1 Revista Educação Agrícola Superior Associação Brasileira de Educação Agrícola Superior - ABEAS - v.27, n.2, p.79-86, ISSN X - DOI: EXPORT OF NUTRIENTS BY GUAVA FRUITS UNDER DIFFERENT WATER DEPTHS AND NITROGEN FERTILIZATION LEVELS José Dantas Neto 1, José L. Maciel 2, Aaron de S. Alves 2, Benjamin C. Lima Junior 2, Carlos A. V. de Azevedo 1 & Vera L. A. de Lima 1 ABSTRACT The objective of this study was to determine the export of macronutrients, nitrogen, phosphorus, potassium, calcium and magnesium by guava fruit under the influence of different water depths (1144, 1465, 1785 and 2106 mm) and nitrogen fertilization levels (50, 100, 150 and 200 kg ha -1 ). Field studies with P.guajava species Paluma with four years of age were carried out at at the Experiment Station of the State Enterprise for Agricultural Research of Paraíba - EMEPA, municipality of Itaporanga, PB. After drying and grinding of the plant material, N was determined by sulfuric digestion and P, K, Ca and Mg by nitric-perchloric digestion. It was found that factors water depths and nitrogen levels, applied together or alone, significantly influenced the concentration of nutrients in guava fruits. Water depths provided a positive linear effect on nitrogen and calcium contents, and quadratic effect on phosphorus, potassium and magnesium contents; however, nitrogen fertilization levels provided linear effect on nitrogen concentrations and quadratic effect on potassium, calcium and magnesium concentrations found in guava fruits. Guava showed macronutrient uptake by the fruit in the following descending order K, Ca, N, P and Mg. KEY WORDS: Psidium guajava L., irrigated fruit farming, located irrigation EXPORTAÇÃO DE NUTRIENTES POR FRUTOS DE GOIABEIRAS SOB DIFERENTES LÂMINAS DE ÁGUA E FERTIRRIGAÇÃO NITROGENADA RESUMO Objetivou-se com este estudo determinar a exportação dos macronutrientes, nitrogênio, fósforo, potássio, cálcio e magnésio, por frutos de goiabeira sob a influência de lâminas totais de água (1144, 1465, 1785 e 2106 mm) e fertirrigação nitrogenada, (50, 100, 150 e 200 kg ha -1 ). Os estudos com a espécie P. guajava Paluma, com quatro anos de idade, foram conduzidos em nível de campo, na Estação Experimental da Empresa Estadual de Pesquisa Agropecuária da Paraíba - EMEPA, município de Itaporanga, PB. Após secagem e trituração do material vegetal realizaram-se as análises de N por digestão sulfúrica e de P, K, Ca e Mg por digestão nítrico-perclórica.verifica-se que os fatores lâmina total de água e níveis de adubação nitrogenada, aplicados em conjunto ou isoladamente, influenciaram sensivelmente as concentrações de nutrientes nos frutos de goiabeira. As lâminas totais de água conferiram efeito linear positivo aos teores de nitrogênio e cálcio, e efeito quadrático aos teores de fósforo, potássio e magnésio, já os níveis de adubação nitrogenada conferiram efeito linear às concentrações de nitrogênio e quadrático, às concentrações de potássio, cálcio e magnésio encontrados nos frutos de goiabeira. A goiaba apresentou extração de macronutrientes pelo fruto, na seguinte ordem decrescente K, Ca, N, P e Mg. PALAVRAS-CHAVE: Psidium guajava L., fruticultura irrigada, irrigação localizada 1 Prof. Dr. linked to the Graduate Program in Agricultural Engineering - Federal University of Campina Grande - CTRN / UFCG. Rua Aprígio Veloso, CEP: , Campina Grande, PB. s: 2 Doctor Degree in Agricultural Engineering - Federal University of Campina Grande - UFCG / CTRN.
