Soil Fertility and Soil Erosion
Soil Fertility
The soil fertility may be defined as the capability of a soil to supply essential plant nutrient elements as per requirement of a crops or plants. A soil is considered fertile when it contains all the essential plant nutrient elements in right proportions. Deficiency of plan nutrient elements in right proportions. Deficiency of plant nutrient elements makes soil unfertile.
Some of the major controlling factors of soil fertility are briefly mentioned below:
1. Mineral Matter
Mineral matters of soil have been formed by the physical disintegration of parent rocks, most of the plant nutrient elements are present in these mineral materials. Plants absorb these nutrient elements and thus grow and produce flower and fruit
2. Organic Matter
Organic matter is product as a result of decomposition of plant and sandal residues, excreta and dead bodies. Organic matters get mixed with the soil and help to increase the nutrient supplying capacity of soils.
3. Unevenness of soil
The hill food and lower gentle slopes are more fertile than the hill tops
4. Cultivation of land
Optimum cultivation of soil makes a soil soft and loose. Added organic matter and chemical fertilizer are well mixed with the soil when a soil is tilled. As a result plant roots can easily spread in the soil and can absorb plant nutrients and it increases the fertility of the soil.
5. Irrigation
Irrigation water when applied to soil makes the soil moistened. Soil moisture makes the nutrient elements soluble and absorbable to plants.
6. Application of Organic Manures
When applied to soil organic manures release nitrogen, phosphorus, potassium, calcium, magnesium, iron etc. in the soil, the micro-organisms are activated and soil fertility increased.
7. Application of Chemical Fertilizer
Soil fertilizer decreases due to continuous cropping Urea, T.S.P. and M.P. are applied as chemical fertilizer. As a result of application of above fertilizer, Nitrogen, Phosphorus and Potash are added respectively to the soil
Preparation of Compost and Green Manures Preparation of Compost
The compost may be defined as the material prepared by decomposing farm and cattle wastes, straw, weeds, water hyacinth, agro wastage etc. in presence of microoganisms. Compost is prepared by mixing and decomposing several types of organic wastes. However, compost can also be prepared by decomposing a single organic waste. Compost may be prepared by main two ways; Such as –
1. Heap method of composting and
2. Trench method of composting
These two methods of composting are briefly described below–
1. Heap Method of Composting
The site for compost preparation should be high enough so that water logging does not occurs. Farm premises or sides of cowshed are suitable places for setting compost heaps. Compost heaps may also be placed under a tree. At first a place measuring 3 metres in length and 2 metres in width should be selected. Four poles may be set at four corners and rope may be used for en circling the place. Farm straws staws, weeds etc, should be placed in layers within the boundary. The height of the first layer should be 30 cm. After the completion of the first layer the following materials should be spread over the layer
Grounded oil cake-1 kg. urea-500 gram, triple super phosphat-200 gram. Instead of the above materials 2 kg of bio-activator many be spread over the composting materials. After that, water may be spread by a water can over the 'layer. It will help to compact the wastes which will accelerate the decomposing process. Then a layer of 5cm thickness consisting cowdung may be given. In this way 7 consecutive layers should be prepared. The surface of the 7th layer should be like a shed having slopes at both sides so that rain water can not stand there or can not enter. The heap may be covered by a polythene sheet.
Trench Method of Composting
At first a high land site should be selected. One trench measuring 3 metres in length, 2 metres in width and 1.2 metres in depth should be dug. Similar 6 trenches may be dug side by side. Shed should be made over each trench. Five trenches should be filled with waste materials like cowdung, straw, house hold wastes etc. After filling the trenches the height of waste materials should be 30 cm above the surface. One of the trenches will be kept empty. After 4 weeks of decomposition the empty trench will be filled up with materials of nearest trench. The trench thus made empty will be filled in by another nearest trench. In this way waste materials will be transferred to the next trench and it will be fully turned. This turning will enhance the decomposition process in composting. The waste materials will be fully decomposed within 2 to 3 months. By this method compost may be prepared throughout the year in a single set of trenches.
