Research Journal of Agricultural Science, 45 (3), 2013 98 EFFECTS OF DROUGHT ON YIELD OF WINTER WHEAT IN LONG-TERM FIELD TRIAL AND VOJVODINA PROVINCE G. JAĆIMOVIĆ 1 , M. MALEŠEVIĆ 2 , V.AĆIN 2 , B.MARINKOVIĆ 1 , J.CRNOBARAC 1 , Dragana LATKOVIĆ 1 , Branislava LALIĆ 1 , Borivoje PEJIĆ 1 1 University of Novi Sad, Faculty of Agriculture, Sq. Dositeja Obradovića 8, 21000 Novi Sad, Serbia 2 Institute of Field and Vegetable Crops, Novi Sad, M. Gorkog 30, 21000 Novi Sad, Serbia E – mail: jgoran@polj.uns.ac.rs Abstract: In order to detect and quantifying drought (its frequency, duration and intensity), Palmer Drought Severity Index and Palmer Moisture Anomaly Z-Index were used in this paper. These indices were calculated by using monthly values of meteorological elements from meteorological station at Rimski Šančevi, Novi Sad, Serbia; for period 1965/66 to 2009/10. Also, yields of winter wheat from stationary long-term field trial, containing 20 different fertilization treatments with increasing doses of nitrogen, phosphorus and potassium were analyzed for the same region and period of time. For determining the most suitable index for quantifying effects of drought on wheat yield, correlation coefficients between two examined drought indexes and detrended wheat yields in long-term trial and Vojvodina province were calculated. Larger number of significant correlations was obtained between the wheat yields and Palmer's Z-index. On the basis of calculated r coefficients, it can be concluded that humidity/ drought conditions in October, December, March and April had the most important impact on grain yield. However, correlation coefficients in X and IV were positive, i.e. lower moisture conditions (drought) reduces yields, while in XII and III negative r coefficients indicated increase in yields at low moisture conditions. By observing the r values at different fertilizing variants in long-term experiment, it could be concluded that drought conditions in X and IV influenced all treatments more or less equally. Treatments with higher nitrogen doses were more sensitive to moisture conditions in XII, while in moisture conditions in III more sensitive were treatments without, or with small doses of nitrogen applied. Key words: drought, drought indices, winter wheat, yield, mineral nutrition, correlations INTORUCTION In Serbia wheat is grown on about 540.000 ha, with average yield of 3,7 t ha -1 and total annual production of about 2 million t. Area under wheat in Vojvodina Province is about 300.000 ha, with average yield about 4 t ha -1 and production near 1,2 mil. t. In comparison with other wheat producers in the world, Serbia is ranked as 32 out of 124 countries and 22/38 wheat producing countries in Europe, which is unsatisfactory considering favourable agro- ecological conditions (especially in Vojvodina) for wheat production. Beside lower yields, wheat production in Serbia is also characterized by high yield variation among years, which shows that our production is still very dependable from weather conditions during the vegetation (MALEŠEVIĆ et al., 2008; DENĈIĆ et al., 2009). For a higher expression of wheat genetic potential, knowing of agro ecological characteristics and adaptation measures of production to such conditions is crucial for obtaining higher and stable yields (MALEŠEVIĆ et al., 2012). Weather conditions during the life of the plant influences its growth, development and finally yield, which shows different sensibility in climatic terms and in variability between years (CHMIELEWSKI AND POTTS, 1995; ASSENG et al., 2004). Variability of climatic elements directly influences phenology, photosynthesis and other physiological processes in plants. Indirect effects on plants are manifested by changing availability of nutrients, presence of weeds, pests and diseases etc. (SOUTHWORTH et al., 2002).