It is essential to characterize and map the irrigation water quality to foresee its adverse effect on soil health and productivity. A study was undertaken to generate irrigation water quality maps of coconut land cover in Coimbatore and Tiruppur districts of Tamil Nadu, India using geographic information system (GIS). Samples were collected from 110 geo-referenced collection sites. The irrigation water quality was assessed and thematic maps were developed. From the maps it was found that nearly 12 per cent area had poor quality irrigation water with respect to pH. Majority of the samples were safe and only around 10 per cent samples showed salinity hazard. Based on sodium adsorption ratio (SAR) the irrigation water of major area were in fair (53%) and poor (50%) classes. Irrigation water quality in terms of residual sodium carbonate (RSC) in nearly 42 per cent of the coconut land cover was under unsuitable class. The soluble sodium percentage (SSP) based classification showed good quality irrigation water in most of the area (97%). Around 51 per cent of the area was having irrigation water of unsatisfactory quality based on potential salinity. The permeability index (PI) of the irrigation water of 14 per cent area was found to be unsatisfactory

Duraisami, V.P.

Selvamani, V.

English

Update Publishing (E-Journals)

34Journal of Plantation Crops, 2014, 42(1): 34-39Research ArticleCharacterization and mapping irrigation water qualityof coconut groves in Coimbatore and Tiruppur districts ofTamil Nadu, IndiaV. Selvamani* and V.P. Duraisami1Central Plantation Crops Research Institute, Kasaragod - 671 124, Kerala, India1Tamil Nadu Agricultural University, Coimbatore - 641 003, Tamil Nadu, India(Manuscript Received: 02-05-13, Revised: 21-10-13, Accepted: 04-11-13)AbstractIt is essential to characterize and map the irrigation water quality to foresee its adverse effect on soil health and productivity.  Astudy was undertaken to generate irrigation water quality maps of coconut land cover in Coimbatore and Tiruppur districts ofTamil Nadu, India using geographic information system (GIS). Samples were collected from 110 geo-referenced collection sites.The irrigation water quality was assessed and thematic maps were developed. From the maps it was found that nearly 12 per centarea had poor quality irrigation water with respect to pH.   Majority of the samples were safe and only around 10 per cent samplesshowed salinity hazard. Based on sodium adsorption ratio (SAR) the irrigation water of major area were in fair (53%) and poor(50%) classes. Irrigation water quality in terms of residual sodium carbonate (RSC) in nearly 42 per cent of the coconut landcover was under unsuitable class. The soluble sodium percentage (SSP) based classification showed good quality irrigation waterin most of the area (97%). Around 51 per cent of the area was having irrigation water of unsatisfactory quality based on potentialsalinity. The permeability index (PI) of the irrigation water of 14 per cent area was found to be unsatisfactory.Keywords: Characterization, coconut, irrigation, land cover, mapping, water quality*Corresponding Author: selvamaniv@gmail.comIntroductionFactors affecting crop yield and quality are site-specific (Reetz and Fixen, 2000). The managementof spatially and temporally dynamic factors likeirrigation water is important in a successful site-specific management strategy. Over drafting ofground water and its quality deterioration are themajor threats to crop production (Boumans et al.,1988). At the farm level, continuous use of poorquality irrigation water and improper irrigationmanagement adversely affects the soil physical andchemical properties and ultimately affects theproductivity of soil.To assess the irrigation water quality relatedconstraints and to foresee its adverse effect on soilhealth and crop productivity, it is essential tocharacterize and map the irrigation water quality.There are several studies related to the regional levelassessment of irrigation water quality. Mahendranand Arunachalam (2002) studied the quality of wellwaters of coastal belts of Radahapuram taluk,Tirunelveli, Tamil Nadu. Minakshi et al. (2006)assessed the ground water quality of Rupnagardistrict of Punjab. Pradhan et al. (2011) studied theground water quality of ‘Gohana’ Block of Haryana.The quantity and irrigation water managementpractice varies with the crop. In the case of perennialplantations like coconut (Cocos nucifera Linn.),which stands for decades and being irrigated withmore water (under irrigated condition), monitoringthe effects of water quality on soil property isnecessary. Mapping irrigation water quality mayhelp the coconut groves to protect the soil healthand improve crop productivity. Hence, a study wasundertaken with the objective to generate irrigation35Mapping irrigation water quality of coconut groveswater quality maps of coconut land cover ofCoimbatore and Tiruppur districts using GIS.Materials and methodsStudy areaThe study area covers coconut land cover ofCoimbatore and Tiruppur districts of Tamil Nadustate, India. Geographical area of the Coimbatoreand Tiruppur districts together is 9,908 squarekilometers. Coimbatore district has coconut as majorcrop in an area of 80,712 hectares with a productivityof 14,831 nuts ha-1 and Tiruppur district has 49,598ha of coconut with a productivity of 8,239 nuts ha-1in the year 2010-11 (CDB, 2011).Groundwater quality analysisAn extensive survey was carried out covering110 geo-referenced collection sites located acrossCoimbatore and Tiruppur districts. The coconutplantations in these districts are not contiguous,hence, the irrigation water sources of coconut coverwere considered for the field studies. Irrigation watersamples were collected from 73 sites in Coimbatoredistrict and from 37 sites in Tiruppur district.Water samples were collected in polypropylenecontainers, which were rinsed with sampling waterseveral times before taking samples and sampleswere collected directly from the outlet points aftercontinuous discharge from the source for 10 to 20minutes. About one liter water was collected toobtain a reasonably good representative sample. Thewater samples were analyzed within 48 hours fortheir chemical composition and the methods adoptedfor analysis were as follows, pH using pH meter(USSL, 1968), EC by conductometry method(USSL, 1968), Ca and Mg by Versenate titrationmethod (Diehl et al., 1950), Na and K by flamephotometry method (Stanford and English, 1949),CO3 and HCO3 by titration with 0.1 N H2SO4(AOAC, 1950), Cl by titration with 0.1 N AgNO3(AOAC, 1950) and SO4 by turbidimetry method(Tandon, 1995).From the analytical results of the irrigationwater, the quality parameters viz., residual sodiumcarbonate (RSC), sodium adsorption ratio (SAR),potential salinity (PS), soluble sodium percentage(SSP) and permeability index (PI) were computed.In all the calculations, concentrations wereexpressed in meq L-1.RSC (Richards, 1954)RSC = (CO32- + HCO3-) – (Ca2+ + Mg2+)SSP (Richards, 1954)SSP = Na+x 100Ca2+ + Mg2+ + Na+SAR (Richards, 1954)SAR = Na+x 100(Ca2+ + Mg2+)/2PS (Doneen, 1975)Potential salinity = Cl- +PI (Doneen, 1975)Permeability index =  (Na+ + HCO3–)                                                           Ca2++Mg2++Na+  x 100Mapping irrigation water quality using GISThe sample sites were geo-coded using thelatitude and longitude recorded using GPS duringthe survey conducted. The base map was preparedusing the digital map of the study area, coconut landcover map and the digitized sample sites.Database on irrigation water quality parameterswere developed and updated with sample numbersusing microsoft excel package. The database wasthen exported to ArcGIS 8.2 via dBase IV formatand the attribute table was geo-coded using samplenumber as the key field. Using the coconut landcover map and database developed on irrigationwater quality, the thematic maps on irrigation waterqualities were generated.Results and discussionThe irrigation water quality has a role in thedevelopment of salinity/alkalinity in the soil,thereby affecting the soil quality. The amount ofsoluble salts and excess of sodium in the irrigationwater determine the uptake by the crops which maylead to the yield variations. Hence, irrigation waterquality of coconut land cover in Coimbatore andTiruppur districts were assessed for various qualityparameters (Table 1) and thematic maps of√√SO42-36Selvamani and Duraisamiirrigation water quality parameters (Fig. 1) in thecoconut land cover were developed and the spatialinformation of the extent of the area coming underdifferent water quality classes were determined(Table 2).pH of the waterIrrigation water pH of the study area rangedfrom 6.61 to 8.93 with a mean of 7.54 and CV percent of 4.16. In Coimbatore district, pH ranged from7.00 to 8.93 and the mean value was 7.56 and theCV per cent was 4.37. In Tiruppur district pH ofirrigation water ranged between 6.61 and 7.97 witha mean of 7.50 and the CV per cent of 3.70.The irrigation water quality of the coconutland cover was classified as excellent, good, fair,poor and very poor based on pH and were found toexist in 21 (23,869 ha), 24 (2,706 ha), 43 (48,217ha), 12 (13,836 ha) and 0.03 (38 ha) per cent ofthe coconut land cover, respectively. Nearly 50 percent of the irrigation water may not have anysalinity hazard.Table 1.  