Agriculture

Tips for Improving Forage Establishment Success 


Establishing a forage stand is a long term investment which should begin a year in advance. 

Preparing the Field

Previous Year Crop Selection

The decision to seed a field down to perennial forages works best if planned well ahead.  If drainage works are to completed it is best to do them beforehand.  Previous crops often have an impact on weed spectrum, fertility levels and stubble amounts into which the forage crop will be seeded. 

A herbicide tolerant crop grown the previous year is an excellent choice for cleaning up weeds because it allows aggressive weed control measures.

Perennial forages should be seeded into soils free of herbicide residues. Consult the “Re-Cropping Restrictions for Residual Herbicides” in the “Guide to Field Crop Protection” published by Manitoba Agriculture & Resource Development along with your herbicide use records to check this out, if you have used residual herbicides in previous years.

Weed Control

There are few choices for in-crop herbicide use on establishing forage stands, especially in blends of grasses and legumes.  Reducing or eliminating perennial weeds such as quackgrass, junegrass and thistles is best done before seeding down to perennial forages.  Reducing annual weed seed densities in the field is also beneficial in improving the likelihood of a good catch.  Application of glyphosate is an inexpensive way to clean up fields; pre-harvest the fall before, or pre-seeding, or post seeding pre-emergent all work well and there is no residual from glyphosate; also it only affects green plant material.

If you prefer to not use herbicides to control weeds, harvesting the previous crop prematurely as greenfeed will help to reduce weed densities.  Harvesting prematurely is also recommended when using cover crops for establishing forages.

Tillage can be used for weed control and to prepare a mellow seed bed ideal for small forage seed establishment.  Care must be taken as tillage results in moisture loss from the soil via evapotranspiration; potentially compromising the forage seed germination and establishment.

 

Seedbed Preparation

Forage seeds are smaller than most other crop seeds, so seedbed preparation is critical.  Small seeds cannot establish as plants when seeded deep.  Best results are obtained when seeded one half inch or less into a firm, smooth, moist, weed free seedbed.

Selecting the Forage(s)

The species and varieties of forage to plant should be selected based on the intended use(s) and the field conditions into which it will be seeded into.  Choose the species, or species mix first; then the varieties.  Species are the broader categories of crops.  For example alfalfa, tall fescue and timothy are species.  Then there are varieties or cultivars within each species.  There are nine species of perennial legumes that are available to Manitoba producers; some of which are bloat causing (when grazed), and some which are non-bloat and therefor adapted to pasture use.  There are nineteen species of tame grasses and at least eleven species of native grasses available as well.  To determine which species are best suited to your field and needs consult the Manitoba Agriculture & Resource Development Forage Adaptation Guide.

The Right Species

Intended uses, desired stand longevity, soil type variabilities (sandy, clay, salinity) and wetness variations within the field should have a bearing on your species selection.

Pure stands such as pure alfalfa are best suited to a very uniform soil type field. 

Grass-legume mixes of 3-5 species are more common; reasons for mixtures include:

1.      the soil type is variable; more species can adapt to this

2.       legumes fix free atmospheric nitrogen reducing fertilizer required

3.       to reduce the bloat risk include a non-bloating legume and grasses in the mix

4.       increase grazing season length

5.       make more efficient use of water, nutrients and sunlight

6.      increase ground cover to reduce the effect of wheel and hoof traffic

 

The Right Variety

Longevity and yield of a forage stand begins with choosing a variety(s) adapted to the intended use and field conditions.  Certified seed is recommended as it provides legal guarantees for both germination and weed seed content. 

Seed cost is only 15 to 20 per cent of the cost of establishing a stand, so purchasing  good quality seed can pay dividends for years.

There are three main types of alfalfa: tap rooted, branch rooted and creeping rooted.  The crown of the alfalfa plant is that part of the plant from which all the stems originate from.  The crowns of tap rooted and branch rooted alfalfa types are about one half inch above ground level, whereas the crowns of creeping rooted alfalfas are at ground level.  For this reason creeping rooted alfalfas are generally more winter hardy and will stand more wheel and hoof traffic than the other types. 

Alfalfa Autotoxicity

Alfalfa is unique in the forage world because it produces a toxin (medicarpin) that allows the plant to manage its own stand densities. Since the toxin only reduces plant vigor on alfalfa, it only presents a problem when re-seeding alfalfa into an existing alfalfa stand, or one that has experienced stand loss due to flooding or winterkill. Wait at least 12 months before seeding alfalfa back into alfalfa residue. Seeding earlier than the 12-month interval will often reduce stand density, but most importantly, will result in reduced plant vigor and lower yields. In a Wisconsin study, seeding alfalfa into soil that had a previous stand terminated within two weeks reduced yield by 80 per cent, seeding within four weeks reduced yield by 55 per cent, and seeding in spring after fall termination reduced yield by 40 per cent.

