INTRODUCTION

Pakistan is basically an agricultural country and irrigation is the lifehood of agriculture. Pakistan’s agriculture is classified as irrigated agriculture with about 18 million hectares (Mha) of irrigated area contributing 90% of total agricultural produce. The area with potential for agricultural productions if water is made available for 26 Mha. Despite enormous losses in the irrigation system and reduced supplies due to prolonged drought and reduced river flow the farmers are still using highly inefficient and obsolete methods of irrigation.

Irrigations practices followed in the Balochistan Province are primitive and highly inefficient. Orchards and Fruits Farms in particular are irrigated by flooding entire fields which reduces water use efficiency to less than 40% from water source to crop use. There is immense need to save water due to severe water crises being faced by the country.

The demand of irrigation is increasing day by day due to increase in population. Chaudary and Ali 1989 expressed that overall scarcity of water, non availability of water at the right time and inefficient utilization of available water appear to be the leading factors restricting expansion in irrigated acreage and causing the gap between actual and potential yields level. At presents the irrigation water application practices are based on the traditional methods and the delivery and application efficiencies especially at the farm level are quite low.

The Indus basin irrigation system is operating at less than 40% efficiency. The shortages of irrigation water particularly during critical crop growth stages (milking and grain forming) significantly affect the crop yields. WAPDA 1995 observed that the availability of canal water supplies also significantly vary over the year and do not match wit the water requirements at various stages of crop development. Storing of surplus canal water during slack irrigation season or catching excess rainfall in a storage reservoir and subsequently using it with sprinkle and trickle irrigation will help the farms to irrigate elevated crop lands.

About 6.0mha Barani areas of the country lack any regular irrigation facilities. The reason for not having irrigation facilities is that the traditional gravity flow irrigation system is not possible due to topography, soil type, shortage of water etc. when water for irrigation is in small quantity, the more efficient use of water becomes necessary. The efficient utilization of irrigation water is possible by adapting pressurized irrigation systems such as sprinkle and trickle irrigation.

These modern irrigation technologies for the field crops and orchards can help increase water use efficiencies to 90%. Though capital intensive, the future of irrigated agriculture in Pakistan depends on adopting theses technologies for crop production as water is becoming an ever- increasing hard-to-get resources and the gap between demand and supply widens.
The term modern technology in relation to irrigation usually refers to on-farm irrigation system such as sprinkle and trickle irrigation. It can also mean the introduction of piped distribution systems for surface irrigation as well as the use of treadle pumps or the use of petrol and diesel driven pumps in areas where such technology is not used.

Sprinkle irrigation is used on approximately 5 percent of irrigated land throughout the world, the majority of which is in the developed countries. It is unlikely to replace the large areas under surface irrigation (essentially the remaining 95 percent except for a small amount of trickle irrigation.

Sprinkle is potentially less wasteful of water and uses less labor than surface irrigation. It can be adapted more easily to sandy soils subject to erosion on undulating ground, which may be costly to re-grade for surface methods. There are many types of sprinkle systems available to suit a wide variety of operating conditions. The most common for smallholders is a system using portable pipes (aluminum or plastic) supplying small rotary impact sprinklers.
The cps (center pivot system) is at the forefront which can irrigate up to 100 ha at a time. In the UK, USA, LIBYA and Kingdom of Saudi Arabia the farmers are using these system for irrigating large desert area. They are taking a lot of profit with minimum cost input. In most developing countries technicians and farmers do this very successfully in the private sectors. This technology can be very adaptable and can be used in the innovative ways when the conditions are right.

Trickle or drip irrigation comprises a system of pipes and emitters that can deliver small frequent irrigations to individual plants. This technology can provide farmers with a method of precise control over the timing and amount of irrigation and so they can easily meet the crop water demand without wasting water. Wastage of water occurs only if the system is left running for too long or there are leaks in the pipes due to hiring unskilled persons, or the less quality materials fittings. Trickle irrigation is not yet widely used on a world scale and covers less than 0.1 percent of irrigated land.

