Harvest Conditions On Newly Seeded Alfalfa
Alfalfa (“Queen of Forages”) has been considered one of the most important forage-legume species in South Dakota. In general, it is a deep-rooted legume that grows best in moderate to well-drained soils. Under optimum growing and soil conditions, along with proper management, yields can exceed from 3 to 4 tons DM/acre of hay on irrigation, whereas, 1 to 2 tons DM/acre are produced on dryland. Some characteristics of alfalfa are: (1) crown-former; (2) high yield; (3) high quality; (4) persistent; (5) very deep taproot; (6) drought hardy; and (7) winter hardy. Understanding how alfalfa grows, harvest conditions, and direct relationship with its storage of carbohydrates in the root system are important aspects to determine its overall production throughout the state.
Seeding-Year Harvest Management
For production, a selection of harvest schedule with the decision on quality of forage desired should be considered. Most of harvest schedule decisions will include: (1) date of cut; (2) stage of maturity; (3) interval between cuts; and (4) cutting height. The interval between the stage of maturity, yield, forage quality, and persistence is frequently used to decide when to harvest alfalfa. For spring seedings without a companion crop two harvests can generally be made the first year. This all will depend on adequate rainfall patterns and optimum levels of soil nutrients (Figure 1).
Figure 1: Example of alfalfa production at various pH levels after the first cut. Source: Adapted from Undersander et al., 1994
First Harvest Seeding Year
- In general, with first harvest, we refer when alfalfa is seeded in the spring and we plan to take one to two cuttings in the same year.
- Should be done after flowers begin to appear, allowing greater energy reserves in the roots. Generally, alfalfa will reach this stage of development between 60 and 70 days after emergence
- Harvesting delays during this stage will cause large reductions in quality and decline in total yield over the season, because fewer harvests are possible.
Second Harvest Seeding Year
- Before the first day of September to ensure an adequate storage of energy reserves for winter, or it could possibly be delayed until after the first killing frost in the fall.
- Some key aspects to harvest alfalfa include good root development and plant vigor. If alfalfa stands look vigorous and the roots are well developed, spring cutting can be made at bud early bloom. However, if plants are relatively small and poorly developed, it might be better to wait until mid-bloom stage before harvesting (Figure 2).
Harvesting Established Alfalfa Stands
This will be based on desired quality and life expectancy. First cutting in spring can be made when the crop is in the bud to early-bloom stage. During this time there is usually less environmental stress due to drought or frost, and alfalfa can tolerate early cutting when compared to fall second cutting. For producers, harvesting at the bud stage could allow them to get more cuttings per year, increasing production and quality of the forage. However, in order to cut at the bud stage, there should be optimum levels of pH, phosphorous, and potassium, so plants are allowed to reach the first bloom stage at least once during the year. Second, third, and fourth cuttings made during the summer should be made when the crop is in the bud to early-bloom stage of development.
Figure 2: Example of alfalfa storage at some stages of development. Source: University of Georgia College of Agriculture and Environmental Sciences
Fall Harvest Management
During this period of time (late summer and early fall), alfalfa plants are preparing for winter developing two major things: (1) cold resistance, and (2) storage for energy reserves in its root system. Harvesting alfalfa during this period of time will probably allow a few weeks of regrowth before the first killing frost. Something important to take in consideration will be the risk of winter injury by environmental factors such as: (1) snow cover; (2) soil moisture; and (3) temperature. Making the decision to cut in the fall requires using the above conditions as necessary to avoid the risk of winter injury. Another recommendation would be not to harvest fields that have a history of frost heaving or accumulating little snow cover. Overall, fall harvesting increases the risks to stand loss compared with not fall harvesting. Some of the risks can be minimized by:
- Taking at least one harvest during the summer at 1/10 bloom.
- Fall harvesting young stands (less susceptible to winter injury).
- Maintaining high soil fertility levels.
- Fall harvest alfalfa varieties that have good disease resistance and winter- hardiness.
source : SDSU