Malpighia emaginata D . C . Growth in Several Substrates and Salt Waters

The acerola tree is one of the most promising fruit trees of the Brazilian fruit sector, demanding the development of studies that indicate the proper conditions to improve its production under adverse conditions. Consequently, our purpose was to evaluate the growth of Malpighia emaginata D.C in several substrates and under ascending levels of irrigation water salinity. The experiment was conducted in a 4 × 5 factorial scheme randomized block design, which comprised four substrates (S1 = soil; S2 = soil with a 10% addition of cattle manure; S3 = soil with a 10% addition of organic compounds; and S4 soil with a 5% addition of cattle manure and a 5% addition of organic compounds) and five CEa salt levels (0.3, 1.0, 1.7, 2.7, and 3.5 dS m). The plant height and stem diameter variables were not affected by the studied factors. The interaction between salinity and the substrates affected the root growth and the build-up of the plants’ fresh and dry biomass, resulting in the increase of the values obtained by the substrates containing manure and organic compounds. The seedlings’ quality, represented by the height/stem diameter and aerial part/root dry mass ratios, and by the Dickson quality index, indicated that the plants produced in the substrates 2 and 3 were more vigorous.


Introduction
The acerola tree (Malpighia emaginata D.C.) is a fruit tree of high acceptance in the Brazilian fruit sector due to its favorable developing environmental features.Additionally, it presents pleasant features of taste and nutritional quality, with high levels of ascorbic acid, vitamin A and B complex, iron and calcium (Esashika, Oliveira, & Moreira, 2013;Bezerra, Leite, Silva, Oliveira, & Mello, 2017).
Obtaining good quality seedlings depends on several factors, including which substrate is used in their production.The choice of the substrate's elements is a fundamental factor to obtain good quality seedlings, and it is essential that such substrate provides a greater root system development and nutrient absorption (F.D. A. Oliveira, J. M. Oliveira, Souza Neta, M. K. T. Oliveira, & Cássia Alves, 2017a).The use of organic residues in the substrate's composition, such as manure, organic compounds, worm castings, etc., improve their physical, chemical, and biological features and are promising alternatives for seedling production (Prates et al., 2012).
The hydric support and the quality of the water used in seedling productions is another feature that directly affects the plants' quality.An excessive high level of salt directly affects the growth of cultures, resulting in harmful effects in every phenological stage, especially during seedling formation (Medeiros et al., 2016).Additionally, it causes osmotic, toxic effects and the nutritional unbalance of the plants, resulting in morphophysiological changes, altering their capacity to produce photosynthetic pigments and, consequently, resulting in harmful effects in the cultures' growth and development (Silva et al., 2017).
Arid and semiarid regions present high salt concentration in their waters, which compromises the establishment of agricultural productions.To deal with the water deficiency and use restriction of the Brazilian Northeastern region, we need to adopt a procedure that would enable us the use water of high salinity levels to satisfy the requirements of the agricultural sector (Nascimento et al., 2017).
In this context, the purpose hereof was to evaluate the influence of different substrates and electrical conductivities of the irrigation water on the growth of Malpighia emaginata D.C.

Material and Methods
The research was performed in the safe environment of the Agri-food Science and Technology Center (CCTA), of the Federal University of Campina Grande (UFCG), Pombal Campus, PB.
The experimental design employed was of randomized blocks, whose treatments were distributed in a 5 × 4 factorial scheme, representing five irrigation water salt levels (0.3, 1.0, 1.7, 2.7, and 3.5 dS m -1 ) and four substrates (S1 = soil; S2 = soil with a 10% addition of cattle manure; S3 = soil with a 10% addition of organic compounds; and S4 -soil with a 5% addition of cattle manure and a 5% addition of organic compounds), with four repetitions and two plants by patch.
Waters of different salt levels were obtained from the water supply (CEa of 0.3 dS m -1 ) through the addition of different concentrations of the salts NaCl, CaCl 2 •2H 2 O, and MgCl 2 •6H 2 O, in the equivalent proportion of 7:2:1, a predominant ratio in the main water sources available for irrigation in the Brazilian Northeast (Medeiros, 1992).
The substrates were obtained through the mixture of fluvic Neosol with the respective proportions of organic matter (cattle manure and/or organic compound), resulting in a homogeneous material.The manure used in the experiment was duly composted, as the organic compound used was made by the addition of cattle manure with rests of the native vegetation and grass straw, as described by Coelho (2008).
After establishing the different substrates, they were stored in 288-cm³ tubes, which were open at their bottoms to allow a free drainage and were placed on trays over a metal bench, at a height of 0.8 m above the soil.
As for our vegetable material, we used our access to the acerola tree 'CMI 102', originated from the Manioc and Pomology Embrapa, Cruz das Almas, BA, where they were equidistantly planted, with five seeds by tube, at a depth of 1.0 cm.After the seedlings presented two pairs of true, totally expended leaves, we performed their thinning, leaving only a seedling by container, the most vigorous one.
During the seedlings' period of germination and emergence, the substrate was kept close to the field capacity with a local supply water of 0.3 dSm -1 , a condition obtained through the drainage lysimetry process, which daily received the volume of evapotranspired water, which was determined by the difference between the applied volume and the drained volume of the previous irrigation, according to Equation 1 (Bernardo, Soares, & Mantovani, 2006).
Where, Av = applied volume; Wcc = weight of the container at its maximum water retaining capacity; n = number of containers.
The irrigations with salt water begun 30 days after seeding through daily, manual irrigations.Sixty days after the application of the treatments, the following variables were measured:  Leaf number (LN): obtained through the counting of the number of totally formed leaves;  Plant height (PH): measured from the plants' aerial part, considering the part above its base, using a graduated ruler with the results expressed in cm;  Stem diameter (SD): performed with the assistance of a digital caliper, with its results expressed in mm;  Root length: after the removal of the plants from the substrate, we washed the roots and measured their length with the assistance of a graduated ruler, whose results were expressed in cm;  Root and aerial part fresh mass: obtained by the weight in an analytical scale of precision, separating the parts at the plants' base height, with results expressed in g plant -1 ;  Total fresh mass: measured by the sum of the root and aerial part fresh mass.The results were expressed in g plant -1 ;  Root and aerial part dry mass: after the separation of the parts, they were stored in paper bags of the Kraft type and deposited into a forced air circulation muffle for drying at 65 °C until they reached a constant weight.Then we weight the material on a precision analytical scale, whose results were expressed in g plant -1 ;  Total dry mass: obtained by the sum of the values of the root and aerial part dry mass.The results were expressed in g plant -1 ;  Plant height/stem diameter ratio: obtained by the plant height by stem diameter division results.

