**3. Results and discussion**

#### **3.1 Irrigation**


The results concerning average frequency of irrigation as a function of depths and salinity levels are shown in **Table 7**.

*L1S1, L1S2, L1S3 and L1S4 (25% water retention capacity - WRC and 0.60; 3.00; 5.40 and; 7.80 dS m<sup>1</sup> , respectively); L2S1, L2S2, L2S3 and L2S4 (50% of WRC and 0.60; 3.00; 5.40 and; 7.80 dS m<sup>1</sup> , respectively); L3S1, L3S2, L3S3 and L3S4 (75% of WRC and 0.60; 3.00; 5.40 and; 7.80 dS m<sup>1</sup> , respectively) and; L4S1, L4S2, L4S3 and L4S4 (100% of WRC and 0.60; 3.00; 5.40 and; 7.80 dS m<sup>1</sup> , respectively).*

**Table 7.**

*Average frequency of irrigation as a function of depths and salinity levels.*

*Effect of Irrigation Depths and Salinity Levels on the Growth and Production of Forage… DOI: http://dx.doi.org/10.5772/intechopen.104985*

According to the results, average frequencies of irrigation varied between 2 and 13 days, considering treatments. In general, the lowest frequencies were obtained under the greatest saline levels (S3 = 5.40 dS m<sup>1</sup> and S4 = 7.80 dS m<sup>1</sup> ).

The lowest frequencies of irrigation using the highest saline waters may have occurred due to the salt effects on soil, altering its physical–chemical properties.

When comparing the same saline level to the other depths, it was observed a progressive reduction of irrigation frequencies, this occurred because irrigation was determined by water decay in soil as a function of water retention capacity. Thus, with the increase of water depths, it was necessary a longer period of time (lower frequency of irrigation) in order to promote the water decay in soil and the application of irrigation.

The total value irrigated per treatment (depth x salinity) are shown in **Table 8**.

In general, the greatest irrigation frequencies resulted in the highest values of accumulated irrigation depths (treatments with 25 and 50% of water retention capacity – WRC). Furthermore, the influence of salt in irrigation water was verified in the crop hydric consumption, demonstrated by treatments with 5.40 and 7.80 m<sup>1</sup> that presented the lowest irrigation depths.

According Souza et al. [18], the accumulation of salts in soil is related to irrigation that compromises chemical, physical and biological properties of soil. Especially in semi-arid regions, where there is a predominance of evaporation over precipitation. Salts present in soils reduce the osmotic potential of its solution and may decrease water availability in plants.

#### **3.2 Growth**

#### *3.2.1 Primary cladodes*

The results of variance analysis (F test at 1 and 5% probability) for the variables of length, width, area, perimeter and thickness of primary cladodes at 334 days after treatment applications, corresponding to a total cycle of 442 days, are shown in **Table 9**.

According to the data obtained (**Table 9**), there were not significant statistical differences (p > 0.05) for any growth variable evaluated. Thus, treatments did not influence the growth parameters of primary cladodes.

Average values were observed for length (PCL), width (PCW), area (PCA), perimeter (PCP) and thickness (PCT), as the following: 30.02 cm; 24.27 cm; 551.86 cm2 ; 79.25 cm and; 15.56 mm, respectively.


**Table 8.**

*Total accumulated irrigation at the end of the cycle as a function of water depths and salinity levels.*


*nsNon-significant by F test (p <sup>&</sup>gt; 0.05). <sup>1</sup> Data transformed by quadratic root.*

**Table 9.**

*Summary of variance analysis of primary cladode length (PCL), primary cladode width (PCW), primary cladode area (PCA), primary cladode perimeter (PCP) and primary cladode thickness (PCT) of forage palm Orelha de Elefante at 442 days of cycle.*

Donato et al. [19] state that morphometric characteristics of forage palm are rarely influenced by management, which was also verified in the present study. The results differed from two other authors, as Silva et al. [20] and Lima et al. [21]. These authors verified that the adoption of management practices on forage palm results in significant effects on the plant growth, by irrigating with different sowing spacing or by supplying fertilization.

Silva et al. [20] evaluated the growth of forage palm clones in semi-arid region conditions and its relations with meteorological variables and verified statistical differences for the average length of primary cladode with 27.73 cm for Orelha de Elefante Mexicana. This value is close to the one observed in this study for the same cultivar.

Lima et al. [21] studied morphological and productive characteristics of forage palm Gigante irrigated with saline water (5.25 dS m<sup>1</sup> ) and submitted to intensive cutting, and obtained average length of 37.87 cm for the second cycle. Significant differences were not observed for this variable. The authors only verified significant effects for average width (20.95 cm), thickness (18.62 cm) and area (583.46 cm<sup>2</sup> ). The aforementioned authors concluded that the differences observed for width and thickness of cladode may have resulted from the best efficiency of physiological and biochemical process of plant, as photosynthesis, respiration and transpiration, being influenced by management practices.

Pereira et al. [22] evaluated the growth of forage palm clones (Orelha de Elefante Mexicana, IPA Sertânia and Miúda), in the municipality of Serra Talhada in the state of Pernambuco, under drip irrigation with a permanent depth (7.50 mm) and three intervals of water application (7, 14 and 28 days). The authors concluded that irrigation promoted the best biometric increments for the evaluated clones. For Orelha de Elefante Mexicana were observed the following average values in the primary cladodes, in absolute terms: 23.80 cm of cladode length and 11.80 mm of cladode thickness. In relative terms, for the frequencies of 7, 14 and 28 days, these values were the following: 18.70 cm (7 days), 15.40 cm (14 days) and 16.20 cm (28 days) of cladode width; 68.60 cm (7 days), 59.00 cm (28 days) of cladode perimeter; and 285.00 cm<sup>2</sup> (7 days), 310.00 cm<sup>2</sup> (14 days) and 377.00 cm2 (28 days) of cladode area. The total

#### *Effect of Irrigation Depths and Salinity Levels on the Growth and Production of Forage… DOI: http://dx.doi.org/10.5772/intechopen.104985*

water received by the crop was equivalent to 558.00 mm (7 days), 475.00 mm (14 days) and 438.00 mm (28 days). Even with different irrigation frequencies performed in this research, these depth values are close to those verified by Pereira et al. [22], which did not present significant effects for primary cladodes as well as the present study.

Sarmento et al. [23] evaluated the influence of different irrigation frequencies on the growth and production of forage palm Orelha de Elefante Mexicana (*O. stricta* (Haworth) Haworth) submitted to different frequencies of irrigation (0, 7, 14 and 21 days) and verified an increasing linear effect in width and length of primary cladodes due to the increase in irrigation frequency. This did not occur to the thickness of primary cladode. Means observed for primary cladode length were the following: 31.16 cm (without irrigation); 32.83 cm (21 days); 34.97 cm (14 days) and; 36.07 (7 days). For average width: 23.86 (without irrigation); 26.46 cm (21 days); 26.73 (14 days) and; 28.90 (7 days). Thickness: 19.14 mm (0 days); 17.60 mm (21 days); 18.36 mm (14 days) and; 17.32 mm (7 days). And perimeter: 92.88 mm, 91.80 mm, 91.15 mm and 92.66 mm (0, 21, 14 and 7 days), respectively. The results corroborate with the values obtained in this study, showing that the growth of primary cladodes were not affected, even with different irrigation depths contributing to different frequencies.

#### *3.2.2 Secondary cladodes*

The summary of variance analysis using F test at 1 and 5% probability for length, width, area, perimeter and thickness of secondary cladode at 334 days after treatment applications are shown in **Table 10**.

According to the results of variance analyses by F test (**Table 10**), as for primary cladodes, treatments did not present effects (*P* > 0.05) on the variables evaluated: length, width, area and perimeter.

