Extending Irrigated Alfalfa Stand Life and Long-Term Profitability by Alteration of Late-Season Harvest Schedules

Extending Irrigated Alfalfa Stand Life and Long-Term Profitability by Alteration of Late-Season Harvest Schedules

Summary

Apparent increases in first cutting yield due to late-season harvest schedule followed the same trend observed in past years, although results were not statistically significant. Overall alfalfa yield was increased by a modified harvest schedule if the final cutting was delayed but utilized, but decreased if the final cutting was not utilized. In a separate study, first 2005 cutting yield and stored carbohydrate levels were greater in plots in which the final 2004 cutting was delayed until after October 15. Fusarium sp. was the only pathogen isolated from the plots during the third harvest year.

Objectives/Performance Targets

Research Objectives:

1) Determine if modification of present late-season alfalfa harvest practices will affect stand persistence.

2) Determine relationships and interactions between late-season harvest management practices and alfalfa varieties on non-structural carbohydrates, alfalfa stem nematodes and root and crown rot diseases of alfalfa.

3) Conduct an economic analysis of traditional and modified late-season harvest practices to determine how long term profitability is affected by management changes.

Education/Outreach Objectives:

1) Demonstrate to growers the effectiveness and economics of modification of late-season harvest management practices in maintaining alfalfa stands.

Accomplishments/Milestones

• Thirteen harvest timing demonstration strips involving seven growers have been conducted to date. The average first-cutting yield increase was 30% following delayed fall harvest in four cutting systems. There has been no impact of fall harvest date on subsequent yield in 3-cutting systems.

  Three years of data have been collected from long-term fall harvest management/variety studies at two locations. Significant yield differences exist between late season harvest schedules, variety dormancy and pest resistance in 4-cutting systems. There have been no significant differences between treatments in the 3-cutting system.

  Two experiments designed to evaluate the impact of fall harvest date on subsequent first cutting yield demonstrated a strong relationship in both years. In 2003/04, first cutting yield increased by 0.8% for each day the previous fall harvest was delayed after September 29. In 2004/05, yield was greatest in plots that were harvested after October 15.

  This project was presented to growers in 2005 at two field tours, three workshops. More than two hundred growers have seen or discussed the demonstration strips and research plots during the past year.

  A one-year project extension will allow for a fourth year of data collection, which will strengthen the case to present to growers. The data collected will be used in extension efforts to publicize the impacts of late-season harvest management on alfalfa yield, persistence and economics.

  The appearance of a previously unknown species of stem boring weevil in western Colorado alfalfa has caused an increase in interest in evaluating the springtime vigor of alfalfa fields. Research and extension efforts regarding the biology and management of this new pest will be incorporated into this program.

Impacts and Contributions/Outcomes

Many growers who have had discussions regarding the impact of timing of the final alfalfa cutting on subsequent yield and stand persistence are altering harvest schedules on at least a portion of their acreage. Several growers that skipped their final 2004 cutting due to weather were impressed by the vigorous growth of their fields during spring greenup in 2005, and delayed their 2005 final cutting to try to duplicate the effect in 2006. We feel that the major impact of this project will come in the next few years, after the longer term data collection from the field experiments has been concluded.

Collaborators: