As I look out my window, it is another snowy day and winter still seems to have a very firm grip upon the land. Yet, looking at the calendar I know that usually by late February and into early March there will be opportunities somewhere in the state to do some pasture renovation, particularly frost seeding.
In fact, I received a question about pasture renovation and pasture reseeding at the beginning of February, so I know there are some graziers looking ahead to our next grazing season. There are two main seeding methods that can be considered for pasture renovation; frost seeding and drilling.
The method that is used depends upon the extent of pasture renovation that is being considered, the forage species that will be seeded and the amount of forage residual cover that is on the pasture paddock.
Frost seeding works well for a less extensive type of renovation where the goal is to add one or two legume species to a pasture paddock. Frost seeding involves broadcasting seed over a pasture area and letting the natural freeze/thaw cycles of late winter and early spring help to move the seed into good contact with the soil.
A basic requirement for frost seeding success is open up the sod cover. When looking down into the sod you should be able to see down to the soil.
The broadcast seed must be able to come into contact with the soil. Frost seeding will fail when there is too much forage residual cover and the seed gets hung up in that residual.
Generally, a pasture is prepared for frost seeding by grazing it down hard, although some light tillage or a close mowing typically done in the late fall could also be used.In general, legumes work better for frost seeding as compared to grasses.
Legume seeds are typically heavier than grass seed and that may explain why they get down to the soil level better than grass seed. The advantage to frost seeding a legume such as red or white clover is that legumes “fix” nitrogen typically in excess of their own needs.
The existing grass plants use the excess nitrogen, which improves their quality as a feedstuff. Once legumes become established in a stand of pasture grass and make up approximately 30 percent of the stand, there is no need to apply supplemental nitrogen so this portion of fertilizer costs is reduced.
Red clover is probably the most widely used forage species when it comes to frost seeding. Red clover has high seedling vigor, is tolerant of a range of soil pH and fertility conditions, and tolerates drought better than white clover.
Red clover produces its heaviest growth during the summer months. Red clover is known as a short-lived perennial, typically persisting in a stand for only a couple of years.
Thus, many producers find themselves frost-seeding red clover every couple of years back into the same pasture.
However, work is underway to improve red clover longevity and there are a couple of varieties on the market that in OSU trials have high yields and stand percentages of around 60 percent or greater after four years.
This seed is higher in cost than some of the more common shorter-lived red clovers, but may be worth it to some producers in some pasture situations. Some producers like a combination of red clover and birdsfoot trefoil in their frost seeding mix.
Birdsfoot trefoil is a persistent perennial once established, but it can be slow to establish, often not showing up in a stand until the second year after frost seeding. This works well for most common varieties of red clover as they begin to decline after the second year in a stand.
After red clover, the next most popular legume that I see being used for frost seeding is white clover. White clover is a perennial clover and begins its production in the cooler spring weather. The older varieties of white clover are known as low growing or prostrate type of growth.
This means that in order for the white clover to thrive, grass must be grazed down shorter so that light can get down to the white clover. However many seed companies now have newer, improved varieties that are more upright growing and compete better with grasses.
Another legume that is sometimes considered for pasture renovation is annual lespedeza. Annual lespedeza is a non-bloating legume that is drought tolerant.Although annual lespedeza will tolerate acidic soils (pH 5-5.5) and low phosphorous level soils, it will also respond to applications of lime, phosphorous and potassium.
Applications of nitrogen will decrease lespedeza yields. Lespedeza is a warm season forage that can be used to fill in the “summer slump” period. Expect growth of annual lespedeza to kick in from late June through early September.
I need to say that in my experience it has been difficult to establish lespedeza by frost seeding. I think it is because the seed is light, similar to a grass seed, and it is difficult to get good seed soil contact.
I would recommend the use of a no-till drill to seed lespedeza. Remember that when seeding a legume species that has not been grown in the pasture for a number of years, it is a good idea to include the proper bacterial inoculum with the seed to insure that the bacteria responsible for fixing nitrogen becomes associated with the plant roots.
No-till drilling should be considered when a grass species is going to be added to the pasture mix and/or the forage residual cover is too thick for a frost seeding to be successful. The no-till drill has the advantage of being able to cut through the forage residual cover and placing the seed in direct contact with the soil.
The disadvantage of using a no-till drill is that the pasture paddock must be dry and firm enough to use the drill without causing ruts or compaction. If weather conditions permit early drilling, the seed can germinate and emerge with the established sod.
If drilling conditions are delayed until pasture growth starts, it may be a good idea to burn back the growth with a chemical herbicide so that the seed has a chance to germinate and emerge without too much competition from the established sod.
No-till drilling can also be used in those instances when an extensive renovation is planned and the existing pasture paddock will be killed using a non-selective systemic herbicide such as glyphosate. In this case, the renovation will take place after the growing season has begun and the growing sod has been sprayed.
In addition to good seed soil contact, the success of any new seeding depends upon soil fertility conditions and the grazing management that will be used once that plant is up and growing. The goal should be more than mere plant survival.
We want the new forage plants to thrive and produce to their genetic potential. Grasses should have a soil pH above 6 and if legumes are included in the pasture mix, then the soil pH should be 6.5 to 6.8. If your soil pH is low the priority should be adding lime before adding seed. Remember that it will take at least 6 to 9 months to reach your pH goal after limestone is applied and incorporated into the root zone.
For applications that must be surface applied, as is the case with most pasture situations, that time frame can be a year to a year and a half. Soil phosphorus test levels should be at 20 to 25 ppm and soil potassium test levels generally between 100 to 120 ppm.
Finally, good grazing management practices must be used to allow the new species to thrive. The species you have in your pasture are those that survive your grazing management. If you don’t change your grazing management you will end up tomorrow with the same species you have today.