The variables of secondary cladode present average values that did not depend on the applied treatment: 21.32 cm of length, 18.66 cm of width, 287.93 cm<sup>2</sup> of area and


*\*Significant (p* <sup>≤</sup> *0.05). nsNon-significant (p <sup>&</sup>gt; 0.05) by F test. <sup>1</sup>*

*Data transformed by quadratic root.*

#### **Table 10.**

*Summary of variance analysis of secondary cladode length (SCL), secondary cladode width (SCW), secondary cladode area (SCA), secondary cladode perimeter (SCP) and secondary cladode thickness (SCT) of forage palm Orelha de Elefante at 442 days of cycle.*

58.38 cm of cladode perimeter. These results were inferior to the results of primary cladodes due to plant morphometric characteristics.

Sarmento et al. [23] obtained secondary cladode length in different frequencies of irrigation: 27.77 cm (without irrigation) 27.28 cm (21 days); 28.23 cm (14 days) and; 29.26 cm (7 days). Regarding cladode width, from the lowest frequencies to the highest frequencies, the average values were the following: 21.84 cm; 24.33 cm; 24.69 cm and; 25.52 cm. And the perimeters: 87.73 cm, 83.24 cm, 85.38 cm and 86.96 cm from the lowest to the highest. In spite of the absence of significant effects, frequent irrigation contributed to the growth of forage palm Orelha de Elefante Mexicana. The results observed by the authors for the species *O. stricta* (Haworth) Haworth were superior to the ones obtained in the present study. The variables evaluated in this work may have been influenced by saline water reducing the growth in relation to the conditions of plant cultivation using non-saline water, even without statistical significance for treatments.

Borges et al. [15] studied three different forage palm (Orelha de Elefante Mexicana, Miúda and Baiana) submitted to nitrogen fertilization via fertigation and observed average cladode length varying between 25.40 to 27.52 cm in relation to the error pattern for Orelha de Elefante Mexicana. Thus, this difference between length obtained in the present study and the values verified by the authors is due to the average values between primary and secondary cladodes.

Sales et al. [24] evaluated the vegetative growth of forage palm Gigante under different densities of cultivation in Curimataú (river located in the states of Paraiba and Rio Grande do Norte) in the state of Paraiba. It was verified that the average value between densities of cultivation for cladode width was 18.98 cm and cladode length 33.89 cm at 710 days after sowing. On the other hand, the variable cladode area was affected by treatments showing values of 440.12 cm2 , 397.95 cm<sup>2</sup> and 383.05 cm<sup>2</sup> . The authors did not perform regular intervals of irrigation during the experiment; the water depth applied was made through precipitation. Thus, the present study as well as the research carried out by the authors did not obtain significant statistical differences in relation to the application of treatments on the growth variables analyzed, except for plant height.

Pereira et al. [22] observed average values for secondary cladodes: 10.40 cm of length, 12.60 of width, 27.30 cm of perimeter and 74.60 cm<sup>2</sup> of area. The results for these variables were inferior to the ones of the present study. Statistically, in this research, the results were not significant (*P* > 0.05) in relation to the treatments applied. However, the salt in water may have influenced plant growth as salinity may have contributed to elevate forage palm evapotranspiration due to sodium (Na+ ) and to stomatal adjustment that fomented plant development. Moreover, according to Campos [25], water availability through irrigation increases real evapotranspiration of forage palm plant in comparison to rainfed cultivations. In this context, the plant increases its transpiration due to greater water availability.

This hypothesis can be affirmed by Fonseca et al. [26] that concluded that higher average values of morphometric characteristics of forage palm under conditions of hydric availability indicates that even with use of saline water, irrigation provides better conditions of crop development due to the increment of photosynthetic taxes.

There were only significant statistical differences (*P* ≤ 0.05) for secondary cladode thickness in relation to salinity levels in the irrigation water applied. Effects of water depths and its interaction with salinity were not observed in forage palm thickness. Data showed low dispersion in the coefficient of variation (CV) of 6.53%. The other variables did not show significant effect (*P* > 0.05) for any factor evaluated.

