Differential response of forage legumes to phosphorus application

Lotus glaber is a perennial Mediterranean forage legume that has colonised the temperate humid Flooding Pampa of Argentina. It thrives in phosphorus-d eficient soils and produces significant herbage increments when fertilised with small amounts of phosphorus. This species has previously responded to phosphorus addition differently than other legumes, and we hypothesised tha t the response to phosphorus fertilisation should depend on the expression of morphogenic and functional traits such as leaf area, plant biomass alloc ation, and relative growth rate, associated with a better nutritional statu s of tissues of high metabolic activity. We compared biomass productivity, morphogenic characteristics, phosphorus status, and phosphorus utilisation efficiency oft. glaber, Trifolium pratense, and Ornithopus micranthus, at d ifferent levels of phosphorus fertilisation. The L. glaber phosphorus respo nse pattern combined a higher aptitude to produce biomass in phosphorus def icient soils and a declining nutrient utilisation efficiency when soils are increasingly fertilised. O. micranthus showed the expected response of spe cies from infertile soils, low productivity, no variation in morphological and functional traits, and a low phosphorus demand. In this sense, T. prate nse showed opposite behaviour with sustained increase in many traits with P application. Phosphorus concentration and biomass allocation within the pl ant are involved in this response to phosphorus fertilisation.