2 80 INTRODUCTION Although Brazil is appearing as one of the largest fruit producers, the use of appropriate handling techniques in agricultural systems is an important strategy for maximizing production, where adequate supply of water and nutrients to crops through irrigation has increased production, thus contributing to the sustainability of this activity. Despite this reality, many fruit trees compose fruit production systems, in which mango, banana, vine, coconut and guava stand out (GONZAGA NETO, 2002). The latter, in turn, has been quite widespread in tropical and subtropical regions (LIMA et al., 2008). The Southeastern and Northeastern regions of Brazil, respectively, account for and 39.35% of the total production (CHOUDHURY et al., 2002), where red pulp Paluma cultivar is the main variety exploited on a commercial scale, and it is estimated that this variety occupies more than 90% of the area planted with guava (GONZAGA NETO, 2002). Its fruits have great acceptance in domestic and foreign markets due to its pleasant flavor, strong aroma and high-quality protein (LIMA et al., 2008). Although guava is an important crop both economically and socially, the use of technologies in order to optimize its exploitation is low (HOJO et al., 2007). As a result, there is need to use irrigation technologies showing maximum efficiency (SOBEL and COSTA, 2005; XAVIER et al., 2006), increasing production using new soil and water management techniques, which provide not only an increase in crop production but also optimum utilization of natural resources (FARIAS et al., 2003). However, the success of an economically viable production depends, among other factors, on adequate nutritional management (GOTO et al., 2001). Thus, Carvalho et al. (2002) pointed out that this practice is a major challenge for researchers in soil fertility and plant nutrition, especially where there are limitations in productivity due to nutrient imbalances. According to Goto et al. (2001), nutrient uptake by plants occurs differently, according to phenological stages, climatic conditions, culture medium, nutrient management conditions and plant age. However, Andrade (2004) reported that determining the amounts of nutrients exported by the fruit is important to calculate replacement with fertilizer, so as to ensure the increase or maintenance of productivity with the production of highquality fruits, thus contributing to an adequate management of crops in order to maintain balanced soil fertility and ensure high productivity and profitability. Given the above, the aim of the present study was to determine the export of macronutrients, nitrogen, phosphorus, potassium, calcium and magnesium by guava fruits "Paluma" variety under the influence of water depths and nitrogen fertilization levels in the dry backlands of the state of Paraiba. José Dantas Neto et al. MATERIAL AND METHODS The studies with the P.guajava "Paluma" variety with four years of age were carried out at field level, under normal conditions of temperature, photoperiod and relative humidity at the Experimental Station of Veludo (07 18'00''S and 38 09'00''W) at the Experiment Station of the State Enterprise for Agricultural Research of Paraíba - EMEPA, municipality of Itaporanga, PB. The study site is 291 m above sea level. According to the Köppen climate classification, the climate in the region is AW' type, hot and humid with summer and autumn rains. The rainy season starts in January and ends in April and the driest months are from June to December. The municipality has annual rainfalls around 806 mm, average temperature about 24 C and relative humidity around 73.8%. The guava crop was planted in single row, with spacing of 6.0 m between rows and 5.0 m between plants in a neosol of typically plan relief, in which several simple samples were collected at different depths: 0-20 and cm in order to compose a composite sample for each specified depth, which were properly identified and referred for physical and chemical characterization, Tables 1 and 2, at the Laboratory of Irrigation and Salinity (LIS) - Federal University Campina Grande (UFCG) in order to determine the phosphorus and potassium levels to be applied to the soil. Table 1. Physical characterization of soil cultured with guava (Psidium guajava L.) cv Paluma The crop was irrigated by a sprayer-type drip irrigation system operated by a KSB-type three-phase electric motor pump with power of 3 hp, speed of 3450 rpm and flow rate of 15 m 3 h -1, main pipeline made with PVC and access to each experimental plot consisting of flexible polyethylene hoses with 16mm in diameter containing self-compensating microsprinklers with nominal flow rate of 50 L h -1, working pressure of 250 kpa, providing a wet radius of 2.5 m, with one microsprinkler at each plant. Irrigation was performed daily after pruning in two productive cycles that lasted, respectively, 202 and 200 days. The irrigation was calculated based on the daily evaporation from tank class A, according to methodology proposed by Maciel et al. (2007). The total water depth applied was a result Table 2. Chemical characterization of soil cultured with guava (Psidium guajava L.) cv Paluma ¹ O.M.: Organic Matter; ² T: Cationic Exchange Capacity and ³ EC: Electrical Conductivity
