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Drip Irrigation for Coconut

KRIsm VIGYAN KENDRA CENTRAL PLANTATION CROPS RESEARCH INSTITUTE ¥ W/J(Indian Council of Agricultural Research ) CPCRI

~ KASARAGOD - 671 124, KERALA IC AR

Published by

M.K. Nair

Director

CPCRI

Kasaragod - 671 124, Kerala

Updated by

M.R. Hegde

P. Gopala Sundaram

April. 1995

Printed a t

Codeword Process & Printers.

Mangalor~.

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Drip Irrigation for Coconut

Coconut palm is a per nnia l crop committed to the land for decades. It produces inflorescen es and bunches through t the year and therefore, needs continuous supply of water. Major area under coconut on the west coasl receiv s an annual rainfall ranginO" from 2000 mm to 3500 mm which is about twice that of the annual evapor tion (1500 to 1750 rum). Yet llie crop experiences moisture stress fr.om Dec mber to May which are rainless months. Coconut has been observed to respond well to irrigati n, the increase in yield being over 30 nuts / palm/ year.

Traditionally. coconut gardens are flood or basin inigated. In such case, Ule irrigation effi~iency is only 30 to 60 per cent du to the wastage of water. Besides, there is wastage of labour and energy in adopting these systems. Scarcity of irrigation wat r and increasing co t of labour and energy are pOsing serious threat to the economic viability of coconut production. It is, therefore, imperative Ulat the water u se efficiency is increased.

Concerted efforts t o use water effiCiently in agricultu re have resulted in astounding advancement in irrigation technology and drip irrigation is one of the latest innovations in this direction. In th is sys tem. application of low volum of water to the plant root zone through nozzles , micro-tubes. dripp rs etc., is done either under or above the soil sm-face. Drip system is the most efficienL system of irrigation witll an irrigation efficiency of about 90 per cent. This method of irrigation is especially well suited to widely spaced crops like coconut.

Advantages of drip irrigation

Water saving Due to partia l wetting of the soH volume, redu ced surface evaporation. decreased run-off and con trolled d ep percolation losses. th re is saving of water upto 60 per cent.

Enhanced plant growth and yield : Slow and frequ n t watering eliminates wide flu tuations in moisture content resulting in better growth and yield.

Saving in labour and energy: If th e sy~ tem is well designed , p roperly installed and water supply is clean, labour is required only for switching on a nd off the system. Because of high iniga tion effiCiency, less time is required to supply required quantity of wa ter, thus savinO" ener . Th operating pressure is also comparatively lower than oUler sy terns.

Most suited to poor soils: ery ligh t soils are d ifficult to irrigate by conventional method due to deepp_rcolation ofwale r. Similarly. very 11 . "OY soil. with low inflltration rates are dim ult- to irrigate by sprinklcr method . Drip irriga .on has been successful "in bo lh the soils.

Sparse weed growth : Due to partial wetting of soil volume. weed infes tation is less in comparison to othcr m Ulods of irrigation.

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Drum 200 lit cap

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Fig. 1 fa) A model layout plan of drip irrigation for coconut plantation (0.2 ha) In lei

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size of the garden. For small gard n s (upto 35 palms) 16 mm ID. LOPE can be u sed forsupply as w II as ficld mains. HDPE or PVC pipe of38 . 50. 75 and 100 mm 10 are u sed for 1.2 .3 and 4 ha gardens respectively. Field m ain s are laid along or across the length for unifo rm pressure. Th ese are a lso HOPE or P TC pipes h avin g lesser diam eter than supply mai n . Only in gardens where water source is a t some distance. supply main is required . In large gard ns sub-main s are need d. In s u ch case, if field main is of 50 mm TO then s ub -main of 38 mm is used. A gate valve is provided in the main pipe to regulate the water flow.

3. Laterals: LOPE or LLOPE pipes of 12 or 16 mm ill are used for later:als. The la terals run a long the rows. The sizes of main . sub-main and laterals a re so selected that gives almosl u n ifonn discharge a t each dripper. Maximum length oflalerals can be upt o 50 m for unifo rm water application. The laterals a re connected with the sub-main through a joint. The ends are closed by plugs or simply by bending the end and tieing wJth thread.

