Intensifying cereal management in dryland Mediterranean agriculture: Rainfed wheat and barley responses to nitrogen fertilisation

Under dryland systems of the Mediterranean basin, water management is widely recognised critical for improving grain yield. It has been proposed that nitrogen (N) fertilisation may be a tool to increase grain yield by increasing water use efficiency. We tested in a multilocation-multiyear study in four different areas of the Mediterranean Basin if durum wheat and barley may respond positively to N fertilisation under rainfed cultivation. The study involved 16 experiments including different genotypes of durum wheat and barley sown at Morocco, Jordan, North-eastern Spain, and Southern Italy, with different nitrogen doses applied at sowing or early in crop development from 2003/04-2007/08 growing seasons. Grain yield increased 26% in average for years, locations and species compared with their respective unfertilised controls. The increased yield in response to N fertilisation was noticeable under low (< 2 Mg ha-1) and under high yield potential cases (> 5 Mg ha-1). There were only exceptional cases with slightly negative or no responses to N fertilisation. Grain number per unit area, and not grain weight, was the main component related to grain yield. Also, total biomass at maturity was closely related to grain yield. Barley and durum wheat responded similarly to N fertilisation