what are the advantages and disadvantages of remote sensing?
Based on energy/pressure reqd Gravity Irrigation. Border, basin & furrow irrigations Pressurized irrigation. Drip & Sprinkler irrigations Based on placement of irrigation water (on, above or below soil surface) Surface irrigation. Border, basin & furrow irrigations Subsurface irrigationRead more
- Based on energy/pressure reqd
Gravity Irrigation. Border, basin & furrow irrigations
Pressurized irrigation. Drip & Sprinkler irrigations
- Based on placement of irrigation water (on, above or below soil surface)
Surface irrigation. Border, basin & furrow irrigations
Subsurface irrigation
Overhead irrigation. Sprinkler & hand watering
- Based on wetted area of crop root zone by irrigation
Flood irrigation (Border, basin & furrow)
Drip (or trickle or localized) irrigation
Sprinkler irrigation
Surface Irrigation Method: Borders
- Best adapted to grain and forage crops
- Good for uniform soils with mild slope
- Not good for crops sensitive to wet soil conditions
- Typical efficiencies range from 70 – 85%
- Major investment is that of land grading or leveling
- Border strip width, W = 3 – 30m; Length, L = 100 —- 800m
- Has zero side slope and uniform longitudinal slope of <1%
- Strips have no cross slope
Surface Irrigation Method: Basins
- Field is divided into small units surrounded by levees or dikes
- Basin size: 1 to 15 ha; up to 100 to 400 m long
- Most commonly practiced for rice and orchard tree crops
- Level basin
- Water is held until it infiltrates or is drained away
- Minimum runoff loss and High application efficiency is possible
- Graded basin (contour levee irrigation)
- Constructed with two levees parallel and two perpendicular to the field contours
- Water enters along the upper contour and flows to the lower.
Advantages
- Water covers the basin rapidly to ensure good uniformity
- Best suited for lands/crops where leaching is required to wash out salts from the root zone
- Involves the least labour of the surface methods
- Design efficiencies can be on the order of 70-85%
Limitations
- Levees interfere with movement of farm equipment
- Higher amount of water is required compared to sprinkler or drip irrigation
- Amajor cost in basin irrigation is that of land grading or leveling
- Impedes surface drainage
Surface Irrigation Method: Furrow
- Irrigation is accomplished by running water in small channels (furrow)
- Constructed with or across the field slope
- Water infiltrates from the bottom and sides of furrows moving laterally and downward to wet the soil and to move soluble salts, fertilizer and herbicides carried with the water
- Widely spaced row crops such as potato, maize, vegetables, and trees
- Loam soil with mild slope, 0.5-2%
- Labour reqd is generally higher
- Major initial cost is construction of furrow
Types
- Level
- Graded
- Contour
Advantages
- Efficiency can be high.as 90%
- Developed at a relatively low cost after necessary land-forming activities are accomplished
- Erosion is minimal
- Adaptable to a wide range of land slopes
Limitation
- Not suitable for high permeable soil where vertical infiltration is much higher than the lateral entry
- Higher amount of water is required, compared to sprinkler or drip irrigation
- Furrows should be closely arranged
Sprinkler Irrigation
- Water is delivered through a pressurized pipe network to sprinklers, nozzles, or jets which spray the water into the air, to fall to the soil as an artificial “rain”
- Light sandy soils are well suited
- Sprinklers can be used on any topography
- Sometimes used to germinate seed and establish ground cover for crops like lettuce, alfalfa, and sod
- Very high efficiency water application
- High capital investment but has low labor requirements
Types
- Portable or hand move
- Solid set & permanent
- Travelling gun system
- Side roll system
- Centre pivot & linear move system
Advantages
- Readily automatable
- Facilitates to chemigation and fertigation
- Reduced labor requirements needed for irrigation
Limitations
- Many crops (citrus, for example) are sensitive to foliar damage when sprinkled with saline waters
- Initially high installation cost
- High maintenance cost
Drip Irrigation
- Constant steady flow of water is applied directly to the root zone of the plants by means of applicators operated under low pressure
- Applicators: orifices, emitters, porous tubing, perforated pipe
- Most efficient irrigation system
- Most suited to high-density orchards, tree crops, and high-value horticultural crops
- Not designed for large root systems
- Suited for situations where the water supply is limited
- Very effective in applying nutrients (fertilizers)/insecticides through the drip system
- Burying the drip system reduces water loss even further by preventing runoff across the surface
Advantages:
- Highly efficient system
- Limited water sources can be used
- Right amount of water can be applied in the root zone
- It can be automated and well adapted to chemigation and fertigation