Claims made about crop yields and water savings need to be judged with care. Sales people often imply there is a magic about trickle irrigation when they refer to substantial increases in the yield and savings in water use. There is no magic. Crops respond primarily to water and not so much to the method of application. They need the same amount of water to grow properly whether this is applied with trickle irrigation or with surface flooding methods. If the right amount of water is applied to the crop at the right time it will flourish. Similarly, water savings can only be made by reducing wastage and not by reducing the amount of water the crop needs. Ironically many farmers end up applying more water when using trickle irrigation because the system allows them to apply water more easily than with other methods.

A major technical problem with trickle irrigation is emitter and lateral blockage from sand and silt, chemical precipitation from ground and algae from surface water. Each of the problems takes the use of trickle into a level of technology and support that can be difficult to sustain in a developing country. However, on a small scale the farmer can simply go around and clean the system regularly, which can overcome these problems. On a larger this would not be practicable.

Smallholders are encouraged in adopting the trickle system in the subcontinent as the spare parts are available local. The trickle system is easily operated by switched off. The potential for making timely and adequate irrigation as well as for reducing water wastage is good and the challenge is to realize that potential.

A critical issue for smallholders is the cost of trickle irrigation. The cost may well be justified by improved crop production and hence financial returns for farmers.

The system cost is determined by crop type, row spacing and the total field area irrigated. System cost can range from US$ 1000- 3000 per ha (Cornish 1998). In addition the system require regular cleaning, skilled management for effective operation and maintenance – filters require regular cleaning, systems may require periodic flushing to prevent build-up of slime. Equipment must be regularly inspected to identify and replace damaged components.

MATERIALS & METHODS

Sprinkle irrigation and its use in Pakistan would enable our farmers to produce maximum possible crop yield with minimum possible water supply. In the recent past, many scientific and technical research efforts have proven quite meaningful in developing suitable irrigation for different countries for growing vegetable or other suitable crops.

Many methods and techniques have been designed, planned, developed and applied successfully in the agricultural fields/ gardens etc for the profitable marketing agriculture. Versatile and powerful sprinkler techniques can be use economically under various topographic conditions because it requires least land development. Sprinkling is suitable for sandy soils or any other soil, where surface irrigation may be expensive, insufficient or where erosion notified. In this system quite low rates and amount of water may be applied as the said amount is needed in the seed germination, delay fru budding and cutting of crops in hot weather.

The most important input components fertilizers is dissolved in the water and applied efficient through the irrigation system. Sprinkles techniques are classified according to principals of operation, pressure discharge and material from which they are made. Sprinklers are manufactured from bronze, aluminum and polyethylene materials. Bronze and polyethylene materials are resistant and longer lasting.

Figure shows impact sprinkle spraying in the farm are spaced according to design specified.

Figure shows pop up sprinkle in the garden and lawn and photo taken Al Wassel Group of industries in Al Qassim Buraidah in the Nadec Agri farm. Pop up sprinkler used for spraying water in the garden and landscaped area

Figure showing:
A simple design describes the pop up and automatic irrigation system of the project.

Figure shows a maxi paw sprinkler used for garden.

Different type includes whirling, propeller, mini and micro. Other may be
(1) Low angle jets- under canopy sprinklers
(2) Giant sprinklers – irrigation of cereals and fodder crops with spacing covering large areas
(3) Part circles sprinklers for part irrigation of marginal areas to prevent water wastage and wetting of roads
(4) Pop – up sprinklers for lawns and house gardens
(5) Regulated sprinklers.

Fig. shows Brass impact sprinkle adjustable inlet 3/4

Pressure =1.8 to 4.3 kg/cm
Flow: 28 to 43 lpm
Diameter: 29mto 32m
Standard nozzle size: 4.76x3.17




Brass impact sprinkle full circle ¾ inlet
Pressure= 2.1 to 3.5 kg/cm
Flow: 34 to 45 lpm
Diameter: 27m to 34m
Standard nozzle size: 5.15x3.17

Fig shows Brass impact sprinkle 1 female full circle
Pressure= 2-5 kg/cm
Flow : 44 to 71 lpm
Diameter: 26 to 35m
Standard nozzle size: 5.55x 4.8m

Fig shows Brass sprinkle ½ female full circle
Pressure=1 to 3 kg/cm
Flow : 29to 39lpm
Diameter: 25m to 29m
Standard nozzle size: 5x3mm

Fig shows Brass Spray ½ female

Fig shows ½ plastic sprinkles (part/full circle)
Pressure= 1 to 3.1 bar
Flow: 10.2 to 17.7 lpm
Radius: 8.8 to 13.1 m


Figure shows full circle plastic impact sprinkle ¾
Bsp male and 1 Bsp male
Pressure = 2 to 5 bar
Flow: 26 to 42 lpm
Standard nozzle size 5x2.5mm

Fig shows micro sprays jets

Spray jet 360 degree
Spray jet 180 degree
Spray jet 90 degree

And 1 inch size having a range of throw of spray depending on size And pressure of water.

