1. INFLUENCE OF DIFFERENT NITROGEN FORM APPLICATION ON THE INCIDENCE OF BER AND ELEMENTARY COMPOSITION OF BELL PEPPERS Nada Parađiković 1, Tihana Teklić 1, Dražen Horvat 1, Tomislav Vinković 1, Andrej Gumze 1 1 University J.J Strossmayer in Osijek, Faculty of Agriculture, Trg Svetog Trojstva 3, HR-31000 Osijek, Croatia e-mail: nadap@pfos.hr Sveučilište J. J. Strossmayera u Osijeku Poljoprivredni fakultet Osijek Trg Svetog Trojstva 3 p. p. 117 HR-31000 OSIJEK HRVATSKA University of J. J. Strossmayer in Osijek Faculty of Agriculture Trg Svetog Trojstva 3 POB 117 HR-31000 OSIJEK CROATIA

2. Introduction  Calcium is a very important nutrient in highly productive fruit growing such as glasshouse-grown sweet pepper, but inadequate Ca supply manifests with clear symptoms, such as, for example, local decay of pepper fruits (blossom-end rot = BER),  Strong cell wall reflects adequate supply of calcium in plants, which ensures longer storage life of fruits, resistance of plants and fruits to diseases, allow longer roots and shoots function and higher tolerance on either lower or higher temperatures.  However, growth on substrates with high concentrations of NH4 +, K + and Mg 2+ may result in insufficient absorption of calcium

3.  The aim of this study was to compare the effect of different N forms on incidence of BER, yield and fruit quality of pepper fruits of the Cecil F1 cultivar in the region of East Croatia.

4. Material and methods  In the region of East Croatia, located Gajić, Baranja, (45 0 49 / N, 18 0 44 / E), the pepper plants (Capsicum annuum L., cv. Cecil F1, Rijk Zwaan) were grown in heated greenhouse, 3.0 plants m -2 on the substrate (soil), made of a mixture of turf, cattle and chicken manure and sand of the following chemical properties: humus 3,74 %, pH 6,09 (in 1M KCl), AL-P 2 O 5 8,8-41,0 mg/100 g, AL-K 2 O 27,1- 47,8 mg/100 g of soil.  Standard fertilization was done prior to planting on entire trial plot of 100 m 2 with 200 kg/ha 8:26:26 and 100 kg/ha of urea CO(NH 2 ) 2, whilst during fruit formation there were 30 fertigations system drop by drop, (over the period 15.03.- 15.09.), by christalon (10x30 kg/ha 11:44:11, 4x30 kg/ha 20:20:20, 10x20 kg/ha 9:12:36 +3 MgO+ ME).

5.  Growing plot was divided in two equal parts, N rate [500 mg N plant -1 week -1 ] NO 3 - - dominated 4:1 ratio NO 3 - : NH 4 +, and levels of NO 3 - -N [133,0 mgl -1 ], and levels of NH 4 + -N [35,0 mgl -1 ]. N rate [500 mg N plant -1 week -1 ] NH 4 + - dominated 1:4 ratio NO 3 - : NH 4 +, and levels of NO 3 - - N [35,0 mgl -1 ], and levels of NH 4 + - N [133,0 mgl -1 ]. NO 3 - dominated NH 4 + dominated

6. There were 14 harvests of fruits (10.05. – 25.09.), and the results obtained with regard to the number and size of all fruits. Fresh weights of ripe pepper with and without BER were recorded for each plant, as well as total yield and yields per harvests were analyzed according to the standard statistical analysis (to determine significant differences between N-application rates within each N form).

7. Results and discussions  Average values of the mass and fruits number, average and yields per harvest (g/fruit) and percentages of commercial fruits, percentage of Ca in leaves and stems dry mass of the Cecil pepper cultivar in the studied treatments, are presented in the Table 1. Table 1. Incidence of BER in pepper fruits under influence of N-form fertilization, Ca concentration in plants and temperature (data are means of 4 repetition) * standard deviation

8. N-formYield per harvest g/fruitFruit number per plantFruit number per plant with BERCa % in leaves DMCa % in stems DMTemperature °C NO 3 - - 121,904,801,500,00 19 dominated 138,504,402,300,00 18 129,007,001,300,00 19 144,008,504,004,881,0025 146,4010,004,004,841,7026 129,3012,103,805,671,7523 149,5011,105,307,981,8027 146,6011,105,804,252,8228 154,8010,303,500,003,5027 140,708,204,000,00 25 146,309,304,300,00 24 129,709,102,500,00 20 Mean139,728,823,522,300,7523,42 STDEV* 10,092,421,392,981,253,55 NH 4 + - 122,105,001,600,00 19 dominated 140,005,702,800,00 18 132,908,202,800,00 19 145,709,204,804,051,4725 158,5011,904,304,081,0726 156,3012,305,503,871,0523 152,2012,206,004,051,0927 151,0011,706,505,601,1228 163,0011,306,300,00 27 151,508,606,500,00 25 150,7010,606,000,00 24 139,3010,503,000,00 20 Mean146,939,774,671,800,4823,42 STDEV*11,602,481,712,270,613,55

9.  By statistical analysis of total number of pepper fruits per plant it was determined: Simple linear correlation analysis for NO 3 - - N fertilization, showed statistical significant and medium high-level correlation (r=0,639*) with total number of BER affected fruits and for NH 4 + - N fertilization showed statistical very significant and high-level correlation (r=0,829**) with total number of BER affected fruits.

10. Analysis between total fruit number per plant and total BER affected fruit number per plant showed statistical significant and high-level correlation (r=0,81**), and relations between NO 3 - : NH 4 + BER affected and unaffected are showed in Fig. 1 Fig. 1. Proportion of total number of pepper fruits

11. Conclusion  Between fertilization level 500 mg N plant -1 week -1 with NH 4 + - N dominated and NO 3 - - N dominated, there was no significant difference in plant-biomass production, pepper yield, and the occurrence of BER. However, BER have appeared in high temperature conditions on this fertilization level in summer period. This is significant for further studies to increase our understanding of the complex interactions that might occur in relation of BER appearance and nitrogen fertilization.

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