The Effect of Root Architecture on Phosphorus Uptake in Alfalfa (Medicago sativa)

Abstract

Nutrient uptake is a multifaceted system which is not fully understood. Many components, such as plant species, root structure, cultivar, nutrient application, nutrient movement within the soil, and mycorrhizal activity all play a part. While it is generally accepted that these mechanisms each play a part, the actual affect of each is not fully known. This study compared phosphorus uptake and plant yield in alfalfa Medicago sativa under varying conditions, including: high or low root system branches; alfalfa or alfalfa/grass mixtures; and with and without added phosphorus (P) on low P-testing soil. This experiment indicates a positive correlation between P uptake and yield with added P, as well as an interaction of root structure with P supply. This interaction indicates that under low P conditions P uptake did not differ significantly in the pure alfalfa stand, while in the alfalfa/grass mixture the high branching root systems show greater P uptake. Further research is examining the mycorrhizal component of uptake and yield through an analysis of nucleotide differentiation of fungi present on the roots. These results will be compared with plant P concentration, P uptake, and yield to evaluate the correlation between P acquisition and mycorrhizal abundance and diversity.