Alley cropping: developing a suitability index of different shrub species grown under semiarid Mediterranean conditions

Abstract

In dry environments alley cropping has the potential to diversify the production through integration of shrubs/trees with crop and livestock. This study investigated the performance of various shrubs species integrated within field crops consisting of wheat, vetch and barley in Mushaqqar Research Station, Jordan. Each crop was planted in 10 m wide and 100 m long, while shrubs were planted in between the crops’ alleys. Shrub species incorporated included leguminous species (Medicago arborea, Colutea istria and Coronilla glauca), Atriplex species (A. canescens, A. nummularia, A. undulata) and spineless cactus (Opuntia ficus-indica). Shrubs were clipped to 25 cm aboveground in the summer of 2018. An alley cropping suitability index was formulated based on four factors for each shrub: stem diameter, stomatal conductance, plant height and estimating shrub biomass production. The results showed that the Atriplex species showed higher suitability index after clipping. A. canescens recorded the highest plant height, stem diameter, stomatal conductance and estimated biomass production across all three field crops. While leguminous species such as C. glauca will improve the soil nutrient status in an alley cropping system, their low biomass productivity in the beginning of summer (May/June) results in a low suitability index as they are not reliable for providing supplement forage for livestock. Therefore, when implementing alley cropping systems, a tradeoff should be considered for shrub species which produce high forage biomass for livestock sustenance and are accessible to livestock after harvesting crop, or shrubs which improve soil nutrient status for improving field crop growing conditions.