Soil Conservation
- Soil conservation is defined as the control of soil erosion in order to maintain agricultural productivity.
- Soil erosion is often the effect of many natural causes, such as water and wind.
- The are also human factors which increase the rate of soil erosion such as construction, cultivation and other activities.
- Some may argue that since it is a natural process, soil erosion is not harmful.
- The truth is that with the removal of the top layer of soil, the organic matter and nutrients are also removed.
- Conservation is not just the responsibility of soil and plant scientists, hydrologists, wildlife managers, landowners, and the forest or mine owner alone.
- All citizens should be made aware about the importance of natural resources as our lives depend on that and everyone should be involved in the process of caring of these sources properly and using them intelligently.
Agronomical measures of soil & water conservation
A) Agronomical measure (Biological)
1] Contour cultivation
2] Strip Cropping
a) Contour strip cropping
b) Field strip cropping
c) Buffer strip cropping
d) Wind strip cropping
3] Tillage practices
a] Mulch tillage
b] Vertical mulching
c] Minimum tillage
d] Conventional tillage
e] Listing
4] Soil management practices
5] Supporting practices
[interplanting, fertilizer application]
6] Vetiver grass planting
B] Engineer practices
1] Terracing
a] Diversion terrace
i] Magnum type
ii] Nichols type
iii] Broad based .type
iv] Narrow based type
b] Retention terrace
c] Bench terrace
2] Bunding:
a] Contour bunding
i) Narrow based
ii) Broad based
b) Graded Bunding
i) Narrow based
ii) Broad based
c] Side bunds
d] Lateral bunds
e] Supplemental bunds
f] Marginal bunds
g] Shoulder bunds
2) Define Runoff. Enlist various factors affecting & Types of runoff and Discuss effect of Rainfall
intensity on runoff yield.
Runoff may be defined as that portion of the rainfall which makes it way towards the river stream and ocean etc. after satisfying initial losses such as interception, depression storage etc.
Climatic Factors affecting the runoff
1) Types of precipitation: Precipitation in the form of rainfall start runoff immediately whereas in case of snowfall or hails it does not start immediately
2) Rainfall Intensity: When rainfall intensity is greater than infiltration rate of soil, the surface runoff takes place very shortly whereas in case of low intensity of rainfall a reverse trend is found
3) Duration of the rainfall: More the duration of rainfall more will be runoff.
4) Rainfall distribution: From a given watershed greater the distribution coefficient greater will be the runoff and vice versa
5) Direction of the prevailing wind: A storm moving in direction of stream slope, produces higher peak in short period of time than a storm moving in opposite direction
6) Other climatic factors: Climatic factors such as wind velocity, temperature, annual rainfall have a great influence on runoff.
TYPES OF RUNOFF
Based on the time delay between rainfall and runoff, it may be classified into following three types
1. Surface runoff,
2. Sub-surface runoff, and
3. Base flow.
1. Surface Runoff: It is that portion of rainfall, which enters the stream immediately after the rainfall.
It occurs, when all losses are satisfied and if rain is still continued, with the rate greater than infiltration rate; at this stage the excess water makes a head over the ground surface (surface detention), Which lends to move from one place to another, known as overland flow. As soon as the overland flow joins to the streams, channels or oceans, terms as surface runoff.
2. Sub-surface Runoff: That part of rainfall, which first leaches into the soil and moves laterally without joining the water-table, to the streams, rivers or oceans, is known as sub-surface runoff. Sometimes sub-surface runoff is also treated under surface runoff due to reason, that it takes very little time to reach the river or channel in comparison to ground water. The sub-surface runoff is usually referred as interflow...
3. Base flow: It is delayed flow, defined as that part of rainfall, which after failing on the ground surface, infiltrated into the soil and meets to the Water-table and flow to the streams, oceans etc. The movement of water in this type of runoff, is very slow, that is why it is also referred as delayed runoff. It takes a long time to join the rivers. or oceans. Some times base flow is also known as ground water flow.
Total Runoff =Surface runoff + Base flow
Rainfall intensity: The intensity of rainfall has a dominating effect on runoff yield. It rainfall intensity is greater than infilteration rate of soil, the surface runoff takes place very shortly, while In case of low intensity rainfall therer is found a reverse trend of the same. Thus high intensities rainfall yield higher runoff and vice-versa.
