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Maize is main field crop on the arable lands of Bosnia and Herzegovina (B&H). In the 2011-2015 period, maize was grown on average 189 137 ha or close to 20% of arable land. The majority of maize growing area was situated in the northern lowland region and in Republic of Srpska (RS). Considerable variation of the yearly yield was found in this period from 2.7 t ha-1 (2012) to 4.7 t ha-1 (2014), mainly under influence of weather conditions. With that regard, precipitation and temperature regimes, particularly in July and August, had considerable effects. 2011, 2013 and 2015 growing seasons were more close to usual values. However, 2012 and 2014 were considerably deviated and characterized by drought and hot stress (2012) and excessive, but for maize more favorable, precipitation and the lower temperature (2014). Six meteorological stations were selected for weather characterization as follows: Bijeljina (BI), Tuzla (TZ), Gradacac (GR), Banjaluka (BL), Prijedor (PR) and Bihac (BH). Precipitation and mean air temperatures in the period 2011-2015 were compared to the long- termmeans1961-1990 (LTM). In general, precipitation in the April-September period (LTM) was lower and temperatures higher in the eastern part (BI: 417 mm and 17.8 oC) than in western part (BI: 664 mm and 16.6 oC) of the country. These values for two deviated growing seasons were as follows: 288 mm and 20.0 oC in BI, 693 mm and 18.9 oC in BH (2012), 731 mm and 18.5 oC in BI, 1135 mm and 17.1 oC in BH (2014).

In the 15-year period 2000-2014 maize was grown in Federation of Bosnia and Herzegovina (FB&H) on the area of average 61405 ha (maize for grain 48208 ha and green maize 13197 ha). Average yields of maize for grain was 3.99 t/ha with considerable variation among the years from 2.18 to 4.92 t ha-1. In three “the poor” years (2000, 2003 and 2012) yield was less than 3.0 t/ha (average 2.66 t ha-1), while in three “the good” years (2006, 2008 and 2009) it was above 4.5 t ha-1 (average 4.74 t ha-1). Precipitation quantity in the April – September period of “the poor” years in Tuzla was 320 mm (3-year average) or 39% of the long-term mean (LTM) 1961-1990, while in “the good” years it was 492 mm. Mean air-temperature at the same period of the favorable years was 17.5 oC or for 1.0 oC lower than in the unfavorable years. The most unfavorable for maize growing in FB&H and the wide region were the growing seasons 2000 and 2012. Precipitation in April – September period (Tuzla) of 2000 was only 282 mm or 54% of LTM. Also, in three summer months (June-August) precipitation was only 98 mm or third part of LTM, while air-temperature was 22.0 oC or for 4.0 oC higher than LTM. Under these unfavorable conditions, maize yield in FB&H was only 2.18 t ha-1. The growing season 2012 was similar to 2000 and especially dry was in July and August (8 mm precipitation and mean air-temperature 23.6 oC or for 4.2 oC above LTM). Maize yields in Tuzla Canton in 2005 - 2012 period were in range from 2.6 t ha-1 in 2012 to 4.4 t ha-1 in 2008 and 2009. However, by statistical analysis were found significant negative correlation only between yield and monthly temperature as follows: August -0.68** , April-August -0.52* (in FB&H), June -0.62*, July -0.72** (in TC). Alleviation of unfavorable effects of “poor” years for maize yields is possible by irrigation and by adequate soil management (ploughing and addition of majority NPK fertilizers in autumn instead of spring, weed control, growing more drought tolerant hybrids etc.).

Maize is main field crop on the arable lands in Croatia and Bosnia and Herzegovina (B&H). In the 2001-2010 period, maize was grown on 333736 ha (average yield 6.50 t ha-1) in Croatia and 195800 ha (4.42 t ha-1) in B&H. Yield variations among years were from 3.86 to 7.98 t ha-1 and from 2.74 to 5.13 t ha-1, respectively. Aim of this study was survey of maize yield and weather data (precipitation and mean air-temperature) in Croatia and B&H in the 2013, 2014 and 2015 growing seasons. Average yields of maize were 6.5, 8.1 and 6.5 t ha-1 (Croatia), 4.0, 5.0 and 4.1 t ha-1 (B&H), for 2013, 2014 and 2015, respectively. The 2014 growing season was very favorable for maize growth. Precipitation and temperature in April- September period were as follows: 520 mm and 18.2oC (Osijek), 910 mm and 17.2oC (Varazdin), 731 mm and 18.5oC (Bijeljina), 1228 mm and 18.0oC (Banja Luka). These precipitation values are higher for 41% (Osijek), 75% (Varazdin and Bijeljina), and 116% (Banja Luka) compared to averages 1961-1990. In extremely unfavorable 2012 (yield 4.34 and 2.74 t ha-1, in Croatia and B&H, respectively), precipitation and temperature at the same period were 293 mm and 20.0oC (Osijek), 461 mm and 18.8oC (Varazdin), 288 mm and 21.0oC (Bijeljina), 488 mm and 20.1oC (Banja Luka). However, in 2013 and 2015, yields, precipitation and temperature regimes in both countries were more close to average values. Considerable variation of precipitation in the short 2012 -2014 period and higher temperatures are in accordance with climate change.

Climate changes, especially precipitation and temperature regimes, have often adverse influences on field crop yields. Based on 5-year data maize for grain is main field crop in Croatia (302 406 ha) and Bosnia and Herzegovina (B&H: 189 557 ha) and covering 34% (Croatia) and 42% (B&H) of used (882 752 ha and 447 181 ha, respectively) arable lands. The harvested areas of maize among years are mainly similar, while yield variation is considerable and in range from 4.3 t/ha to 8.0 t/ha (Croatia) and from 3.75 t/ha to 5.12 t/ha (B&H). The lower precipitation and the higher air temperatures, particularly in July and August, are in close connection with the lower yields. In both countries the lowest maize yields were realized in 2012 (4.30 and 2.90 t/ha in Croatia and B&H, respectively) and they were lower for 48% (Croatia) and 40% (B&H) than in 2008. Precipitation and mean air temperature in July + August of 2012 in Osijek were 52 mm and 24.5 oC (average 1961-1990: 123 mm and 20.7 oC), while in 2008 these values were 145 mm and 21.8 oC. The data for Tuzla (average 1961-1990: 138 mm and 22.4 oC) were 8 mm and 23.5 oC (2012), 156 mm and 20.8 oC (2008). The western parts of both countries had the higher precipitation and the lower air temperatures (July + August 1961-1990: 178 mm and 19.7oC in Zagreb, 159 and 21.5 oC in Banja Luka) and this trend was found also in the 2008-2012 period