Advances on apple production under semiarid climate : N fertigation

R E G U L A R A R T I C L E *Corresponding author: Italo Herbert Lucena Cavalcante, Federal University of São Francisco Valley, Campus of Agricultural Sciences, Petrolina, Pernambuco, Brazil. E-mail: italo.cavalcante@univasf.edu.br Received: 13 April 2015; Revised: 22 June 2015; Accepted: 26 June 2015; Published Online: 26 June 2015 Miranda, et al.: Apple production under semiarid climate Emir. J. Food Agric ● Vol 27 ● Issue 10 ● 2015 745 methods (foliar or soil applications). De Angelis et al. (2011) reported that the time and method of nitrogen fertilizer application can affect both plant growth and production of the following year and it can also affect the different forms of storage and nitrogen mobilization in the tree. The present work aimed at evaluating the fruit production, yield and leaf chlorophyll of ‘Princesa’ and ‘Eva’ apples as a function nitrogen fertigation under Brazilian semiarid conditions. MATERIALS AND METHODS Plant material and growth conditions Princesa and Eva apple (Malus domestica) trees propagated by grafting (with ‘M9 interstock and Maruba rootstock) and transplanted in 2010 were used in this study. The study was conducted in 2012 and 2013 on an experimental orchard located in Campo Doro farm, in Petrolina (09°21' S and 40o34' W; at an altitude of 375 m above sea level), Pernambuco State, Brazil. The climate of this region is classified as Bswh (Köeppen), which corresponds to a semiarid region. During the execution of the experiments the precipitation was 94 mm, the temperature range was between 24.3oC and 29.4oC, and air humidity between 48.8% and 64.9%, while the average radiation was 535 ly/day and the average sunshine hours was 7.9 hours/day. The physical and chemical characteristics of the soil (Oxisol) where the experiment was performed are shown in Table 1. Before the execution of the experiment leaf samples were taken to access the plant nutritional status (Table 2). According to recommendations of Nachtigall et al. (2004), four leaves per plant were taken from the middle part of the canopy at each cardinal point from 25 plants. Leaves were chemically analysed after washing and rinsing with distilled water and drying at 70oC for 48 h using the methodology described by Malavolta et al. (1997). After hand defoliation (July 2012), the apple trees were pruned and treated with 0.08% hydrogen cyanamide and 3.0% mineral oil (Assist®) and 3.0% of color fix (Hi-Light®) following the recommendation of Lopes et al. (2012). Fruit thinning also was performed when fruit measured nearly 2.0 cm in diameter, keeping one or two fruits per floral bunch. The orchard conduction system was set up with a central leader, and it was composed of Eva and Princesa (pollinator cultivar) apple cultivars. The spacing between the rows was 4.0 m, and the spacing between the trees was 1.25 m. The trees were drip-irrigated each day with ten self-regulated emitters per tree with a flow of 2 L hour-1 based on daily evapotranspiration registers recorded by the Embrapa Meteorological Station and corrected according to the apple culture coefficient (Kc). The nitrogen source used was calcium nitrate (15.5% of N), applied twice a week, during 40 days, reaching 12 fertilizings through irrigation water. The first N fertilizing was performed at 40 days after breaking dormancy. All plants were also fertilized with potassium sulphate (50% of K2O), triple superphosphate (45% of P2O5), magnesium sulphate (15% of Mg), boric acid (17% of B) through irrigation water, according to instructions Table 1: Chemical and physical characteristics of the soil (0‐20 cm and 20‐40 soil depths) where the experiment was carried out Soil Characteristic Soil Depth 0 – 20 cm 20 – 40 cm pH (in water) 6.9 6.8 cmolcdm −3 Ca2+ 3.2 2.5 Mg2+ 1.8 1.0 Ca+ Mg 5.0 3.50 Al3+ 0.05 0.05 H+Al3+ 2.8 2.47


INTRODUCTION
Brazil is the third main worldwide producer of apples (Fao, 2014) with more than 42 ton millions produced, nowadays concentrated in regions with warm climate, although the potential for production under different climates.
The apple tree is native to temperate climate zones where most commercial cultivars satisfy their required chilling temperature, expressed as hours at less than 7ºC (Tromp, 2005).Thus, to produce temperate fruit crops, such as apple, in tropical areas it is necessary to overcome plant dormancy and choose low chilling requirement cultivars, such as 'Anna' (Njuguna et al., 2004) and 'Princesa' apples.This way research projects have been performed aiming to grow apples under different conditions from those required by this crop such as Ashebir et al. (2010) in northern Ethiopia, Njuguna et al. (2004) in Kenya and Liu et al. (2008) in China.In Brazil, apple crop has been studied in São Paulo State Northeast (Chagas et al., 2012) and in Brazilian Semiarid (Lopes et al., 2012;Lopes et al., 2013;Oliveira et al., 2013).Such publications concluded that it is possible to obtain apple yield under semiarid conditions for the pollinator cultivar, although, additional studies especially for technical and fertilizing management are necessary to generate an apple production system that is reliable under semiarid conditions.
The fertilizing management for apple tree is essential, especially for nitrogen, one of the most important mineral nutrient affecting fruit yield and the red coloration in apples (De Angelis et al., 2011).Specifically for apples N is the nutrient with a particularly strong negative impact on the yield and fruit quality, especially regarding to the fruit flesh firmness, delayed degradation of chlorophylls in the epidermis and soluble solids content (Sadar et al., 2013).In addition, annual N fertilizing is needed to ensure high levels of production year after year, and these fertilizations can be performed in different times of the year by different methods (foliar or soil applications).De Angelis et al. (2011) reported that the time and method of nitrogen fertilizer application can affect both plant growth and production of the following year and it can also affect the different forms of storage and nitrogen mobilization in the tree.
The present work aimed at evaluating the fruit production, yield and leaf chlorophyll of 'Princesa' and 'Eva' apples as a function nitrogen fertigation under Brazilian semiarid conditions.