3) Define Surveying. State its Objectives. Give Uses & classification of Survey.
Surveying :
It is the art of making such measurements to determine the relative positions of points on the surface of earth, in a horizontal plane.
Object of surveying:
Following are the objects of surveying -
i) Preparation of a plan or map
ii) To draw the results of survey on paper
iii) To know the relative positions of point on ground
iv) To collect different information.
v) To collect data for analysis.
Classification of surveying:
Variety of ways are there for classifying the survey as: the nature of field survey:
(A).. Classification based upon
(i) Astronomical Surveys
(ii) Marine or Navigation Surveys
(iii) Land surveys
(a) Topographical survey
(b) Cadastral Survey
(c) City survey
(d)Engineering Survey
(b) Cadastral Survey
(c) City survey
(d)Engineering Survey
(B). Classification based upon the object of survey
(i) Archaeological Survey
(i) Mine Survey
(i) Military Survey
(iv) Geological Survey
(C). Classification based upon the instrument used:
(i) Compass survey
(ii) Plane Table Survey
(iii)Chain Survey.
(iv) Photographic Survey.
(v) Aerial Survey.
(vi) Cross-staff survey.
(vii) Theodolite Survey.
(viii) Tacheometric Survey.
(D). Classification based upon the methods employed in survey:
(i) Triangulation Survey.
(ii) Traverse Survey.
(a) Open Traverse Survey.
(b) Closed Traverse Survey.
4) Define Contour. Explain Uses & Characteristics of Contour line.
A contour may be defined as the line of intersection of a level surface with the surface of the ground. The elevation and depressions of the surface of the ground are shown on map by mean of contour lines.
Uses of Contour map:
(1) By inspection of a contour map the character of a tract of the country is obtained whether it is undulating or mountainous or flat etc.
(2) In agricultural work contour map are useful as guidelines in planning of land improvement projects.
(3) The most economical site the construction work such as reservoir, canal, road, sewage line, drainage lines or railway may be approximately selected.
(4) Quantities of road, canals, reservoir, and earthwork may be computed from the contour map.
(5) Contours are used to determine the capacity of reservoirs and area of the drainage basin.
(6) Contour maps are used for watershed planning.
(7) Contour maps are used for irrigation planning and design the irrigation system.
Characteristics of contour lines
The following characteristics of contours are observed while preparing an reading a contour map.
(1) All points on a contour have the same elevation
(2) Contour lines close to each other represent very steep ground.
(3) Contour lines are widely separated represent flat ground.
(4) A uniform slope is indicated when the contour lines are uniformly spaced and a plane surface when they are straight, parallel and equally spaced.
(5) A series of closed contour lines on the map represent a hill it the higher values are inside (fig.7.1)
(7) Contour lines cross ridge or valley lines at right angles. If the higher values are outside the bend, it represent valley (fig 7.3) and if the higher values are inside the bend or loop in the contour represent ridge (fig 7.4)
5) Define Watershed. Classify watershed & Enlist causes of watershed deterioration.
Definition: "Watershed can be defined as a unit of area which covers all the land which contributes runoff to a common point or outlet and surrounded by a ridge line". It is also known as ridge line.
OR
Definition: Watershed management implies, the judicious use of all the resources management i.e. land and vegetations, and water of the watershed to achieve maximum production with minimum hazard to the natural resources and for the well being of people. It includes treatment of land with most suitable biological as well as engineering measures
Classification of Watershed:-
A] A large number of terms are very frequently and loosely used to classify watersheds in different sizes [based on size]
a) Micro watersheds
b) Small watersheds
c) Large watersheds, etc.
B) Watersheds are also classified in different categories based on area that the watershed contains:
a) Micro watershed
b) Small watershed
c) Mini watershed
d) Sub-watershed
e) Macro watershed.
f) River basin
C) Classification based on shape:
a) Square
b) Triangular
c) Rectangular
d) Oval
e) Fern leaf shaped
f) Palm shaped
g) Polygon shaped
h) Circular
i) Secator shaped
6) Define Soil Erosion. Give types of Soil erosion and define each of them.