Benefit of Compost Fertilizers
Compost fertilizers play an important role in increasing soil fertility. Nitrogen, Phosphorus, potassium nutrients are added to the soil through compost fertilizers. Besides, compost fertilizers make the soil more suitable for crop cultivation through improving the soil texture and structure. Water holding capacity and soil aeration is also increased due to compost application. The cost for compost production is also low. For these reasons use of compost is beneficial and profitable.
Preparation of Green Manures
The manure prepared by decomposing green crops grown at young stage within soil through ploughing is known as green manure. Sesbania or Dhaincha, Cowpea, Sunhemp, Kalai, Crotalaria when mixed with the soil before flowering through ploughing starts decomposing. After that when soil is pulverized thoroughly by 3 to 4 ploughings, cross ploughing and laddering. Then these materials are completely decomposed within two weeks. One of the benefit of green manure is that it is used in the place where it is grown.
Cultivation and Preparation of Sesbania Green Manure
Sesbania or Dhaincha may be cultivated in any types of soil. After one or two ploughing fertilizer should be applied to the soil at the rate of 70 gm of Triple Super Phosphate and 50 gm of Muriate of Potash per one decimal of land. Then Dhaincha seed should be shown at rate of 200 gm. 200 gms of Dhaincha seeds in one decimal of land. It will result very thick population of Dhaincha seedling. Within 75 days after seed sowing flowering will start. At this stage the plants will be mixed with the soil by ploughing. If the plant, become too tall it may be cut into pieces by Dao or sickle. The Dhaincha plants will be fully decomposed of three ploughing are done after two weeks of initiation of rottening, 350 to 450 gm of nitrogen and 12 to 100 kg organic matter are added to one decimal of land from such green manuring.
Benefits of Green Manure :
Green manure influences soil fertility and conservation of soil in many ways. Some of the important benefits are as follows-1. Green manure increases the fertility and productivity of soil.
2. Green manure supplies sufficient amount of organic matter in the soil.
3. Green manure increases the nitrogen content of soil.
4. Green manure rapidly activates the soil micro-organisms.
5. Green manure conserves plant nutrients in soil.
Soil Erosion and Conservation
Soil erosion may be defined as the transportation of surface soil by the direct action of natural forces like water stream, air flow, etc. Plant nutrients are usually stored within the 15 to 20 cm depth of soil. Soil erosion causes the loss of these surface soil nutrients. As a result agricultural soil become unfertile gradually.
Types of Soil Erosion
Soil erosion is mainly of two types. Such as
A. Water erosion
B. Wind erosion
A. Water Erosion
Water erosion may be defined as the transportation of soils from one place to another by the action of water stream. Water erosion may be of the following types-
1. Sheet Erosion
Sheet erosion may be defined as the process of soil removal in a thin sheet due to rainfall and irrigation water flows at mild slopes of land. The soft, loose and surface soil is removed by this process. Slopy land is very vulnerable to sheet erosion. Sheet erosion is very slow in flat land.
2. Rill Erosion
Rill erosion is the second phase of sheet erosion. When the speed and volume of water stream increases, the soil is removed forming narrow surface rills. This is known as rill erosion.
3. Channel Erosion
Channel erosion is the phase of erosion, which is next to rill erosion. The process of channel erosion may be defined as the transportation of soil through the channel formed by enlarging the form and structure of rills. Usually the uncared rills are transformed to channels. The land suffering from channel erosion losses its fertility and productivity rapidly.
4. River Bank Erosion
River bank erosion may be defined as the loss of river bank soil due to strong flow of stream causing damage of land. The intensity of river bank erosion is high at the beginning and at the end of flooding. Farmers frequently loose their land and houses due to river bank erosion every year in Bangladesh. Thus they become landless and poor.
5. Sea Shore Erosion
Sea shore erosion may be defined as the loss of sea shore soil and land due to tidal upsurge and waves. The coastal area and the islands of the sea are seriously affected by this type of sea shore erosion.
