EFFECTS OF FERTILIZATION AND IRRIGATION ON THE ELEMENTS OF YIELD OF THE WINE GRAPE VARIETY VRANAC

This work presents the three-year results of the effects of mineral and different types of organic fertilizers on the elements of the yield (the relative coefficient of fertility, the absolute coefficient of fertility, cluster weight and the yield of grapes per area unit) of the Vranac variety of grape. The research was carried out in Podgorica vineyard, at the location Lješkopolje. Eight different variants of nutrition were applied: (1) control (without fertilization); (2) NPK (8:16:24) 500 kg/ha; (3) cow manure 20 t/ha; (4) poultry manure 10 t/ha; (5) peat 10 t/ha; (6) cow manure + poultry manure 10 + 5 t/ha; (7) cow manure + peat 10 + 5 t/ha; (8) poultry manure + peat 5 + 5 t/ha. All the variants of nutrition were tested under irrigated and non-irrigated conditions. The results showed that the relative coefficient of fertility in all the tested variants of nutrition had high values. Regarding the number of inflorescences per productive shoot in a three-year average, a particularly good variant was the cow manure and the variant with the combination of poultry manure and peat. The application of mineral and different types of organic fertilizers had a positive effect on the average cluster weight. The variant with the combination of poultry manure and peat gave the highest average cluster weight in the three-year average. All the tested variants of nutrition in the three-year average had a higher yield than the variant without fertilization. The variant with cow manure had the highest yield of grapes. Irrigation had a positive effect on all the tested indicators of the yield.


Introduction
The viticulture of Montenegro is mainly located in the region of Podgorica, where the cultivation of vine and the production of grapes and wine are an integral part of the economy of this region.In the structure of wine varieties the leading Tatjana Đ. Popović et al. 82 place is taken by the autochthonous, high quality Vranac variety that produces premium quality wine.
For all agricultural crops the organic matter has multiple importance and role.The application of organic fertilizers, besides the repairing nutritional regime of soil, can significantly improve water, air, absorption and thermal regime, as well as microbiological properties.For this reason the organic fertilizers, besides the certain direct influence on the nutrition of plants, also have an indirect influence on the complex mineral nutrition by improving many factors of general soil fertility, which is certainly not the case with the application of many mineral fertilizers (Džamić, 2000).
It is well known that plant cannot use nutrients directly in the form of solid or dry fertilizers.Therefore, the vine requires a sufficient amount of water in the soil for development of all vital functions (Mirošević and Karoglan-Kontić, 2008) This is particularly important in the climates characterized by proportionally heavy rainfalls, as well as their uneven distribution throughout the year, causing the moisture in such conditions to occur as a limiting factor in grape production (Popović, 2008).
The yield of a single variety of grapes is in the first place genetically determined but it is heavily influenced by both internal and external factors.Internal factors are hormones, and the most important external factors are mineral nutrition, water, heat, light, agro and phyto techniques (Kuljančić et. al., 2007).The emergence and development of flowers on the vine largely depend on the presence, conditions and degree of utilization of many nutritional elements from the soil that the vine uses at a particular time and in a specific manner, first to create and differentiate flower buds, and then to produce, grow and develop bearing shoots, inflorescences and clusters.
Due to the lack of experience and the results on the influence of organic fertilizers and irrigation on the elements of the yield of the Vranac variety of grapes, we carried out experiments in order to select the best types or combinations of fertilizers, as well as to address the issue of the lack of moisture in soil and thus to ensure regular and high quality yield of the Vranac variety as a major variety in the production of red wines in Montenegro.

Material and Methods
Studies were performed in the period 2003-2005 on the experimental farm of the Biotechnical Institute in Podgorica.The experimental vineyard was planted in 1986.The spacing between rows was 2.5 m and the distance between the vines in the row was 1.2 m.Training form is a double cordon with the height of about 80 cm.
Studies were performed on the Vranac variety of grapes which was grafted on a rootstock Kober 5BB.
The experiment included the following combinations and variants: Combinations: A -Irrigated B -Non-irrigated Fertilizers were applied during the period of rest by ploughing a furrow in the middle of the space between the rows at the depth of 25-30 cm.The furrows were filled with a calculated amount of fertilizer for a corresponding variant, half the amount on one side and the other half on the other side of the row.
The irrigation was carried out over the surface -not flowing through the furrows.In the space between the rows a single furrow was ploughed.The irrigation was carried out as soon as the soil moisture dropped below 17%.It was carried out by pumping the water from the canals near the experimental location.
Each variant had 18 vines, arranged in three replications with six vines.Selected vines in each year of the research were pruned by the same criteria, using the mixed pruning with two canes with 10 buds and two spurs with two buds each.This made a total load of 24 buds per vine which was in accordance with the usual way of pruning of the Vranac variety in the plantation growing of Montenegro.
The yield potential was determined by recording the number of total and activated buds, the number of formed and unproductive shoots, the number of inflorescences, the number and weight of clusters.On the basis of the acquired data the following indicators were determined: average number of inflorescences per shoot (relative coefficient of fertility), average number of inflorescences per productive shoot (absolute coefficient of fertility).Yield was obtained by measuring the harvested grapes and by the conversion of yield per m 2 .The cluster weight was determined from the ratio of actual yield from six vines and the number of clusters.
The data were analyzed statistically by using the method of analysis of variance of a completely random block system.The significance of differences was determined by using the LSD test.

Results and Discussion
Based on the results presented in Table 1 it can be seen that the relative coefficient of fertility or the number of inflorescences per shoot had high values in the examined variants of nutrition.Two variants of nutrition were distinguished by a very high relative coefficient of fertility (cow manure -1.48; poultry manure + peat -1.42).A high coefficient was also proved in the variant of peat (1.40).In other variants the average number of inflorescences per shoot had lower values compared to the control (1.35).
Irrigation had a positive impact on this indicator of fertility.The average number of inflorescences per shoot in irrigated area for all tested variants was 1.40, whereas in non-irrigated area it was only 1.32.
Regarding the number of inflorescences per productive shoot (Table 2) in the three-year average, two variants proved particularly good: the variant with cow manure (1.64), and the variant with the combination of poultry manure and peat (1.63).
In the group with the medium values of the absolute coefficient of fertility there were the variants with peat (1.57) and mineral fertilizer (1.53), while in other variants of nutrition this coefficient was below 1.50.The minimum number of inflorescences per productive shoot (1.46) was recorded in the variant 4 (poultry manure).The absolute coefficient of fertility was within the values which, for the same variety and in different environmental conditions, were found by other authors (Avramov, 1991;Burić, 1995).
Irrigation had a positive impact on this indicator of fertility.In the irrigated experimental area the average number of inflorescences per productive shoot ranged from 1.47 to 1.70 while in the non-irrigated area in all the tested variants, this number was significantly lower and ranged from 1.34 to 1.62.In the three-year average this coefficient of fertility in irrigated area was 1.58 and it was higher by 0.08 compared to the experimental area that was not irrigated.
The highest yield of grapes, on average for all three years of research (1.49kg/m 2 ) was measured in the variant with cow manure (Table 3).In the combination with poultry manure and peat and the variant with poultry manure alone the yield was a little lower (1.43 and 1.42 kg/m 2 respectively).In the area that was fertilized with mineral fertilizer the yield was 1.41 kg/ m 2 .The variants 7, 5 and 6 had the yield lower than 1.40 kg/m 2 (1.38, 1.33, and 1.23 kg/m 2 respectively).The variant 6 had the yield that was higher by only 0.06 kg/m 2 than the control.All the tested variants of nutrition in the three-year average had a higher yield than the variant without fertilization where the yield was only 1.16 kg/m 2 .Despite demonstrated differences in the yield of grapes, there were no statistically significant differences between the different variants of nutrition.
Besides variations in yield according to the variants of nutrition, Table 3 shows the variation of yield depending on the application of irrigation as well.
Comparative results of the two combinations of the experiment (irrigated and non-irrigated) reveal interesting details that lead to the conclusion that the application of fertilizers has a completely different character in the non-irrigated conditions in comparison to the irrigated conditions.In fact, under non-irrigated conditions the variants of fertilization like 5, 6 and 7, which gave a very low yield of grapes, proved to be very good under irrigation.In the three-year average the yield of grapes in the irrigated area was 1.44 kg/m 2 while in the non-irrigated area it was 1.26 kg/m 2 .Despite the clear positive tendency of the influence of irrigation on the yield of grapes there were no statistically significant differences in the threeyear average compared to the yield obtained under the non-irrigated conditions.: Control -without fertilization; A 2 : NPK (8:16:24) -500 kg/ha; A 3 : Cow manure -20 t/ha; A 4 : Poultry manure -10 t/ha; A 5 : Peat -10 t/ha; A 6 : Cow manure + poultry manure -10 + 5 t/ha; A 7 : Cow manure + peat -10 + 5 t/ha; A 8 : Poultry manure + peat -5 + 5 t/ha.
The yield of grapes in all the variants of nutrition was within the results that various authors reported for the Vranac variety of grapes (Pejović, 1982;Ulićević et al.1991;Burić, 1995;Cindrić, 2000;Popović, 2003).
Cluster mass is the biological property of each grape variety.The variations of this characteristic depend on the variants of nutrition and irrigation, which is shown in Table 4.
The control had the lowest cluster mass of only 180 g in average.The variants with poultry manure, peat and cow manure had 21, 27 or 28 g higher cluster mass respectively compared to the unfertilized area.However, these differences were not rated as statistically significant.The area fertilized with mineral fertilizers had cluster mass of 215 g which was 35 g higher than in the control, and the difference was rated as statistically significant.There were significant differences between the variants 6, 7, and 8 compared to the control.The highest cluster mass in the threeyear average was recorded in the variant 8 (218 g).Most of the tested variants, except the control, had the cluster mass at the level of values which was characteristic of the Vranac variety, as reported by other authors (Pejović, 1982;Ulićević et al., 1991).
Under irrigation, the average cluster mass ranged from 175 g in the control to 232 g in the variant 8, while under non-irrigated conditions the average cluster mass was significantly lower with all the variants of nutrition and it ranged from 185 g (control) to 207 g (mineral fertilizer).The average cluster mass in the irrigated area for all the variants of nutrition was 217 g and it was significantly higher than the cluster mass under non-irrigated conditions (196 g), so that one can say for certain that the use of irrigation has a positive effect on this indicator of productivity.

Table 1 .
Relative coefficient of fertility of Vranac variety.

Table 2 .
Absolute coefficient of fertility of Vranac variety.

Table 3 .
The yield of grapes (kg/m 2 ) of Vranac variety.