WHAT PASTURE LEGUME?
 

In the cereal zone of the WANA region.


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Limitations of this chapter

    The West Asian and North African farming zone covered by this chapter stretches from Morocco in the west to Iraq in the east.

It stretches from the extremely arid rangeland with 150 mm and much less of annual rainfall to the high rainfall zones where rainfall exceeds 1000 mm.

The soil varies from heavy clay to light sand.

With all these possible combinations of soil, rainfall, winter cold  and other factors it is not possible to provide a precise guide to cultivar selection for annual self-regenerating legume pastures.

The chart below shows three levels of soil pH, four of rainfall, three of soil texture (36 combination to this stage) before other management factors are introduced into the selection process.

    Actual selections of cultivars should be based on the generalisations provided by this chapter and the practical experience on the ground. As more pastures are established more practical knowledge is gained and can be exchanged.

   Local ecotypes

    The WANA region has a rich flora of annual legumes suitable as pasture plants.

Most of the pasture legumes used in Australia come from the WANA region or the nearby countries on the north shore of the Mediterranean. Some have been deliberately introduced and others were introduced accidentally as a contamination of cereal seed.

The local pasture plants in the WANA region have been suppressed by a combination of over-grazing. deep ploughing and fallow.

To restore the pasture through natural regeneration can be a slow process and seeding is usually necessary.

However, over time the local ecotypes will regenerate once the pasture environment is suitable for legumes.

If the local ecotypes are better adapted they will gradually replace the introduced cultivars.

This is completely different from the situation in Australia where legumes have been introduced and there are no local pasture legumes.

Changing composition of the pasture

Annual legumes are also different to the more traditional perennial pastures of the northern temperate regions.

If one sows a pasture of perennial ryegrass, lucerne or even atriplex shrubs the selection of the optimum cultivar is vital. The pasture remains the same for the life of the pasture.

That is not the case with annual regenerating legumes. Management of the pasture is aimed at achieving a legume dominance but the proportion of individual species, cultivars or ecotypes within the legume pasture can vary from year to year.

For the sake of argument let us say a field is sown to a mixture of medic cultivars that germinate and form a pasture of 500 seedlings per square metre.

Let us also say that the locally adapted ecotypes germinate in the pasture from reserves of hard seed at the same time and form 5 seedlings / sq. m.

To begin with the local ecotypes are insignificant forming only 1% of the pasture.

Let us also say that the local ecotypes have a greater seed production, better seed survival and germination so they produce double the seedlings relative to the introduced medic cultivars.

If the management of the pasture is good and a seedling germination of 500 per sq. m. is maintained year after year there is a gradual shift from 5 seedlings of the ecotypes to 10 to 20 to 40 to 80 etc.

It can be seen that over a five year period the local ecotypes become more and more important.

The relative strength of the selection process will depend on the degree of adaptation of the introduced cultivars.

The fact that local ecotypes will eventually become dominant in the pasture means that it is possible to sow pasture mixtures of introduced cultivars that are not optimal for that particular environment in the knowledge they will be replaced over time by local ecotypes that are better adapted. This would not be the case with perennial pastures.

This is not a theoretical argument. I have observed the process taking place in Algeria.

A farm near El Khemis sowed a medic pasture based on the Australian cultivar Jemalong. The cultivar has a leaf mark that makes identification easy. Over a number of years the Jemealong medic declined and was replaced by local Algerian types. After about five years it was hard to find a single jemalong plant.  

    Seed mixtures

    Seed mixtures will be used to establish legume pastures because there is rarely a "perfect cultivar" for a particular place and because the soil varies over individual fields.

Even the seed of the best cultivars is not always available or is too expensive to use exclusively.

Mixtures provide a range of cultivars that will reorganise themselves over time to become dominant in particular parts of a field or under particular management conditions.

    Australian dominance

    It is not surprising that Australia dominates the field of named cultivars of annual self-regenerating legumes. 

Legume pastures have been used in the WANA region since mankind began to graze flocks of animals.

The process of selecting named legume pasture cultivars began in South Australia more than 120 years ago when a farmer, Amos Howard, identified the Mt. Barker cultivar of sub clover.

More cultivars were identified by other farmers and during the last 50 years agricultural research organisations in Australia have carried out a large program of selection within Australia.

They have also carried out an extensive search of the WANA region for local ecotypes to add to their collections.

Many of these ecotypes have been tested and registered as new cultivars.

Lack of WANA cultivars due to poor market

While Australian dominance of the annual self-regenerating legumes is not surprising the lack of cultivars from the WANA region can be attributed to a lack of a seed industry and a reliable market for seed.

Research has been conducted in the WANA region.

For example the ITGC in Algeria selected a number of excellent frost resistant cultivars of medic for the high plateau during the 1970s. I have photos of the trial plots in my collection but all records of the work have disappeared from the Algerian archives and there is no seed available either in collections or commercially.

The author and Adam Lakhdar (researcher into medic farming) examining cold resistant medic plot at Tiaret in Algeria.

ICARDA later carried out similar selections of medic in Syria.

Some commercial seed was produced in Australia under contract but there was no reliable market for the seed in the WANA region and production was abandoned once the contracts expired.
 

   Does Australian dominance matter?

    The lack of a seed industry in the WANA region is due to the high price of livestock.

Jordan, Tunisia, Algeria and Morocco have all demonstrated their capacity to produce medic seed but except for a small amount produced on government farms in Tunisia the production of seed has been discontinued.

There is no incentive for private farmers to produce seed when the returns from livestock are so high.

Seed production requires additional investment, substantial extra cost and considerable expertise.

It is not worthwhile unless there is a considerable profit margin over the simple grazing of pasture with livestock.

Many of the modern Australian cultivars have been collected directly from the WANA region.

For example Borung barrel medic was collected in Tunisia, Serena burr medic in western Libya and Ghor barrel medic in the occupied West Bank.

The older cultivars were collected in Australia but were introduced accidentally from the Mediterranean region as a contamination of other seeds.

Some people in the WANA region have considered them to be Australian but Australia has only provided the description and the name.

Most of the time the origin of the seed and the name of the cultivar is unimportant but there are climatic zones within WANA that do not exist in Australia.

Australian scientists have not bothered to select for these zone.

The result is a poor range of cultivars for the cereal zone with extreme winter cold and high rainfall zones with alkaline soils.

These gaps in the range of available cultivars will be discussed in more detail elsewhere.
 

    Pod harvesting is the future for WANA
 

 ICARDA has developed a simple pod harvester for small farmers that has completely transformed the situation in the WANA region. It has solved the seed problem and the cultivar problem.

The pod harvester is a simple machine that does not require a large investment.

The skills required are much less than those needed for specialist seed production.

Pod harvesting can be incorporated into a normal pasture.

The fact that the harvesting is carried out with family labour reduces the cost.

The pods are not threshed to remove the seed. Nor is the seed cleaned. It does not pass through seed merchants and is not transported from Australia.

All in all the production of pods and the exchange or sale of pods among farmers is a low cost means of establishing a medic pasture and is most competitive with imported Australian seed.

Pod harvesting also solves the cultivar problem.

As I have already explained the presence of local ecotypes even at a very low level provides a long term solution to any lack of adaptation by imported cultivars.

Natural selection will shift the balance toward the best adapted plants.

With pod harvesting one pasture takes off where the last one finished.

Instead of a process of change taking place over years it is more rapid.

For example, say a pasture is established on a government centre using a selection of good imported cultivars.

Over the years local ecotypes become more important (see above).

If the pasture is harvested by local farmers with their pod harvesting machines they harvest the pods that reflect the stage of change.

They take the pods to their own farm and again each shift in the cultivar balance is reflected in the pods harvested and used for the next pasture.

Rather than starting afresh with a cultivar seed mixture for each new pasture there will be a mixture of pods that reflect the evolving adaptation of the annual legumes.

Pasture establishment based on local pod harvesting introduces a completely new concept of cultivar selection from that provided in this chapter.

Here I am presenting cultivars that fit the environment and the management regime.

The pod harvesting and establishment system depends of selecting similar pastures (that is similar rainfall, soil and management), harvesting the pods and using them the establish the next pasture. The composition of the pod mixture is not relevant.
 

    Some suitable pastures for pod harvesting
 

 There are medic pastures in the region that can be used in this way for multiplication using pod harvesters.

Some were established using Australian cultivars but have long since moved to a new balance with local ecotypes.

In Morocco there are good pastures in the Abda plains near Safi.

In Algeria they can be found on research centres at El Kroub near Constantine and at Guelma where the centre has developed top quality pastures.

There are purely local pastures on a few farms in the Tiaret region.

High altitude (950 m.) medium rainfall medic and other annual legume pastures exist at Djemila near Setif and at Timgad near Batna where the rainfall is lower but the winters are also very cold.

In Tunisia the OEP farm at Saouaf has medic pasture that could be used a multiplication centre for the low rainfall zone.

Private farms near Le Kef are representative of medic in a 400 mm zone.

In Libya pods could be harvested from farms in the Jebel al Akhdar area.

In Syria there is a strong centre for locally adapted medic pastures at the village of Tah.
 

    Organising the information
 

Traditionally the information on pasture cultivars has been based on the plant family and species.

Most of the research has been carried out in Australia but other work has been done by ICARDA in Syria and ACSAD in Syria and national research institutes.

Unfortunately some of the national research (for example in Algeria has been lost) and almost all to the research in the WANA region is unavailable to farmers because of a lack of commercial seed.

Concentrating on the botany of the plant is the traditional means of organising the information on pasture cultivars but farmers are interested in pasture legumes that are productive and do not care about the botany.

In this chapter I will try and approach the selection from the farmers' viewpoint rather than the viewpoint of the plant selector or breeder.
 

  Physical factors in cultivar selection

    Summary of cultivar selection process
 

Environmental factors are the first stage in the selection process.

    There is a long list of physical factors that determine cultivar selection for annual pasture legumes.

The major ones are:

    * Soil pH.

   * Rainfall.

   * Soil texture.

    In addition there are factors such as:

    * Resistance to water logging.

    * Resistance to frost.

    * Tolerance of salinity.

* Resistance to pests and diseases.

    If we use all the factors in the above list the whole process becomes unbelievably complex especially if we add management factors (see below). Fortunately simplification is possible.

    Some of the factors can be eliminated:-

    * Resistance to pests and diseases.

    This is important but applies to all cultivars in all locations. One does not choose a cultivars without resistance unless there is no other suitable cultivar available.

Generally the more recent a cultivar has been released the more resistant it is to the two main aphid pests (Blue green aphid BGA and Spotted alfalfa aphid SAA) and Sitona weevil.

For example Jemalong Barrel medic is an old cultivar and is susceptible to many insect pests.

Selection has been aimed at this important characteristic over the last several decades.

Farmers should select resistant cultivars provided the seed is not too expensive.

If the seed is costly a small amount can be included in the mixture and if the resistance proves to be important the natural selection in the pasture will shift the plant population towards the resistant cultivar.

    * Tolerance of salinity.

    This is a special case. Salinity can be excluded from the normal selection process.

    * Resistance to frost.

    The high plateau of Algeria (and small extensions into Tunisia and Morocco) and parts of northern Iraq and Syria have extremely cold winters.

Frost can cause damage to most common medic cultivars.

Many seedlings are killed but those that survive will form a vigourous pasture in the spring.

Winter production is lost.

There has been a considerable amount of research into this problem in Algeria where many frost resistant cultivars have been selected.

Unfortunately these cultivars have been lost and are no longer available either to researchers or commercially.

ICARDA has selected cultivars of Medicago rotata and Medicago rigidula that have high levels of frost resistance. The seed exists in seed collections but there is no commercial production available for farmers.

In these zones with extremely cold winters farmers are forced to use mixtures that are not optimal.

If frost is a severe problem it will apply considerable selection pressure on the pasture and local ecotypes (that are resistant to frost) will quickly become dominant.

    * Resistance to water logging

    This is not a common occurrence in the cereal zone of the WANA region and is treated as a special case where cultivars are available.
 
 

     Soil pH 

    pH is a convenient measure of soil acidity and alkalinity.

When the pH is 7 the soil is neutral.

A pH above 7 indicates the soil is alkaline.

A pH below 7 indicates acidity.

pH is not necessarily the most important criteria for cultivar selection but as the species fall into various categories it is a good starting point in the selection process.

Measuring the pH

 pH is measured in water solution or CaCl.

 It can be seen from the above chart that a pH of 7 in water is only 6 in CaCl.

The chart below gives a general picture of pH and species selection.

Soil pH

Species

Acid soil with a pH from 5 to 6.5 

Sub clovers (Trifolium subterraneum)

Acid to neutral soils with pH from 6 to 7

Sub clovers of the brachycalcinum (Clare) sub group and Burr medic (M. polymorpha)

Alkaline soils with pH above 7

Most other medic species and Burr medic


 More details on soil texture, pH and water-logging tolerance is provided in the following charts.

  In the WANA region the soils of the cereal zone are overwhelmingly alkaline. That is they have a pH above 7. Acid and acid to neutral soils are a footnote to the main cultivar selection process within WANA.
 

 Medic species commonly used on alkaline soils for pastures in the cereal and marginal zones of the WANA region.  

Quick botany check will remind you of the botanical features of medic

Medic -  common name of  species 

 Medic -  botanical name of species

Comments

Barrel medic 

M. truncatula

The name Barrel medic refers to the seed pod which is shaped in the form of a barrel. Barrel medic was the original selection of medic multiplied for seed in South Australia. It was favoured because of the relatively few spines and therefore less likely to become a contamination of wool. Barrel medic has proved a good species in WANA. There are many cultivars.

Snail medic

M. scutellata

Snail medic has pods shaped like a snail shell. Does not contaminate wool. Has been used with great success in WANA region. The large seed improves establishment under poor seedbed condition. The large pods are easily eaten by sheep.

Gama medic

M. rugosa

Excellent on heavy soils and clay that cracks. Has less hard seed which can be a problem in the classic medic-cereal rotation.

Strand medic

M. littoralis

Used in Libya and other WANA countries in zones with less than 200 mm rainfall.

Burr medic

or spineless burr

M. polymorpha

Very common form of medic. Most ecotypes have large numbers of spines but the cultivars have been selected for few spines and less contamination of wool. Suitable for a wider range of soil pH than other medics.

Disc medic

M. tornata

Used in Libya and other WANA countries in low rainfall zones.

Hybrid disc

Hybrid between M. tornata X M. littoralis

Sphere medic

M. sphaerocarpus

Murex medic

M. murex


  Other medic species that have been identified as potentially useful pasture plants for alkaline soils but which are not available commercially.

Medic - botanical name of species

Medic  - common name of species

OmCommentseComnts

M. rigidula

Tifton medic

ICARDA selections in Syria proved to be very frost resistant.

M. turbinata

Cogwheel medic

M. laciniata

Cut leaf medic

Useful in areas with very low rainfall.

M. minima

Gold field medic

Also a low rainfall species.

M. orbicularis

Button medic


    Rainfall
 

  Rainfall is a convenient guide to the length of the growing season.

Rainfall figures are readily available for the WANA region whereas growing season figures are not.

Unfortunately rainfall is only a guide to growing season as the same amount of rainfall can be more effective in cooler regions where evaporation is lower.

Annual rainfall is higher than effective rainfall.

Effective rainfall is the rainfall that falls within the growing season. Rainfall that falls in summer, particularly light falls are wasted. Mediterranean regions vary in their ration of annual rainfall and effective rainfall.

    Pasture legumes are adapted to a range of growing seasons. For example:

    *  Gama medic (M. rugosa) cultivar Paragosa has a growing season of 110 days between sowing and flowering. Further moisture is required for seed maturation.

    * Burr medic (M. polymorpha) cultivar Serena has a growing season of 62 days between sowing and flowering.

    The length of the period between sowing and flowering is a factor of the cultivar (or ecotype) not the species. Another Burr medic (M. polymorpha) cultivar Circle Valley has a growing season of 96 days between sowing and flowering compared to 62 days fro Serena.

    It is important to select a cultivar that is adapted to the average growing season. It is obvious that a long growing season cultivar will not survive in a low rainfall/early season zone. It will dry off through lack of moisture before the flowers have formed and produced pods and seed. The reverse is not true. A early season cultivar will survive in a late season environment but pasture production is lost if early season cultivars are sown in higher rainfall/late season zones.

Maturity

Days to first flowering

Minimum growing season length (months)

Rainfall - guide

mm

Very early

less than 85

4.0

Below 200

Early

81 to 95

4.5

200 to 300

Early/mid

91 to 110

5.0

Mid

106 to 125

5.5

300 to 400

Mid/late

121 to 135

6

Late

131 to 145

6.5

400 to 500

Very late

More than 140

7

Above 500

    It is important to remember that these rainfall figures are only a guide as it is always the length of the growing season that is important.

Of course the length of the season varies from year to year and in some drought years the medic will fail to produce seed.

In other years an early season medic will produce seed but a late season medic will fail.

It is a mistake however to select heavily for drought evasion.

While these early medics will produce seed in poor seasons their production is lower in good years as they flower, produce seed and dry off when there is still a considerable part of the growing season left.

The recommendations below are based on a balance between production and an ability to survive poor seasons.

Selection of medic for physical factors

The above charts and texts gives a general idea of selecting the most suitable medic for a particularly environment selection needs to go beyond the species level.

The species tells you that Burr medic will grow on neutral soils while most other medic require higher pH. Species will tell you that Strand medic is well suited to light textured soil but to select the actual cultivar that fits soil, pH and rainfall GO TO:-

 MEDIC AND CLOVER CULTIVAR SELECTION 

Management factors in cultivar selection
  

    Obviously the most important selection factors for cultivars of medic and other annual legumes is their ability to survive and produce in a particular environment but the environment is not only physical but includes management.
 

Seed and pod size.

    Seed and pod size for the various medic species differs greatly.
 

Seed weights of common medic species. 

Medic species

Average Seed Weight

Snail medic

15.0 mg

Gama medic

6.3 mg

Barrel medic (depending on cultivar)

2.9 to 8.9 mg

Disc medic

4.2 mg

Burr medic

2.7 mg

Strand medic 

2.4 mg

    Seed weight is also related to pod size. Large seed species have large pods.

    Advantages of larger pods and heavier seed.

    *  Seedlings are more vigourous

They germinate from a greater depth.

They survive better in poor seed beds.

    * Pods easier to harvest with pod harvesting machine.

    * Pods easier to harvest by sheep and provide more feed.

    Disadvantages of larger pods and heavier seed.

    * Pods easier to harvest by sheep.

Over-grazing of green and dry pods needs to be avoided or pasture will not regenerate.
 

    Large pods have considerable advantages provided spring and summer grazing is well managed.

On arable areas where medic pastures are usually grown in rotation with cereals large pods are particularly important.

If the Zaghouan 4 rotation is used the large pods will be easier to harvest.

They will also establish better if seed beds are not ideal.

In the classical medic-cereal rotation large pods and seed are also useful as they allow seedlings to grow from a greater depth.

Pods are partially buried during the cereal phase even when shallow cultivation is used.

Even though large pods have these advantages it is wise to include some medium to small pod cultivars in the mixture. They will survive better if spring and summer grazing is excessive.

 On the parcour or any area where summer grazing may be difficult to manage correctly small seeds and pods are better.

They are more difficult for sheep to harvest.

The sheep will bury many of the pods with their hooves and the pasture will survive poor management better than species with large pods.
 

Growth habit
 

    Snail medic (and to some extent Gama medic) has a more erect growth habit compared to other medic species.

It can look as if it is more productive but pasture height is a poor measure of pasture production.

A dense low mat of medic can be just as productive.

Tall growing medic needs to be grazed (during the growing period) with more care.

It can be cut for hay more easily.
 

Hard seed.

Hard seed and seed dormancy are different.

Hard seed is a characteristic of the seed coat. It does not allow water to enter and germinate the seed.

Harvesting the pods and threshing them causes slight damage to the seed coat. Purchased seed therefore has a germination rate of more than 95%

For the seed in the pods (either harvested on on the ground) the break down of the hard seed coat takes place more slowly. It is due to heating and cooling over summer.

Dormancy is a chemical characteristic of seeds. Medics have a low level of dormancy.

Medic seed in pods

The hard seed characteristic of medic applies only to seeds still in their pods.

Figure 1 below compares two cultivars of Barrel medic with two cultivars of Sub clover.

The starting point on the left is seed set or seed maturation. At this point all the seed is hard for all cultivars. That means that seed that is still in the seed pods will not germinate.

During the summer the hard seed coats break down due to heating and cooling.

The "false break" is an Australian term that describes a short period of summer rain. The rain is is sufficient to germinate all the seed that is now "soft." Hard seed does not germinate. The false break is not followed by further rain and the seedlings die.

It can be seen that little of the medic seed is lost if a false break occurs.

A high proportion of Woogenellup Sub clover is lost and a significant amount of Junee Sub clover.

The "break of the season" is the major autumn rain. Seeds germinate and further rainfall allows them to grow and establish a pasture.

The actual amount of hard seed at the end of summer will vary according to weather conditions.

 
 

The following chart provides more detailed information on medic cultivars.


 

    Even further details is provided in Cultivar selection

The significance of hard seed for medic cultivar selection.
 

    * Classic medic-cereal rotation

Operation - season

Comment on cultivar selection

Medic seed sown in autumn.

YEAR ONE

Germination high as hard seed coats broken by threshing and cleaning processes.

Grazing in winter and spring

Snail and Gama medic are more erect. Easier to over-graze.

Green and dry pods - spring and summer.

Large pods of snail easy to over-graze.

Summer rain - false breaks.

Hard seed a great advantage. Most medics except Gama medic have high levels of hard seed at this stage.

Autumn - break of season.

YEAR TWO

Our recommendation is to leave the medic for a second year to build up pod reserves and to give farmers a better idea of long term profits from medic. Germination should be good. High levels of hard seed can be a problem. Some medic cultivars are still 90 or even 95% hard at this stage. These cultivars have a long term benefit but in the short term other cultivars should be included in the mixture and summer grazing should leave a large pod reserve.

Spring - more pods produced and some added to reserve.

See above.

Autumn - break of season.

YEAR THREE

Germination of medic is good because there is seed from the two previous season available but land is cultivated for cereals. Medic seedling are killed. Pods remain near surface if shallow cultivation is used.

Autumn - break of season

YEAR FOUR

Medic pasture germinates from seed produced in year three. The high level of hard seed is a great advantage. In fact the classic medic-cereal rotation is difficult to sustain unless hard seed levels are over 50%

    * Establishment using pods. 

Operation - season

Comment on cultivar selection

Harvesting pods in summer

Medium and large pod species and cultivars are easier to harvest with the ICARDA broom harvester.

Storage of pods over summer

As pods are not exposed to extreme heating and cooling hard seed percentage will remain higher than usual.

Autumn - winter pods broadcast over cereal crop

High level of seed hardness an advantage. Any seedlings that germinate are a weed in the cereal crop.

Summer

Seed hardness breaks down in pods over summer.

Autumn - break of the season.

Medic pasture germinates from the pods broadcast in previous season. With some cultivars can be still quite high but there should still be enough seedlings to form a good pasture.

    * Medic on the parcour

Operation - season

Comment on cultivar selection

Harvesting pods in summer

Medium and large pod species easier to harvest but more easily over-grazed. Grazing control on parcour can be poor. Most important to include some small pods.

Storage of pods over summer

Store in a hot place. More hard seed that breaks down the better.

Autumn broadcast on parcour

High percentage of hard seed a problem in the first season. Germination can be poor. Compensate with higher rates and/or some cultivars with less hard seed.

Autumn in future years

High percentage of hard seed a definite advantage. Germination will be good because there is seed available from many seasons. If seed production fails in a single year due to drought or over-grazing the reserves of pods in and on the soil will allow the pasture to regenerate.

Price and availability.
 

     Having selected a suitable mix of cultivars for the physical and management environment the next stage is to check prices and availability.

The price for new cultivars can be high.

Some are also included in Plant Breeders' Rights laws.

These cultivars should be avoided if possible because of their high cost.

Farmers will need to balance the price against the possible benefits remembering that the better cultivars will become more dominant over time through natural selection if their advertised advantages have real merit.

The source of medic cultivar seed is Australia.

The seed is harvested in January, cleaned and sold before the sowing season in April and May.

Northern hemisphere consumers are often forced to accept a restricted list of cultivars because they order seed after May when all the best cultivars have been sold.