An Exploration of the Effects of Crop Rotation Regime on Modem Weed Floras

Fallow-cereal is the primary crop rotation regime used in the Mediterranean and Near East in the recent past. This may not always have been the case and legume-cereal rotation may have played an important role in certain periods. In the short-term, cultivated fallow is beneficial to soil moisture and fertility and, therefore, the subsequent cereal crop. In the long-term, however, this regime causes soil erosion and nutrient deterioration through the loss of soil organic matter. The use of legumes in a rotation regime adds soil organic matter but, in the short-term, can reduce cereal yield. Weed seeds in archaeobotanical assemblages provide the best method to identify the use of cultivated fallow and legume-cereal rotation in the past. This paper presents the results of a field-study in northern Jordan in which the effects of crop rotation regime on arable weeds are explored. The main factor affecting weed composition is location in the two main topographic zones of the study area, the hills and the plains. Crop rotation regime does have a detectable effect on weed composition, and fallow-cereal and legume-cereal rotation can be distinguished in the hills. It is difficult to distinguish the effects of location and crop rotation regime between the hills and plains because the choice of crop rotation regime is strongly correlated with location in each area.