Tillage system, preceding crop, and nitrogen fertilizer in wheat crop: I. Soil water content

Under rainfed Mediterranean conditions, water economy must be based on a suitable choice of agronomic techniques. A 6-yr study was undertaken to determine the effects of tillage system, preceding crop, and N fertilizer on soil water at wheat (Triticum aestivum L.) planting and harvest in a Vertisol. Tillage treatments were no-tillage and conventional tillage. Preceding crops, in 2-yr rotations, were sunflower (Helianthus annuus L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), fallow, and continuous wheat. Nitrogen fertilizer rates were 0, 50, 100, and 150 kg N ha(-1) applied to wheat only. No-tillage did not provide more water at wheat planting for any of the rotations. Preceding crop effect on soil water content (SWC) at planting was as follows: fallow >= faba bean > wheat >= chickpea > sunflower. At harvest, SWC was higher in continuous wheat. Only at harvest were there differences among N fertilizer rates for SWC. Besides, measurement of SWC at harvest for sunflower, chickpea, faba bean, and fallow were performed to determine soil water storage and precipitation storage efficiency (PSE) for 2 yr. Soil water storage was higher for rotations with sunflower or fallow. Nevertheless, fallow PSE was the lowest (10%). The mean PSE was 29%. Under the conditions of this study, no-tillage is not more efficient than conventional tillage in soil water accumulation. Fallow is not a useful tool for increasing water availability.