The recent agricultural policies in the Sudan have focused on mechanized large-scale, rainfed agricultural ventures achieving increased grain production through expansion of the cultivated area only, not through increased per unit yield. The total harvested area increased steadily from about 4 . 5 million ha in 1961 to about 14 million ha in 1996, with great year-to-year variations of harvested areas, and therefore total yields, revealing a fragile balance between production and need. Per unit yields of all crops are steadily decreasing, currently reaching rates far below their genetic potential. The work reported here was intended to look into the causes of the ¯uctuations in yield and to propose some strategic approaches that may oer a path to sustainability of such crop production.
Several factors may be contributing to these poor yields. This study shows that loss of soil fertility and rainfall variability are among such factors. Crops yields were negatively correlated at a one per cent level of signi®cance with the cropping season indicating signi®cant decline in soil fertility. Soil fertility management and fertilizers use could therefore be of great importance in formulating proactive strategies to enhance productivity in the rainfed agriculture in the Sudan. Rainfall in dierent production subregions had dierent levels of correlation with yields of all crops. Comparison of long-term rainfall in the four subregions of the study area showed that rainfall decline had been in the magnitude of 30± 40 per cent. The western parts of the study area (Kordofan and Darfur) experienced extreme rainfall anomalies than the eastern and central parts (Gedaref and Damazin), and had suered greater periods of desiccation than the eastern and central parts. The decadal rainfall means showed below average rainfall for the last three decades in all subregions; the western parts again showing greatest desiccation.