Drought occurrence and irrigation requirements in central Vojvodina

Soil and climate conditions in Vojvodina Province, the largest granary in Serbia located at the northern part of the Republic, are very favourable for successful crop production. The most common type of soil is chernozem, with favourable chemical and water-physical properties, where field and vegetable crops can be grown in conventional and organic production without restriction, therefore achieving high yields of good quality. Generally observed, climate conditions in Vojvodina are also suitable for crop production. Limiting factors are the sum and especially the distribution of precipitation, both in years and seasons, and in shorter periods, especially if they coincide with plants’ critical stages for water. Therefore, it is necessary to monitor and analyse all the parameters in the process of crop production in order to spot the negative trends that could threaten the stability and quality of production. In that case, it is necessary to react timely with measures that will stop or slow down the negative processes in order to maintain or repair existing state of production. This paper analyses the climate parameters that significantly affect water and nutrient regime of soil and crops. Average daily air temperatures were particularly analysed as a factor on which a potential evapotranspiration and crop needs for water depend, as well as the precipitation, which is the main source of crops’ water supply. Mutual influence and connection of these climate parameters, crops and soil affect the occurrence of drought and need for irrigation as a measure for the most successful regulation of water deficit for successful crop production. The sum and distribution of precipitation, as well as the average daily air temperatures, were analysed per years, seasons and months for the period of 30 years (1987-2016) in Bački Petrovac, which is located in central part of Vojvodina (φN 45° 20´, λE 19° 40´, 82 mnm). Based on the analyses, potential plant evapotranspiration was determined using Thornthwaite and Türc method, in order to define crops’ water supply through de Martonne aridity index (IdM), as well as drought occurrence, its duration and intensity in this area. A high percentage of dry years were found by the analysis of meteorological data for central Vojvodina. Drought occurrence due to uneven distribution during growing period is even more frequent and occurs in almost all years, as well as in those with average and above average precipitation sum. These results were compared to the meteorological data on precipitation and mean daily air temperatures for Bački Petrovac from previous years (1948-1990), which analyses were shown in Osnovi zaštite korišćenja i uređenja poljoprivrednog zemljišta opštine BačkiPetrovac (Basics of protection and use of agricultural land in the municipality of Backi Petrovac) (Hadžić et al., 1996). Increase of mean daily air temperatures can be seen in all months, especially during growing period (1.0-1.4°C), and averagely 0.8°C or 7.3% per year. Thus, potential evapotranspiration (ETP) was increasedas thermic process depending on air temperature. The lack of water needed to meet the crop needs for water was increased, especially in July and August, in spite of precipitation sum that was at the same level or insignificantly higher than the sum in previous period (346.5 mm in previous period versus 371.4 mm in the last thirty years for growing period).