The interpretation of trends from multiple yield maps

Yield data over 6 years (1993-1998) wen investigated for spatial and tempor al trends from a 7-ha field growing winter wheat and oil seed rape. The dat a were combined into two maps, which characterised the spatial and temporal variability recorded over those years. Techniques were developed to show t he maps in either the single crop form for winter wheat, or multiple crops that included the oil seed rape data. The two maps were then combined into a single classified management map, which denoted three categories, each wi th different characteristics that can have an impact on the way the held is managed. These categories were; high yielding and stable, low yielding and stable, and unstable. The spatial and temporal trends in the single crop w ere more stable than those in the multiple crops. In percentage terms, with a single crop, the proportions of these three classes were 55, 45 and 0%. respectively. For the multiple crops, the proportions were 58, 39 and 3%, r espectively. The economic significance of these areas was assessed by the p roduction of a gross margin map and further analysis showed that the catego ries returned 741, 691 and 644 pound/ha, respectively. (C) 2000 Elsevier Sc ience B.V. All rights reserved.