Plant material and growth conditions
Princesa and Eva apple (Malus domestica) trees propagated by grafting (with 'M9 interstock and Maruba rootstock) and transplanted in 2010 were used in this study.
The study was conducted in 2012 and 2013 on an experimental orchard located in Campo Doro farm, in Petrolina (09°21' S and 40º34' W; at an altitude of 375 m above sea level), Pernambuco State, Brazil.
The climate of this region is classified as Bswh (Köeppen), which corresponds to a semiarid region.During the execution of the experiments the precipitation was 94 mm, the temperature range was between 24.3ºC and 29.4ºC, and air humidity between 48.8% and 64.9%, while the average radiation was 535 ly/day and the average sunshine hours was 7.9 hours/day.
The physical and chemical characteristics of the soil (Oxisol) where the experiment was performed are shown in Table 1.
Before the execution of the experiment leaf samples were taken to access the plant nutritional status (Table 2).According to recommendations of Nachtigall et al. (2004), four leaves per plant were taken from the middle part of the canopy at each cardinal point from 25 plants.Leaves were chemically analysed after washing and rinsing with distilled water and drying at 70ºC for 48 h using the methodology described by Malavolta et al. (1997).
After hand defoliation (July 2012), the apple trees were pruned and treated with 0.08% hydrogen cyanamide and 3.0% mineral oil (Assist ® ) and 3.0% of color fix (Hi-Light ® ) following the recommendation of Lopes et al. (2012).Fruit thinning also was performed when fruit measured nearly 2.0 cm in diameter, keeping one or two fruits per floral bunch.The orchard conduction system was set up with a central leader, and it was composed of Eva and Princesa (pollinator cultivar) apple cultivars.The spacing between the rows was 4.0 m, and the spacing between the trees was 1.25 m.The trees were drip-irrigated each day with ten self-regulated emitters per tree with a flow of 2 L hour -1 based on daily evapotranspiration registers recorded by the Embrapa Meteorological Station and corrected according to the apple culture coefficient (Kc).
Other cultural treats of the orchard were performed according to the recommendations of EPAGRI (2006).

Treatments and experimental design
The experimental design was randomized blocks with treatments distributed in a factorial arrangement (4 × 2) referring to nitrogen doses (160, 120, 80 e 40 kg of N ha -1 ) and apple cultivars (Eva and Princesa), with four replications and three plants in each parcel.Nitrogen doses were defined according to Ernani and Dias (1999).

Data gathered and statistical analysis
The following fruit variables were also recorded: i) accumulated number of fruits per plant; iii) fruit production per plant, which was measured using a Filizola ® CF15 brand precision scale (0.5 g precision) and expressed in kilograms/plant (kg/plant); and iii) fruit yield, which was obtained by multiplying the fruit production per plant by the total number of plants in one hectare.
During fruit production the total leaf chlorophyll was measured using a chlorophyll meter (Falker ® , Brazil) in four leaves per plant from the middle part of the canopy at each cardinal point within the canopy of each replication (plant), following the methodology described by El-Hendawy et al. (2005).Readings were taken in the middle, apex and basis of the leaf, avoiding necrotic areas by the attack of pests and disease.Therefore, each repetition consisted of an average from twelve leaf chlorophyll readings.
The same leaves were collected immediately after performing leaf chlorophyll readings, and chemically analyzed.After washing and rinsing with distilled water, the leaves were dried at 70ºC for 48 h.Total N concentrations were analyzed using the Kjeldahl method.
Statistical analyses included analysis of variance (ANOVA), mean separation of apple cultivars using Tukey test and regression analysis of nitrogen doses, using combined data.All calculations were performed using the Sigmaplot software, and terms were considered significant at p < 0.01.

