title: Soil solution phosphate, root uptake kinetics and nutrient acquisition: implications for a patchy soil environment.
abstract: The importance of increased root phosphate (P) uptake kinetics, root proliferation and local increases of soil solution P (P1) for P acquisition from fertile soil microsites was explored with a simulation model and calculated uptake was compared with experimental data. Based on the partitioning of added P in microsites to P1and P adsorbed on soil particles and the results of a dual-isotope-labeling experiment (Caldwell et al. 1991a), acquisition of P from the fertile microsites was some 20 X that of uptake from an equal volume of soil which received only water. Simulations were in general agreement and also showed that elevation of root P uptake kinetics could contribute more to the increased acquisition than did root proliferation under these circumstances. Although increased physiological uptake capacity for P has generally been considered to be of little benefit because of diffusion limitation, in patchy soil environments selective elevation of P uptake kinetics in fertile microsites may be of considerable benefit. These tests were conducted in calcareous soil which releases much less P into the soil solution than do many other soils. In many noncalcareous soils the benefits of selective elevation of root uptake kinetics would likely be greater.
authors.affiliation: Department of Range Science and the Ecology Center, Utah State University, 84322-5230, Logan, UT, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Caldwell
authors.affiliation: Department of Plants, Soils and Biometeorology, Utah State University, 84322-4820, Logan, UT, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Dudley
authors.affiliation: Department of Plants, Soils and Biometeorology, Utah State University, 84322-4820, Logan, UT, USA.
authors.forename: B
authors.initials: B
authors.lastname: Lilieholm
keywords: Agropyron desertorum; Artemisia tridentata; Root kinetics; Root proliferation; Soil phosphate