HIGH RAINFALL ZONE

Better returns from pasture


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FARMING ZONES

Farming zones in WANA

Overview of the zone

GUIDE  FOR FARMERS AND EXTENSION AGENTS

TECHNICAL BACKUP FOR EXTENSION PROGRAMS

POLICY MAKERS AND PROJECT PLANNERS

 HIGH   RAINFALL  ZONE

  ABOVE 500 mm

YOU ARE HERE

CEREAL  ZONE

     500 mm  to 200 mm 

    Medic overview

Deep ploughing overview

What cultivar?

 How does your medic grow?

   MARGINAL  ZONE 
   

  250 mm  to 150 mm

 Tenure and grazing management

RANGELAND

Below 200  mm

Rangeland overview

Action plan for flockowners

Water harvesting

 

What is the high rainfall zone?

    The easy, but superficial, answer is that the high rainfall zone is the area with over 500 mm of annual average rainfall. 

As with the cereal zone, the marginal zone and the rangeland we have avoided a definition using these simple rainfall or length of growing period measurements.

The same is true of the high rainfall zone.

The characteristics of the zone are more complex than just rainfall above 500 mm. The zone is associated with hills and mountains. Steep slopes influence land use. Throughout the WANA region hills and mountains are responsible for the increase in rainfall - steep slope, altitude and rainfall go together.

The farms are usually smaller in the hills and mountains and populations higher.

The farming system changes with increased rainfall and a more diversified range of crops is grown.

The cereal zone is wheat or barley with fallow but the high rainfall zone includes other crops such a oilseeds. There are also tree crop. This in not a sudden change but depends on local conditions.

When I was Minister of Africulture in South Australia, I recall receiving a letter from a high official in the World Bank in Washington telling me that my proposal for the use of the medic - cereal rotation in a part of Morocco was unworkable because the rotation was for the cereal zone according to his reading of the technical literature.

The district under discussion had a rainfall of 520 mm which he pointed out meant that it was no longer in the Cereal Zone but the High Rainfall Zone as it was over the critical 500 mm. It was therefor unsuitable for medic.

    As the rainfall becomes even higher there is also an increase in altitude, slopes become too steep for cultivation. The land is used for grazing and forestry.

    The High Rainfall Zone is also important for water collection. Many large dams have been built in the zone over the last few decades.

The water is used for urban centres and for irrigation (outside the scope of this site).

The protection of the catchment from erosion is an important aspect of the management of the zone.

Why is the 500 mm rainfall line important?

     Tipping point.

     A tipping point is where certain changes accumulate and take off.

It is normally used with social behaviour or ideas.

For example a tipping point with smoking occurs when it becomes socially unacceptable. At a certain point in an anti-smoking campaign social disapproval feeds on itself to reduce the rate of smoking in the population dramatically. That has occurred in Australia where it has become quite unfashionable to smoke and smokers are regarded as a relic of an earlier era.

Here we use it in a different sense.

The agriculture of the WANA region has suffered from the introduction of technology from the northern temperate regions of Europe and USA.

These technologies have totally failed in the Cereal Zone and Rangeland because of the low rainfall and short growing season.

Above 500 mm their failure is not so glaringly obvious.

The higher rainfall, the longer growing season and lower temperature mean that the region is closer to the temperate north. It is still different.

The summers are still hot and dry.

We argue that the slightly better performance of the northern technologies in the High Rainfall Zone of the WANA region still does not justify their use.
 

    Nitrogen Fertiliser

    Nitrogen fertiliser has been the great disappointment of the modernisation of agriculture in the WANA region over the last 50 years.

It was hoped that the low fertility of the soil could be corrected with large amounts of nitrogen. That has not happened.

In Making sense of fertilisers we explain in detail the mechanism.

The lack of rainfall causes a critical stress to occur in the cereal plant which reduces the response of nitrogen to zero or even reduces yields.

In the High Rainfall Zone the risks of using nitrogen are greatly reduced. There is more rain and responses are more reliable.

In spite of this we still recommend the use of legume pastures as the basic source of nitrogen.

Legumes provide nitrogen at low cost. They also replace the organic matter in the soil.

While cereal yields are higher in this zone so are pasture yields. The relative profit from pasture is still good and justifies the livestock side of the enterprise alone.

    Fallow

    The argument about fallow becomes even more extreme.

The strongest economic argument against the fallow-cereal rotation is that it takes two years to grow a single cereal crop and little else.

In the High Rainfall Zone with the high potential productivity of pasture the opportunity cost of using the land for two years for a single cereal crop is enormous.

On the technical side of fallowing the possible storage of moisture from one winter over the summer to the next autumn become more likely.

The soil during winter is more likely to be full to field capacity.

The summer is shorter and cooler but because of the better rainfall in the autumn the advantage of a small additional amount of moisture in the following autumn is negligible. In other words fallow may work better but is needed less.

   Deep ploughing

    Deep ploughing is still bad for profits as in the Cereal Zone but farmers are more likely to get away with it.

The higher yields provide a great margin for costs but why waste potential profit on something as unnecessary as deep ploughing.

The longer growing season makes early sowing not quite as important.

    Harvesting

    The failures of the northern harvesters are not as extreme in the High Rainfall Zone because of higher yields.

Crop yields are high enough is many cases for an open or comb front to operate with equal efficiency (See Harvesting cereals )

Straw is longer and tougher reducing the problem of the straw walkers and sieves.

The stripper is still the best machine for small farmers (See  Stripper )

Rotations

    Rotation in the High Rainfall Zone are more diverse.

Grain legumes and oil seed crops are grown as well as cereals.

This has reduced the use of the traditional medic rotation as practised in Australia.

With the traditional medic rotation the pods carry over from one season of pasture through the cereal season to regenerate in the next season. If the rotation has a cereal crop followed by a grain legume crop the carry over of medic pods will be poor.

There is still a need for a legume pasture phase in the rotation to restore soil fertility and improve soil structure.

The use of pod sowing provide a low cost means of establishing a medic pasture and could provide the solution. See  Sowing medic pods

The Zaghaoun rotation has considerable potential for the small farms in the High Rainfall Zone.

Livestock production is a profitable form of farming and greatly reduces erosion.

It is also good for catchment management.

Many of these small farmers will still want ot produce some cereals for their family use. A high yielding cereal crop every four years is a good rotation for this purpose.

Pasture species

Grasses.

     Annual legumes (either medic of forages such as vetch) are the most suitable for arable rotations but it is possible to grow perennial grasses in the high rainfall zone where pastures are often retained for longer periods.

The concept of a perennial grass pasture is based on the northern European tradition where grasses have become the basis of pastures.

These grass pasture were in the past grown with a mixture of perennial clovers but are now fertilised with very large amounts of nitrogen fertiliser and contain no clover.

Many of the classic European pasture grass species such as Ryegrass and Cocksfoot have cultivars that are sufficiently summer dormant to survive in the High Rainfall Zone of WANA.

In addition there is Phalaris (a North African grass much used in Australia).

We do not recommend grasses for the reasons outlined below.

    * High cost and difficulty.

    Grass seeds for cultivars resistant to the dry summers are expensive. They are difficult to establish. A good seed bed needs to be prepared. The grass seeds are small, light and difficult to sow.

    * Legumes more important.

    Grass pastures need to be sown with legumes to provide fertility.

The concept of using large quantities of nitrogen fertiliser is uneconomic in the rainfall conditions of the WANA region.

Annual legumes are the most suitable pasture species to include in the mixture.

Research has shown that such mixed pastures are really legume pastures with some grass rather than grass pastures.

The reason is that the perennial grasses cannot grow into a dense sward as they would in northern Europe.

The dry summers require a lower density of plants. Even though the grasses are summer dormant they cannot survive at high densities due to interplant competition.

The ecological gap between the grass plants is filled with annuals that germinate in the autumn.

The farmer can sow and manage the gap with annual legumes or ignore it and allow it to be filled with annual grasses and weeds.

Obviously the legume option is more productive but research has shown that well managed legumes will provide more than half the output of the pasture and the great part of the protein content.

What is the role of the grass?

    * Down hill all the way.

    Perennial grass pasture do not reseed themselves.

The usual pattern is for a reasonable density of plants to be established.

This will thin out during the first summer due to inter-plant competition.

This density should remain for some years provide there is not a severe drought. If there is a drought the density can fall further.

It is difficult to restore the grass pasture without a complete reseeding program.

With legumes the density may also fall after a severe drought due to a large loss of legume seed from cultivars with a low level of seed hardness. It can be restored through management without a complete reseeding program.

    Legumes

    * Medics

    Medics are a most versatile family of plants.

People wonder how they can be used in the Rangeland, Marginal Zone, Cereal Zone and now in the High Rainfall Zone.

There are many different species and cultivars of medics with a large range of growing season.

Short seasoned medics are used in low rainfall areas. They germinate, flower and produce pods quickly enough to avoid the summer drought.

In the High Rainfall Zones long season medic cultivars are used.

Medics are generally adapted to alkaline soils as found in the Cereal Zone and Rangeland. In the High Rainfall Zone soils often have a lower pH.

Some M. polymorpha cultivars are adapted to neutral soils but as the pH fall even further it is hard to find suitable medic cultivars.

    * Sub clovers.

    Sub clovers is the term used to describe the T. subterraneum species and other similar species of annual clovers that bury their seed pods after flowering.

The sub clovers are generally better adapted to neutral and acid soils although cultivars such as Clare and Rosedale overlap in their soil pH with medics.

Sub clovers are similar to medic in their management except their hard seed content is usually lower.

Again one cannot be dogmatic. Some sub clovers such a Bacchus Marsh have virtually no hard seed content.

There are also medics with low hard seed - certainly lower than Rosedale, a sub clover.

Even allowing for these overlaps the generally lower hard seed content makes the sub clover group less suitable for a rotation with cereals.

The carry over of hard seed from one season through the cereal phase to regenerate in the following autumn is not as reliable.

They are used in the Western Australian cereal zone. Much of Western  Australia has low rainfall and low pH and medics are replaced by sub clovers used in cereal rotations.

    * Other legumes

    There are many other annual legumes used for pastures. Some are specialist legumes for particular soil types such as sand but there is a continual expansion of the the range for all soil types.
 

Pasture Under trees.

    Tree crops such as olives and fruit tree are common in the high rainfall zone. The land is often cultivated under the trees and sometimes cereal crops are grown.

    * Cultivate or pasture?

    We have stated in  Fallow and soil moisture  that fallowing is an ineffective and costly means of transferring soil moisture from one winter period to the next.

One of the reason for the failure of fallow is that in reality (rather than in theory) most of the moisture is used in the spring or summer by weeds.

With tree crop there is no doubt that more winter moisture can be used by the trees in spring if weed competition is eliminated.

Most orchards and olive groves in low rainfall regions are cultivated to kill weeds in late winter. This kills the weeds and soil moisture is available for the tree crop.

In the High Rainfall Zone the need for additional moisture is less as the rainfall increased over 500 mm. The farmer has a difficult judgement to make.

Cultivation will make more soil moisture available to the trees.

Cultivation, particularly on a slope will seriously increase erosion.

Yields may increase.

Alternatively a pasture under the trees will increase the production of livestock.

It will reduce erosion.

If the pasture is legume dominant it will improve the fertility of the soil and benefit the trees.

    * Best of both?

    An annual legume pasture can be used a a compromise.

Firstly it is not as deep rooted as most perennial species and does not compete as much in the deeper root zone of the trees.

Pasture legumes such as medic and the more hard seeded cultivars of sub clover can also be used in a cultivation-pasture rotation.

Alternate rows of the orchard or olive grove can be cultivated each year.

One row is cultivated while the next is left as pasture.

It protects the soil and provides a barrier against erosion.

It also produced pods for future regeneration. In the following season the pasture row is cultivated and the cultivated row regenerates from hard seed in the ground.