3 Export of nutrients by guava fruits under different water depths and nitrogen fertilization levels of irrigation plus effective precipitation (Pe), the latter being obtained according to Blaney e Criddle (1962). The experimental design used in this study was randomized blocks with treatments arranged in a 4 x 4 factorial, with water depths and 4 nitrogen levels, resulting in 16 treatments with four replicates each, thus making 64 experimental plots with two plants each. The water depths applied (WD) corresponded to 1144, 1465, 1785 and 2106 mm for the first cycle, and 915, 1308, 1686 and 2093 mm for the second production cycle and nitrogen levels (N) were 50, 100, 150 and 200 kg ha -1 applied in the form of potassium nitrate and urea through fertigation, three times per week during the production cycle, and to this end, a venturitype fertilizer injector with flow rate of approximately 900 ml min -1 was used. From the results of soil analyses and fertilization suggested for the cultivation of guava, 60 kg ha -1 of P 2 O 5 were applied in the form of simple superphosphate and 90 kg ha -1 K 2 O as potassium nitrate. The first was applied in coverage after pruning at dosage of 0.8 kg plant -1. The second, by having nitrogen in its composition, had the value corresponding to this nutrient supplemented with urea, in amounts that were calculated according to dosages already specified in this study for Nitrogen (N), according to each experimental treatment. To assess the export of nutrients by fruits, five samples in each plot were collected at the 190 th day after production pruning, being packed in paper bags and properly identified as each experimental treatment and dried in oven with forced circulation at temperature of 60 C for a period of 72 h. After drying and grinding of the plant material, according to methodology proposed by Malavolta et al. (1997), N was determined by sulfuric digestion and P, K, Ca and Mg by nitric-perchloric digestion. Results were submitted to analysis and polynomial regression variance, evaluating the effects of each factor alone, as well as the interaction between them using the SISVAR statistical package. RESULTS AND DISCUSSION The results shown in Table 3 correspond to the variance analysis of the levels of macronutrients nitrogen (TN), 81 phosphorus (TP), potassium (TK), calcium (TCa) and magnesium (TMg) exported by Paluma guava fruits as a function of water depths and nitrogen levels applied to the crop. Based on results, there was a linear factor of the total water depth on the nitrogen (TN) and calcium (TCa) concentrations and quadratic effect on the phosphorus (TP), potassium (TK) and magnesium (TMg) contents present in guava fruits at 1% probability level in both statistical models obtained. As the irrigation levels applied to the crop, nitrogen fertilization evaluated in this study provided linear and quadratic effects at 1% probability level to the nitrogen (TN), potassium (TK), calcium (TCa) and magnesium (TMg) levels found in fruits. Therefore, it was found that potassium averaging g kg -1 was the nutrient most extracted by P. guajava fruits, followed by calcium with g kg -1, nitrogen with g kg -1, phosphorus with 1.38 g kg -1 and magnesium with only 1.29 g kg -1. In figure 1 shows the results corresponding to the regression analysis to assess trends and behavior of macronutrient exported by guava fruits in function of the different water depths applied to the crop. According to statistical models used in this study, Figure 1A shows that there was a positive linear effect, resulting in increased nitrogen content (TN) in guava fruits by increasing the water depths, obtaining 11.g kg -1 when the highest water depth (2,106 mm) was applied, thus representing increases of 11.23, 7.48 and 3.45%, respectively, when compared with water depths of 1144 mm with g kg -1, 1465 mm with g kg -1 and 1785 mm with g kg -1. Similar behavior can be observed in Figures 1B and 1D, where the increase in total water depth resulted in increased phosphorus (TP) and calcium (TCA) contents in guava fruits between 1.48 and g kg -1. When total water depth corresponding to 2106 mm was applied, the phosphorus (TP) content showed an increase of 13.39, 8.92 and 4.47% of this nutrient in fruits compared with depths of 1144, 1465, 1785 mm, respectively. As for calcium (TCa), the value found corresponds to an increase of 10.38, 6.91 and 3.46%, respectively, when compared to total water depths of 1144, 1465 and 1785 mm. Based on results shown in Figure 1C, the potassium content (TK) estimated in fruits was g kg -1 with the application of Table 3. Analysis of variance and regression for nitrogen (TN), phosphorus (TP), potassium (TK) calcium (TCa) and magnesium (TMg) contents in guava fruit cultivar Paluma * and ** significant at 1% and 5% probability, respectively, ns - not significant.
