Intercropping of winter crops with perennial summer grasses in central Spain

Resumen

The intercropping of summer-growing perennial grasses with winter crops or "Pasture cropping" is a no-tillage technique that might adapt to the climatic conditions of the central region of Spain. This system would allow growing annual crops into perennial grasses when these become inactive to increase the overall productivity of the system (grass and/or grain) while improving several environmental features. The effects of such system on the establishment and production of winter crops, the behaviour of the perennial grasses, the development of weed populations and the levels of inorganic soil nitrogen were analyzed in order to determine its feasibility. Three cropping systems (Conventional cropping, pasture cropping with Cynodon dactylon and pasture cropping with Eragrostis curvula) were assessed over two winter crops (Barley and Vetch) during two years. There were no differences in the establishment of winter crops in any management assessed. In spite of this, pasture cropping reduced winter crops yields up to 50-60% in years with low rainfall in spring. Regarding weed control, pasture cropping showed a significant suppression on total weed density and biomass when rainfall was no limited. The growth of perennial grasses was limited by the severe drought conditions and high temperatures present during the summer in some of the study years. As a result, their summer dry biomass production was highly variable ranging from zero to approximately 6 Tons/ha. Pasture cropping management recorded a reduction in inorganic N content that ranged from 37% to 64% compared to conventional management, regardless of the perennial species used. In conclusion, the pasture cropping technique would not adapt to the environmental conditions of central Spain. Future work should be directed at investigating the effects of managing irrigation to avoid or reduce yield losses for competition between crop and pasture and the use of legume as a perennial crop instead a tropical grass