*Effect of Irrigation Depths and Salinity Levels on the Growth and Production of Forage… DOI: http://dx.doi.org/10.5772/intechopen.104985*

There was an increment for cladode thickness up to 9.79 mm under a salinity level of 1.22 dS m<sup>1</sup> , verified by the graphic adjustment equation. On the other hand, with a higher salinity level, cladode thickness decreased. The value of R<sup>2</sup> in the adjustment equation was 0.70 (**Figure 2**).

Forage palm thickness is related to the accumulation of water in its cladodes. This stored water, according to Nobel [27], may favor palm gas exchange. This content may be an indicative of stress tolerance caused by saline water.

The effects of treatments (*P* < 0.05) on secondary cladode thickness may denote the development of tolerance mechanisms to salinity through juiciness. According to Willadino and Camara [28], sodium tends to be transported via xylem and accumulate in plant shoot system. Thus, plant may have developed juiciness in order to mitigate the effects of accumulated salts on secondary cladodes or even due to the osmotic adjustment, the responsible for causing a potential difference and induce water movement into guard-cell.

Although, Freire [29] concluded that higher salinity levels of 3.60 dS m<sup>1</sup> or more, result in the decrease of forage palm juiciness. This maximum salinity level on thickness was 60% lower than the one verified by the author.

It can be inferred that osmotic adjustment contributed to prevent restrictions to plant stomatal opening, promoting the increase of transpiration and the reduction of water content in cell and, consequently, its thickness. This justifies the reduction of thickness of secondary cladode due to the increase of salt in irrigation water.

Cladode thickness is one of the species characteristics directly correlated to plant turgidity. Thus, the higher the thickness, the greater water quantity in cells, which is one of the main attributes of CAM plants [22].

Pereira et al. [22] obtained average values of cladode thickness in OEM, IPA and Miúda cultivars: 11.80; 18.50 and 14.10 mm, respectively. The thickness observed by the authors was approximately 17% superior.

Sarmento et al. [23] verified a significant effect of cladode thickness as a function of irrigation frequencies, which presented a decreasing quadratic effect, showing values of 12.31 (0 days); 13.58 (21 days); 11.44 (14 days); 11.30 (7 days). On the other hand, it did not occur for primary cladode.

When comparing the results of the thickness of primary cladode to the results of Pereira et al. [22], Sales et al. [24] and Sarmento et al. [23], it was verified that thickness was lower than the ones verified by the other authors. However, the

#### **Figure 2.**

*Secondary cladode thickness (SCT) of forage palm (Orelha de Elefante) as a function of salt in irrigation water (ECw) at 442 days of the cycle.*

aforementioned works studied the species *Opuntia fícus-indica* Mill while the present research analyzed the species *O. stricta* (Haworth) Haworth.

According to Rocha, Voltolini, and Gava [30], cladode thickness is of great importance for the photosynthetic capacity and for water storage in plant.

Orelha de Elefante clone has a great potential to adapt to conditions of low water availability in soil, presenting a greater capacity of water storage in its cladodes [22]. Thus, this capacity also contributes to plant tolerance in relation to salts.

#### **3.3 Production**

#### *3.3.1 Number of primary and secondary cladodes*

The results of variance analysis by F test at 1 and 5% probability showed a significant effect (*P* ≤ 0.05) only for the number of primary cladodes in relation to water depths. Regarding the other variables, the number of secondary cladodes and the total number of cladodes did not present significant statistical differences (**Table 11**).

The number of primary cladodes showed a quadratic tendency with R<sup>2</sup> equal to 0.8643 (**Figure 3**). The greatest average was presented by the number of primary cladodes, based on the graphical adjustment equation, for the water depth of 376.00 mm with 4.03 cladodes. The same depth is the closest to L2 (370.66 mm), which corresponds to 50% of water retention capacity of soil – WRC. The other depths presented average values of 3.43 cladodes (L3–75% of WRC equal to 321.04 mm), 3.76 cladodes (L4–100% of WRC equal to 338.87 mm) and 2.72 cladodes (L1–25% of WRC equal to 457.12 mm), also obtained using the adjustment equation.

