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 accounts for leaf number and tiller population density.
2. Ascertain how partial and complete stubble removal, and plant growth regulators 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:

Predictable patterns of leaf and tiller development were evident in both seedling and established fields of all major perennial grass seed crops grown in the Pacific Northwest. Nevertheless, staging of established stands by using leaf development characteristics was not adequate to track progress toward crop maturity prior to reproductive development of the plant. Under dryland production conditions, perennial ryegrass seed crops are under moderate to severe water stress during the critical early regrowth period in most years. Water stress during regrowth of the crop was manifested as reduced tiller production. Complete stubble removal in creeping red fescue reduced rhizome production and improved flowering to levels comparable to field burning, but reduced critical carbohydrate reserves. Ethylene application before regrowth consistently reduced flowering in older stands, but did not affect younger stands.

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 seed yields. Understanding how the presence of stubble affects regrowth is key to developing techniques to produce creeping red fescue and Kentucky bluegrass seed crops without fire.