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Adaptation of maize sowing date in Croatia to climatic changes

Maize is main field crop in Croatia (status 2008: 314062 ha or 37 % of used arable land). General recommendation for maize sowing in Croatia are the second half of April and the first half of May, for Pannonian region (PR) and Mountain region (MR), respectively. Climatic changes and global warming have considerable impacts on field crops growing. For this reason, aim of this study was testing temperature and heat units sum ([daily Tmin + daily Tmax] : 2 - 10: calculation only for days with Tmin above 10 oC) trends (comparison 1961- 1990 and 2001-2010 periods) in PR (localities: Osijek, Slavonski Brod, Krizevci and Zagreb) and MR (Gospic). Mean soil temperatures in April at 5 cm of dept for 1961-1990 were 11.0 oC and 8.6 oC, for PR and MR, respectively. However, for 2001-2010 it was increased for 2.1 oC and 1.7 oC, respectively. Heat units sum from April 25 to October 10 (expected frost- less period in Osijek for 90% of probability) in PR were 1301 and 1540, for 1961-1990 and 2001-2010, respectively. Analogical data for MR were 882 and 1158, respectively. The last spring frost date after April 15 in Osijek for 1961-1990 was found in 15 years. However, in 2001-2010 it was found only in April 15, 2001, in five years in the first ten-days of April and in four years in March. Based on these findings, April 5 and May 1 are recommending date for beginning maize sowing, for PR and MR, respectively. However, because of possible risks due to climatic excesses (for example, the last spring frost date in Osijek: May 2, 1962 and May 12, 1978), only 20 % of planned area is recommend for the „earlier sowing“.

maize sowing date ; climatic change ; global warming ; soil-temperature ; heat units ; Croatia

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