Published in the 2009 Grass Lands Conservation Initiative Proceedings, Reno,

Nevada, December 2009

Establishment and Retention of a 50/50 Grass-Legume Pasture by Keith Vander Velde, UW Extension Marquette County, Wisconsin

Situation:

The concept of combining grasses and legumes in a pasture has been an important feature of agriculture from the early days of historical records. In fact the first records of the use of clover in pastures appear in the sixteenth century. A grass-legume mix has been used in many countries of the world due to its ability to increase the forage yield in a pasture compared to individual stands of grasses or legumes when no fertilizer is applied. The use of legumes in pastures results in increased N content and higher digestibility along with a high well-balanced mineral content of the grass-legume forage.

The rising costs of N based fertilizer and the need to increase forage yields in pastures has many producers wanting to know the proper seeding rates of grass to legumes in a pasture mix. There is a very evident competition between legumes and grasses. Some of this competition can be influenced by soil type, pH, grazing height and frequency of grazing. It is generally accepted that grasses have a competitive advantage over legumes and therefore tend to dominate pastures, however in order to maintain high pasture productivity a balance between grasses and legumes is desirable.

Often the question asked is “What is the proper seeding ratio of grass to legumes when seeding a field?” This on-farm trial was designed to help answer this question and involved 5 farms with fields ranging from 10-25 acres. A review of the literature on the proper seeding rate for a grass-legume pasture is 2:1. Literature reviews also show the rate of emergence and growth from seed varies by species. Alfalfa relative to many grasses and legumes is an aggressive species at the seedling stage. Using 100 as the seedling vigor for alfalfa, red clover and white clover had values of 63 and 38 respectively, whereas orchardgrass, bromegrass, and timothy had values of 42, 52, and 17 respectively. However, it is well known that orchardgrass develops slowly from seed and seedling growth is slower than most legumes, but when established orchardgrass is aggressive.

Using the most commonly grown species of grass and legumes were chosen for this pasture forage trial. White clover (Trifolium repens) is one of the most important pasture legumes grown in most of the upper Midwest United States. Alfalfa (Medicago sativa) is another very important legume grown for both hay and grazing that ranks as the most widely grown legume in the United States. Red Clover (Trifolium pratense) is another widely grown legume in Wisconsin and is easy to establish in most pastures. Orchardgrass (Dactylis glomerata.) has been one of the favorite grasses for pasture mixes in the Upper Midwest due to its high annual forage yield and its ability to regrow quickly after being grazed. Meadow brome (Bromus biebersteinii) is one of the best forage grasses for use in the Northern states under intensive rotational grazing systems due to it’s high forage yield, faster regrowth, and winter hardiness. Timothy (Phleum pratense) is a perennial, bunch-type, shallow-rooted, cool- season grass that is well adapted to the Northeast and upper Midwest... Timothy is popular in the northern half of United States because of its natural adaptation to moist, cool environments. Timothy is grown primarily for hay for horses but is frequently included in pasture mixtures. It is less competitive in a legume mixture than most sod-forming grasses and is frequently grown in a legume mixture for hay. However, special attention must be made to match the maturity of the timothy with the maturity of the legume to ensure timothy persistence and quality forage.

Implementation:

Seeding Rates on a per acre basis in these trials for the control were: 8 pounds alfalfa, 4 pounds red clover, 2 pounds white clover, 5 pounds of orchardgrass, 3 pounds of timothy, and 2 pounds of meadow brome. One-third of the field was seeded with the control, one-third seeded with the legume portion increased 50% ( high legume) and the grass at the control seeding rate, and one-third seeded with the grass portion increased 50% (high Grass) and the legumes seeded at the control rate. Seeding rates varied from a grass-legume ratio of 2:1 for the control, to a 2.5:1 for the high grass and a 1:1 ratio for the high legume. Seeds per square foot varied from 151 (101 grass, 50 legume) for the control, 203 (148grass, 53 legume) for the high grass and 180(103 grass and 73 legume) for the high legume. These rates are higher than the recommended rates but we wanted to Oats was used as a cover crop at the rate of 50 lbs per acre. Fields were sprayed with a glyposate and 2,4-D prior to seeding. A Great Plains No-Till drill was used for the seeding establishment. Two fields were seeded in early May 2007 and due to extreme drought after initial emergence the new seedlings died and were seeded to annual forages in early July. Two fall seedings were successfully done in August/September 2007 on a total of 35 acres. In 2008 two additional fields (40 acres) were seeding using the same seeding rates as 2007.

Results from Year One: Seedling survival from the fall seeding was measured in the spring of 2008 and 2009. In all the stands the legumes had a higher stand rate than the grasses. The stand counts were taken in random areas of each field in one square foot areas in 5 locations per plot. Stand counts are found in Table 1

Table 1: Established Plants per Square Foot

Year 1 Year 2 / Year 1 Year 2 / Year 1 Year 2
Field 1 (2007) / Control / High Grass / High Legume
Grasses/sq ft / 21 / 34 / 20
Legumes/sq ft / 33 / 32 / 48
Field 2 (2007)
Grasses/sq ft / 18 / 28 / 17
Legumes/sq ft / 25 / 27 / 39
Field 3 (2008)
Grasses/sq ft / 18 / 30 / 18
Legumes/sq ft / 29 / 28 / 40
Field 4 (2008)
Grasses/sq ft / 20 / 28 / 17
Legumes/sq ft / 27 / 29 / 42
Emergence % Ave. / 31% / 29% / 35%

The number of seeds per square foot was very high due to good seed to soil contact and timely rains to these seedlings. The legumes did emerge early and provided competition to the grasses early in the growing season.

Stand count of the 2007 seeding did not show a significant change in plant populations in the well managed pastures where the pastures were grazed to 4-5 inches and then allowed to recover in 30 days before grazed. However, there was a loss in the percentage red clover and orchardgrass in the pastures that were grazed down to 2 inches in the establishment year. We will again be taking winter survival counts again in the spring 2010 to determine the survival rates after one or two years of managed intensive grazing.

Pastures recommendations were to begin rotational grazing at a height of 10 inches and grazed to 3-4 inches height per rotation. In 2008 the grazing period began May 20 and persisted to Oct 15. In 2009 the grazing period began May 30th and persisted until Sept 25th due to hot, dry conditions in late summer and an early frost in mid-September.

Table 2. Forage Yield per Acre (Tons of Dry Matter per Acre)

YEAR / 2008 2009 / 2008 2009 / 2008 2009
Control / High Grass / High Legume
Field 1 (2007) / 3.9 4.1 / 4.4 4.8 / 4.6 4.6
Field 2 (2007) / 4.3 4.9 / 4.7 5.1 / 5.4 4.5
Field 3 (2008) / 4.2 / 4.4 / 4.7
Field 4 (2008) / 4.7 / 5.0 / 5.4

Summary:

Seeding rate has a direct affect on establishment forages with legumes having an early advantage in establishment since they emerge faster that grasses. In this trial the control and high grass seeded areas had final stand that was very close to a 50/50 ratio. The grasses seeded in the areas of high legume seedings had a very high loss rate and the legumes dominated the final stand after two years of grazing. Forage yields were very similar and weather was the major factor affecting yields. Cool, wet condition favored grasses and hot, dry weather gave legumes an advantage.

Overgrazing legumes has a negative impact on forage yield and survival and allows grasses to dominate over a long period of overgrazing legumes. Overgrazing orchardgrass also reduces its vigor and regrowth that affects yield and survival.

Well managed intensively grazed pastures produce large amount of quality forage and have the ability to respond to various seeding ratios of grasses and legumes.