Figure shows solenoid valves Of sizes ¾, 1, 11/2, 2, and 3 inch sizes
Taking 24 volts electric current from timer And used for automatic irrigation system

Safety devices
Air relief valve of sizes 2 inch and 3 inch size

With micro- sprinklers the water jet fitted in the system strikes a bearing with one or two channels causing the sprinklers to rotate quickly and distribute the water. When selecting a sprinklers, suitable reliable workable factors such as crop, soil, quality of irrigation water, irrigation schedules, water availability or supply conditions such as pressure, discharge, labor, manpower, economic evaluation etc must be taken into consideration.

The sprinkler characteristic must also be considered such as quality of water application pressure and discharge range and sensitivity to wind etc. Medium pressure sprinklers are the most widely used ones, operated at a correct pressure and spacing appropriated the nozzle, they give good uniformity of water application with little risk of damage to crop except in sensitive cases. An irrigation system of sprinkle type is planned so that the correct amount of water will be applied efficiently at the right time.

The system should be selected after a complete evaluation and planning consideration such as crop requirement , irrigation schedule, soil type , available water infiltrations rate , climate, precipitation, wind velocity, evaporation, water quality, water supply condition discharge , pressures and proper time, landscape topography and shape of the field, existing irrigation network and labor and economic factors.

MAIN ADVANTAGES & DISADVANTAGES OF SPRINKLER IRRIGATION

The main advantages of sprinkler irrigation,

Ø Expansive land leveling is not required.

Ø Water saving irrigation intensity can be changed in accordance with the infiltration capacity of soil.

Ø High efficiency due to uniform water distribution.

Ø No special skills trained personal can operate the system reasonably well.

Ø Ease and uniform application of fertilizers and pesticides through irrigation system.

Ø Possibility of applying minute quantity of water for germination and other irrigation systems.

Ø Frequent and light irrigation possible giving better response from the crops.

Ø Increase in yield and quality, early ripening, water conservation and alternative value of specific period saving of labor, machinery, fertilizer and pesticides.

Ø Soil moisture is maintained at optimum level by sprinkler irrigation and 20 higher yields are obtained of crops and the quality of other crops is also good.


There are certain disadvantages of sprinkler system.

v Higher initial cost.

v High and continuous energy requirement for operation.

v Under high wind condition and high temperature distribution and application efficiency is poor.

v Highly saline water 7mm hos/cm causes leaf burning when temperature higher than 95 F.

v When lands have been already leveled and developed for surface or other irrigation methods

sprinkler irrigation is not so economical.

v Loss of water due to evaporation from the area during irrigation.

v Above canopy sprinkling may cause washing of spray, materials and aggravate the incidence

of pests and diseases.

DESIGN

A well designed sprinkler system applies water uniformly to the soil surface, and is capable of applying enough water to meet the peak demands of the crop without producing excess runoff. Good design considers such factors as pressure nozzle size and spacing, wind, air temperature and humidity (day versus night), soil intake rate, crop rooting depth and water use.

The flow rates from a sprinkler nozzle depend upon nozzle size and water pressure. Flow rates for selected nozzle sizes and pressure are given in table 1. Typical sprinkler flow rates may vary from 4gpm from a 5/32 inch nozzle at 30 pounds pressure to over 11gpm from a 7/32-inch nozzle at 70 pounds pressure. The nozzle sizes are usually stamped on the side of the nozzle. Wheel move systems typically have 3/16-inch nozzles.

On sloping fields there may be considerable pressure differences between sprinkler heads on high and low ends of the line. In this situation flow control nozzles may be used to improve the uniformity of water application. Flow control nozzles apply water at nearly the same rate when operated within the rated pressure range of the nozzles.
Precipitation Rate (how hard is it raining)

The precipitation Rate (Pr) is the rate at which water is delivered from the nozzle, averaged as inches per hour, over the area covered by one nozzle. It is important to consider the Pr when designing a sprinkler system, since water will run off if applied faster than the soil can absorb it. Precipitation rates can be calculated using the following formula.

