Effect of frost damage on leaf macronutrient status of eight apple cultivars in integrated apple orchard in Eastern-Hungary

The climate condition and orchard management practises are the main key factors in the production of high and qualitative yields of apples (Bramlage, 1993) In the last few years irregularity of yield is one of the main problems in fruit production. Year-to-year variations in crop production have been traditionally related to weather conditions is spring all over the world (Rodrigo & Herrero, 2002). Frost is a dangerous climatic hazard that can be responsible for yield losses and serious injuries to orchard trees. The resistance to frost damage is associated with the nutritional status of plant. In temperate climates, important damages on deciduous fruit trees are caused in buds, flowers and developing fruits after dormancy and the losses due to frosts during the blooming are usually more important than those due to low winter temperatures (Rodrigo, 2000). 2007 was a critical year for fruit growing in EasternHungary. At the beginning of May there were two days when the temperature of early dawn was approximate 3–5 °C. Due to it there was not yield in lot of orchards in this region. The frost damage caused entirely crop failure and created new conditions for plant uptake. In the orchard of TEDEJ Rt. the flowers and fruit sets of apple trees were fallen down (Figure 1). Due to the frost there was not measurable yield in the orchard. The aim of our research was to study how frost changes the mineral content of different apple cultivars. Effect of frost damage on leaf macronutrient status of eight apple cultivars in integrated apple orchard in Eastern-Hungary


Introduction
The climate condition and orchard management practises are the main key factors in the production of high and qualitative yields of apples (Bramlage, 1993) In the last few years irregularity of yield is one of the main problems in fruit production. Year-to-year variations in crop production have been traditionally related to weather conditions is spring all over the world (Rodrigo & Herrero, 2002). Frost is a dangerous climatic hazard that can be responsible for yield losses and serious injuries to orchard trees. The resistance to frost damage is associated with the nutritional status of plant.
In temperate climates, important damages on deciduous fruit trees are caused in buds, flowers and developing fruits after dormancy and the losses due to frosts during the blooming are usually more important than those due to low winter temperatures (Rodrigo, 2000).
2007 was a critical year for fruit growing in Eastern-Hungary. At the beginning of May there were two days when the temperature of early dawn was approximate 3-5°C. Due to it there was not yield in lot of orchards in this region. The frost damage caused entirely crop failure and created new conditions for plant uptake.
In the orchard of TEDEJ Rt. the flowers and fruit sets of apple trees were fallen down (Figure 1). Due to the frost there was not measurable yield in the orchard.
The aim of our research was to study how frost changes the mineral content of different apple cultivars.

Materials and methods
Our investigations were carried out in 2006 and 2007 in an apple orchard (Malus domestica Borkh.) of TEDEJ Rt., Hajdúnánás-Tedej, in Eastern Hungary. The orchard was set up on lowland chernozem soil. It was established in the autumn of 1999, using grafted on MM106 rootstocks at a spacing of 3.8×1.1 m. The orchard has been treated according to the Integrated Fruit Production guidelines.
The orchard was irrigated. Soil samples were taken from three layers (0-20 cm; 20-40 cm and 40-60 cm) of each plot, at the middle of the section by using manual soil sampling equipment. For the characterisation of the soil the most important soil parameters were determined. Sampling was performed at the beginning of the vegetation period on April, in 2006.
The soil samples were dried outdoors in an airy place in a 1-1.5 cm layer, then the soil was sieved through a sieve of 2mm holes size, homogenized and stored in plastic boxes until the examination. For extracting the available phosphorus and potassium content of soils, ammoniumlactate extractant (so called AL soluble) was used. AL soluble phosphorus was quantified by colorimetrically with phospomolybdovanadate method, using a spectrophotometer (Metertech VIS SP-850 Plus; Metertech Inc., Taipei, Taiwan). The amount of potassium was quantified by flame atom emission spectrophotometry method using an Unicam SP90B Series 2 Atomic Absorption/Emission Spectrophotometer (PYE Unicam, England).
Healthy, fully developed leaves were taken from the midthird portion of extension shoots current year were collected. Leaf samples were collected 100 days after full bloom, from 50 uniform trees in 2006 and 2007, respectively. Leaf samples were dried outdoors in an airy place for a week. After drying samples in a well-ventilated drying oven for 6 hrs at 40 C, the whole sampled material was finely grounded and homogenized. Samples were then stored in paper bags in a dark and dry place until use.
Nitrogen content of plant samples was determined from homogenized samples directly using the dry combustion method according to Nagy (2000), using an Elementar Vario EL analyser (Elementar Analysensysteme GmbH, Hanau, Germany).
Plant phosphorus and potassium were qualified as described for soil samples.
Calcium and magnesium were measured by flame atomic absorption spectrophotometry, using a SpectrAA-10 Plus spectrophotometer (Varian Australia Pty Ltd. Mulgrave, Australia).

Soil analysis
Obtained results of soil analysis are represented in Table 1.
Besides conventional soil testing procedures, 0.01 M CaCl 2 was used to give further information about the easily soluble and available mineral N contents of soil. The pH of soil was near the neutral value. The physical category of soil was clay loam. The soil P and K was medium, while the soil N was suitable for growing.
The values of easily soluble N form correspond to the type of examined soil and decreased by depth.

Plant analysis
Values and status of leaf N, P, K, Ca and Mg at different species in 2006 and 2007 were shown in Table 2-6. In 2006, leaf N was sufficient at most of cultivars (Table  2). In 2007, after frost damage, leaf N was lower at most cultivars, except 'Mutsu' and 'Jonagold'. Remarkable that significantly higher leaf N was measured at 'Mutsu' in 2007 than in 2006. Leaf N was significantly affected by years.   (Table 3). In 2007, higher leaf P was measured at most cultivars than in 2006, except 'Jonagold' at which leaf P was the same amount in both years. Increase of leaf P may be explained with the fruit failure. Falling down of flowers and fruit sets hindered the translocation of the uptaken P towards fruit sets. Leaf P was affected by cultivars. Outstandingly high phosphorus was measured at 'Braeburn' in both years and at 'Summerred' in 2007. In 2006, leaf K was sufficient at six cultivars. It was low at 'Topaz' and it was high at 'Mutsu' (Table 4). In 2007, leaf K was sufficient at four cultivars and it was high at four cultivars also. Higher leaf K was measured at six varieties in 2007 than in 2006. Leaf K was shown similar tendency observed leaf P. Value of leaf K was affected by cultivars also. Extremely low leaf K was observed at 'Topaz' in 2006.
In 2006 leaf Ca was sufficient at five cultivars and it was low at three cultivars (Table 5). Values of it were slightly increased in 2007, except 'Braeburn'. Leaf Ca increased significantly at the following varieties: 'Topaz', 'Jonagold', 'Golden Reinders' and 'Mutsu'.
The increase of leaf Ca can be explained by the hindered translocation also. The lack of generative organ resulted a larger Ca accumulation in leaves.
Leaf Mg was higher in 2006 than in 2007 at all studied cultivars. The degree of decrease was significant at all cultivars, except 'Topaz'. The highest leaf Mg was measured at 'Topaz' in 2006 and 2007 respectively. The Mg status of leaf became low at 'Idared', 'Summerred' and 'Braeburn' cultivars in 2007. Effect of frost damage on leaf macronutrient status of eight apple cultivars in integrated apple...

Binary macronutrient ratios
Besides the absolute element content, the ratio of the different elements was also determined according to Papp (1997) andFüleky (1999). Our assumption is that these ratios can provide a better indication of nutritional status than conventional sufficiency range approaches. It has been suggested that using these ratios minimize the effects of dilution or concentration due to dry matter and age factors and better evaluates possible nutritional interactions.
From results, the most frequently used ratios were calculated from the main average of cultivars (Table 6).
The ratio of N/P was almost twice as much in 2006 than in 2007. The significant decrease of it was explained by the contrary changing of N and P content of leaf.
The ratio of N/K and N/Ca were lower in 2007 than in 2006 also. The opposite was true for the N/Mg ratio. This contrary tendency was pointed out that the degree of decreasing of leaf Mg was higher than the decreasing of leaf N. The ratio of P/K, P/Ca and P/Mg increased which means the ratio of their removed from the optimal value because these ratios were near the optimal values in 2006.
Similar tendency was observed regarding K/Ca and K/Mg ratios. It means that founded harmonies between these elements in 2006 were overturned.
The ratio of Ca/Mg was increased also. This changing came the ratio of Ca/Mg closer to the optimal value. Both absolute content of nutrients and their ratios pointed out that the frost damage significantly affected the uptake of nutrients and their storing processes.