Frost Seeding Pays Big Dividends

Peter Callan, Extension Agent, Farm Business Management, Northern District

Frost seeding, also called overseeding, is an excellent way to incorporate legumes into a pasture. Preparation for frost seeding starts in the previous growing season. Pastures that will be frost seeded need to be grazed close prior to seeding.  Since the seed is broadcast, there must be spots of bare soil showing so that there is soil/seed contact. If there is residue on the soil, it will be difficult for the seed to reach the soil and the young seedlings to grow through the residue.

There are several advantages of frost seeding legumes into grass pasture. Yields are higher with grass-legume mixtures. There will be higher tolerance to drought if a legume with a taproot (e.g. red clover) is seeded into the pasture. Legumes fix nitrogen which is used for fertilizer in grasses. By incorporating legumes into a grass pasture there will be a major reduction in fertilizer costs because no additional nitrogen is needed if legumes make up 30% of the total sward on a dry matter basis. Past research has shown that legumes increase animal performance by increasing forage quality of pasture swards. Even more important to producers in Virginia is the dilution effect from adding legumes to endophyte infected tall fescue stands.  The addition of legumes increases animal performance and improves conception rates. 

Seed selection is important to insure that the frost seeding generates a stand. Alfalfa does not frost seed as well as white and red clover and should be drilled if possible. Red and white (ladino) clovers work well in frost seeding. Red clover is a key pasture legume because it is easily established with frost seeding. It is a short lived perennial with of a life of 2-3 years. One disadvantage of red clover is that it does not self-reseed consistently. White clover is well adapted to short, close grazing and produces high quality forage. Another important advantage of white clover is that it re-seeds.  There are three types of white clover available, common or Dutch, intermediate or grazing type, and ladino or large type.  The use of intermediate or ladino types is recommended.  The ladino types will produce 3-5 times as much dry matter compared to the common white clover.  Although the intermediate white clovers producer less dry matter than the ladino types, they tend to be more tolerant to grazing. 

The seeding rates on a per acre basis are as follows: red cover 8-10 pounds and white clover 1-2 pounds (VA Tech Agronomy Handbook, 2000). A mixture of red and white clover is often used at a rate of 4-6 lb./A and 1-2 lb./A for red and white clover, respectively.   The cost of frost seeding a mixture of red and white clover is approximately $30 per acre (Table 2).  The value of the nitrogen fixed by this clover mixture will be around $100 to 120/A/year (Table 2).  It is important to remember that clover shares its nitrogen with the grasses in pastures indirectly.  In a healthy grassland ecosystem ruminant livestock graze legumes and then deposit the nitrogen back onto the pastures in the form of dung and urine. With good grazing management a strong and vigorous nutrient cycle develops overtime. 

Soil fertility plays a major role in determining the success of frost and the maintenance of clovers in pastures.  A current soil test takes out the guesswork and prevents the producer from under or over-applying lime and fertilizer, either of which will decrease your efficiency and profitability.  Virginia Tech soil test laboratory recommendations are based on research conducted for Virginia soils and climate. “Red and white clovers require soil pH levels from 6.0-6.4 while alfalfa requires a pH of 6.8 or higher. Fertility levels for phosphorus and potassium should be in the med+ to high- ranges.” (1) Soil testing needs to be done in the fall prior to seeding. Lime may be applied in the fall to bring pH up to desired levels. The table below lists value and amount of nitrogen fixed by several legumes.

Table 1: Cost of frost seeding legumes

Crop

Seeding rate lb./acre

Seed cost/$ lb.

Seed cost

Spreading cost

Total cost

Red clover       

10

2.40

$24

$10

$34

White clover

2

4.00

$8

$10

$18

Red and white clover

5 and 2

2.40 and 4.00

$20     

$10

$30

Table 2: Value and amount of nitrogen fixed by various legumes (2)

Crop

N fixed lb./acre/year

N value, $, @

0.55/lb.

0.65/lb.

0.75/lb.

Alfalfa

150-250

$83-138

$98-163

$113-188

Red clover

75-200

$42-110

$49-130

$56-150

White clover

75-150

$42-83

$49-98

$56-113

 

 

Frost seeding is generally done in late winter since freezing and thawing of the soil is required to incorporate the seed into the soil.  There must be good seed/soil contact for the seed to germinate and produce a viable seedling. In Virginia, pastures should be frost seeded starting in early February and ending in early March.

Frost seeding legumes enables producers to improve the quality and yields of their pastures. Furthermore by maximizing grazing efficiency, producers can maximize recycling of nitrogen, phosphorus and potassium that will reduce purchase fertilizer inputs for their pastures.

1. Personal communication Chris Teutsch.  January 23, 2014.
2.
Ball, D.M., C.S. Hoveland and G.D. Lacefield. 2002. Southern Forages, Third edition.

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