4 82 José Dantas Neto et al. application of the highest nitrogen fertilization level (200 kg ha -1 ), providing an increase of 17.74, and 5.91% in the levels of this nutrient in fruits, respectively, when compared with the nitrogen fertilization levels corresponding to 50, 100 and 150 kg ha -1. Figure 1. Nitrogen (A), phosphorus (B), potassium (C), calcium (D) and magnesium (E) contents in guava fruit cultivar Paluma as a function of the water depths applied water depths corresponding to 1754 mm at the maximum point of the statistical model obtained, decreasing after this point with the application of 2,106 mm, giving an increase of 13.44% in the content of this nutrient in relation to the estimated value with the application of 1,144 mm (16.76 g kg-1) and 4.44% and the value estimated with the application of greater water depths adopted in this study with g kg -1. Figure 1E shows that the magnesium content (TMg) estimated in fruits was 1.33 g kg -1 with the application of water depth corresponding to 1636 mm at the maximum point of the statistical model, decreasing 8.22 % after this point with the application of greater water depth (2,106 mm), providing also an increase of 9.13% over the estimated value with the application of total water depth corresponding to 1144 mm with 1.21 g kg -1. Based on results, except for nitrogen (TN), phosphorus (TP) and calcium (TCa) levels, the export of other macronutrients by guava fruits was significantly influenced by water depths applied to culture, verifying that the application of the lowest and highest water depths (1,144 mm and 2,106 mm, respectively) provided the lowest potassium (TK) and magnesium (TMg) levels in guava fruit, demonstrating that both the deficit as excess water in the soil significantly reduce the levels of these nutrients in fruits. As for nitrogen (TN), phosphorus (TP) and calcium (TCa) content, it was verified that only water deficit in the soil provided reductions in their contents in fruits, since they increased with increasing irrigation level applied to guava cultivar Paluma. Similarly to total water depths, nitrogen fertilization levels applied to the crop significantly influenced the export of nutrient by guava fruits. Thus, Figure 2 shows an isolated effect of this factor on the nitrogen (TN), potassium (TK), calcium (TCa) and magnesium (TMg) levels obtained in guava fruits cv. Paluma. From the results obtained and according to statistical models, it was observed in Figure 2A that there was an increase of g kg -1 in nitrogen content of guava fruits with the Figure 2. Nitrogen (a), potassium (b), calcium (c) and magnesium (d) contents in guava fruits cultivar Paluma as a function of the nitrogen levels As for potassium (TK) levels, according to the statistical model that best fit (Figure 2B), it was found that there was an increase of 9.71% of this nutrient in guava fruit, from the lowest nitrogen fertilization level (50 kg ha -1 ) with g kg -1 to the application of 148 kg ha -1 of nitrogen at maximum level of the statistical model with g kg -1, decreasing approximately 2.70% from this point up to the application of the highest nitrogen fertilization level (200 kg ha -1 ). From results shown in Figure 2C, it seems that the highest calcium content (TCa) in guava fruit estimated at the maximum point of the statistical model (14.15 g kg -1 ) was obtained when applying nitrogen doses corresponding to kg ha -1, decreasing, about 0.89 and 14.12% when applying nitrogen doses corresponding to 50 and 200 kg ha -1, respectively. According to Figure 2D, the estimated magnesium content (TMg) in guava fruits was 1.35 g kg -1 at the maximum point of the quadratic statistical model obtained with the application of nitrogen fertilization level corresponding to 152 kg ha -1, providing an increase of and 2.39%, respectively, compared to the lowest and highest nitrogen fertilization levels tested in this study. In this context, it was found that guava cv. Paluma showed macronutrient uptake by the fruit, in g kg -1, in the following order and amounts: K (17.31)> Ca (13.46)> N (11.37)> P (1.38)> Mg (1.29). Therefore, it was observed that the values found are higher than those obtained in other studies with the same culture, such as those by Natale and Prado (2004), whose exports of macronutrients in g kg -1, occurred in the following order and amounts: K (12.4)> N (8,6)> P (0,9) = Mg (0.9)> Ca (0.7). However, Cardoso et al. (2010) assessed mineral fertilizer in Paluma guava in the micro-region of the vale do Curu-CE and found the following order of macronutrient export by fruits: K> N> Ca> P> S> Mg. The high potassium contents exported by fruits compared to other macronutrients, possibly were due to the fact that this nutrient acts directly in the transport of soluble solids, as well as in the maintainance of the high water content in
