WHAT IS MEDIC?


 HomeYou are here > Kit No. 1.3 (What is medic? Where does it grow?)

Also useful information in Botany of annual legumes 

Details of medic cultivars Cultivar selection

Shorthand.

    We have used "medic" is on this site as shorthand for "annual self-regenerating pasture legumes."

These include other botanical families besides Medicago.

    "Annual self-regenerating pasture legumes"  is quite a mouth full and "medic" while not strictly accurate is much easier to handle.

    It may seem illogical to use the short version of a scientific name in this non scientific way but "medic" has become a farming term not a scientific one and is justified by usage.

The farming use of the self-regenerating legumes is more important than their position in the botanical identification table.

    In the early years, medic was referred to as burr or barrel clover. As clover refers to the Trifolium family the name also lacked logic.


What does medic stand for?

     Medic is short for Medicago but it is used more widely as a farming term.

Medicago is the scientific family name of a group of legumes that includes a large varieties of annual legumes, some perennial plants such as lucerne (alfalfa) and the lucerne fodder shrub.

While Medicago includes all the members of the family the term "medic" is restricted to the annual self-regenerating legumes.

    In Australia sub clover is of great importance as it generally prefers acid soils.

Large areas of acid soil are found in the Australian cereal and high rainfall zones.

In the WANA region the great majority of soils are alkaline.

Medics (in the sense of the family Medicago) are better adapted to these soils.

    Medic has become a universal word is the Mediterranean.

There are Arabic words for medic but on the north shore of the Mediterranean the local words apply to lucerne.

Thus we have "erba medica" in Italian and "luzerne" in French.

There have been attempts to turn these local words into "medic" by adding "annual" to the word for "lucerne."

This is a great mistake.

While lucerne and medic are related botanically they are quite different in farming.

Farmers are not interested in the scientific relationship and to call medic an annual form of lucerne creates immediately a confused picture in the farmers' mind.

Some translations of "medic" into French have mentioned the "annual" qualification to "luzerne" but then forgotten it later in the text which creates further confusion for those readers who have not read the material from the beginning.

    For those worried about the Anglicisation of international communication "medic" is not an English word but shortened form of the Latin.


Why is medic different?

        Agricultural sciences is still heavily influenced by the northern temperate regions where the most important early research work was done.

BROWN FARMING SYSTEMS

I have classified the classic farming systems of the world in temperate and tropical areas as brown systems.

The default position is a brown cultivated field.

There are splashes of green on this brown canvas where weeds grow.

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This is a brown field that is the foundation of classic farming systems.

There are splashes of green due to weed invasion but these are controlled as much as possible.

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The farmer plants various crops or even pasture but the field reverts to brown after that.

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On the brown field the farmer sows various crops.

Cereals.

Grain legumes or forage.

Oilseeds.

Even pastures

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When the crop is harvested the field reverts to brown. There may be a few poor quality weeds but the production is low and the farmer would normally sow another crop or forage,

GREEN FARMING SYSTEMS

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The green farming system is based on medic or similar legumes in a Mediterranean climate.

In dry tropical areas it is based on other annual legumes.

The default position is a regeneration of these legumes year after year from seed in the ground.

Regeneration takes place even after a cereal crop as there are reserves of hard seed in the soil.

If the farmer does nothing the field does not revert to brown but to a good legume pasture,

Green farming systems are ideal for semi arid areas (winter or summer rainfall) because of the high risk of drought. If the rainfall is low cultivating and sowing a crop is risky. It is better to do nothing and grazing the legume pasture.

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When the farmer wants to grow a crop he establishes a brown area on the green.

He can then sow

cereal

oilseeds

grain legumes or other crops

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The crop is grown on the established brown area.

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When the crop has been harvested the area reverts not to brown with a poor cover of weeds but to green with a dense pasture of annual legumes.

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Where does green farming start?

Green farming come into its own in semi arid regions where there is a risk of crop failure due to drought. It is not possible to say exactly where the line is drawn. Obviously rainfall and reliability of rainfall are important but equally important is assessing risk is the economic return.

Before global pricing of cereals farmers supplies a local market and poor yield were offset by higher prices. It was worth sowing crops in dry years because the returns could be as good as those in good years. Now prices are determined on a global scale and poor yield produce poor returns. If the drought is particularly severe and World Food Program aid is supplied the prices may drop even further.