Pr (inches/hr) = 96.3 x nozzle flow rate (gpm) / area covered (ft)

Note: flow rates are for agricultural sprinkler heads with brass nozzles. Sprinkler nozzle flow rate is proportional to the square root of the water pressure at the base of the nozzle thus doubling the pressure does not double the flow rate.
Precipitation rate can be calculated as follows:
In a typical wheel move system, each sprinkle covers 2400 square feet. This is based on a spacing of 40 feet between sprinklers on the line, and a 60 foot move
(40’ x 60’ =2400 square feet). With 3/16 inch nozzles that are operating at 50 pounds pressure, the nozzle flow rate is 7.0 gpm (from table 1.) the precipitation rate would be.

Pr = 96.3 (7.0gpm)/2400 ft = 0.28 inches per hour.

Application Rate (how much of the rain stays in the soil)
The application rate (Ar) is the average rate at which water is stored in the soil, in inches per hour.
Ar = Application Efficiency (Ea) x Precipitation rate (Pr)

Typical sprinkler application efficiency values vary from 60% to 80% with 70% a reasonable average.

IRRIGATION SCHEDULE

Irrigation scheduling is the process of determining when to irrigate and how much water to apply. It depends upon design, maintenance, and operation of the irrigation system and the availability of water. The objective of irrigation scheduling is to apply only the water that the crops needs, taking into account evaporation, seepage, and runoff losses and leaching requirements. Scheduling is especially important to pump irrigators if power costs are high. Common irrigation scheduling approaches includes the following.
1. Irrigation on fixed intervals or following a simple calendar, i.e. when a water turn occurs or according to a predetermined schedule.

2. Irrigation when the neighbor irrigates.

3. observation of visual plant stress indicators

4. Measuring (or estimating) soil water by use of instruments or sampling techniques such as probes.

5. Following a soil –water budget based on water data and / or pan evaporation.

6. Some combination of the above.

Figure shows the centre pivot sprinkle system.

The centre pivot system sprinkle parts and nozzle are in the following.

Supper spray sprinkler for centre pivot irrigation system

Supper spray nozzle from 4 to 25

Supper spray deflector

Supper spray nozzle for centre pivot syste

I perform this experiment in the Al-Wassel Groups for the center pivot sprinkler having length eight towers(171 ft each tower) of 1368 feet, total system 900.00GPM and pivot pressure 36.3 psi with friction c-factor 140.

Good sprinkle irrigation requires:
Understanding of soil-water-plant relationship.
Irrigation timing and amount depends on soil water holding capacity, weather, and crop growth progress.
Adequate design and installation
Proper operation and maintenance
Dedication and commitment of resources to manage.

ADVANTAGES & DISADVANTAGES OF SPRINKLER SYSTEM

ADVANTAGES OF SPRINKLE SYSTEM

o System losses (runoff, seepage) substantially reduced

o Over irrigation is completely eliminated and uniformity of application is high.

o Irrigation water requirement reduced as compared to other methods.

o No land leveling required in the field and land use for productive purposes can be maximized.

o Fertilizer can be injected in the irrigation water to reach the root zone directly

o The system allows better weed control.

LIMITATIONS OF SPRINKLE SYSTEM

§ Poor uniformity and application efficiency in high wind regimes and / or dry and hot conditions.

§ Capital cost is high with greater operational costs due to higher energy requirements.

§ Not suitable for paddy crops

§ Crops prone to diseases due to moist environment.

§ Water with impurities and sediments may damage the system.

COST OF SPRINKLER IRRIGATION SYSTEM

As for trickle irrigation, the cost of these systems is highly variable and depends on the selected system type. A simple rain-gun would cost around Rs 30 000 and can used to irrigate over 25 acres under a rotational system. Center pivot are meant for very large farms and may cost Rs 5 million for a moderate sized system to irrigate 20 ha of cooped area in one go. Pop-up systems used for irrigating lawns are relatively cheaper and cost about Rs 50 000 per ha. As the system operates under high heads the pumping costs are high.

