Best Management Practices of Tillage and N Fertilization of Winter Cereals in Mediterranean Semiarid Rainfed Conditions.

Water and N are two of the most important factors for yield production in the rainfed conditions of the Mediterranean area. They must be managed in a balanced way to maximize yield. Conservation tillage leads to larger accumulations of water in the soil and water use by the crop. This leads to a different amount of soil N mineralization and N use by the crop. The improved water status must be matched with suitable crop N nutrition for the best crop performance. However, high variability of climatic conditions, such as precipitation, makes it extremely difficult to define long-term strategies for stable farming production. The search for appropriate management practices by the combination of long-term field experimentation and simulation modeling is a key factor in the agricultural development of this semiarid area. Previous studies in the area have shown no response to N fertilization under intensive tillage. However, the effects of a tillage reduction, specially no tillage, on N fertilization have not been studied yet under Mediterranean conditions. These alternative soil management systems have been implemented in this area over the last 25 years. This study shows the effect of tillage and N fertilization on yield, soil water and N mineral dynamics, and water and N use efficiency of the crop. Data from three experimental locations in Northeast Spain (Guissona, Agramunt and Canadasnos) are used to show different types of response and to suggest the best management practices depending on the soil and climatic conditions. The CropSyst model was used to simulate growth; yield and water use of barley in a dryland cropping system under various tillage and N fertilization regimes. At the Agramunt location, an 11 year long-term experiment established in 1996 was used to validate the performance of the model and as the starting point for recommended cropping strategies.