Thus, it was verified that the number of primary cladodes increased due to the water depth increase up to 376.00 mm and, for values higher than that, it decreased.

The other variables did not present significant effect (*P* > 0.05) with average values of 11.48 of secondary cladodes (NSC) and 17.20 of total number of cladodes (TNC).


Cavalcante, Leite, Pereira and Lucena [31] evaluated forage palm Orelha de Elefante Mexicana with and without cure of cladodes and did not verify statistical

*\*Significant (p* <sup>≤</sup> *0.05). nsNon-significant by F test.*

*1 Data transformed by quadratic root.*

#### **Table 11.**

*Summary of variance analysis for the number of primary cladodes (NPC), number of secondary cladodes (NSC) and total number of cladodes (TNC) of forage palm Orelha de Elefante Mexicana at 442 days of the cycle.*

*Effect of Irrigation Depths and Salinity Levels on the Growth and Production of Forage… DOI: http://dx.doi.org/10.5772/intechopen.104985*

**Figure 3.**

*Number of primary cladodes of forage palm Orelha de Elefante Mexicana as a function of water depths at 442 days of the cycle.*

differences (*P* > 0.05) in the number of primary cladodes, number of secondary cladodes and total number of cladodes. But, the average values were 2.35 for primary cladodes, 5.37 for secondary cladodes and 12.31 for total number of cladodes. However, tertiary cladodes were considered by the authors when counting the number of total cladodes, and, in the present research, tertiary cladodes were not observed in forage palm. The values obtained in this study were superior to the ones by Cavalcante, Leite, Pereira and Lucena [31] probably due to the application of water depths, promoting the production of the cultivar.

Lima et al. [21] did not verify significant interaction (*P* > 0.05) in the number of primary cladodes, but obtained significant effect in the total number of cladodes with a maximum value of 20.60 of cladodes per plant. The authors also used saline water on forage palm, but productive characteristics were evaluated in forage palm Gigante. Lima et al. [21] concluded that the great number of cladodes tent to increase CO2 capture, which results in a higher photosynthetic tax, contributing to maximize the production.

Sarmento et al. [23] obtained values that corroborate with the present research. The authors verified that Orelha de Elefante Mexicana, under different irrigation frequencies (0, 7, 14 and 21 days), presented number of cladodes equal to: 6.06 (0 days), 4.92 (21 days), 4.85 (14 days) and 4.82 (7 days) of primary cladodes; 12.40 (0 days), 11.91 (21 days), 11.91 (14 days) and 10.50 (7 days) of secondary cladodes; 18.60 (0 days), 17.20 (21 days), 16.94 (14 days) and 15.44 (7 days) of total number of cladodes.

According to Borges et al. [15], the greatest number of cladodes in forage palm plants reflects in a greater production. The authors verified that Orelha de Elefante Mexicana under fertigation presented 13.00 cladodes per plant, which is equivalent to the total number of cladodes.

Pereira et al. [22] verified that hydric availability conditions did not affect the number of primary cladodes and the total number of cladodes of forage palm *O. stricta* (Haworth) Haworth. However, there was significant effect for the number of secondary cladodes. The authors observed the following average values: 8.11 of primary cladodes and 13.50 of total number of cladodes. The number of secondary cladodes showed the following values, respectively: 7.67 units (7 days frequency with a total water depth of 558.00 mm); 1.56 units (14 days frequency with water depth of 475.00 mm) and; 4.22 units (frequency of 28 days with water depth of 438.00 mm).

In the present study, the number of secondary cladodes presented average values of 11.48 units for water depths that varied between 321.04 mm and 457.12 mm. Comparing these results to the ones obtained by Pereira et al. [22], there was a better use of water irrigation by plant in the production of cladodes, since palm produced a quantity of 33% higher under water depths inferior than the ones applied by the authors.
