Nitrogen and Dry Matter Distribution by Culm and Leaf Position at Two Stages of Vegetative Growth in Winter Wheat

Authors

Wally Wilhelm, University of Nebraska-LincolnFollow
G. S. McMaster, USDA-ARSFollow
Dorothy M. Harrell, University of Nebraska-LincolnFollow

Date of this Version

August 2002

Comments

Published in Agron. J. 94:1078–1086 (2002).

Abstract

Knowledge of N and assimilate partitioning in wheat (Triticum aestivum L.) improves management efficacy and crop model development. Our purpose was to describe N and dry matter distribution during vegetative growth of blades, sheaths, and internodes on four culms. Winter wheat grown at the Colorado State University Horticultural Farm was sampled at Haun Stage 5 and jointing. Samples were dried, weighed, and analyzed for N. As the canopy developed and older tissue contributed more of total tissue, N concentration decreased although N mass and dry weight increased. Dry matter and N mass decreased from MC to T1 and T2 to T11, while the reverse order was found for N concentration. Dry weight and N mass decreased as culm order increased (culm age decreased), because phyctomers were smaller and fewer existed. Nitrogen concentration had the opposite trend because new tissue contained about 40 g N kg^-1 but declined as the tissue aged to 30 g N kg^-1. Initial growth of all tissues had concentrations >50 g N kg^-1 and at senescence declined to 19 g N kg^-1. Phytomer positions on different culms tended to have similar N concentrations while identical phytomers on primary tillers tended to have greater dry weights than those on the MC and secondary tillers. Phytomers tended to increase in N concentration and mass and dry weight acropetally. Results show that viewing the canopy as the interplay of appearance, growth, interaction, and senescence of culms or phytomers can increase understanding of canopy N and dry weight dynamics.