B. Wind Erosion
Like water stream wind of low also causes significant soil erosion. Wind erosion may be defined as the movement of soil from one place to another by the direct action of strong wind. Wind erosion causes the movement of sand of deserts off to hundred miles and makes the fertile soil unproductive.
Causes of Soil Erosion
The major causes of, soil erosion are :
1. Excessive rainfall
2. Land slope and Topography
3. Soil texture
4. Cultivation techniques or cropping system
5. Flow or air
6. Human activity
1. Excessive Rainfall
The torrential rain directly and seriously heat the soil. As a result the soil particles are broken. Rainfall for a longer duration cause flow of water on the soil surface. The flow of this excess water carries fertile soil along with from the surface and makes the soil as unproductive.
2. Slope of the Land
Erosion is found to be accelerated in sloppy land. The speed of water run off become higher when the slope of the land is higher.
3. Soil Texture
The porosity of heavy texture or clay soil is less. The infiltration of water is also less in case of heavy clay type soil. A light rainfall even can cause water logging in clay soil. If the land is slopy then the water flows to the lower ends. On the other hand more organic matter is less vulnerable to soil erosion because of its higher water holding capacity and higher porosity.
4. Cultivation Techniques or (cropping systems):
a. Soil with shallow rooted crops vulnerable to soil
b. When cultivated along the slope of hillyareas, the erosion becomes accelerated.
c. Intensive cultivation of soil cause soil erosion due to influence of water and wind.
5. Air Flow
Wind causes removal of loose surface soil of agricultural lands.
6. Human Activity
Vegetation and forest are the gift of nature. If these vegetation or forests are destroyed by human activities the soil erosion gets accelerated. Loss of forest encourages soil transportation from one place to another.
Affect of Soil Erosion
Plant nutrients and soil fertility ingredients are mainly stored in the soils of 15 to 20 cm depth. Soil erosion dominantly causes the loss of this fertile surface soil. The plant nutrient elements and level of soil fertility are thus reduced due to soil erosion. The gradual loss of soil fertility makes the soil unsuitable for crop production after certain time.
The process of soil erosion gradually results in the silting of channels rivers basins and other water ways. Char lands are raising in rivers. These Char lands seriously hamper navigation during the dry season and cause floods during the rainy season.
Soil Conservation.
Long term Occurrence of soil erosion causes loss of agricultural land. So it is important to follow scientific conservational practices to protect the soil from erosion. Some of the important soil conservation practices are described here :
Controlling Water Stream Velocity
Soil erosion may be controlled by reducing the speed of water flow or stream. The speed of water stream may be reduced by the following ways-
a. Preparing dikes or ails across the water run off in the land.
b. Leveling the small rills and channels.
c. Allowing the growth of submerged weeds and putting appropriate wire nets at the end of channels.
The land will be improved through removal of rills and channels if the above practice are regularly followed
2. Right Arrangement for Drainage
Soil may be protected from erosion taking appropriate measures for drainage. The sub soil tile drainage system is very suitable for draining out of excess rainfall water. Water drainage speed should be slow enough so that it cannot cause soil erosion.
3. Increasing Organic Matter Content of Soil
Application of organic matter increases the water absorption and water holding capacity of soil. More absorption of water from the soil surface reduces water run off. In this way increased use of organic matter will soil erosion.
4. Terrace Cultivation
Water streams can not move so fast in hill slopes if terrace are prepared for crop cultivation cross the slope By adopting this most important technique soil fertility may be conserved in slopy hill areas.
5. Cultivation in Contours
Cultivation of crops directly across the slope is known as contour method. Soil may satisfactorily be conserved by cultivating perennial crops in the contour method.
6. Segmentation of Field Plots
The soil with moderate slopes may be segmented according to the nature of land to reduce downwards of soil transportation. Then one type of crop may be cultivated in one small plot without loss of considerable soil materials.
7. Establishing Forest on Open Hand
Growing plants or afforestation always reduces water run off and thus helps to control soil erosion.
0 Comments