Forage production and nitrogen fixation in Medicago polymorpha L. managed as mixed sward or pure stand.

This paper refers to the quantification of forage production and nitrogen fixation in burr medic (M. polymorpha L.) under different management (pure stand undisturbed herbage accumulation vs. grazed mixture sward) in North-Sardinia (Italy). The potential of nitrogen fixation in burr medic was estimated by the 15N isotopic dilution method. In late spring forage mass ranged from 2.5 to 8 tons ha-1 of DM in mixture and pure stand with a burr medic contribution of 50 and 98% respectively. The corresponding estimates of fixed nitrogen were 52 and 154 kg ha-1, respectively.