4. Drippers : Small water-tap-type emitters are used in this system (Fig.4) . Emitters are conn ected .0 the laleral' wi th the help of small pi ce of black polythene micro-tubing (4 mm ill). The lateral ar carefu lly punched so that when microlube piece is inserted, there is no leaJ(age. The advant' ge oftap type dripper is that discharge rate can be adjusted vruying from 1 to 12 tit / hr. according to Hle soil type. The probl m of decrease in discharge ratc d\..le to decrease in pressure i . sol d by regulating the rate ofdischarge. Thus uniform discharge ral is m aintained at all the dlippin~ paints. Such drippers are most s uited to garden with uneven topography for maintaining uniform a pplication of water. Cleaning of emitters if needed. is also very easy.

5. Micro-tubes: Pieces ofblack polythene t.ubings ( 4 mm ID) are used to connect drippers with the laterals. One end of tlJe micro- tube i.s altached to lat ral and the other to the drippei:'. The length of micro-tube varies according to the distance f dripping poinl from the la teral. Microtubes of 1 or 2 mm TO can be connected La the la rals and u sed fOl' irrigation wiiliout drippers.

6. Filter: The fil ler is an essen tial part of the drip ystem, its main rol bem to reduce emitt r cloggin . A s imple fil ler is fabricaled by making perforations in sm all piece of PVC pipe of deSired diameter. A stainless st .el / copper wire me., h (200-300 mesh size) or -ynthelie cloth is wrapped over the perforated pipe and tied . This is onnected to the main line a t the entrance In the storage tanlc

7. Fitting accessories : Some a cessories uch as gale valve, 110se collar. start connectors. reducers and plugs for main . sub-main. laterals e tc. are n eeded for assembling the whole unil.

Layout ofdrip system: Depending upon the situ aUon . main pipe i laid out a long or perpendicu lar to the length of tl1C garden . Sub-mains run perpen dicu! r to the main a nd la lera ls are laid perpen dicular to the sub-main

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along the rows. Main and sub-main pipes may be buried about 30 cm below the ground. Four pits of 20 x 20 x 30 cm are opened opposite to each other at one metre distance from the trunk A 40 cm long PVC conduit pipe (16 mm ill) is placed in a slanting position in each pit leaving about 10 em above ground. Emitters are placed inside the conduit pipe. Pits are mulched with coir dust or dry leaves to reduce evaporation loss. Thus water is allowed to drip a t 30 cm below the soil surface. This gives 50% higher wetted volume than plaCing drippers on surface.

Water quantity and rate of appUcation : Daily water need varies according to the evaporative demand . As water need does not vary much. a fixed quantity of 30 to 40 litres per palm pel" day is sufficient for realizing higher production under Kasaragod conditions. Discharge rate depends on the intake rate of the soil. In most of the coconut soils. the intake rate is very high (> 20 cm/hr).

Therefore. any rate between 2 to 10 lit/hr per emitter can be maintained . If clogging of emitters is a problem. higher discharge r ate may be maiptained. The duration of discharge is to be adjusted in accordance with tile quantity of water to be given. Under nonnal conditions four hour discharge is sufficient.

Fertigation : TI1e process of adding fertilizer to the plants alongwith inigation water is called fertigation. Under drip irrigation. all the fertilizers b roadcast over the soil surface are not moved into the root zone due to partial wetting of root zonc. Therefore. application of tbe required n u trients. specially water soluble nitrogen and potaSSium fertilizers directly to the water. will help to reduce the cost of manuring. besides improving fertilizer use efficiency. .

Emitter clogging :

Emitter clogging is a serious problem that affects the rate and unifOrmity of water application. It may be due to the presence of sand. silt and organic matter in the water. development of algal and bacterial growth in the lubes and presence of dissolved iron in conjunction with iron bacteria . The analysis of the water for clogging agents is essential [or determining the type of clogging problem. Once the causative factor is identified, preventive measures should be followed. Sometimes the solutions are not practical and economically feasible eventhough the cause is known. Therefore. the following general preventive measures are suggested.

1. Water filtration : When clogging occurs due to physical factors (presence ofsand. sUtand organiC matter in water). good ftlters made ofstainless steel (200-300 mesh size) or synthetic cloth should be used. Filt ers should be cleaned manually atleast fortnightly.

2. Flushing of pipe Unes : Frequent field inspections of emitters. pipelines and accessory equipUlents are required to detect faults to keep the system in proper function. PIpeline flushing is essential where irrigaUon water

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contain s s ilt. sand. organic matter etc. Provision may be m ade to fl u sh main. sub-main and latera ls.

