Phosphorus and Potassium Effects on Alfalfa Yield Components, Physiology, and Stress Tolerance. (A09-berg559158-oral)
Authors:
W.K. Berg* - Purdue University S.M. Cunningham - Purdue University S.M. Brouder - Purdue University B.C. Joern - Purdue University K.D. Johnson - Purdue University J.J. Volenec - Purdue University
Abstract:
In addition to nutrient and water acquisition, alfalfa (Medicago sativa L.) roots store vast amounts of carbon (C) and nitrogen (N) that is used for initial shoot growth in spring and shoot regrowth following defoliation. Phosphorus (P) and potassium (K) fertilization enhances alfalfa yield and persistence, but the impact of P and K on storage and remobilization of these C and N pools in not known. A factorial arrangement of two P (0 and 75 kg/ha) and two K (0 and 400 kg/ha) treatments was replicated four times. Forage harvests occurred four times annually, and yield, mass/shoot, and shoots/area determined.
Roots were sampled at defoliation in mid September, and 7, 14, 21, 28, 42, 56, 70, and 80 days after shoot removal until early December. Roots also were sampled at defoliation in late June (Day 0), and 1, 3, 6, 10, 14, 21, and 30 days after shoot removal. Concentrations of sugar, starch, buffer-soluble protein, amino N pools, and vegetative storage proteins (VSP) in roots were determined. Addition of P increased utilization of starch reserves following defoliation. Roots supplied K contained less sugar throughout regrowth. Expression of genes for P transporters, sucrose synthase, and VSPs, and polypeptide profiles using SDS-PAGE also were analyzed. Enhanced shoot growth rates after defoliation resulted in greater forage yield in response to P and K application.
Speaker Information: William Berg, Purdue University, 915 West State Street, Lafayette, IN 47907;
Phone: 765-494-8070; E-mail: [email protected]
Session Information: Monday, November 3, 2003, 12:55 PM-3:00 PM Presentation Start: 2:00 PM
Keywords: Alfalfa Yield and Persistence; Phosphorus Nutrition; Potassium Nutrition; Root Physiology