Annuals and Perennials

NORTHERN TEMPERATE AGRICULTURE

    Climate is cold, wet winters with short days and no plant growth.

Mild, wet summers and long days with abundant growth.
 

   + Annuals.

    Mostly cereals and other crops (oilseeds, grain legumes etc.).

These are sown and harvested within a single season. There are also annual fodders such as kale.

    + Perennials.

    Mostly pasture grasses such as perennial rye grass, cocksfoot etc.

Also before the days of cheap nitrogen fertiliser included perennial clovers and lucerne.
 

MEDITERRANEAN AGRICULTURE

     Climate is mild, wet winters.

Winter and spring main period of plant growth.

Summers hot and dry.

Plant growth stops once moisture is exhausted.
 

    + Annuals.

    Mostly cereals and other crops such as grain legumes.

Also forage crops such as vetch, oats, lupins and peas.

    + Perennials

    The perennial grasses have not been a great success.

Lucerne is used but mostly under irrigation. 

Perennial fodder shrubs have been used in the arid zones.

    + Self regenerating annuals.

    This is the area that has been totally ignored by northern science.

This is nature's way of avoiding the summer drought.

The great bulk of pasture production in the WANA region comes from annuals (grasses, legumes and weeds) that regenerate from seed each year.

The objective of agricultural improvement is to select the best pasture species.

Legumes are the ones that provide the best pasture and add to the fertility of the soil.

Books written in the northern regions still completely ignore the most important medic species.

They also ignore the management of annual pastures that regenerate year after year.


Important characteristics of medic.

What cultivar? and Botany of annual legumes

   * Self-regeneration - stage one

    The medic pasture must produce abundant seed to succeed year after year.

This seed is contained in a pod and is carried over the dry summer and germinates in the autumn.

The most important group of self regenerating legumes is Medicago but there are also many important self regenerating legumes from the Trifolium subterranium group and other less well known Trifolium families and other legumes.

     * Self-regeneration - stage two hard seed

    The WANA region has low and erratic rainfall.

The medics have a good adaptation to erratic rainfall through their hard seed characteristic.

Hard seed is a drought evasion characteristic.

Medic is particularly good for areas affected by drought but it is important to disregard preconceptions that plants must be drought resistant.

Medic is not particularly drought resistant.

That is it does not survive severe moisture stress.

Instead the hard seed breaks down over a number of seasons and provides waves of seed ready to germinate again and again after drought.

    Hard seed is not seed dormancy.

Seed dormancy is a chemical feature.

It breaks down with chemical changes in the seed.

Hard seed is a hard seed coat. It breaks down with physical action.

Naturally this is through heating and cooling.

The seed pods remain on the surface. They are heated during the day and cooled at night. The hard seed coat cracks.

Water can enter and the seed germinates.

    When medic is harvested and threshed by machine the hard seed coat is cracked.

This means that harvested and threshed seed has a germination of over 95%.

Harvesting pods has no effect on the hard seed character.

    When the seeds first mature in the pods in spring they have a very high rate of seed hardness (over 95%).

This means that the medic will not germinate with later spring rains or summer thunder storms.

During the summer some of the seed hardness breaks down.

The amount depends on the family, variety and cultivar (or ecotype) as well as the physical conditions.

    The Trifolium families usually have less hard seed at the end of summer than the Medicago group.

Within the Trifoliums there have been selections such as Clare and Rosedale that have more hard seed at the end of the first summer than most sub clovers.

Some such as Bacchus Marsh have virtually none by the end of summer.

    The Medicago group varies considerably with some families having a hard seed level similar to the Trifoliums and others with considerable more.

    * What happens next with hard seed?

    Some of the hard seed coats are broken down in the first summer.

The rain comes in autumn and these seeds germinate.

Those with hard seed coats intact do not germinate.

They remain in the soil or on the surface (inside the remains of the old pod).

Next summer there is more heating and cooling.

More hard seed coats are broken down.

In autumn more seeds germinate.

For Trifolium and some Medicago families most of the seeds will now have germinated. Other families of Medicago with high hard seed levels will still have some hard seeds left.

These will be broken down in the third summer and germinate in the third autumn.

   * The use of hard seed in nature.

    The hard seed mechanism is a marvellous means of adaptation to the climate.

Firstly is means that few of the seeds are ready to germinate until the autumn.

