Conservation Agriculture to increase water productivity of durum wheat under semi-arid Mediterranean conditions

Tunisia is facing twin challenges, namely, food and water security, which are pressing now and likely to increase in the future mainly due to climate change. To face this alarming situation, the implementation of conservation agriculture (CA) remains crucial for facing interannual variability in climatic conditions that impact durum wheat production. The current study aims to assess the effect of tillage systems on grain yield (YLD), above-ground biomass (AGB), and crop water productivity. The experiment was conducted at the Bourabia experimental station of the National Institute of Agricultural Research of Tunisia, located in a semi-arid zone of Tunisia, during cropping seasons (2013-2014 and 2014-2015). At harvest, above-ground biomass, yield, and yield components of durum wheat (Maali cultivar) were determined. Tillage practices included no-tillage (CA) and conventional tillage (CV). Preceding crops were either common vetch or bread wheat. The N rates applied were: 0, 75, 100, 120, and 140 kg N ha⁻¹. The experiments were laid out in a ‘Split-Plot’ design with three replications. The results show that the relationship between water productivity (quantity of water used to produce a ton of grain) and grain yield illustrated a better water valorization in CA system. For yields lower than 2 t ha^-1, more water was needed in AC than in CV to produce the same amount of grain; Whereas for yields greater than 2 t ha^-1, the opposite was revealed. On the other hand, grain yield and above-ground biomass were higher under CA compared to CV (+806 and +2468 kg ha⁻¹ for YLD and AGB respectively) in the dry growing season (year2), while in the favorable growing season (year1), the opposite was observed (-315 and -604 kg ha⁻¹ for YLD and AGB respectively). This feature illustrates the positive effect of CA in low-rainfall growing season due to good soil infiltration and reduction of evapotranspiration. Therefore, these findings provide evidence of the positive impact of CA on rainfed durum wheat under semi-arid Mediterranean conditions.