ANALYSIS OF CLIMATE ELEMENTS IN THE NORTHEASTERN REGION OF CROATIA FOR THE PURPOSE OF DETERMINING IRRIGATION REQUIREMENTS OF MAIZE AND SOYBEAN ON DRAINED SOIL.

The aim of this research was to determine crop water requirements (soil water deficit) in years with average precipitation amounts and dry years in order to estimate the decline in maize and soybean yields in such years, as well as to determine the actual yields of maize and soybean in years with/almost average precipitation amount and both in dry and wet years. In the examined 20-year period, annual air temperature in the northeastern region of Croatia increased by 1.7o C, while a very slight negative trend in annual precipitation amount, -0.18 mm/20 yrs, has been identified. The determined soil water deficit in the years with multi‒annual mean of precipitation amount ranged from 139.3 mm (soybean) up to 152.7 mm (maize), while in the dry years, water deficit ranged from 299.7 mm (soybean) up to 316.3 mm (maize). The estimation of yield decline (%) in the years with multi‒annual mean of precipitation amount ranged from 21.5% (soybean) up to 33.9% (maize), while in the dry years it ranged from 40.5% (soybean) up to 65.0% (maize). In the 5‒year period, the lowest yields of both crops were in the year with the lowest annual precipitation amount (maize 5,175 t.ha-1 and soybean 2,153 t.ha-1), while the highest crop yields were when the annual precipitation amount was on a par with the average value (maize 9,652 t.ha-1 and 9,817 t.ha-1 and soybean 3,454 t.ha-1 and 3,584 t.ha-1). In the year with the highest precipitation amount, crop yields ranged between the value of the yield aged in the drought and the year with the average precipitation amount (maize 8,875 t.ha-1 and 8,929 t.ha-1 and soybean 3,188 t.ha-1 and 3,202 t.ha-1). Yield decline problem in the northeastern region of Croatia in dry years can be largely solved through irrigation (need to build/expand the irrigation system) and better maintenance of the existing drainage system because the problem can appear during the period with heavy rains. [ABSTRACT FROM AUTHOR]