TILLAGE SYSTEMS AND STUBBLE MANAGEMENT IN A MEDITERRANEAN-TYPE ENVIRONMENT IN RELATION TO CROP YIELD AND SOIL MOISTURE

Abstract

The effect of tillage and crop rotations can only be seen over many crop years. Crop yield and soil results are evaluated from two long-term trials, established in 1978–79 and 1985–86 to investigate various forms of tillage and the timing of such operations in various wheat (Triticum aestivum)-based rotations on a Calcixerollic Xerochrept in northern Syria. In a tillage systems trial involving two wheat–legume–watermelon (Citrullus lanatus) rotations, deep tillage showed no advantage over a shallow sweep-tillage system, either for soil moisture storage or yield increase of any crop. The zero-till system suited legume crops but gave lower productivity in wheat due to a build up of grassy weeds, and was not suitable for watermelon. Minimum tillage, with its higher energy-use efficiency and yield levels equal to or even slightly above those of deep-tillage systems, appears promising for the lowland areas of West Asia and North Africa. In a tillage timing trial, wheat in a wheat–lentil (Lens culinaris) rotation yielded best after conventional deep disc-plough tillage, but lentil yields were higher in a zero-till system.