Interactive effects of tillage and crop rotations on yield and chemical properties of soils in semi-arid central Spain

This study evaluates the potential of no-tillage practices in the management of soils in semi-arid Mediterranean areas from central Spain, Field experiments on the interactive effects of tillage and crop rotations on soil chemical properties and crop parameters were conducted on a Calcic Haploxeralf (non-calcic brown soil), The experimental design included the comparison of plots subjected simultaneously to (a) no-tillage or conventional tillage and (b) barley (Hordeum vulgare L. cv. 'Aramir') monoculture or crop rotations, The latter consisted of barley-vetch (Vicia sativa L.) or barley-sunflower (Helianthus annus L.) rotations, The results were analysed for 3 growing years. Irrespective of tillage systems, crop yield depended greatly on environmental conditions. Crop parameters in the no-tillage system were not significantly different from those under conventional tillage. When compared with conventional tillage, no-tillage favoured the surface accumulation of soil C as well as of available P and K. Crop rotations increased barley yield in comparison with a barley monoculture. The barley-sunflower rotation gave the greatest barley yield and improvement in soil fertility. Our results suggest that no-tillage can lead to a progressive improvement in soil nutrient status, but have little or no effect on crop parameters; the latter may be successfully controlled through suitable crop rotations. Of the factors examined, the environmental conditions of temperature and rainfall in the Mediterranean climate showed the greatest influence on the results between different cropping years.