PRODUCTION AND POST HARVEST OF ‘KENT’ MANGO UNDER DIFFERENT IRRIGATION SYSTEMS

1 Doctor in Agricultural Engineering, Federal University of Viçosa, Researcher Embrapa Semiárido 2 Doctoral student in Phytotechnics, Federal Rural University of Semiarid, Agronomist IF Sertão PE 3 Doctor in Agronomy, Paulista State University, Researcher Embrapa Semiárido 4 Doctor in Agricultural Engineering, Rural Federal University of Pernambuco 5 Undergraduate student in Biological Sciences, University of Pernambuco


INTRODUCTION
Mango production (Mangifera indica L.) has represented great economic expression for Brazilian agriculture, with an average productivity of 16.2 tonnes per hectare. The largest production is located in the Northeast, with the states of Bahia and Pernambuco being the largest producers (KIST et al., 2018).
'Kent' mango is cultivated in Brazil to produce between the months of November and December. Despite the characteristic of difficult handling for floral induction, it has been well cultivated due to the lack of fibers and the better taste of its fruits, which places it among the most appreciated fruits in some European countries and in Japan (SILVA et al., 2010). Thus, the 'Kent' mango cultivation provides a good return to producers.
The northeastern semi-arid region has scarce and irregular rainfall, which results in a major limiting factor in agricultural production (SOARES et al., 2013). Thus, the rational use of water is required in order to increase the efficiency of irrigation.
Although the mango tree is considered a drought-tolerant plant, studies have shown that the low water availability in the soil, due to the incorrect irrigation management system, can affect physiological characteristis, the growth of the aerial part and the root system, productivity and fruit quality (PRAKASH et al., 2015).
Under low water availability, plants tend to decrease water loss by partially closing stomata, thus avoiding a reduction in water potential. However, this response negatively affects several physiological processes important for plant growth and development, such as transpiration, stomatal conductance, photosynthesis and sugar synthesis, causing a reduction in productivity (OTTO et al., 2013).
Many factors are considered to choose the irrigation system and management, such as the available technologies and their cost, the type and depth of the soil, the quantity and distribution of rainfall, the fertilization practices and the production objective. In turn, the productive and qualitative response of plants to irrigation depends mainly on the frequency, the method and form of installation, the cultivation stage, the edaphoclimatic conditions and the type of cultivar (COELHO et al,. 2015;LÉCHAUDEL;JOAS, 2007). In the localized irrigation, emitters can be arranged in different positions, and their efficiency will depend on their characteristics, handling, environmental attributes and the culture itself (BOMAN, 2007).
Thus, the objective of this study was to identify an efficient arrangement of the localized irrigation systems for the productive and post-harvest characteristics of the fruits of the 'Kent' mango tree, in the conditions of the Brazilian Semi-Arid.

