Harvest conditions on newly seeded alfalfa

News
Jun 28, 2013
by WLJ

Alfalfa has been considered one of the most important forage-legume species, explains Karla A. Hernandez, a South Dakota forages field specialist.

“In general, it is a deeprooted legume that grows best in moderate- to welldrained soils. Under optimum growing and soil conditions, along with proper management, yields can exceed from 3 to 4 tons of dry matter per acre of hay on irrigation to 1 to 2 tons of dry matter per acre are produced on dryland,” Hernandez said.

She says that understanding how alfalfa grows, harvest conditions, and the 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, she encourages producers to develop a harvest schedule based on producing the highest quality forage.

She says most 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,” Hernandez said.

Depending on the maturity of the alfalfa stand, Hernandez shares some tips to consider: 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.

Harvesting established alfalfa stands

She says 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,” Hernandez said.

For producers, she says 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.

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,” Hernandez said.

She says growers should take the following into consideration to avoid winter injury due to environmental factors including: (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,” she said.

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. — WLJ

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