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Aerial part/root dry mass ratio: calculated by the division of the values obtained for aerial part and root total dry mass, according to the methods of Fernandes, T. J. D. Rodrigues, Medeiros, and L. R. D. A. Rodrigues (2005).The results were expressed in g g -1 .
The data were submitted to an analysis of variance and significant cases were submitted to a Polynomial Regression analysis.To perform the analyses, we employed the System for Variance Analysis-SISVAR ® software, version 5.6 (Ferreira, 2011).

Results and Discussion
The values obtained for height and stem diameter of the acerola plants were not affected by the applied treatments.
The leaf number was affected by the substrates, where the one composed of soil with a 10% addition of cattle manure promoted a greater leaf number increase of the acerola tree.The substrate composed of soil with a 10% addition of organic compound promoted an increase similar to substrate 2's.However, it was not statistically different from all other substrates (Table 2).Note.Averages followed by the same letter do not differ from each other by the Tukey test at 5% probability.
This effect might have been promoted due to the greatest availability of nutrients, resulting in better conditions for the plants' development.The use of cattle manure promotes improvements in the substrate's physical, chemical, and biological features, which happens due to the possibility of generating a better aeration and nutritional balance, jas.ccsenet.

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As for roo addition of the salt lev manure, it composed descending 1).

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The buildfeatures, r occurred.T of organic composed The ratio o of soil with greatest va obtained f organic co with As for a 5% ies of This effect proves that the ratio presented a greatest investment in the growth of the plants' aerial part.This ratio may occur due to a reaction of the plants to luminous stimuli, promoting a greatest growth of the aerial part (Oliveira et al., 2013).
The Dickson quality index (DQI) presented a descending linear effect for the plants produced in the soil and in the substrate soil with a 10% composted cattle manure, while the seedlings of the substrates composed of soil with a 10% addition of organic compounds and soil with a 5% addition of cattle manure and a 5% addition of organic compounds presented an ascending linear effect according to the increase of salinity (Figure 4C).
The results imply that the salinity was mitigated by the addition of organic matter contained in the substrate, since the substrates that contained cattle manure and organic compounds in their composition promoted a linear increase of the DQI, promoting the generation of more vigorous plants.The inclusion of several variables in the establishment of the DQI indicates a greater balance in the distribution of the plants' biomass, as the ones with greater value represent the plants that are more vigorous (Azevedo, Alencar, Barbosa, & Almeida, 2010).

Conclusions
(1) The plant height and stem diameters of Malpighia emaginata D.C. were not affected by the substrates and by the irrigation water's salinity.
(2) The build-up of fresh and dry biomass of M. emaginata plants were affected by salinity and by the substrates, presenting the greatest increases in the substrates that received the addition of organic matter.
(3) The height/diameter and aerial part/root dry mass ratios and the Dickson quality index indicate that the substrates composed of soil with a 10% addition of cattle manure and soil with a 10% addition of organic compounds more vigorous plants.

Figure
Figure Figure qual

Table 1 .
Physical and chemical features of the soil used in the experiment

Table 2 .
Number of leaves of Malpighia emaginata D.C. as a function of different substrates, submitted to the Tukey test at 5% probability