MATERIAL AND METHODS
The research was performed on the Agranvil agricultural property, in the municipality of Petrolina-PE, in the Vale do Submédio São Francisco region, at geographical coordinates 09º 24 'S and 40º 20' O and an average altitude of 370 m. According to the Köppen classification, the climate of the region is of the BSh' type, very hot dry steppe (MEDEIROS et al., 2013), which can be observed in Figure 1 with the climatic data. The soil of the experimental area was classified as Quartzarenic Neosol (EMBRAPA, 2013).
The experimentation took place over two productive cycles, in a 'Kent mango orchard, with 8 x 5 m spacing, with 9 years of age. The productive management of pruning, fertilization, plant health and floral induction was performed as described by Mouco (2015).
The experiment was conducted in a randomized block design, in subdivided plots, with the plots being four irrigation system arrangements, and the subplots two cultivation cycles, with five blocks, totaling 20 experimental plots. Each plot consisted of 4 plants, being the two central plants useful. The tested treatments were: a drip line in a circle shape (DLC) around the plant; two drip lines per plant line (2DP); a micro sprinkler below the canopy (MSC), located 0.3 m from the plant's trunk; and a micro sprinkler between plants (MBP). All treatments provided a flow of 56 L h -1 plant -1 . The 2DP and DLC treatments had 14 drippers with a spacing of 0.5 m and generated wet strips of 0.55 m in width. The wet radius of the micro sprinklers from MSC and MBP treatments was 2.3 m.
Irrigation management was performed using reference evapotranspiration (ETo) data calculated using the Penmam-Monteith method equation. Data were collected daily by a meteorological station installed close to the experimental area. The cultivation coefficients (Kc) used to calculate crop evapotranspiration (ETc) were those proposed by Teixeira et al. (2008), as described in Table 1. At the end of each production cycle, all fruits were harvested at the initial stage of maturation (E2), in two useful plants from each plot, being counted and weighed. The E2 maturation stage is adopted as a standard for export, characterized by a light green color of the peel, which corresponds, in the pulp, to yellowing limited to the surrounding of the seed (BRECHT; YAHIA, 2017).
Thus, the number of fruits, average fruit weight and productivity were determined. For postharvest, three fruits were harvested in each of the different quadrants of the plants (North, South, East and West), in rows arranged in the North-South direction, constituting an arrangement in subdivided plots. The arrangements of the irrigation were the plots, the quadrants the subplots and the productive cycles the subsubplots. The post-harvest analyzes of fruits were performed in the post-harvest physiology laboratory of Embrapa Semiárido.
The fruits were analyzed for pulp firmness, determined using a manual penetrometer (Effegi, model FT 327). The measurements were taken after the peel was removed, at two opposite points, in the equatorial region of the fruits. The pulp of the fruit was homogenized in a domestic juice processor, after peeling it, for analysis of the content of total soluble solids (SST) and of the titratable acidity (ATT). The SST was determined using a manual refractometer (Pocket pal-1 model). ATT was determined by titrating 1 g of homogenized pulp and diluted in 50 mL of distilled water, in which three drops of the 1% phenolphthalein indicator were added, proceeding to titration using a digital burette, under constant agitation, with 0.1N NaOH solution. The results were expressed in grams of citric acid per 100 g of pulp.
During cycles, data regarding the production and postharvest of the fruits were obtained, being evaluated as plots subdivided over time.
The data were submitted to analysis of variance (P <0.05) and the means, when significant, were compared using the Tukey test at 5% probability.

