UNIT 1: Farm planning Sample
IMPORTANT TERMINOLOGY
Soil – this is the production factor for goods and services.
Soil texture – Texture is the relationship between the amount of sand, silt and clay which is present in the mineral fraction of the soil.
pH – The soil reaction refer to the acidity or alkalinity of the soil and is expressed in pH.
Productivity of soil MUST first be evaluated, regardless of whether it is rented or owned.
Determine the carrying capacity of the soil.
Possible yield of crop production.
Which agricultural recourses have a determined influence on the productivity of a farming unit?
SOIL
It is the most basic resource of agriculture.
Soil is the medium for the production of food and industrial crops. Soil must be preserved and improved to ensure sustainability.
Lesson 1: SOIL
SOIL DEPTH:
Soil depth plays a cardinal role in the development and production of plants. Some yearling plants with a smaller root system are, for example, more adaptable in soil with limited depth of 30 cm and less. On the other hand, some yearling and most perennial plants need soil with sufficient soil depth of 1 m and more.
Soil depth also has an influence on available reserve soil moisture, as well as root development. Limited soil depth limits root development – which results in plants not being able to take up sufficient food and water and to ensure sufficient above-soil growth to get maximum production.
Soil with sufficient soil depth of, for example, 60 cm, insures normal root development to take up enough water and food for maximum production. Perennial plants such as fruit trees, shrubby plants, etc., develop poorly on shallow soil with limited depth. Because shallow soil does not drain well, it tends to cause the build-up of sodium and calcium. Deeper soil has a higher drainage capacity, increased reserve soil moisture, as well as sufficient soil oxygen for plant roots. Most plants can burrow themselves better in deeper soil than in shallow soil.
IMPORTANT:
Man cannot improve or change the texture of soil, he can only adapt his farming practices to the soil texture.
SOIL TEXTURE:
Soil texture is classified according to the size of the particles. This is known as the soil fraction of the soil properties. Study the following table:
Smaller than 0,002
There are 12 texture classes, but soil is ranked in three broad categories, for example:
• Coarse
• Medium
• Fine textured
A good mixture of sand and clay in soil is an ideal texture class.
Soil in different texture classes has a huge influence on the productivity of soil. Soil properties must be interpreted and valuated as a combination
Physical activity of soil:
Is not only determined by clay content, but also by clay mineralogy. The thickness of the soil layer is also important.
Shallow soil that is physically very active will cause constructions to crack less than deeper soil.
Normal farming activities have NO influence on the soil texture, but influence other soil characteristics, such as:
• Structure
• Nutritional status
SOIL WITH A COARSE TEXTURE:
Characteristics of sandy soil:
o The soil is usually aerated very well
o This soil does not have the ability to hold water
o The macropores cannot hold the water.
o Capillary water movements do not take place
SOIL WITH A FINE TEXTURE:
Characteristics of clay soil:
Sample
The water capacity is high, in other words it can hold the water a lot better
The capillary water movement is slow, but very good.
Due to the little amount of macropores, screening is not so good
In this soil the plant roots suffer from a lack of oxygen.
pH OF SOIL:
The soil reaction refers to the acidity or alkalinity of soil and is expressed in pH. Soil acidity is associated with the presence of hydrogen ions. The pH-figure indicates pH and it varies between 0 and 14.
What does pH mean?
o At pH = 0 the medium is as acidic as possible
o At pH = 7 the medium is neutral.
o At pH = 14 the medium is extremely alkaline
An indication of the soil reaction according to the pH scale is given by the following figures:
pH 3,0 – 4,5
pH 4,6 – 5,5
pH 5,6 – 6,5
6,6 – 7,5
7,6 – 8,5
8,6 – 10,0
The pH of most agricultural soil varies between 5,5 and 7,5. We get acidic soil in high rainfall areas. Here the pH varies between 4,0 and 5,5.
SOIL TEMPERATURES:
Solar radiation is the primary source of all energy. It warms the air, soil and the organisms. Only part of the energy emitted by die sun reaches the soil. Part of the radiation that reaches the soil surface gets lost owing to reflection and radiation by the earth itself.
FACTORS THAT INFLUENCES SOIL TEMPERATURE:
colour of soil
slope
specific heat of soil
evaporation
length of the day
plant covering
soil depth
INFLUENCE OF SOIL TEMPERATURE ON CROP PRODUCTION:
1. Seeds germinates sooner and the germination percentage is much higher if the soil temperature is high. The optimum temperature for the germination of seed is about 25 ºC.
Sample
2. In South Africa, the soil temperature is too low during winter and too high during summer for optimal plant growth. The soil temperature is usually favourable for plant growth during spring and autumn. The optimal temperature for crop growth is about 25 ºC.
3. Early crops are obtained on quite warm soil and late crops are harvested on cold soil. This is important when crops are planted where the price depends on supply and demand.
4. Southern slopes in South Africa are more subject to frost damage than northern slopes. Crops that are damaged by frost must therefore not be planted on southern slopes.
5. Soil microbes’ activities increase with the increase in temperature. They prefer an optimal temperature of about 25 ºC. The soil microbes release nutrition to the plants.
6. Because microbes are more active in warm soil than cold soil, they will use organic material from the soil as source of energy. A decrease in organic content in the soil leads to the destruction of the soil structure and leads tp unfavourable growth conditions for plants.
7. The higher the soil temperature, the faster the chemical reactions in the soil progress. This leads to more nutrients being released and made accessible.
8. More nutrients are disolved in groundwater by higher soil temperatures and therefore more nutrients will be available for plants.
9. More evaporation takes place in warm soil. Therefore, the soil will dry out faster and create unfavourable conditions for plant growth.