Earlier rain is usually wasted as it is usually a single storm.

The plants that germinate usually die before they produce seed.

    If there is a autumn and winter drought the medic still survives as there are more reserves of hard seed in the ground to germinate in future autumns.

    The hard seed mechanism is particularly useful in the arid zone where the failure of the winter rain is frequent.

    * The use of hard seed in farming.

    In farming the hard seed is used in the same way. Instead of a failure of the winter rain causing a loss of seed production it is the deliberate action of the farmer.

    The pasture produces seed in the spring.

The pasture germinates in the autumn.

The farmer cultivates the land to sow cereals.

The pasture seedlings are destroyed.

No medic seed is produced in the spring.

After the cereal crop the pasture germinates in the following autumn from the hard seed reserves in the soil.

The same applies to hay production.

In this case the medic pasture grows in autumn and winter but is cut for hay in the spring. The hay removes the new pods.

The pasture regenerates again in the following autumn from hard seed in the ground.

    This medic-cereal rotation can be practised year after year without the need to reseed the pasture.

With medic (true Medicago and the right families) the system works well.

When other pasture legumes are used with lower levels of hard seed the system is not as reliable.

Of course a permanent legume pasture (regeneration year after year) works well with lower levels of hard seed and can still withstand periodic drought.

    * Adapted to grazing.

    The medic pasture is well adapted to grazing.

During the winter and spring the pasture grows as a dense mat.

It is easily grazed by sheep but is not easily cut for hay.

There is a difference between families and some such as Medicago scutellata (Snail Medics) grow in a more erect form and are therefore more vulnerable to over-grazing.

In summer the pods drop readily on the ground.

While this makes harvesting of the pods difficult it is an excellent adaptation to grazing as it is also hard work for animals to eat the pods off the ground.

While animals are eating the pods they are also burying some on most soil type.

Small pods sized are also better adapted to heavy grazing.

    * Nitrogen.

    Medics fix nitrogen from the air as do other legumes.

They fix large quantities unlike some legume fodder shrubs.

As pasture plants a large part of the nitrogen is returned to the soil through the animal.


Where does medic come from?

    Medic is widespread throughout the world.

It is particularly common in regions with a Mediterranean climate - that is a winter growing season and dry summer.

The probable origin of medic is the countries surrounding the Mediterranean.

Medic is common in Australia where it has been developed into an agricultural plant but medic was introduced to Australia accidentally.

It is still being introduced as part of a program to improve its productivity and extend its range.

Most of the common cultivars have Australian names.

This means they were accidentally introduced to Australia and named after the place in Australia where they were found. For example Jemalong. 

Others have been introduced deliberately and named after after places in the Mediterranean where they were collected ( for example Meteora in Greece or Swani in Libya) or given an Australian code name. For example those that were introduced through the South Australia plant introduction centre at Parafield were all called Para..... For example Paraponto.

All the countries of the WANA region have medic growing naturally.

Sometimes it has been almost eradicated from farm land due to fallowing, deep ploughing and heavy grazing but it is always present somewhere and will return when the conditions are favourable.


How did medic become recognised in agriculture?

    Obviously farmers and livestock owners in the WANA region have recognised the value of medic as a pasture for sheep for thousands of years.

The Arabic words for medic indicate that it has been recognised in the WANA region by shepherds for a considerable time.

The recorded description of the self-regenerating mechanism and the value of legume pastures in science comes from Amos Howard in the 1880s in South Australia.

He identified the first cultivar of sub clover (Trifolium subterranium) call Mt. Barker.

It created little interest except among his farming neighbours. It took the scientific community another 20 or 30 years to realise the important of his discovery. Other farmers discovered further cultivars of sub clover that extended its climatic range.

It is not possible to identify a single person for the discovery of the annual Medicago group. It occurred in South Australia in the 1920s and 1930s. A seed merchant call Alf Hannaford played a great part in the popularisation of medics as pasture plants and source of nitrogen but he never claimed to have discovered them.

Later a cultivar of M. truncatula was name Hannaford after him but it was not his discovery.

The scientific community in Australia recognised the importance of medic in the 1950s.

The transfer of the concept to the WANA region was begun by the Libyan Government in the early 1970s. They employed Australians to develop medic pastures in their cereal zone.

