Rising demands for food and uncertainties about climate change call for a paradigm shift in water management with a stronger focus on rainfed agriculture. The objective here was to estimate water productivity of different crops under no-till (NT) and conventional till (CT), in order to identify rotations that improve the water productivity of dryland agriculture. We hypothesized that NT and cereal crops would have a positive effect on overall water productivity. Crop yield and water use data were obtained from a 15 year experiment (1993 to 2008) on an entic Haplustoll in the semiarid Pampa, Argentina, with a rotation of wheat ( Triticum aestivum L.), corn ( Zea mays L.), sunflower ( Helianthus annus), and soybean ( Glycine max L. Merr.) . The results indicated an improved water productivity of all crops under NT compared with that of CT; however, the response of cereals (corn +1.0 kg ha ？1 mm ？1, wheat +1.3 kg ha ？1 mm ？1) was higher than that of sunflower (+0.3 kg ha ？1 mm ？1) and soybean (+0.5 kg ha ？1 mm ？1). Crop type had a higher impact on water productivity than did tillage system. In agreement with our hypothesis, cereal crops were more efficient (corn 9.8 and wheat 6.9 kg ha ？1 mm ？1) compared with soybean 2.4 and sunflower 3.9 kg mm ？1, but the economic water productivity of sunflower (0.9 US$ ha ？1 mm ？1) almost equaled that of wheat (1.1 US$ ha ？1mm ？1) and corn (1.2 US$ ha ？1 mm ？1). We concluded that the use of the synergy between NT and water efficient crops could be a promising step towards improving food production in semiarid regions.
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