SIMPLE SOIL CALSSIFICATION
Soil classification refers to the grouping of soil according to specific characteristics, such as properties or factors like climate also soil can be classified according to the age, texture and color. One common classification is that based on texture.
According to the soil texture triangle, there are three main texture namely sand, silt and clay. This is based on the size of their particles as discussed earlier. There percentage content of each one of these determines the type of soil according to texture. Note that sandy soil have sand content of over 45% clay soil have above 27% while silt soil have silt content of above 40%.
SOIL TEXTURE TRIANGLE
SAND
This soil consists mainly of course and fine sand and contain very little among of clay such that it not sticky when wet and is lose when dry, percentage of sand is above 85, that of clay is up to 10 and silt is up to 10. When such soil is rubber, it does not leave any film on the figures.
LOAMY SAND: This consists most of sand but with sufficient clay such that it gives it a slight plastic quality when it is very moist. When it is rubbed between figures it leaves a slight film of fine material, sand particles account for 70% to 90% clay up to 15% and silt up to 30%.
SANDY LOAM: This soil has high percentage of sand between 43% and 85% with clay content of up to 20% and silt up to 50%. It moulds easily when it is sufficiently moist but does not stick easily to the figures.
LOAM
In this soil, sand and silt dominate an average of 40% each while clay account for about 20% on average. It moulds easily when it has sufficient moisture and does stick to the figures to some extent.
SILT LOAM
It has a high percentage of silt of between 50% and 87% sand between 13% and 50% and clay up to 27%. It is moderately plastic and not very sticky it has a smooth soapy feeling due to high content of silt.
SAND CLAY LOAM
This has over 45% sand, up to 28% silt and clay between 20% and 35%. It can be a bit sticky because of the clay content but quit porous because of the sand.
CLAY LOAM
Sand content between 20% and 54% silt between 15% and 53% clay between 27% and 40%. This one has sticky distinction when moist because of clay.
SILT CLAY LOAM
The amount of sand is between 27% and 60%, silt between 40% and 78% and clay between 27% and 40%. The high silt content makes it smooth and has a soapy feeling. It is less sticky than clay loam or silt clay.
SILT
This have over 80% silt particles, up to 20% sand and less than 12% clay. It is predominantly smooth and has a typical soapy feeling of silt.
SANDY CLAY
Sand between 45% and 65% silt up to 20% and clay between 35% and 55%. In the presence of sufficient moisture this soil is plastic and sticky clay and sand is dominated.
CLAY
The proportion of sand goes up to 45%, while that of silt is up to clay account for above 40%. The soil is sticky when moist has a plastic feel. It can be rolled into threads when moist and can be molded into different shapes. And can retain fingerprint.
SILT CLAY
Sand up to 20% silt between 40% and 60% and clay between 40% and 60%. This soil is composed of almost fine particles throughout. It is smooth and has to some extent the soapy feel of silt but has a degree of stickiness because of the high proportion of clay
SOIL EROSION
Soil erosion is the wearing away, detachment and removal of soil material from one place to another place through the agents like water, wind, ice etc
AGENTS OF SOIL EROSION
1) Water
This is the most important agent of soil erosion
Erosion by water involves:
- Splash erosion caused by rain drops
- Sheet erosion which involves the removal of the maximum cover of soil by surface water
- Sill erosion which leads to the formation of small channels called sills on the surface
- Gully erosion that leads to the formation of deep troughs called gullies due to severe under cutting
- River erosion that takes place in the specific channels called river valleys
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2) Wind
This is another agent of soil erosion. It takes place in arid and semi arid areas or where the soil is loose
3) Ice
It is also another agent of soil erosion. It takes place in cold areas where there is the formation of ice
4) Gravity
This leads to the gradual movement of weathered material down the slope without involving transporting agents.
TYPES OF SOIL EROSION
1) Normal geological erosion
It is the wide spread type of erosion that occurs wherever there is a natural flow of energy and matter on the earth’s surface without man’s influence. It is normally very slow and so infectious to the soil cover of the world.
2) Accelerated soil erosion
Is the type of erosion associated with man’s activities [man included] it is spectacular in nature therefore it has attracted man’s attention.
FACTORS AFFECTING /ACCELERATING SOIL EROSION
1) Climate
Where there is heavy rainfall erosion tends to be severe while where there is low rainfall erosion is low
2) Topography
On steep slopes soil erosion can be fast while on gentle slopes the rate of erosion tends to be low
3) Nature of soil
This depends on the characteristics or features like texture, structure, permeability e.tc. Unstable soils with coarse textures are prone to severe erosion than fine textured stable soils
4) Vegetation cover
Where there is dense vegetation soil erosion is less or low rate unlike where there is scanty or no vegetation cover.
HUMAN FACTORS
5) Good management of the soil
Which involves the way human beings use soil wisely and skillfully and undertaking conservation measures to reduce or mitigate erosion through afforestation.
6) Poor management
That involves unwise use of soil through over cultivation, over grazing and deforestation.
7) The increase in pollution
This leads to the over exploitation of resources especially minerals, forests and over cultivation.
EFFECTS OF SOIL EROSION
Soil erosion is a serious challenge which has many effects on social and economic activities.Some of these effects are explained below:-
(i)loss of productive soil.
