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

Late-season alfalfa cutting schedules were compared at 10 sites. When the fourth 2002 cutting was skipped, first-cutting 2003 yields were 30% greater than in traditionally managed strips. There were no differences in yield when the third cutting was skipped in three-cutting systems. Alfalfa stem nematodes were present one month after planting new alfalfa fields, but damage was minimal during the first year of growth. Varieties with dormancy ratings of 4 or 6 had greater yield than those with a 2 rating. Varieties with multiple pest resistance yielded greater than those without in the first year of the study.

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

Ten demonstration strips were established with alfalfa grower/cooperators in the fall of 2002. These strips compared the impact of modifying traditional cutting schedules on subsequent cuttings. Eight harvest strips were done in four-cutting systems and two were in three-cutting systems. Strips in which the fourth 2002 cutting was skipped had 30% greater 2003 first cutting yield than those in which fourth 2002 cutting was taken at traditional times. There was no difference in yield in the harvest strips in the three-cutting systems. Alfalfa stem nematodes were present in all fields, and nematode damage symptoms of stunting, swollen nodes, and irregular growth were more prevalent in the traditional cutting systems. In late fall samples, total non-structural carbohydrate levels were greater in all fields in which the final cutting was skipped. This trend did not carry over to spring samples, when there were no differences in non-structural carbohydrate levels.

Long-term small plot experiments were established at Fruita and Yellow Jacket, Colorado, to investigate the interactions between alfalfa variety dormancy rating and alfalfa stem nematode resistance rating with late season cutting schedules over time. The Fruita plots were planted in August 2002, with both harvest schedule treatments applied to the plots in 2003. The Yellow Jacket plot planting was delayed until May 2003 because of severe drought and limited irrigation water in 2002. The harvest schedule was limited to two cuttings in the traditional treatments, with the second cutting skipped in the alternative cutting schedule. Another small plot experiment was established near Grand Junction, Colorado. Fourth-cutting plots were taken on each of five dates in October. These replicated plots were established in a two-year-old alfalfa field. The roots were sampled for non-structural carbohydrates and yield taken on each date. First-cutting yield will be measured in the spring of 2004 to determine optimum timing for the final cutting at the site.

Impacts and Contributions/Outcomes

This is the end of the first year of a three-year study. It is too early to state definitive results, but it appears that the timing of the final alfalfa cutting can play a significant role in determining the yield of subsequent cuttings. Preliminary results have been presented at three field days, in radio interviews, and in several newsletter articles. Growers have shown interest in the project, and two of the cooperators with the 2002 harvest strips are experimenting on their own on modifying harvest schedules to increase yield. Other growers have moved from a four- to a three-cutting schedule in response to discussions about the project.

Collaborators: