukey test (p < 0.05) to compare treatment combinations and interpret the results.
The chlorophyll
a content varied between the fertilization sources and the 2B, 3B, and 4B conduction systems. The highest chlorophyll
a content in the 2B system was obtained with an M of 27.10, and the lowest value was reported with a CM of 21.37. The other sources did not differ from each other in this system. However, with 3B, the highest chlorophyll
a content was obtained with CM of 24.83, followed by CL and M. The lowest content was obtained with an SM of 21.80. The plants with 4B presented the highest chlorophyll
a content, with a CM of 24.73 and an SM of 23.83, and the lowest value was recorded when an OC of 21.23 was used. The plants submitted to the espalier system did not differ statistically between the sources (
Table 7).
The chlorophyll
b levels exhibited similar behavior to those of chlorophyll
a in the fertilizer sources and training systems. In the 2B and espalier systems, the highest chlorophyll
b levels were obtained with M of 12.60 and 11.27, respectively. The lowest chlorophyll
b values were obtained with a CM of 7.53 in the 2B system, and with espalier at a CM of 9.06 and CL at 9.53, which were statistically equal. However, when there was an increase in the number of branches using the 3B and 4B systems, the highest chlorophyll b levels were obtained using CM in the order of 11.63 and 10.57, respectively. The lowest chlorophyll b levels for the 3P and 4P systems were verified using OC with 8.35 and SM with 8.90, respectively (
Table 7).
For total chlorophyll values, the 2B and espalier systems presented the highest levels with mineral fertilization of 40.36 and 36.88, respectively. The lowest levels were verified using CMs of 28.80 and 30.70, representing reductions of 28.64% and 16.76%, respectively (
Table 7).
However, when the 3B and 4B systems were used, the plants fertilized with CM presented the highest total chlorophyll values, 37.13 and 35.67, respectively, equivalent to increases in total chlorophyll content of 16.32% and 17.21%, respectively, compared to the lowest levels reported by OC of 31.07 and CL of 29.53, respectively (
Table 7).
3.3. Nutritional Content
The two factors studied also affected the nutritional content of the leaves. There was a significant interaction for the macronutrients N, P, K, Ca, and Mg (p < 0.01), as well as for the micronutrients Fe, Zn, and Mn (p < 0.01). The conduction systems significantly influenced Cu in isolation (p < 0.01). Due to these significant interaction effects, the combined means were analyzed using the Tukey test (p < 0.05) to compare treatment combinations and interpret the results.
The 2B system presented the highest nitrogen content using M (50.84 g kg
−1) and CL (49.91 g kg
−1), which were statistically equal (
Table 8). In the espalier system, the highest content was obtained with mineral fertilization (56.90 g kg
−1), followed by the second-highest value (CL; 49.90 g kg
−1). The lowest N contents were obtained using SM (36.08 g kg
−1) and OC (43.01 g kg
−1) in the 2B and espalier systems, respectively. In the 3B system, the highest contents were obtained with M (49.70 g kg
−1) and OC (47.90 g kg
−1), while the lowest was obtained with SM (32.43 g kg
−1). In the 4B system, the highest content was obtained using OC (49.71 g kg
−1), which did not differ statistically from CL (48.30 g kg
−1) (
Table 8).
The espalier system’s highest phosphorus (P) content was obtained using an M fertilizer of 0.94 g kg
−1, which did not differ statistically from the CL, SM, and CM sources. The lowest value was obtained with an OC of 0.61 g kg
−1. The highest content in the 2B system was obtained with an SM of 1.55 g kg
−1, while the lowest values were obtained with M (0.79 g kg
−1) and OC (0.60 g kg
−1). The highest content in the 3B system was obtained with SM, with 1.04 g kg
−1, not differing statistically from CL and OC. The lowest contents were verified with M with 0.60 g kg
−1 and CM with 0.56 g kg
−1. The plants with 4B did not differ statistically among the fertilizer sources (
Table 8).
The highest potassium (K) content was verified using M fertilization at 22.50 g kg
−1 in the 2B system, which did not differ statistically from the CM, OC, and SM sources. In the 3B system, the highest K content was obtained with OC, which was 23.18 g kg
−1. In the 4B system, the highest values were obtained using the M (21.42g kg
−1), CM (21.29 g kg
−1), and OC (20.50 g kg
−1) sources, which were statistically equal. The highest K content was obtained with CM of 22.33 g kg
−1 in the espalier system, not differing statistically from the M fertilization of 21.47 g kg
−1. Fertilization with CL corresponded to the lowest K values (19.29, 18.34, and 18.00 g kg
−1) in the 2B, 3B, and espalier systems. In the 4B system, the weakest content was obtained from the SM of 17.90 g kg
−1 (
Table 8).
The highest calcium (Ca) contents in plants subjected to the 2B system were obtained using SM with 10.54 g kg
−1, CL of 10.23 g kg
−1, and M with 9.72 g kg
−1. In the 3B system, the highest contents were obtained with CM (10.51 g kg
−1), SM (10.18 g kg
−1), and CL (10.17 g kg
−1), statistically equal. In the 2B and 3B systems, the lowest Ca contents were verified with OC, corresponding to 7.86 and 7.93 g kg
−1, respectively. However, in the 4B system, fertilization with CL provided the highest value (11.94 g kg
−1). The lowest contents were obtained using CM, SM, and M, statistically equal. In the espalier system, the use of OC provided the highest value of 12.09 g kg
−1, followed by CL and SM, and the lowest Ca content was obtained with M fertilization of 8.53 g kg
−1 (
Table 8).
The plants submitted to the 2B system did not exhibit significant differences in magnesium (Mg) content among the different fertilizer sources used. In the 3B system, the highest magnesium content was obtained with M (3.64 g kg
−1), which was statistically equal to that of CL (3.64 g kg
−1); the other sources did not differ significantly. The plants with 4B presented the highest Mg contents using OC (3.49 g kg
−1), followed by CL (3.00 g kg
−1) and M (2.96 g kg
−1), which were statistically equal, and the lowest content was verified with SM (1.89 g kg
−1). In the espalier system, the highest Mg contents were obtained with SM (3.74 g kg
−1) and M (3.67 g kg
−1), and the lowest Mg content was obtained with the use of CM (3.10 g kg
−1) (
Table 8).
The highest iron (Fe) content in plants subjected to the 2B system was obtained using an OC equivalent to 388.10 mg kg
−1, and the other sources did not differ significantly from this value. In the 3B system, the highest Fe content was verified in fig trees fertilized with OC of 437.28 mg kg
−1, and the lowest content was verified in plants fertilized with CM of 207.64 mg kg
−1. In the 4B system, the highest contents corresponded to CL and OC fertilizations of 346.26 and 305.72 mg kg
−1, respectively, and the lowest value was obtained with M fertilization with 117.07 mg kg
−1. In the espalier system, the highest Fe content was obtained with CL with 308.21 mg kg
−1, and the lowest Fe contents were obtained using the OC and SM sources (
Table 9).
Plants submitted to the 2B system did not differ significantly in zinc (Zn) content for the sources used. Plants with 3B presented higher Zn contents, as measured by SM, CM, and OC, which were statistically equivalent. The lowest contents were obtained with CL and M, which did not differ from each other. In the 4B and espalier systems, the highest Zn contents were also verified using SM of 47.76 and 43.61 mg kg
−1, respectively. The lowest values were observed in plants fertilized with a CL of 29.84 mg kg
1 and a CM of 36.34 mg kg
1 (
Table 9).
The highest manganese (Mn) content in the 2B system was obtained using CL equivalent to 41.03 mg kg
−1, which did not differ from the other organic sources. The lowest Mn content was obtained with M fertilization (29.39 mg kg
−1). The plants with 3B presented the highest content of CM (46.79 mg kg
−1), not differing statistically from SM (38.52 mg kg
−1), and the lowest contents were observed in M (20.95 mg kg
−1) and OC (16.98 mg kg
−1). The plants with 4B had the highest Mn content, using CL of 41.05 mg kg
−1, and the lowest was obtained with SM of 16.58 mg kg
−1. In the espalier system, the highest contents were obtained with M fertilization (38.94 mg kg
−1), followed by SM (35.56 mg kg
−1), which were statistically equal, and the lowest contents were obtained using CM (22.24 mg kg
−1) and CL (2.98 mg kg
−1) (
Table 9).
The highest Cu contents were verified in the espalier system, equivalent to 1.39 mg kg
−1, which did not differ statistically from the 2B (1.15 mg kg
−1) and 3B (1.17 mg kg
−1) systems. The 4B system resulted in a lower content of 1.03 mg kg
−1 (
Table 10).