Soil Erosion:- It is defined as detachment, transportation and deposition soil particles from one place to another place under influence of wind, water or gravity forces.
Types of water erosion:
1. Raindrop Erosion:
It is also known as splash erosion. It results from soil splash caused by the impact of falling raindrops. Factor influencing the rate of erosion are:
1. Climate, Rainfall, temperature.
2. Soil its resistance to dispersion and its infiltration rate.
3. Topography-steepness and length of slope.
4. Plant cover-living or dead vegetation.
2. Sheet Erosion:
Removal of the fairly uniform layer of soil from the land surface by the action of rainfall and runoff. More or less uniform removal of soil in the form of thin layer or in sheet form by flowing water from a given width of sloping land.
3. Rill Erosion:
It is sometime known as micro channel erosion. It is the removal of soil by running water with the formation of a areas of small branching channels. It is regarded as a transition stage between sheet erosion and gully. Rills of small depth can be smoothened by ordinary farm tillage.
4. Gully Erosion:
It is removal of soil by excessive concentration of running water, resulting in the formation of channels ranging in the formation of channels ranging in size from 30 cm to 10 m or more. Gully erosion is advanced stage of rill erosion, much as rill erosion is an advanced stuge of sheet erosion. A gully is too large to be filled by normal tillage operations
5. Stream Channel Erosion:
Stream channel erosion is the sourcing of material from the side and bottom of a stream or water channel and the cutting of banks by running water. It is mainly doe to removal of vegetation, over grazing or cultivation on the area near to the streurs banks
7) Explain steps (phases) involved in Watershed management. Give Objectives & advantages of
Watershed management.
Objectives of watershed management:
1. To control the damaging runoff and degradation and thereby conservation of soil and water
2. To manage and utilize the runoff for useful purposes of watershed development concern
3. To protest, conserve and improve the land of watershed for more efficient and sustained production
4. To protect and enhance the water resources originating in the watershed.
5. To check the sell erosion and reduce the effect of sediment yield on the watershed
6. To rehabilitate the deteriorating lands
7. To moderate the flood peaks at downstream areas.
8. To establish the watershed management practices and measures
9. To enhance the ground water recharge, wherever applicable.
10. To improve and increase the production of timbers, ranges and wild life resources
11. To expand electricity programme
12. To intensify agricultural extension activities
8) Define Strip Cropping. Explain different types of Strip cropping.
Strip cropping is an agricultural technique used to control erosion and conserve soil nutrients. It involves planting different crops in alternating strips or bands across a field, creating a pattern that helps reduce water runoff and soil erosion.
Types of strip cropping
1. Contour strip cropping: In contour strip cropping, crops are planted along the contour lines of the land. Contour lines are lines that connect points of equal elevation on a landscape. This method is particularly effective on sloping lands because it helps slow down the flow of water, preventing it from eroding the soil and carrying away valuable nutrients. The contour strips act like small dams, allowing water to infiltrate the soil, reducing erosion and increasing water retention.
2. Field strip cropping: Field strip cropping involves planting different crops in long, narrow strips across the field, usually perpendicular to the direction of the prevailing wind or water flow. The strips can consist of different crops, vegetation, or cover crops that help to stabilize the soil, reduce erosion, and prevent the spread of pests and diseases.
3. Windbreak strip cropping: Windbreak strip cropping is a technique where rows of windbreaks, such as trees or shrubs, are planted along with the crops. These windbreaks serve as barriers to protect the main crops from strong winds, which can cause erosion and damage to the crops. The windbreak strips are typically planted in the direction of the prevailing winds to offer maximum protection.
4. Alley cropping (agroforestry): Alley cropping involves planting rows of trees or shrubs in between strips of agricultural crops. The trees or shrubs provide multiple benefits, including reducing soil erosion, improving soil fertility through nutrient cycling, and providing shade and shelter for crops and livestock. The pruned branches or leaves from the trees can be used as mulch, adding organic matter to the soil.