 

Factors affecting the level of alfalfa autotoxicity in the soil

Age of stand

Soil toxin levels require two years of alfalfa growth to build up. Therefore, fields in production for only two years can be re-seeded with relative safety.

Soil type

Effects are most severe in the initial year on sandy soils, but the toxin is water soluble and can leach out of the rooting zone with sufficient moisture. Effects are most prolonged on clay soils, a function of poor drainage and soil type.

Plant density

Higher stand densities have higher concentrations of the toxin in the soil.

Residue

Fields with more top growth residue will require more time for safe seeding. Therefore, remove all residues during harvest if you plan on re-seeding.

Tillage practice

Tilling the stand as soon as possible following harvest can also reduce autotoxic effects.


Seeding

When to Seed

Spring seeding is ideal for germination and establishment because of the cool, moist conditions. However, excessively wet spring conditions, seedbed/soil preparation or weed control timing issues may limit this seeding period.  The Manitoba Agricultural Services Corporation spring forage insurance seeding deadline is June 25.

 Summer seeding should be timed late enough to avoid hot mid-summer temperatures that stress young seedlings, but early enough for the plant to develop a crown before freeze-up. The crown is a small swollen area on the stem near the soil surface. Because of the different stem structures, it is easier to find crowns on legumes than grasses. With a crown the seedling is much more likely to survive winter. Alfalfa requires six weeks and most grasses three to four weeks to develop a crown.  The Manitoba Agricultural Services Corporation forage insurance summer seeding eligibility period is from July 25 to August 15.

Dormant seeding is the practice of seeding the crop with the intention of it remaining ungerminated until optimum temperatures exist. The options are to plant either late in the fall, allowing the seed to lay dormant over the winter and germinate early in the spring, or in early spring before the soil temperatures reach +2 degrees celcius.  The concerns are pre-mature seed germination, making the seedling vulnerable to loss from fall or spring frosts, and seed loss to rodent feeding. Seeding rates should be increased by at least 25 to 30 per cent to accommodate seed and seedling mortality.  Dormant seeding is not eligible for Forage Establishment Insurance via Manitoba Agricultural Services Corporation as it is the least consistent of the three seeding timeframes. 

Seeding Method

Seeding forages can be done successfully a variety of ways including using a disc opener, hoe opener or broadcast.  The type of seeder is less important than the conditions in which you seed into.  Be sure your seeder will allow long, light fluffy grass seeds to pass through the metering mechanism accurately without bridging, or shaking the more dense seeds (legume) to the bottom of seed box.  Mixing forage seed with a cover crop seed such as 1 bushel/acre oats will improve flowability.  Seeding shallow into a properly fertilized, firm, moist, weed free seedbed early enough in the season for the species to reach physiological maturity matters MOST. 

Optimum seeding depth ranges between one-half to three-quarters of an inch (1.25 to 1.90 centimetres), and is best when some seed can be seen on the soil surface. Seeding too deep can significantly reduce emergence for most forage species.

 Table 1: Rate of Seedling Emergence vs. Seeding Depth

 

Seeding Depth

 

1/2"

1 1/2"

2"

3"

Timothy

89%

39%

12%

0%

Smooth Bromegrass

95%

45%

24%

10%

Alfalfa

64%

26%

14%

0%

Packing after seeding is also a very effective tool to cover seed and improve seed-to-soil contact; this helps the seed to more rapidly imbibe soil moisture and get off to a quick start. 

 

Seeding Rate

Seeding rates should be determined based on a combination of the end use, moisture conditions, predicted survival rate of the seedlings, and number of seeds per pound.

Typical Seeding Rates in Pounds per Acre

Species

Pasture

Hay

 

 

 

Alfalfa

1

6

Bird’s foot trefoil

1

1

Cicer milkvetch/sainfoin

4

0

Meadow bromegrass

3

2

Tall fescue

2

2

Timothy

1

1

 

 

 

Totals

12

12

 

 

Average number of seeds per pound for some popular Manitoba forage species

CROP

AVERAGE NUMBER SEEDS/POUND

Legumes

Birdsfoot trefoil

1,000,000

White clover

800,000

Alsike clover

700,000

Red clover

275,000

Sweet clover

260,000

Alfalfa

220,000

 

Grasses

 

 

Timothy

1,230,000

Orchardgrass

650,000

Meadow Fescue

577,000

Reed Canarygrass

530,000

Tall Fescue

227,000

Slender Wheatgrass

160,000

Smooth Bromegrass

137,000

Meadow Bromegrass

80,000

 

 Fertility

Like any crop, forages require adequate nutrient levels to establish successfully. Soil testing your field for nutrient requirements before seeding your forage crop is a very valuable management tool. All nutrients should be applied according to recommended soil test rates, preferably before seeding to help with establishment.