TRICKLE IRRIGATION SYSTEM

Trickle irrigation can be defined as the supply to plants of filtered water through a low pressure piping system in an exact predetermined pattern that eliminates water spraying or running down furrows and that delivers only a few gallons of water /hour/”emitter”. In the soil under each emitter is a “turnip” of (figure 1) that can be utilized by the trees. The size and shape of the “turnip” is determined by the characteristics and the rate and duration of water application. The application of water is on daily or alternate day basis with the trickle irrigation. This frequent irrigation keeps soil moistures tension at low levels when compared to the less frequent water application typical in other systems(2)

Trickle irrigation gives only partial ground coverage. For widely spaced trees crops a 20% to 30% is necessary for adequate moisture availability.
The trickle system transport water through an expansive pipeline network to the soil near the plant and puts the water directly into the root zone. Trickle irrigation methods are high frequency – low volume, localized over a long period of application, have a low pressure requirement, and apply water near or into root zone (bucks and Davis 1986).

United state of America started using it in 1964. Today, studies are done on the design , operation, and management principal of the trickle system(Davely et al. 1973; Jobling 1973; Keller and Karmeli 1975; Goldberg et al. 1976; Merriam and Keller 1978; Howel et al. 1981; Nakayama and Bucks 1986; Keller and Bliesner 1990; Kanber 1999). Its advantages and disadvantages and the effects on the crop yield are subjects of intensive study throughout the world(Schweers and Grimes 1976; Maber 1979; Mostaghimi et al. 1981; Pai Wu 1982; Armstrong and Wilson 1982; Oron et al. 1982; Wamble and Farrar 1983; Oron 1984; Tekinel et al. 1989; Tekinel and Cevik 1993; Yavuz 1993; Cetin 1997; Ertek 1998; Keser 1998; Senyigit 1998; Kanber1999).

Drip irrigation has contributed to a marked increase in agricultural yield over the past decade. The system transports water directly to the plant and its roots for ready use. One snag in these techniques is that in contrast to the other methods, it is not applicable to all plants and land types. Before and following the years of World War 2nd, British farmers used plastics pipes in drip irrigation on land and in greenhouses (Goldberg et al. 1976; Hall 1985)

Because it is low pressure system drip irrigation is also called low-pressure irrigation. It takes water through drippers or injectors. Water leaves the dripper at zero pressure and gravity moves it to the soil and downward. The distribution in the soil has the shape of a dry onion head. The lateral flow of the water in the soil limits the area each dripper wets.

A drip irrigation system comprises a pump, control unit, network, and drippers. A schematic diagram for a typical trickle system is given in figure. The network comprises the main, manifolds, and drippers. Although this system may use all the water resources, farmers should take care to ensure the water contains no sediments or floating matter.
The dripper outputs vary 1-10 L/hour, depending on their use, operating pressures and type. Fruit orchards require flow rates ranging 4-10L/hour, but the vegetable can do with 1-2L/hour.

TYPES OF TRICKLE IRRIGATION

There are two types of trickle irrigation system that can be installed. These are:

On- surface drip
It is the slow, nearly continuous application of water as discrete drops. It is most suitable for new plantation or very young trees in the orchards.

Sub-surface drip

It involves the use of point and line source emitter to apply water below the soil surface. It is most suitable for shallow rooted crops like vegetables, strawberries etc.
Discharge rate is generally the same as in drip irrigation

ADVANTAGES & DISADVANTAGES OF TRICKLE IRRIGATION

ADVANTAGES

Ø The depth of water penetrating in the root zone can be improved appreciably.

Ø Water saving is achieved by low application rate, reducing the total evaporation surface, reducing run off, and controlling deep percolation.

Ø Greater weed control and improved quality of crops through direct fertilizer application and meeting exact crop water requirements.

Ø Dry soil between crop rows makes cultural operations and labor movements easier.

Ø Fertilizer can be injected in the irrigation water.

Ø Use of saline water is possible because irrigation are frequents and salts are diluted.

Ø Requires low energy requirements while achieving fairly high application uniformity.

Ø Bacteria, fungi, pest and diseases that depend on moist environment are reduced.

Ø Applicable to all types and topography.

Ø Minimum labor requirements to maintain and operate the system.



DISADVANTAGE

Clogging of system components by physical, chemical and biological factors.