5. Contour buffer strips: Contour buffer strips are vegetated strips planted along the contours of the land. They act as a buffer zone between cropped areas and sensitive areas like water bodies, streams, or neighboring properties. These strips help reduce the flow of sediment, nutrients, and pesticides into waterways, protecting water quality and aquatic ecosystems.
6. Grass waterways: Grass waterways are strips of grass or grassy vegetation planted along natural or constructed drainage paths within a field. They are designed to convey excess water during heavy rainfall, preventing concentrated flow and erosion. Grass waterways help to slow down the flow of water, allowing it to infiltrate the soil and reducing the potential for soil loss.
9) Define Wind erosion. Explain types of Soil movement in Wind erosion.
Wind Erosion: It is the removal of soil from the lands surface by wind in motion. The most serious damage caused by wind erosion is the change in soil texture. The smaller particles of soil are more subjected to movement by wind.
Depending upon the degree of erosion and its location, water erosion is further classified as:
(i) Raindrop erosion
(ii)Sheet erosion
(iii) Rill erosion
(iv) Gully erosion
(v) Stream channel erosion
10) Write Universal Soil Loss Equation (USLE) with notations used.
The universal soil loss equation (USLE) developed by Wischmeier& Meyer; & the same was published in the year 1973 by Wischmeier& Meyer.
This equation was designated as Universal Soil Loss Equation, and in brief it is now as USLE. Since, simple & powerful, tool for predicting the average annual soil loss in specific situations. The associated factors of equation can be predicted by easily available meteorological & soil data.
The term ‘Universal’ refers consideration of all possible factors affecting the soil erosion/soil loss; and also its general applicability.
The USLE is given as under:
A = R K LS C P
Where,
A = computed soil loss, expressed in t/ha/y for a given storm event.
R = rainfall erosivity factor, which is the measurement of the kinetic energy of a specific rain event or an average year’s rainfall.
K = soil erodibility factor. It is the soil loss rate per erosion index unit for a given soil as measured on a unit plot. (22.1 m long with 9 % slope in continuous clean –tilled fallow)
L = slope length factor. It is the ratio of soil loss from the field plot under existing slope length to that from the 22.1 m slope length (Unit plot) under identical conditions.
S = slope gradient factor. It is the ratio of soil loss from the field slope gradient to that from the 9% slope (unit plot) under identical conditions.
C = cover or crop rotation (management) factor. It is the ratio of soil loss from the area under specified cover and management to that from an identical area is tilled continuous fallow (unit plot).
P = erosion control practices or soil conservation practices factor. It is the ratio of soil loss under a support practice like contouring, strip cropping or terracing to that under straight – row farming up and down the slope.
14) Define the following:
1. Contour
Contour is an imaginary line of constant elevation on the surface of the ground.
2. Gully erosion,
Gully erosion is the removal of soil by running water, with the formation of channels that cannot be smoothed out completely by normal cultivation.
3. Time of concentration,
Time of concentration is the time required for the runoff water to flow from the most remote point of the area to the outlet.
4. Form factor,
Form Factor is ratio of average width to axial length of watershed.
5. Geological erosion,
Geological erosion refers to the formation and loss of soil simultaneously which maintain the balance between formation and various losses.
6. Base line,
The longest chain line in chain surveying is called the base line.
7. Water harvesting,
Water harvesting term was firstly used in Australia by H.J. Geddes, to denote the collection and storage of any farm water either runoff or creek flow for irrigation use.
8. Bench terracing,
Bench terracing consists of transforming relatively steep land into a series of level or nearly strips or steps running across the slope.
9. Contour interval
Elevation differing by a fixed vertical distance between two successive contour line called contour interval.
10. Watershed,
Definition: "Watershed can be defined as a unit of area which covers all the land which contributes runoff to a common point or outlet and surrounded by a ridge line". It is also known as ridge line.
OR
Definition: Watershed management implies, the judicious use of all the resources management i.e. land and vegetations, and water of the watershed to achieve maximum production with minimum hazard to the natural resources and for the well being of people. It includes treatment of land with most suitable biological as well as engineering measures
11. Off set,
12. Runoff.
Runoff is that portion of the rainfall or irrigation water applied which leaves a field either as surface, or as subsurface flow.