Phosphorus is especially important for establishing plants as it improves root development. Adding as little as 30 pounds/acre (33 kilograms/hectare) of phosphorus has shown to quadruple plant size within one week of emergence under ideal conditions.

Potassium improves the ability of a young seedling to survive over the winter. Applying potassium is especially important on sandy soils.

Sulfur and nitrogen are important for increasing yield and protein.  High levels of nitrogen will make the grasses and companion crops more competitive and may result in a poor legume catch.  Lower nitrogen rates, reduced seeding rates of companion crops, and early harvest for greenfeed, generally facilitate a better forage stand catch.  

For sulfur, elemental sulfur (0-0-0-90) is by far the cheapest form, but takes three years to become fully available to the plant.  Sulphate sulfur (20-0-0-26) is all readily available to the plant, but comes with 20% nitrogen which may or may not be desired

Nitrogen is not important for legumes as they produce their own, provided they are properly inoculated.

 

Inoculants

Legume seed should be inoculated immediately prior to planting to encourage early and increased development of nodules on the root, which in turn makes nitrogen available to the plant.  Legumes via nodulation have the unique ability to take all the free nitrogen they need from the air and put into the plant for nutrition.  Enhanced nitrogen availability gets the plant off to good start and increases yield.

Inoculants are bacteria, and as living organisms, they have an expiry date. Inoculants and seed treated with inoculants must be stored in a cool, dry place to maintain the viability of the bacteria. Once treated with inoculants, bacteria can remain on seed viable and stored for one season if properly stored in a cool dry location.

Inoculants are host-specific, so not all inoculants work on all legumes. For example, inoculants for clover or trefoil will not work on alfalfa. Normally, this is not an issue when purchasing seed from a seed company as they will often pre-inoculate the seed before packaging it. This type of inoculant may also have a longer shelf life, depending on the polymer coating the seed company may have used.

You can check for nodulation (the success of inoculation) to determine if the legumes are taking in free nitrogen. Approximately one month after emergence, carefully dig out a few plants from the soil and check for nodules on roots. The number of nodules and the rate of nitrogen fixation peaks just before bloom. There should be clusters of nodules growing around the crown area on the roots about one half inch to 5 inches below ground level, the nodules should be pink to reddish orange in colour on the inside.  Once the inoculant is successfully growing on the legume roots, it will remain alive and fixing free atmospheric nitrogen for as long as that plant is alive.  Creamy white indicates the nodule is immature, and pale green indicates the nodule is not healthy.

 

Companion Crops

Companion crops, nurse crops or cover crops are NOT essential for good forage establishment, but can be beneficial if properly managed. The emphasis should be on providing a good environment for the establishing perennial forage crop, and not on producing a "bumper" companion crop.  A bumper companion crop will often result in a poor catch of the perennial forage. Companion crops can aid in suppressing weeds, maintaining soil moisture at the soil surface and providing slower-growing seedlings with protection from excessive heat (from hot winds) and frost during establishment.

However, the competition that companion crops provide can reduce yields in the seeding and subsequent years.  Species such as Russian wild rye grass, birdsfoot trefoil, cicer milkvetch and sainfoin are poor competitors and should be sown on weed-free soil without a companion crop. Alfalfa, sweet clover, alsike clover, timothy, wheat grasses and brome grasses are reasonably competitive and under normal conditions can be sown with a companion crop.

Forage stands seeded without companion crops can yield one decent cut in the seeding year provided they are seeded early.  If seeding with a cover crop, it is key to select a cover crop that will minimize competition. Most small grains such as wheat, oats, barley, fall rye, winter wheat, millet and flax are acceptable cover crops using reduced seeding rates and harvested early as greenfeed. Canola is less desirable because of its aggressive ability to stool thus providing excessive shading, and because it is less desirable as a greenfeed. In all cases, establishment success can be further improved by direct seeding into standing stubble; the stubble will provide some protection from the elements.

  

Companion Crop Management Factors

  • Use the least competitive crop in your rotation. An example order of crop competitiveness from least to most is:
    • Flax
    • Millet
    • Wheat
    • Oats
    • Canola
    • Barley
  • Reduce seeding rate of companion crop to 30 to 50 percent of normal.
  • Seed forage at right angles if possible to the companion crop to reduce in-row competition.
  • Harvest cereal grain companion crops at heading to soft dough stage for green feed.
  • Leave high stubble to trap snow and improve winter survival

The following agencies worked collaboratively and provided funding support for this publication:

  • Manitoba Agriculture & Resource Development
  • Agriculture and Agri-Food Canada
  • Manitoba Forage & Grassland Association