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A 2-year field experiment was carried out to assess the effects of various rotational systems on crop yield, crop water use (CWU) and water use efficiency (WUE) in a semi-arid region of Central Anatolia. Five crops (winter lentil, Lens culinaris L.; chickpea, Cicer arietinum L.; sunflower, Helianthus anuus L.; spring lentil, Lens culinaris L. and winter wheat, Triticum aestivum L.) and fallow were rotated with winter wheat. The experimental set-up involved a rotation of alternative crops (2003-2004) and wheat (2004-2005). Similarly, wheat plots in the 2003-2004 season were then planted with alternative crops in the 20042005 season. This experiment took place during the last 2 years of a 21-year long field experiment. Soil moisture was measured using a soil moisture neutron probe, and then soil water storage (SWS) of the plant root zone was calculated up to the depth of 90 cm using precipitation and evapotranspiration values.

In the first year, the highest SWS throughout a depth of 90 cm from sowing was determined to be in the fallow plot (171 mm), followed by winter wheat and winter lentil with 153 and 150 mm, respectively. In the second year, high SWS values were determined for winter lentil (163 mm), fallow (156 mm) and spring lentil (151 mm). The CWU of wheat changed depending on the preceding crop; the highest CWU (254 mm) was obtained in the fallow plot in the first year and in the plot of winter lentil (290 mm) in the second year. The average over 2 years showed that fallow treatment had the highest CWU, 271 mm. The highest crop yield was recorded for wheat, with an average of 2243 kg ha(-1) over the 2 years in fallow, followed by spring lentil (2232 kg ha(-1)) and chickpea (1943 kg ha(-1)). These differences were not statistically significant. The highest ME of wheat was obtained in the preceding spring lentil treatment with 9.4 kg/(ha mm(-1)), followed by chickpea and fallow treatments with 8.6 and 8.4 kg/(ha mm(-1)), respectively. On the other hand, WUE in the continuous wheat plots was the lowest, with a 2.3 kg/ (ha mm(-1)) average over 2 years. According to the 2-year experimental results under the conditions in Central Anatolia, compared to fallow spring lentil was the most promising crop among the alternative crops for the two-course rotation system in terms of ME and yield. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.