GRAZING PADDOCKS:
GRAZING PADDOCK DIVISION:
1. Determine the different veld types.
2. Try to have one veld type per paddock.
3. Each veld type must be divided into smaller paddocks.
4. All paddocks must have drinking places.
5. Paddock fences must not be against slopes, because the animals stamp out trails, which can lead to erosion.
6. Animals must have enough grazing paddocks.
PADDOCK-SYSTEM ADVANTAGES:
1. Rotational grazing can be applied.
2. Spare paddocks are available for times of need.
3. Less labour is required, because livestock stay in paddocks.
4. Less erosion occurs, because the livestock don’t stamp out trails.
5. Animals are in a better shape because they can graze more composedly.
6. Grazing is better controlled and deterioration of paddocks is quickly determined.
ROTATIONAL GRAZING (OR PASTURE ROTATION)
Rotation grazing is performed to control the grazing of paddocks and the number of livestock, as well as the engagement period.
Pasture rotation is determined by the kind of animals, the rainfall and nature of the veld Grazing habits of animals differ. Cattle graze less selectively than sheep, while cattle prefer long grass and sheep prefer shorter grass.
The rule of thumb is that sour veld is grazed for two years and left for one year to rest. With sweet veld, better results are achieved if one half of the veld is grazed during winter and the other half is saved during summer.
Reasons for rotational grazing
• The veld must be able to recover. As soon as a camp is left to rest, the grass has a
chance to run to seed and multiply. When crops and grass are grazed continuously, the roots die. As a result the plants are unable to absorb nutrients and die.
• To keep the veld healthy. Continuous grazing cause the larvae of certain pests to increase and animals are more vulnerable to diseases as a result of larvae searching for suitable hosts.
• To maintain tasty grass. Continuous grazing causes tasty grass to stay short and may later even die.
• To prevent harmful weeds. Weeds appear quickly in overgrazed pastures.
• To prevent increase of poor quality grass and shrubs. With continuous grazing grass die, while grass and shrubs with a low productivity increase.
• To ensure enough food. Pasture rotation ensures that there is always a spare paddock that can be used in times of need.
SIGNS OF OVERGRAZING:
In many cases, too many units of livestock are kept on farms. A farmer may think there is enough plant coverage, but the typical signs of overgrazing are:
• low calf percentage, less than 75%, is an indication that feeding is insufficient
• low weaning weight in calves
• high fatality rate
• poor growth of young cattle
• heifers don’t calf at three years
• lick intakes are very high
• cattle are in a poor condition
• slaughter weight of oxen and heifers are very low
• slaughter cattle don’t achieve high grades
• bush infestation occurs
• tasty grass vanish in late winter
• termite problems may occur in certain soil types
DEFINE:
GRAZING – Good grazing is important for effective livestock farming. Grazing provides juicy food and while the animals graze, they also get some exercise.
CONTOURS:
IMPORTANT:
The main reason farmers make contour banks is to combat soil erosion.
TOPOGRAPHY:
Contour banks are quite common with crop farmers – especially in high rainfall areas with an undulating landscape – to prevent land being washed away. On natural veld it is
almost unknown to make contours. It can, however, be used to give degraded/ruined veld a good chance to recover.
The principle used to prevent water runoff, and aerate barren an trodden soil, is to loosen the soil. This happens through measuring out a zero-slope (exactly on the contour) with a dumpy level.
The contour must be measured at intervals of 50 m to 70 m – depending on the slope of the surface.
CRITERIA FOR THE MAKING OF CONTOURS:
The process takes place away from the pilot contour up to about halfway to the next pilot.
An old, heavy and strong Soilmaster is ideal. The width of the tooth is a maximum of 50 mm, and the teeth are spaced at 1,5 m (tractor wheel width). The depth, on which there must be worked, varies according to soil types of 75 mm to 125 mm. If the soil is ploughed deeper, the soil surface is disturbed too much and recovery takes longer. If tillage is done this way, Snyman suggests, remarkable results will be seen within the first year – should it rain enough.
The perfect time for action is after the first spring rains. If the soil is too dry during tillage, the results will be unsatisfactory. Also avoid soil that is too wet.
Other methods can be used, such as packing stones in rows on the contour on very rocky fields. This will prevent runoff and erosion. It is not necessary to make contours every year, because it takes at least 10 years before the field will need attention again.
REASONS:
Even crop farmers sometimes ignore contour banks – especially on more level surfaces and in parts of the country where rainfall is lower. In certain circumstances farmers in these areas can get away with not having contour banks by planting and cultivating the land according to the natural contours of the field. This still reduces the runoff of rainwater, which limits erosion and promotes moisture intrusion.
ADVANTAGES:
Making contours on cultivated soil increases production by improving moisture intrusion. It is therefore beneficial to plant pastures in rows according to the contour. If the pastures are loosened regularly to increase gas exchange (screening) and moisture intrusion, each row forms a contour bank. Erosion is therefore kept to a minimum while moisture penetrates the soil, resulting in optimal production
Barren veld is caused by long-term overgrazing and the natural action of termites, which exposes the surface in order to maximise the water runoff so that they can survive in the dry underground. The easiest and cheapest way to get rid of termites, is to wet these surfaces. Farm with nature and your labour will be rewarded with continued optimal production.
IMPORTANT:
ACTIVITY 1.1:
1. Why must productivity of soil first be evaluated? (2)
2. Supply the information that is asked in the table. (6)
3. List the characteristics of soil with a coarse structure. (4)
4. On what is the pH of soil based? (6)
5. List the factors that influence soil temperature. (7)
6. List the advantages of a good paddock-system. (6)
7. Explain the difference between: Rotation grazing (3) Pasture rotation (3)
8. Give in short the reasons for pasture rotation. (6)
9. Discuss the advantages of contour banks (7)
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