3. Maintaining high rate ofdischarge: Sometimes emitter blocking occurs due to entrY of the air bubbles with low discharge rate. Also when concentration of iron j more than 1 ppm in water. frequent blocking of mitters i observed. Such b lackings can be reduced by maintaining higher discharge rates (> 4 lit/ hr).

4. Avoid GI water storage tank and pipelines: Of .en emitters are blocked due to rust and iron scraps from the iron tanks and galvanized iron pipes. Masonry or plastic tanks should be used for water storage and PVC or HOPE pipe be used for conveying water La solve th is problem.

Cost ofdrip irrigation units: The cost ofdrip inigation unlts for different sizes of coconut gardens is given in Table ].

Table 1. Approximate lnslallatlon cost of drip irrigation units.

(i) For 0.2 ha (35 palms)

S.No. Items App. cost Rs.

1. Main pipe LOPE (16 mm ID 55 m length) @ Rs. 5.00/m

275.00

2. Laterals LOPE (1Omm ID) 240 m length @ Rs. 4.00/m

960.00

3 . Micro-tube (4 m m 10) 150 m length @ Rs. 1.50/ m

225.00

4. Micro tube connector

connector 150 nos: @ Rs 0 .50 per 75.00

5. Emitters (4 / palm) 140 Nos. @ Rs. 1.50 / emitter

210.00

6. PVC pipe (12.5 mm) 60m @ Rs. 7.00/ m 420.00

7 . Drum and Simple filler 500.00

8 . Gate valve and fittings 500.00

Total 3.165.00

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(ii) For 0.4 ha (75 palms)

S.No. Items App. cost Rs.

1. Pump 1 HP 3000.00

2. Masonry tank 300 0 lit capacity 2000.00

3 . Main pipe HOPE (50 mm) length @ Rs. 15.00 750.00

4. End stops (50 m m ) 2 Nos. @ Rs. 20.00 each 40.00

5. Connectors ( 50 mm) 2 Nos. @ Rs. 25.00 each 50.00

6. Laterals LOPE (16 mm ID) 550 m length @ Rs. 5 .00 per meter 2750.00

7. End stops (16mmJ 18 Nos . @ Rs . 0 .50 each 9 .00

8. Start connectors (16mm) 18 Nos . @ Rs. 4.00 each 72 .00

9. Micro-tube (4mm IDJ 250 m length @ Rs. 1.50 /m 3 75. 00

10. Micro-tube connect ors 300 no 's @ Rs 0 .50 per 150.00 con nectors

11. Emitters 300 Nos. @ Rs. 1.50 each 450 .0 0

12. PVC pipe (12.5 mmJ 120 m length @ Rs. 7.00/m 840.00

13. Filter 400.00

14. GI fi ttings, gate valves , pipe connections etc. 750 .00

15. Ins tallation charges @ 10% of the total 1000.00

Tot.al 12.636.00

Exclusive of p ump & tank 7 ,506.00

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(iii) For one hectare (175 palms)

S.No. Items App. cost RB.

I. Pwnp 2 HP 4500.00

2. Masonry tank 6000 lit capacity 4500.00

3. Main pipe HOPE (50 mm) 110m length @ Rs. 15.00/m 1650.00

4. End stops (50 mm) 2 Nos. @ Rs . 20.00 each 40.00

5 . Connectors (50 mm) 2 Nos. @ Rs . 25.00 each 50. 00

6. Laterals LDPE (16mm ID) 1400 m length @ Hos. 5.00/m 7000.00

7. End st.ops (16 mm) 40 Nos @ Rs. 0.50 each 20.00

8. Start connectors (16 mm) 40 Nos. @ Rs. 4 .00 each 160.00 \9 . Micro-tube (4 mm ID) 630 m length @ Rs. l.50/m 945.00

10. Micro-tube Connectors 700 no's @ Rs 0.50 per 350.00 connector

\ 1l. Emitters 700 Nos @ Rs . 1.50 each 1050.00

12. PVC pipe (1 2.5 m m) 280m @ Rs. 7.00/m 1960.00

13. Filter 400.00

14. GI fittings, ga te valves, pipe connections tc. 750.00

15. Ins ta llation charges 10% of the total cost 1500.00

Total 24,875.00.. Exclusive of pump and tank 15.875.00

Precautions :

1. For longevity of U1e system. only quality materials especially in the case of laterals should be used.

2 . Fr quent checking should be done to maintain the system in proper order.

3. For long liIe an d protection from rodents and dogs. la terals sh ould be buried il. the ground a t abou l30 em depth.

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