Title:

Influence of Post-harvest Leaf and Tiller Development on Seed Yield in Grass Seed Crops

Objectives:

1. Investigate the physiological nature of leaf and tiller development in grass seed crops prior to vernalization and identify potential relationships to seed yield. Develop staging system for fall vegetative development of grass seed crops that takes into account both leaf number and tiller population density.

2. Ascertain how partial and complete stubble removal, and plant growth hormones influence post-harvest vegetative development and subsequent seed yield of fine fescue and Kentucky bluegrass seed crops.

3. Develop educational programs for producers and agricultural support industries to disseminate information produced by the study.

Principal Investigators:

Thomas G. Chastain, Oregon State University
William C. Young III, Oregon State University
Gary M. Banowetz, USDA-ARS

Cooperators:

Gary Kiemnec, Oregon State University
Glen Murray, University of Idaho
William Johnston, Washington State University

Abstract:

Removal of all stubble without burning in creeping red fescue produced the same tiller regrowth, rhizome production, and flowering responses as open-field burning. Partial stubble removal (one and two inches) reduced tiller number, increased rhizome weight, and reduced fertile tiller production. All nonthermal management practices evaluated to date reduce creeping red fescue seed yield. Ethephon application reduced fertile tiller production in creeping red fescue providing possible evidence of the role of ethylene in reducing seed yield in this species when stubble is not burned. The order and rate of tiller appearance was similar in seedlings of all major perennial grass seed crop species grown in the Pacific Northwest. Three surges in leaf development during fall regrowth were observed in perennial ryegrass and tall fescue tiller populations.

Justification:

The fate of tillers determines the productivity of grass seed crops. Since tillers are short-lived, the ability of the plant to persist from year to year depends on its genetically determined capacity to replace dead tillers. The post-harvest period of tiller regrowth is a critical phase of seed crop development that can have a strong influence on seed yield. If we could understand how development during the regrowth period influences the flowering and seed yield potential of grass seed crops, then we could develop management strategies for enhancing crop regrowth. Understanding how the presence of stubble affects regrowth is key to developing ways to produce creeping red fescue and Kentucky bluegrass seed crops without fire. Staging systems are essential for quantifying development of tillers so that the impact of management can be known, and to improve the timing and efficacy of cultural practices for protection of the environment.