Crop root development is normally limited to the wetted portion of the root zone, which reduces the plant’s stability to withstand winds.

Not economical for high plant density crops.

Excess salts may accumulate at the soil surface and towards the fringes of the wetted soil.

SYSTEM COST OF TRICKLE IRRIGATION

Trickle systems are generally considered capital intensive. However they have a long life –in some cases exceeding 20 years with high quality component materials. The per land unit cost of the systems is highly variable and depends on the land area to be brought under trickle system, the type of crop , and the spacing between plants.

Typically, in Pakistan, the cost varies from Rs 60,000 to 80, 000 per hectare for system installed with imported components. For systems laid with local components the cost may reduce to 40,000 to 60,000 per hectare.

SYSTEM COMPONENTS MATERIAL

The main components of the system are: main and lateral pipes (polyethylene), fertilizer tank/injector (aluminum or GI), pump, tricklers /dripper (polyethylene), and system control assembly (polyethylene) and is locally available.

Emitters:
The component about which centers the designing of a trickle system is the emitter. This device is attached to the lateral lines and feeds the water to the soil at flows ranging from 0.5 to 4 gph. A suitable emitter for an irrigation system should be (1) have a uniform and constant discharge rate (2) have a large flow cross-section to reduce clogging and (3) be inexpensive and compact. Many and varied emitters are currently manufactured and each has certain characteristics which affect the design of the system.

Emitters can be classified into three types.

Long path emitter
Tortuous path emitter
Nozzle type emitter

Fig shows hi flow dripper Pressure compensating Dripper 24 lph (6gph

octa shrubbler with 4mm Barbed inlet Adjustable
Flow 0-50 lph

4mm barb octa shrbbler on a 5 inch Spike

Adjustable Flow0-50 lph Adjustable flow dripper Single outlet 2-100 lp

Adjustable flow dripper Double outlet 2-100 lph

Super flow dripper Of 4, 8, 16 lph

Micro jet sprayer Flow 260 lph Pressure 1.5bar

Punch dripper

This classification depends upon the construction of the chamber through which the water flows. Additionally emitters can be self- flushing and can be designed to compensate for the pressure variations in the water supply. The water flows through the emitter can be classified as laminar, partially, turbulent or turbulent. The emitter type, the associated water flows along with the specific construction of the emitter, all effects its overall suitability for a given irrigation application. Careful consideration should be given to emitter selection, particularly to their susceptibility to clogging.

The figure shows the turbo key dripper used for vegetable crops in green houses.

The figure shows the pipe fitted with dripper and they are called GR Pipe with spacing and discharge specified, as from 30 cm to 80 cm spacing and discharge 4 litre/hr or 8 litre/ hr.

Figure shows inline dripper tube for surface and subsurface irrigation, this type is used for vegetable crops in green housed and for roses in garden

FILTRATION

Filter requirements are determined by the quality of the water source and the requirement of the particular emitter. Screens of various mesh size are the most common filtration device. Graded gravel and sand filters with back flushing capabilities can also be used. If large quantities of very fine sand are to be removed, a vortex separator is very efficient. A vortex separator will not remove organic debris and requires another filter (such as a screen), if this is a problem. Settling ponds are an efficient means of removing very large quantities of sand ans silt. Filtration of the mineral and organic particles from the water entering the system is of prime importance to the continued serviceability of a trickle system. A trickle system should receive 100% filtered water or no water at all

Plastic filters
Plastic filters 120 mesh filter element for 1 inch size
Plastic filters 120 mesh filter element for 11/2 inch size

Epoxy coated steel screen filtersSteel screen filter 120 mesh

Replaceable filter element Of size 3 inch flow 36 m/ hr

4 inch 72 m/ hr 6 inch 125 m/hr

Replaceable filter element Of size 3 inch flow 36 m/ hr
4 inch 72 m/ hr 6 inch 125 m/hr

Chemical injection.

An irrigation system offers the possibility of applying various chemicals through the system. Many different kinds of equipment are available for these applications. Fertilizers can be applied through a trickle system. Phosphorous is not recommended for the application through a trickle system due to problems with its solubility in water, its likelihood of precipitating and clogging emitters, and its immobility in soil.