5 Export of nutrients by guava fruits under different water depths and nitrogen fertilization levels fruits (MARSCHNER, 1995), favoring the formation and translocation of carbohydrates and efficient use of water by the plant, improving product quality (FILGUEIRA, 2003). The results for the export of macronutrients: nitrogen (TN), phosphorus (TP), potassium (TK), calcium (TCa) and magnesium (TMg) by P. guajava fruits cv. Paluma as a function of the interaction between different water depths and nitrogen fertilization levels used in this study, respectively, can be observed in Tables 4 and 5. The results in regression components of factor water depths at each nitrogen fertilization level (Table 4) showed that the guava culture responded positively to the combined applications of these factors at 5% probability level only when the lowest nitrogen fertilization level was applied; for the other fertilization levels, there was significant effect at 1% probability level. Regarding the results of the nitrogen fertilization levels in each water depth applied (Table 5), a positive response was observed, regarding the combined application of factors assessed at 1% and 5% probability level for variables nitrogen 83 (TN), potassium (TK), calcium (TCa) and magnesium (TMg) contents exported by P. guajava fruits cv. Paluma, ranging from linear to cubic, indicating a strong dependence between the effects of both factors on these variables. Figure 3 shows the trends and behaviors of macronutrients nitrogen (TN), potassium (TK), calcium (TCa) and magnesium (TMg), exported by guava fruits cv. Paluma as a function of different water depths and nitrogen levels tested in this study. According to the statistical model that best fit, Figure 3A shows a positive linear effect, where the highest nitrogen fertilization levels (TN) in guava fruits were obtained when the highest water depth (2,106 mm) was applied, associated with nitrogen fertilization equivalent to 200 kg ha -1, totaling g kg -1. This value represents an increase of 28.58% in nitrogen content exported by fruits starting from the lowest total water depth and nitrogen fertilization applied. Based on the quadratic statistical model obtained for the potassium (TK) content, Figure 3B showed that the highest value found for this variable, g kg -1, was obtained when Table 4. Regression analysis of water depths as a function of the nitrogen fertilization levels for variables nitrogen (TN), phosphorus (TP), potassium (TK), calcium (TCa) and magnesium (TMg) contents of guava fruits (TN) in g kg -1 * and ** significant at 1% and 5% probability, respectively, ns - not significant Table 5. Regression analysis of the nitrogen fertilization levels as a function of water depths for variable nitrogen (TN), phosphorus (TP), potassium (TK), calcium (TCa) and magnesium (TMg) contents of guava fruits (TN) in g kg -1 * and ** significant at 1% and 5% probability, respectively, ns - not significant
6 84 Figure 3. Nitrogen (a), potassium (b), calcium (c) and magnesium (d) contents in guava fruits cv. Paluma as a function of the water depths applied 150 kg of nitrogen ha - 1 was applied together with water depth corresponding to 1611 mm at the maximum point of the statistical model, leading to an increase of 12.36% compared with the lowest water depth applied and to 14.11%, when compared to the highest water depth adopted in this study. Figure 3C shows that the increase in irrigation level resulted in increased calcium levels (TCa) in guava fruit, where the highest values found (15.10 and g kg -1 ) were obtained when the highest water depth was applied (2.106 mm) combined with nitrogen levels corresponding to 50 and 100 kg ha -1. By applying total water depth corresponding to 1723 mm associated with 150 kg ha -1 nitrogen (Figure 3D), an increase of 17.12% in the magnesium content (TMg) was observed, starting from the lowest water depth applied with 1.28 g kg -1 to 1.55 g kg -1 at the maximum point of the statistical model (1723 mm). From this point, the magnesium content found decreased 7.37% using the highest water depths applied to the culture (2106 mm). According to the statistical models obtained (Figure 4), influence of the different nitrogen levels in all water depths