THE CEREAL CROP

The correct weight for tractors

How to obtain the best results

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Better cereal yields and lower cost production

CHAPTER HEADING

SUMMARY

This is a practical guide to the use of shallow cultivation for seed bed
preparation and seeding. Shallow cultivation is essential for cereals after
medic in order to ensure regeneration. It is a low cost means of seeding
for cereal, grain legumes and vetches.

This chapter provides the economic justification for shallow cultivation.

Deep plough and cultivation is entrenched in the WANA region. The
technology is wasteful and costly.

This is an overview of deep ploughing and shallow cultivation.

Once the decision has been made to use shallow cultivation it is absolutely
essential to have the proper implements. These are simple and cheap. Their basic design principles are described.

Cultivation, hay production and rotations are the main methods of
controlling weeds in the WANA region. Herbicides have a role. Practical
problems are discussed.

The response of cereals to nitrogen fertiliser in the WANA region is erratic. This is explained and strategies developed to overcome the problem. Phosphate placement can also increase yield responses.

Mechanical harvesting is the main method of harvesting cereals in the
WANA region. The machines imported from Europe and North America
perform badly as they are designed for high yielding, damp crops.
Australian adaptions will improve efficiency in low to medium yielding
crops with short, brittle straw.

Even a modified harvester will not work efficiently on small farms, around
olive trees and with many types of cereal crops. The stripper is a genuine small scale machine suited to these conditions.

YOU ARE HERE

Using shallow cultivation will often require more weight on tractors. Why
and how?

Small farmers often employ contractors to carry out cultivation, seeding and
harvesting. This is expensive and various forms of group ownership provide
a low-cost alternative.

FOUR COMMON ROTATION ON THE GROUND IN THE WANA REGION

SEASON

CEREAL - FALLOW

CEREAL - MEDIC

(Traditional rotation)

CEREAL - VETCH

CEREAL - GRAIN
LEGUME.

AUTUMN

Cereal crop sown

Cereal crop sown

Cereal crop sown

Cereal crop sown

WINTER

Cereal crop grows

Cereal crop grows

Cereal crop grows

Cereal crop grows

SPRING

Cereal crop matures

Cereal crop matures

Cereal crop matures

Cereal crop matures

SUMMER

Cereal crop harvested
Stubble grazed by livestock

Cereal crop harvested
Stubble grazed by livestock

Cereal crop harvested
Stubble grazed by livestock

Cereal crop harvested
Stubble grazed by livestock

AUTUMN

Weeds germinate naturally

Medic regenerates from seed
produced 18 months earlier.
No cultivation of the land
required.

Land cultivated and sown to
vetch or similar forage
legumes.

Land cultivated and sown to
grain legume such as lentils or
chick peas.

WINTER

Weeds grazed. Low stocking rate.

Medic pasture grazed. High stocking rate.

Grazed or more often left for
hay.

Grain legumes grow.

SPRING

Land cultivated for fallow

Medic grazed. Pods produced
for future regeneration.

Cut for hay.

Grain legumes mature.

SUMMER

Bare soil vulnerable to
erosion.

Pods and stubble grazed.

Stubble grazed.

Harvested.

Stubble grazed.

AUTUMN

Cereal cycle begins again.

Cereal cycle begins again

Cereal cycle begins again

Cereal cycle begins again

What is the problem?

    Farmers who change from deep ploughing to scarifiers and seeders will need to change to trailed implements in many cases. Currently they use implements mounted on the linkage of their tractors.

    To obtain the best results from shallow cultivation with a scarifier they will need to use implements that are wider and longer than those currently used. They will soon find that these implements are too heavy and too large to handle on the linkage of their tractor.

    If a farmer also adopts a scarifier seeder which cultivates and sows seed and fertiliser they will be forced down the trailed implement track.

The weight of these implements including the the seed and fertiliser is too great to handle on the linkage of the tractor.
 

Why do tractors need to be modified for trailed implements?

    Linkage implements are carried by the tractor.

Their weight adds to the weight of the tractor.

There is no need to add weight.

With trailed implements it is possible to transfer some weight to the tractor draw bar but it will not be sufficient.

Tractors will need addition weight to reduce wheel slip and increase efficiency.

    Farmers need to modify their tractors to achieve the right balance.

    * Too light.

    If the tractor is too light there will be excessive wheel slip.

This will waste power and fuel and cause rapid tyre wear.

In extreme cases the tractor may not even be able to pull the implement in spite of the fact that it has adequate power.

This has occurred on a number of occasions when scarifier seeders have replaced linkage implements.

    * Too heavy.

    If the tractor is too heavy some of the power is wasted because of the extra and unnecessary weight being moved. The transmission components may fail due to the extra strain being put on them.

    Modern tractors are built for many tasks.

They tend to be lighter and will require additional weight when used for shallow cultivation.
 

* An example
 

    * Tractor 1

    Tractor too light  -  weight 7200 kg.

    Wheelslip    ..................................................................... 25%
    Power at axles ...............................................................100 kW
    Less wasted in wheelslip ...............................................25 kW
    Less amount wasted in moving the tractor ............ 16 kW
    Amount available at the draw bar ............................  59 kW

    * Tractor 2

    Tractor too heavy - weight 15,700 kg

    Wheelslip    .....................................................................    7%
    Power at axles ...............................................................100 kW
    Less wasted in wheelslip ...............................................  7 kW
    Less amount wasted in moving the tractor ............ 34 kW
    Amount available at the draw bar ............................  59 kW

    * Tractor 3

    Tractor just right  - weight 9800 kg

    Wheelslip    .....................................................................    12%
    Power at axles ...............................................................  100 kW
    Less wasted in wheelslip ...............................................  12 kW
    Less amount wasted in moving the tractor ............    21 kW
    Amount available at the draw bar ............................    67 kW

Acceptable levels of wheelslip.

Table 1

Tractor type

Hard soil

Cultivated soil

2 wheel drive

7 to 11%

10 to 15%

4 wheel drive 

6 to 10%

8 to 12%

Wheelslip should be measured with the tractor working in the field.

It cannot be estimated.

If the tractor is working within the ranges shown above the tractor will be working near its optimum efficiency.

Reducing wheel slip below the figures given above will not save money and can overload the tractor.
 

How to add weight to the tractor.

    Weight can be added to the tractor by:-

    * Putting water in the tyres.

In the WANA region this can be done without anti-freeze in most areas but in the colder regions anti freeze must be added.

    * Adding solid weights to the centres of the wheels and to the front of the tractor.

    * If even more weight is required wider wheel rims can be fitted with wider tyres.

These will hold more water and carry more weight. Farmers will be reluctant to modify their tractors in this way but for new tractors the additional cost is small and often worthwhile.