Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: July 5, 2000
Publication Date: N/A
Technical Abstract: Plant root length often is correlated with P uptake because of diffusion- limited P supply in soil. We determined whether differences in P uptake occurred between alfalfa (Medicago sativa L.) populations with different root system architectures. In Experiment 1, populations representing the parental composite and the progeny from the first and second cycles of selection for either tap- or branch-rooted architectures were seeded on low-P testing soils, a sandy loam soil (Becker, MN), and a silt loam soil (Rosemount, MN). Exp. 2, at Becker, included only second cycle progeny. In both experiments, P was added to one-half of the plots by injection of potassium phosphate (monobasic) at 224 kg P/ha into the topsoil. Added P did not affect herbage dry mass in the first and second years following stand establishment but increased herbage P concentration and uptake. Progeny did not differ in root mass, but the relative proportion of thickened to total root mass was larger below 30 cm for the tap-rooted selection. Selection for either root trait improved herbage yield and P uptake compared to the parent because yield was a co-criterion for selection, but no differences in P uptake were observed under these conditions between alfalfa populations with different root system architectures.