Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/17/2004
Publication Date: 5/1/2005
Citation: Kovar, J.L., Kelly, J.M., Schroeder, P.D., Wang, Z.Y. 2005. In-situ dynamics of four macronutrients in the rhizosphere soil solution of maize, switchgrass, and cottonwood. In: Hartmann, A., Schmid, M., Wenzel, W., and Hinsinger, P., editors. 2004 Rhizosphere, Perspectives and Challenges - A Tribute to Lorez Hiltner, September 12-17, 2004, Neuherberg, Germany. p. 192.
Technical Abstract: Knowledge of the spatial and temporal variability of nutrients in rhizosphere soil solution, and the effect on nutrient uptake by various plant species within an agricultural landscape is limited. The recent development of a technique to sample rhizosphere soil solution in situ was an important step in improving our ability to understand nutrient dynamics in rhizosphere soil. In this study, a mini-rhizotron experiment was conducted with juvenile maize (Zea mays L.), cottonwood (Populus deltoides L.), and switchgrass (Panicum virgatum L.) grown for 10 days in a Kennebec silt loam (Cumulic Hapludolls). Micro-samples ('200 µl) of rhizosphere and bulk soil solution were collected at 24-hour intervals with micro-capillaries at a tension of -100 kPa, and analyzed for phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentrations via capillary electrophoresis. Plants were harvested at the end of the 10-day period, and tissue digests analyzed via Inductively Coupled Plasma (ICP) spectroscopy. During the 10-day period, rhizosphere solution P and K concentrations decreased by approximately 24 and 8%, respectively, for maize, and 15 and 6% for cottonwood. For switchgrass, solution P and K remained relatively constant. Calcium and Mg concentration gradients did not develop for any of the species. Shoot P, K, and Mg concentrations of maize were 57 to 79% higher than those of switchgrass and cottonwood, whereas cottonwood shoot Ca concentration was 41 to 57% higher than that of maize and switchgrass. Nutrient accumulation efficiency of cottonwood was 37% higher for P, five- to 20-fold higher for Ca, and one- to five-fold higher for Mg than that of maize and switchgrass. However, K accumulation efficiency of maize was two- to five-fold higher than that of the other species. These results further demonstrate that differences in rhizosphere solution chemistry are both element- and species-specific. Characterization of rhizosphere nutrient dynamics has been initiated under field conditions.