Alternative Crop Rotations under Mediterranean No-Tillage Conditions: Biomass, Grain Yield, and Water-Use Efficiency

In Mediterranean semiarid areas, barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) are major crops because they are well adapted to limited-water environments. In this study we tested the performance of alternative rotations to the typical barley and wheat monocultures in a rainfed Mediterranean semiarid area of northeastern Spain under a no-tillage (NT) system. Four rotations were established and maintained over 6-yr period (1999-2000 to 2004-2005): a wheat monoculture (W-W-W), a barley monoculture (B-B-B), a wheat-barley-rapeseed (Brassica napus L.) rotation (W-B-R), and a wheat-barley-vetch (Vicia sativa L.) rotation (W-B-V). Aboveground biomass, grain yield, water use (WU), and water use efficiency (WUE) were measured several times every season during the study period. All the parameters studied had a strong dependence on the rainfall variability found between growing seasons. Barley under rotation performed better than barley under monoculture in yield and WUE terms. However, wheat performed as well in a monoculture production system as it did in rotation. Rapeseed and vetch failed the 80 and 35% of the growing seasons, respectively. However, in semiarid Mediterranean agroecosystems of northeastern Spain, despite the beneficial rotation effect of theses alternative crops on barley performance, economical benefit of the overall rotation is doubtful since vetch failed in 2 out of 6 yr and rapeseed failed 5 out of 6 yr.