Unfortunately the use of medic in WANA has been associated with the medic-cereal rotation and the the role of medic and other self-regenerating legumes such as sub clover as a permanent pasture on the parcour has been neglected.

The medic and sub clover were used in this way in Australia before the cereal rotation was developed.


Is there a choice?

    Self-regenerating annual plants dominate the flora of the WANA region and are the most important pasture plants.

In the High Rainfall Zone there have been attempts to develop pastures based on perennial grasses and legumes. These have had mixed success.

The striking thing about most of these pastures is that after a few years they are over run with "weeds" which provide the bulk of the pasture production.

The "weeds" are the naturally occurring self-regenerating plants including medics.

The question is whether the cost of the perennials is worthwhile.

Would it be easier and more productive to manage the "weeds" and try to achieve medic dominance?

In the arid zone enormous sums have been spent on planting fodder shrubs such as Atriplex or spineless cactus.

Again research indicates that the sheep actually obtain more nutrition from the annual weeds growing between the shrubs.

Again one has to ask whether it would not be a better strategy to encourage a better type of "annual weed" such as medic?


Barriers to medic.

    Medics has the ability to grow everywhere in the WANA region.

The barriers are almost universally farming barriers.

There is evidence that the disappearance of medic has been cause by farming factors. The main ones are:

    + The use of the cultivated fallow in the spring.

    + Deep ploughing that buries medic pods.

    + Over-grazing of the parcour.



 

Selecting medics

     The most important characteristics of medic is the cultivar.

Unfortunately this fact has not been recognised by some experts who have merely specified the variety when they have recommended medic for a particular project.

If we use Barrel medic as an example of a variety of medic we find there is an enormous difference between say Jemalong and Cyprus.

Jemalong and similar long season medics are suitable for the medium rainfall parts of the cereal zone while Cyprus is suited to the lower rainfall parts below 300 mm.

    The suitability of the medic cultivar to a particular zone is in the first place determined by the time the medic takes to produce seed.

Normally the time between germination and flowering is measured for a cultivar.

Of course the medic must survive for a few more weeks in spring or summer for the flowers to turn into seed pods and for the seeds to mature.

The whole process from germination to pod fall must fit within the normal growing season.

The growing season varies from year to year but the medic hard seed in the ground provides a reserve for the years of drought.

    Length of growing season figures are available for the WANA region.

They are similar to rainfall zones but not exactly the same.

Lower temperature in spring reduce evaporation and mean that less rainfall will produce a slightly longer growing season.

Usually the rainfall figure are easier to obtain so they are used for medic cultivar selection.

    More details are provided later on medic selection. What cultivar for the cereal zone? What cultivar for the marginal zone? What cultivar for the rangeland?


Medic names 

Medic -  botanical name of  variety 

 Medic -  common name of variety

M. truncatula

Barrel medic 

M. scutellata

Snail medic

M. rugosa

Gama medic

M. littoralis

Strand medic

M. polymorpha

Burr medic

M. tornata

Disc medic

M. rigidula

Tifton medic

M. turbinata

Cogwheel medic

M. laciniata

Cut leaf medic

M. minima

Gold field medic

M. orbicularis

Button medic

M. murex

Rough medic

Ley farming

    Ley (pronounced "lay") farming has been used to describe the classic medic - cereal rotation.

"Ley" is an archaic English agricultural term that was used to describe a short duration pasture.

When I studied agriculture at the University of Reading in Britain in the early 1960s it was already disappearing as a common word.

In the 1970s it was revived by the South Australia Department of Agriculture (possibly elsewhere but this is the first reference I can find) as a description of the medic - cereal rotation.

As far as I can see it was done to try and put the medic cereal rotation into a world context and was not a term that was used by Australian farmers.

It has not been adopted as a common term in Australia since the 1970s.

I have avoided the use of "Ley" in this site because it is confusing.

It does not create a context for the rotation.

The ley was a short term pasture within a cereal rotation.

It consisted of a sown pasture of grasses and clovers and more recently of sown grasses alone.

Of course medic is a legume and the objective is to manage the medic pasture to have medic dominance not grasses.

The ley is sown.

While medic is sown in the first year of the classic Australian medic - cereal rotation the whole point is that in future it regenerates without sowing.

While medic is a "short term pasture" there are so many difference between medic and ley that the use of the word "ley" (if people understand it anyway) creates more questions than it answers.