applied to guava culture was observed, for the variables evaluated in this study. Based on results, Figure 4A shows that nitrogen fertilization equivalent to 200 kg ha -1 associated with the highest water Figure 4. Nitrogen (A), potassium (B), calcium (C) and magnesium (D) contents in guava fruits cv. Paluma as a function of the nitrogen fertilization levels José Dantas Neto et al. depth applied (2,106 mm) provided the highest nitrogen levels (TN) in guava fruits, of g kg -1, representing an increase of 28.01% of this nutrient, starting from the lowest nitrogen fertilization level (50 kg ha -1 ) and total water depth applied to the culture (1,144 mm). Regarding potassium content (Figure 4B), there was an increase of g kg -1 of this nutrient in the lowest nitrogen fertilization level (50 kg ha-1) up to g kg -1 at the maximum point of the statistical model, when 125 kg ha -1 of nitrogen applied together with total highest water depth of 1785 mm, which corresponds to an increment of and 12.81%, respectively, compared to the smallest and highest nitrogen fertilization levels. There is also a linear increase in potassium levels from the application of 50 kg ha -1 nitrogen with g kg -1 up to g kg -1 with the application of 200 kg ha - 1 of nitrogen associated with total highest water depth of 1,465 mm, representing an increase of 15.02% in the levels of this nutrient. As for calcium contents, Figure 4C shows that the largest estimated value of this nutrient in guava fruits, of g kg -1, was obtained when nitrogen fertilization level corresponding to 50 kg ha -1 was applied together with the highest water depth (2,106 mm), decreasing approximately 18.37% when applying the highest nitrogen fertilization level assessed in this study (200 kg ha -1 ). Based on results shown in Figure 4D, the highest magnesium content (TMg) in guava fruits was obtained when 136 kg ha -1 of nitrogen was applied together with total highest water depth of 1785 mm, with an increase of 1.3 g kg -1 of this nutrient applying 50 kg ha -1 nitrogen up to 1.50 g kg -1 at the maximum point of the statistical model obtained, corresponding to an increment of 13.57%; from this point, there is a decrease of 7.20% with the application of 200 kg ha -1 nitrogen. Except for calcium (TCa), which had the highest value obtained with the interaction between the lowest nitrogen fertilization level and the highest water depth applied (Figure 4C), the other macronutrients had their levels increased with higher nitrogen fertilization levels and highest water depths. This fact highlights the importance of knowing the chemical composition of fruit as fertilizer with the use of safer and more efficient fertilization programs, contributing to maintainance of soil fertility and improving the final quality of the fruit produced. In this sense, Porto et al. (2006) reported that knowing the amounts of nutrients accumulated in the harvested part of plants is one of the main factors used in economic fertilizer recommendations. According to Maia et al. (2007), the application of fertilizer to perennial crops is based on the replacement of the amounts of nutrients removed by fruits, and their immobilization is also considered. In experiments with guava culture in the São Francisco valley, Lima et al. (2008) found that fertilization levels corresponding to 200 kg N ha -1 and 100 kg ha -1 of K provided better quality of fruits produced, resulting in lower ascorbic acid degradation and pulp firmness maintainance. Brizola et al. (2005) observed that among macronutrients obtained in fruits, only potassium showed its values increased by the effect of fertilization. However, Maia et al. (2007) found that N and K were the nutrients most removed by guava fruits.
7 Export of nutrients by guava fruits under different water depths and nitrogen fertilization levels Given the importance of guava culture for Brazil and in particular for the Northeastern region and due to the lack of information regarding nutritional requirements of the guava crop, Guerra and Bautista (2002) and Cavalcante et al. (2005) point out that there is need to develop studies aimed at the mineral nutrition of this culture. According to Medeiros et al. (2004), fertilization of guava culture is usually performed empirically, without proper technical and scientific support. CONCLUSIONS Factors water depths and nitrogen fertilization levels applied together or separately significantly influenced the concentrations of nutrients in guava fruits. 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