Four Tips for a Great Lucerne Stand

Everett Thomas is an agronomist based in New York State. He has worked with Cornell University Cooperative Extension and the William Miner Agricultural Research Institute. He edits the Miner Institute’s Farm Report newsletter.

Reprinted with the kind permission of Agrimedia, New Zealand.

Image of a healthy lucerne field

Article written by Everett Thomas (abridged)

LUCERNE IS TRULY ‘THE QUEEN OF FORAGE CROPS’, BUT CAREFUL MANAGEMENT IS NEEDED DURING SEEDLING ESTABLISHMENT.

This includes a firm seedbed, properly calibrated seeding equipment, enough seeds per square metre to give maximum yield potential, careful variety selection and making sure that soil pH and fertility are at least at the recommended levels.

A great stand of lucerne begins with a proper start and then careful management during its first year of production. Here are some suggestions that can make the difference between ‘good’ and ‘great’.

ONE:

The seedbed should be smooth and firm. Many years ago I was in Minnesota and remarking at the excellent stands of lucerne farmers were achieving and asked for their secret.

They said that they didn’t have a secret, but were firming their seedbeds with a roller or culti-packer (Cambridge roller) before coming in with the seeder or grain drill. If the drill didn’t have press wheels to pack each row during the seeding process the field got a second rolling, or culti-packing, immediately after sowing.

This had two advantages. First, it resulted in a firm seedbed and, therefore, a more uniform stand.

How firm? An old guideline is that just before seeding a farmer walking across the field shouldn’t make an impression any deeper than the depth of the sole of his boot. (This is a useful guideline except, perhaps, if the farmer is overweight and has small feet!)

Another tip I recently heard from a lucerne breeder, based in Idaho, is that you should be able to bounce a basketball on a properly firmed seedbed.

The second advantage of a firm seedbed is that there is less loose soil to be picked up during mowing, especially if a disc mower or mower-conditioner is used.

The action of the discs can result in a slight vacuum that picks up loose soil. Some wide mowers can scalp the soil surface, especially when lucerne is mowed to a 2.0-3.0 cm stubble height.

This is why in the US the average ash content of virtually all hay crop silage samples submitted to forage testing labs has increased along with the now almost universal use of disc mowers.

TWO:

Make sure that the seeding rate is adequate to provide a proper stand without wasting seed. Just because the drill or seeder was calibrated a year or more ago doesn’t mean the setting is right for this year’s seed.

This is particularly important if you are using coated seed. The key is to have the correct population of pure live seed. With the increased use of one or more types of seed coatings, however, you may have to increase the seeding rate by up to about 33 percent. Research has found that only 50 to 75 percent of planted lucerne seeds will produce a plant, and this is why recommended seeding rates have many more seeds per square metre.

The recommended lucerne seeding rate in the US is about 17 kg/hectare. Using a 60 percent success rate, this results in about 500 seedlings per square metre. Seeding rates in Australia are somewhat lower than in much of the US and depend both on rainfall and whether the crop will be irrigated.

THREE:

Variety selection is important, and there are differences between the lucerne varieties for insect and disease resistance and winter dormancy.

It is important to be aware of the insect pests and diseases affecting lucerne in your area, and then select the variety that best combines pest resistance and the desired winter growth habit (winter dormancy) for your fam.

One of the most serious diseases in New Zealand is phytophthora root rot, a fungal disease that destroys the root system. Selecting a phytophthora-resistant variety is especially important for lucerne grown on heavy soils and/or under flood irrigation.

Varieties with winter growth ratings of 8, 9, and 10 usually grow through the winter while dormant varieties (rated 3 and 4) stop growing during late autumn and start again in spring. Popular lucerne varieties in warmer areas are highly winter active with vigorous seedlings, while dormant varieties often persist better under tough conditions.

FOUR:

Maintaining a good stand of lucerne requires good harvest management, but it’s almost impossible to fully meet the nutritional needs of the plant while harvesting the quality of lucerne needed by today’s high-producing dairy cows.

Lucerne stores the carbohydrates needed for the following crop in its tap root. The plant does not completely accumulate nutrients in the root until it is in bloom, but to harvest ‘milk cow quality’ lucerne, farmers often mow the crop when it is in the late bud stage.

A single harvest at the late bud stage isn’t too harmful, but continued harvests at the bud stage eventually take their toll. The result is lower yields and, sometimes, a shorter life for the stand.

This is one reason for the recent interest in the US in reduced-lignin lucerne varieties. Harvesting low-lignin lucerne can be delayed until early bloom while maintaining good forage quality.

Research at the University of Wisconsin on conventional lucerne varieties over a three-year period found higher annual yields with three harvests per season than with four harvests. Part of the higher yield was because of better plant nutrition, but part was probably due to less field traffic from one fewer harvest per season. Every trip we make over a field of lucerne causes a bit more damage to the crowns of the plant.

Between this, and the less than adequate root carbohydrate levels, lucerne doesn’t die – we kill it through our aggressive (but necessary) harvest management.