When the to productive soil is eroded it is lost forever only the unproductive stony soil is left behind the consequently is the lowering of agriculture productivity of land.
(ii)Depict of vegetation cover.
The eroded land cannot hold the plants including crops are washed away or are buried in the deposit soil way from their original location.
(iii)Destruction of structures.
when erosion takes place bridges can being taken away from their original areas . other structures like road ,railways, as well as buildings can collapse after erosion of soils.
(iv)pollution to environment.
Eroded soil that is carried into rivers lake s and oceans may contain chemical pollutants collected by water from farm and dumping grounds, hence resulting to loss of aquatic organisms.
(v)provides sand for building and construction activities.
sand which is eroded from steep slope is deposited on river bed from where it is scoped when the water flows in the river has diminished or even stopped.The sand is then used for construction purpose this is common in
Mpiji river at Bunju Dar es salaam and most parts of kisarawe II in coastal region.
POPULATION GROWTH AND SOIL EROSION
When the region is severely affected by soil erosion, where crop production impeded when useful soil are carried away, the region experience shortage of food.even the vegetable that used to grow wild become non-existence, This causes famine and malnutrition with inadequate nutrition ,child mortality rate goes up and population growth is impeded.
Soil erosion renders the land unsuitability for habitation when gullies develop the land is unsuitable for settlement and farming . The foundation of existing buildings and roads are eroded
Soil erosion leads to lowering of the water table in a region.this causes destruction of the vegetation in the water catchment areas and leads to shortage of water resources ,the wells may dry up this means that women and children have to travel long distance in search of water that means children may not go to school general health of both women and children becomes poor this may lead to early death and linear population
Also when land become more eroded it can lead land to be unfertilized therefore it accelerate rural-urban migration especially for men who migrate to urban areas.Then led to increase of the population in urban area than the rural areas where man power decrease due to rural urban migration.
SOIL EROSION CONTROL MEASURES
soil erosion is a geological process, However when it exceeds normal rate, That is when it becomes a problem. we can not talk about stopping soil erosion .The following are some of the measures that can be taken to control soil erosion
(i)Afforestation and reafforestation
Afforestation is the planting of trees where no forest has been known to exist . Reafforestation /Reforestation is the process of planting trees on land that previously had a forest the trees help to hold
soil particles
together so that they can not easily blown away by the wind or carried way by running water.
(ii)Control of bush fires
When the grassland ,are burnt the soil is directly exposed to agents of erosion , IF the piece of land has to be cleared for cultivation the old grasses and bushes should be cut down and grasses put
aside in heap,this
will prevent soil from erosion
(iii) controlling overgrazing
There should be matching the number of livestock kept in a piece of land with the carrying capacity of land .The land can also be divided into paddocks i.e individual division of blocks of land and there after animals are grazed in one paddock at a time ,they then transferred to another division in later days.
TECHNIQUES FOR SOIL CONSERVATION
When using the land it must at the same time be properly maintained by apply proper farming techniques to reduce erosion and then to improve it productive capacity. Therefore a number of ways of doing this for example
(a)Crop rotations
This practice offers protection to the land from soil erosion and good chance to cover its original fertility crop rotation makes it possible to have the land occupied with crops most of the year. In addition the loss of crop most of the year. In addition the loss of nutrient elements by leaching is minimized and losses from erosion are greatly reduced
Erosion hazard are n important factor in determining the kind and sequence of crops to be grown in a rotation of a particular piece of land n area where erosion can easily occur due to either slope or soil characteristic, permanent crops such as trees or pasture should be planted rotation will not provide erosion protection on steep slopes.
(b)Contour farming
Contour farming is ploughing, planting and cultivating across the slope following the contours, generally on gently sloping land each contour row can be viewed as a small dam that checks the speed of non-off water and reduce erosion on well drained soil. Contour farming is simple and easier of all the supplemental soil conservation
(c)strip cropping
This is a system in which crops are grown in strips that are arranged across the general slope or at right angle to the path of the prevailing wind .The strip don not necessary have to follow contours.
(d)terracing
A terraced is an embankment of earth or stone or other suitable materials or combination of these materials made across the slope for the purpose of controlling run-off.
Terrace decrease the length of the slope thus reducing erosion and run-off .There are two types of terraces
(i)level terrace
Is a ridge built generally on sandy soil with little or no grade it is designed to hold water in the field until absorbed it adopted in areas where rainfall and soil characteristics are such that there is only slight danger of water accumulating on the soil and breaking the soil surface.
(ii)channel terraces
Consist that are cut across the slope these channel carry the excess rain water fro the fields but at a low speed thus minimizing erosion .they are commonly constructed in regions that receive heavy rainfall.
(e) Planting of trees and grasses
Trees and grasses can act as wind breakers and can also control water erosion .In controlling erosion caused by wind trees or grasses may be planted in strips so that soil particles carried by wind may be deposited on or near the grass strip.
f) controlled grazing
Overgrazing can be dangerous as most or all the vegetation can be removed with resultant exposure of the land to erosion rotational grazing with the optimum number of animals in one area can help to maintain the vegetation cover.
(g)mulching.
Mulch act as a huge sponge which absorbs the water that fall on to it and release it slowly and harmlessly to the underlying soil if there is no protective cover over a wide area erosion may occur rapidly.