- Reduces nutrient leaching, labor requirement, and operating cost
- Nearly uniform distribution of water
- Lower pressures are required-low energy for pumping
Limitations:
- High initial cost
- Technical skill is required to maintain and operate the system
- The closer the spacing, the higher the system cost per hectare
- Damage to drip tape may occur
- Cannot wet the soil volume quickly (to recover from moisture deficit) as other systems
- Facilitates shallow root zone
- Needs clean water
Other Forms of Irrigation
Hand watering
- Nurseries and Fruit trees
Capillary irrigation
- Wet the root zone by capillary rise
- Buried pipes or deep surface canals
Localized irrigation
- Water is applied around each or group of plants
- Wets root zone only
Subsurface irrigation
- Water is applied below the ground surface either by raising the water table within or near the root zone or by using a buried perforated or porous pipe system
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nikeetasharma
Advantages of remote sensing :- 1. Large area coverage: Remote sensing allows coverage of very large areas which enables regional surveys on a variety of themes and identification of extremely large features. 2. Remote sensing allows repetitive coverage which comes in handy when collecting data on dRead more
Advantages of remote sensing :-
1. Large area coverage: Remote sensing allows coverage of very large areas which enables regional surveys on a variety of themes and identification of extremely large features.
2. Remote sensing allows repetitive coverage which comes in handy when collecting data on dynamic themes such as water, agricultural fields and so on.
3. Remote sensing allows for easy collection of data over a variety of scales and resolutions.
4. A single image captured through remote sensing can be analyzed and interpreted for use in various applications and purposes. There is no limitation on the extent of information that can be gathered from a single remotely sensed image.
5. Remotely sensed data can easily be processed and analyzed fast using a computer and the data utilized for various purposes.
6. Remote sensing is unobstructive especially if the sensor is passively recording the electromagnetic energy reflected from or emitted by the phenomena of interest. This means that passive remote sensing does not disturb the object or the area of interest.
7. Data collected through remote sensing is analyzed at the laboratory which minimizes the work that needs to be done on the field.
8. Remote sensing allows for map revision at a small to medium scale which makes it a bit cheaper and faster.
9. Color composite can be obtained or produced from three separate band images which ensure the details of the area are far much more defined than when only a single band image or aerial photograph is being reproduced.
10. It is easier to locate floods or forest fire that has spread over a large region which makes it easier to plan a rescue mission easily and fast.
11. Remote sensing is a relatively cheap and constructive method reconstructing a base map in the absence of detailed land survey methods.
Disadvantages of remote sensing :-
1. Remote sensing is a fairly expensive method of analysis especially when measuring or analyzing smaller areas.
See less2. Remote sensing requires a special kind of training to analyze the images. It is therefore expensive in the long run to use remote sensing technology since extra training must be accorded to the users of the technology.
3. It is expensive to analyze repetitive photographs if there is need to analyze different aspects of the photography features.
4. It is humans who select what sensor needs to be used to collect the data, specify the resolution of the data and calibration of the sensor, select the platform that will carry the sensor and determine when the data will be collected. Because of this, it is easier to introduce human error in this kind of analysis.
5. Powerful active remote sensing systems such as radars that emit their own electromagnetic radiation can be intrusive and affect the phenomenon being investigated.
6. The instruments used in remote sensing may sometimes be un-calibrated which may lead to un-calibrated remote sensing data.
7. Sometimes different phenomena being analyzed may look the same during measurement which may lead to classification error.
8. The image being analyzed may sometimes be interfered by other phenomena that are not being measured and this should also be accounted for during analysis.
9. Remote sensing technology is sometimes oversold to the point where it feels like it is a panacea that will provide all the solution and information for conducting physical, biological or scientific research.
10. The information provided by remote sensing data may not be complete and may be temporary.
11. Sometimes large scale engineering maps cannot be prepared from satellite data which makes remote sensing data collection incomplete.