ChileanJAR

Nutritives defficiencies that could limit the growth of annual Medicago spp., in the interior dryland of the subhumid Mediterranean zone of Chile, were investigated through pot experiments (Chaminade). Also, the effect of phosphorus on the growth and nodulation of Medicago polymorpha and M. arabica, was evaluáted. It was found that phosphorus is the most limiting nutrient. Calcium and potassium are defficient in the more intensively cultivated si tes. Results show that the annual Medicago spp. respond up to high concentrations of phosphorus in the soil. Finally, the role of the soil's trophic level in the productivity and relative populations of the annual Medicago spp., in the natural pastures of the subhumid interior dryland, is discused.