Nitrogen fertilizers generally work well in trickle applications. Anhydrous ammonia and aqua- ammonia generally don’t work well due to volatilization of gaseous ammonia and precipitation of soluble calcium and magnesium that may be in the water. Potassium oxide works well in the trickle systems.

Caution should be used in supplying trace elements through a trickle system due to the low quantities needed, possible reaction with salts in the water and the possibility of excess levels being toxic. Chlorine (5-10ppm) can be injected into the trickle system to combat algae growth.

Acid can be injected into the system to remove bicarbonate buildup.
Herbicides can be be injected to control weed growth around emitters. Other chemicals may be suitable for irrigation application. Any unfamiliar compound being injected into an irrigation system first is tested for compatibility with system materials.

Epoxy coated fertilizer tank Inlet size ½ inch bsp female
Outlet size ½ inch bsp female Drain valve connection
1 inch size female Air relief valve connection ½ inch
Max operating pressure 8 bar

Figure shows the fertilizer tank and their spare parts.

Cleaning.
Fine sand, silt and clay tend to settle out in the slow flow at the ends of submains and laterals. Valves or capped ports should be placed at the end of each lateral and along submains to allow the periodic flushing of fine particles from the system.

HUYDRAULIC DESIGN

Careful attention must be paid to producing uniform water pressure in the irrigation system (ken worthy 1974). An elevation map of the irrigation area should be made prior to installation, although this is not always necessary. Use of pressure regulators frictional characteristics of pipe, and pressure changes due to elevation, are all important aspect of designing a system that has constant pressure characteristics. Use of pressure compensating emitters simplifies the hydraulic design of a system. Consultation with a knowledgeable trickle irrigation engineer regarding hydraulic design is time and money well spent.

METERING AND MONITORING:
Keeping account of the amounts of water pumped into various areas is an important control in a trickle system. Due to the discontinuous, visually subtle, nature of trickle irrigation, water application according to the “look” of an area is very imprecise. Use of moisture-tension measuring devices for the trees and/ or soil is a requirement for development of an enlightened irrigation regime


LEVEL OF AUTOMATION:
Due to the non-visual nature of irrigation through a trickle system an automatic shut-off should be built into the pump controls. A system that approaches complete automation is possible. The complexity of these systems and their susceptibility to malfunction argue against a high level of automation. Some level of automation is usually desirable although systems are likely to quickly discover malfunctions due to the attention required to operate the system.

A simple design describes the trickle system for dates and center pivot system in the following figure.
The dripper used in the design is pressure compensating of 24 lph and the tube used is 25 mm 4 bar.

BUBBLER IRRIGATION

This system is modified version of trickle irrigation system. In this method water is applied to the land surface as a small stream by tubular shaped bubblers that are attached to a buried or on the surface lateral line. The system is suitable for growing orchards (particularly for trees over two years of age).
Water is delivered at or near the root zone of plants in small basins around the trunks of the trees to cover the root zone. Efficiency is achieved through minimizing evaporation and deep percolation losses and eliminating runoff.

Generally discharge rate variations from bubblers due to system head losses and unevenness in land topography can be easily reduced with the help of a screwdriver. Deep percolation, where water moves below the root zone, can occur if a bubblers system is operated for too long a duration. On the other hand operating the system with short duration can cause deficit irrigation.
The following are bubbler used in the irrigation systems are,

Adjustable flood bubbler

Inlet size ½ bsp Female thread Operating pressure 1-2.75 bar
Flow rate 0-22 lit/ minute, Radius 0-60 cm

Adjustable flow bubbler Screw type Inlet size: ½ bsp Female thread
Operating pressure 0.7 – 4 bar Flow rate 4 to 9 lpm Radius 30cm to 90 cm

Stakes for bubbler Bubbler stakes 13mm Inlet size ½ Bsp outlets
Bubbler stakes 16mmInlet ½ inch Bsp outlet

Figure shows bubbler and bubbler nozzles with filter,

Photo taken by Al-Wassel group of industries in Saudi Arabia.

Distribution can be adjusted for uniformity throughout a field or for precise water delivery to individual plants based on calculation of the moisture holding capacity of the root zone and the daily irrigation requirements of the crop. Bubbler systems consisting of bubblers, pipes, valves, trenches, and basins etc. requires routine maintenance, which is not very technical.