RESULTS AND DISCUSSION
The data referring to the number of fruits per plant, average fruit weight and productivity are shown in Table 2. There was an interaction between the different provisions of irrigation systems and the two production cycles for these variables. No difference was observed in relation to the different quadrants where the fruits were located.
The disposition of the irrigation systems that provided the largest number of fruits per plant was the MBP, in the two productive cycles. The MBP treatment was statistically similar to the 2DP treatment in the first cycle and similar to the MSC treatment in the second cycle. Kent mango is a vigorous cultivar, presenting difficult flowering management (SILVA et al., 2010). Thus, considering that the MBP treatment had an emitter located between the plants, in a little shaded area, the exposure of the wet bulb to the sun was greater (on average 7.16 m² between plants), increasing evaporation and reducing water availability for plants. This exposure may have contributed to the break in the vigor of the plants, favoring flowering, as described by Sandip et al. (2015) and consequently providing the highest number of fruits per plant. The 2DP treatment also had part of the wet strip exposed to the sun (on average 2.38 m² between plants). The temperature and evapotranspiration were higher in the first cycle than in the second cycle, accentuating the degree of water stress in the plants, which possibly contributed to greater flowering and consequent greater number of fruits and productivity in this treatment.
In addition to the aforementioned factors, what confirms the difference in the number of fruits between the cycles is the alternation of production, a characteristic present in the mango culture . Thus, the MSC treatment also provided a greater number of fruits in the second cycle, in contrast to the first cycle of low fruit production.
The highest average fruit weight was obtained in the second production cycle, for all irrigation system provisions, except for MSC. This result was possibly due to the lower number of fruits per plant, resulting in fewer drains for the photosynthetic production of the plants. Another factor that may have contributed to this difference between cycles is the alternation of production, a characteristic present in the mango culture (DAVENPORT, 2007). As a result of the greater number of fruits, without reducing their average weight, the MBP treatment also provided the highest productivity in the two production cycles, being statistically equal to the 2DP in the first cycle.
The treatments that provided the highest fruit production (MBP and 2DP) were those that had part of the wet soil strip exposed to the sun, with greater losses by evaporation and less efficiency in water application. According to the Teixeira et al.  were overestimated for this cultivar, mainly during the floral induction phase, as previously described, which suggests the need for research on the water demand of the mango Kent, in the conditions of the region. The data regarding the volume, density and titratable acidity of fruits are shown in Table 3. It was observed that there was an interaction between the different provisions in the irrigation system and the different quadrants where the fruits were located for these variables.
The lowest volume of fruits was obtained with the MBP treatment in the south quadrant, which can be justified by the fact that it was the treatment with the highest density of fruits, thus having a greater ratio between fruits per leaf area. Due to the arrangement of the rows, the fruits located in the south quadrant received direct solar radiation throughout the day, which may have contributed to the stomatal closure of the leaves of these branches. According to Vasconcelos et al. (2010), the canopy quadrant most exposed to the sun has its water potential reduced. Insufficient water supply induces stomatal closure of the plant, thus preventing the reduction of water potential. However, this response negatively affects several physiological processes such as sweating and photosynthesis, causing reduced productivity (OTTO, 2013).
The highest titratable acidity was observed in fruits harvested in the South and West quadrants for the MSC (Table 4). In view of the geographic location and the time of year, these were the quadrants with the greatest exposure to sunlight. The greater solar incidence in the western quadrant results in a higher production of hexoses in the fruit (ROSALES et al., 2009). These monosaccharides can favor the antioxidant defense mechanisms by providing precursors of antioxidant compounds, such as acid ascorbic and carotenoids (COUÉ et al., 2006).
The fruits of the plants submitted to the MBP treatment showed greater firmness in the first productive cycle, not differing statistically from the DLC treatment (Table 4). This greater firmness observed for the MBP treatment corroborates with Sams (1999), who states that smaller fruits, in general, present greater firmness of the pulp because they have a higher percentage of their volume occupied with cell wall materials. This characteristic provides to the fruits greater density and resistance to penetration of the penetrometer plunger. No difference was observed between treatments in the second cycle.  The highest TSS content was obtained by the MBP treatment in the first cycle, which did not differ statistically from the MSC treatment and by the DLC in the second cycle, which did not differ statistically from the 2DP treatment. The number of fruits was a determining factor for the SST content, as it directly influences the source-drain relationship. In the second cycle, the lower number of fruits in the DLC and 2DP treatments contributed to the increase in the concentration of solutes, considering the smaller number of drains for the production of photoassimilates such as sugars and organic acids, as was observed in the 'Palmer' mango tree (OLIVEIRA et al., 2019;SIMÕES et al., 2020), melon (DALASTRA et al., 2016) and watermelon (LINS et al., 2013). In the first cycle, possibly, the higher temperature and the exposure of the wet bulb of the MBP treatment to the sun caused a water deficit in the maturation phase, and consequently an increase in the concentration of soluble solids, as was also observed by Andrade et al. (2019) in the 'Kent' mango tree and by Reis et al. (2013) in the 'Haden' mango.
The lowest titratable acidity (Table 4) was observed in the fruits harvested in the first cycle, which had a higher temperature during the maturation period, except for the MSC treatment. According to Chitarra and Chitarra (2005), the increase in temperature increases the respiration rate of the fruits, causing the consumption of organic acids. In the MSC treatment, the smaller number of fruits in the first cycle was possibly a more prevalent factor than the climate for the accumulation of organic acids, due to the greater source-drain ratio.

CONCLUSION
• The use of micro sprinkler between plants is an efficient form of cultivation for 'Kent' mango tree irrigated in the Brazilian semiarid region, providing a greater number of fruits and productivity; • The greater firmness and titratable acidity, associated with the lower content of soluble solids in the fruits at the time of harvest, characteristics that induce longer shelf life in mangoes, are obtained with the handling of a micro sprinkler between plants.