Water deficit and corn productivity during the post-socialist period. Case study: Southern Oltenia drylands, Romania

摘要

Water deficit (WD) typically associated with drylands and poor land use currently represent a major limiting factor for agricultural systems in numerous regions of the world. The present study aims to analyze the relationship between water deficit and corn (Zea mays L) crop yields in southern Oltenia drylands. The study includes the post-1990 period, which is representative for Romania in terms of ample climate changes and poor land planning decisions affecting water resources. This analysis targeted the vegetation period of corn (April-September), the reference period covering a 14-year interval, from 1990 to 2003. The entire analysis was based on spatialized WD data (mm), obtained by interpolation methods used on climate data provided by regional weather stations, and agricultural yield data (tons/hectare/year), recorded in 113 administrative territorial units. Both data sets were analyzed in terms of interannual statistical relationships, established in compact climate zones delineated by Thiessen-Voronoi polygons. The results showed a clear statistical relationship between the two variables, with an average dependence of corn yields on water of approximately 65%. The range was from 55 to 78%, depending on region. The results showed an average yield decrease of 16.5 kg/ha/year for each mm rise of the WD, or loss of 1.65 t/ha/year when considering a deficit rise of 100 mm. Therefore, in the context of increasing future WD, urgent action is needed in order to reintroduce irrigation systems.