RESULTS AND DISCUSSION
As can be seen in Table 3 nitrogen levels significantly affected total leaf cholrophyll (CHLO) and leaf nitrogen concentration (Leaf N), while fruit production, fruit yield and Leaf N were influenced by apple cultivars.In addition, no significant interactions between N levels and apple cultivars were registered for all variables recorded in the study.
Fruit production (kg plant -1 ) was nearly 18% higher for 'Princesa' apple cultivar in relation to 'Eva' ones (Table 3), result which was not previously expected because most apple cultivars require crosspollination using a compatible cultivar to obtain desirable set fruit, and in commercial orchards 'Princesa' has been used for cross-pollination and not for yield, but under semiarid climate the 'Princesa' has shown potential to be grown as a production cultivar.The average fruit productions contained in Table 3  Following the same tendency of the fruit production (kg plant -1 ), fruit yield was also significantly higher (18%) for 'Princesa' cv.Both apple cultivars studied presented fruit yield, in average, higher than those quoted in the scientific literature by Lopes et al. (2012) and Lopes et al. (2013) who reported 10.3 t ha -1 and 12.73 t ha -1 , respectively for 'Eva' and 'Princesa', under semiarid climate.Moreover, the present yield results are compatible to 29.3 t ha -1 ('Princesa') and lower than 31.3t ha -1 ('Eva') obtained by Chagas et al. (2012).It detaches that Chagas et al. (2012) were recorded in the second fruit harvest, traditionally higher than the first one, when data of Table 3 were collected.When compared to apples produced under temperate climate the average yield values of the present study were superior to those reported by Naor et al. (2008) for 15-yearold Smoothie apples grown in Israel (13.1 t ha -1 ), Nava and Dechen (2009) for Fuji apples in Brazil (16.1 t ha -1 ) and superior to the range reported by Di Vaio et al. (2009) for Annurca Rossa del Sud apples in Italy (7.4 -25.1t ha -1 ).
Accordingly, due to the importance of new producing areas around the world, especially for apples, Basannagari and Kala (2013) studied the climate change and apple farming and concluded that it is important to understand the variations in the patterns of climate change and also to identify management practices and alternatives for farmers in order to cope up the vagaries of changing climate, trying to contribute for fruit production sustainability.
It is important to note that apple trees take four to five years to produce their first fruit (Ferree and Warrington, 2003).In the present study, the trees were transplanted in 2010, so the fruit production was anticipated in two or three years.Moreover, it is common that the first harvest presents a low yield, but it is strongly recommended the evaluation of this variable because yield is one of the most important characteristics of apple crops.
The Princesa apples plants of the present study produced more fruits than those evaluated by Lopes et al. (2013) and Chagas et al. (2012), while Eva apples promoted a number of fruits higher than Lopes et al. (2012) but lower than Chagas et al. (2012).
Fruit production (kg plant -1 ), fruit yield and number of fruits per plant were not affected by nitrogen (N) fertilizing through fertigation that is in agreement with Nava and Dechen (2009) who identified no effect of N fertilizing during the first evaluation year and concluded that it had been caused by the buds that originated the fruits of the first harvest had already been differentiated in the previous year.Accordingly, both apple cultivars studied were adequately N supplied before the beginning of the experiment, whether compared to adequate range statement reported by Nachtigall et al. (2004).According to Nava (2007) apple trees are able to store a large N amount as protein and reuse it in later cycles.
It is important to infer that the lack of N fertilizing effect on fruit yield could be associated with some characteristics such as low N requirement of apple tree (Ernani and Dias, 1999), good conditions for N release from soil organic matter, and poor conditions for N leaching.
In a general form, it observes in the scientific literature a huge disagreement about the effect of N fertilizing on apple yield.In Brazil, Ernani et al. (2000) found no effect of N doses and fertilizing times on apple fruit yield and, explained this result by the high N mineralization rate contained on soil organic matter.On the other way, in experiment performed on a shallow and stony soil Nava and Dechen (2009) obtained a positive result, and Nava et al. (2007) concluded that increasing N doses promoted higher fruit mass, fruit yield and number of fruits per plant, maybe caused by a better bud nutrition.
Leaf chlorophyll meter reading presented a quadratic adjustment of the data with a minimum fit of 0.93, with a calculated peak at 120 kg of N ha -1 (Fig. 1a), followed by a consecutive decay.This result could be explained by Cavalcante et al. (2012) who argue that nitrogen is the core component of chlorophyll molecule as the structural component in porphyrin ring, and thus its content in the leaf is directly proportional to chlorophyll content, although there is a maximum of sufficiency when this pigment is decreased.
Nitrogen foliar concentrations of apple trees significantly increased with N fertilizing doses enhancement (Fig. 1b) that could be caused by the low soil organic matter where the experiment was performed (Table 3), associated to the N demand of apple tree.In addition, N is the second nutrient more demanded by apple tree (Nachtigall and Dechen, 2006).All average values of Fig. 1B from 80 to 160 kg of N ha -1 are compatible to 21.5 g kg -1 reported by Nava et al. (2007) and only apple plants fertilized with 40 kg of N ha -1 reached the stated adequate range of supply described by Nachtigall et al. (2004).
In the present work, however no significant effects of N fertilizing on fruit production and yield have being registered, there was increasing on leaf N concentration and total leaf chlorophyll meter reading.According to Nava et al. (2007), this effect could stimulate the plant photosynthetic hate, carbohydrate synthesis, leaf specific weight, total plant mass production and carbon allocation on different plant organs, thus exerting a positive effect on bud nutrition.

Fig 1 .
Fig 1.Total chlorophyll meter readings (a) and nitrogen leaf concentration (b) of apple as a function of nitrogen doses.