Range and mean values of irrigation water quality parameters of Coimbatore and Tiruppur districtsDistrict pH EC SAR RSC SSP (%) PS PI(dS m-1) (meq L-1) (meq L-1)Coimbatore Min 7.00 0.02 0.69 -28.54 16.31 0.80 51.02Max 8.93 6.47 9.61 16.65 71.26 105.30 429.74Average 7.56 1.74 3.79 3.81 43.33 17.54 146.16CV (%) 4.37 78.15 62.06 199.44 31.60 107.33 47.81Tiruppur Min 6.61 0.16 0.40 -102.43 17.58 1.77 43.96Max 7.97 9.28 10.89 9.23 66.87 145.59 325.98Average 7.50 2.29 4.35 -5.23 41.56 25.59 111.95CV (%) 3.70 87.41 65.14 -369.49 28.00 110.24 50.91EC- electrical conductivity, SAR - sodium adsorption ratio; RSC - residual sodium carbonate; SSP - soluble sodium percentage,PS - potential salinity and PI - permeability indexFig. 1. Irrigation water quality thematic maps of the study area, a) pH, b)EC, c) SAR, d) RSC, e) SSP, f) PS andg) PI potential37Mapping irrigation water quality of coconut grovesElectrical conductivity (EC)Salinity hazard is determined using EC of theirrigation water. The EC range observed inCoimbatore district was 0.02 to 6.47 dSm-1 with amean of 1.74 dSm-1 and the CV per cent of 78.15.In Tiruppur district, the EC of irrigation water rangedfrom 0.16 to 9.28 dSm-1 with the mean of 2.29 dSm-1and the CV per cent of 87.41.Based on EC the irrigation water quality wasclassified as excellent in 1(1,223 ha), good in 42(47,701 ha), fair in 46 (51,982 ha), poor in 10(11,562 ha), very poor in 0.3 (382 ha) andunsuitable in 0.2 (172 ha) per cent area. Majorityof the area were safe and only around 10 per centarea showed salinity hazard. Similarly Balachandaret al. (2010) reported that around 24 per cent ofobservation wells of Coimbatore district haddoubtful irrigation water quality (EC>2250 micromhos cm-1) with respect to EC.Sodium adsorption ratio (SAR)The SAR value of irrigation water gives theinformation about the ill effects of exchangeablesodium. Richards (1954) proposed calculation ofSAR using calcium, magnesium and sodium.Sodium hazard is also usually expressed in terms ofthe SAR. SAR of the irrigation water in the studyarea was found to be within the range of 0.40 – 10.89with a mean value of 3.97. The data showed CV percent of 63.47. In Coimbatore district, SAR rangedfrom 0.69 to 9.61 with the mean of 3.79 and the CVper cent derived was 62.06. In Tiruppur district SARof irrigation water ranged from 0.40 to 10.89 andthe mean was 4.35 with a CV per cent of 65.14.Based on SAR, the irrigation water was excellentin 0.5 (612 ha) per cent, good in 6 (7,033 ha) percent, fair in 53 per cent (59,683 ha), poor in 40(44,643 ha) per cent and very poor in 0.9 per cent(1,051 ha) of the samples under coconut land coverof the two districts. Alkali hazard is high when theSAR value is high since the proportion of sodium ishigh. If calcium and magnesium predominate, theSAR value is low which leads to low alkali hazard.The results showed that around 40 of the area havingthe irrigation water with high sodium hazard.Chemical amendments like gypsum have to beapplied to the soil while irrigating with high SARwater.Table 2. Irrigation water quality limitations and their areaextent in the coconut land cover of Coimbatoreand Tiruppur districtsSI. Parameter Class Area Per centNo (ha)  to the total area1 pHExcellent (6.5-7.5) 23869 21Good (7.5-8.0) 27061 23Fair (8.0-8.5) 48217 42Poor (8.5-9.0) 13836 12Very poor (9.0-10) 38 0.03Unsuitable (> 10)2 EC (dS m-1)Excellent (< 0.5) 1223 1Good (0.5-1.5) 47701 42Fair (1.5-3.0) 51982 46Poor (3.0-5.0) 11562 10Very poor (5.0-6.0) 382 0.3Unsuitable (> 6) 172 0.23 SARExcellent (< 1) 612 0.5Good (1-2) 7033 6Fair (2-4) 59683 53Poor (4-8) 44643 40Very poor (8-15) 1051 0.9Unsuitable (> 15) - -4 SSP (%)Excellent (< 30) 2771 2Good (30-60) 109544 97Fair (60-75) 707 0.6Poor (75-80) - -Very poor (80-90) - -Unsuitable (> 90) - -5 RSC (meq L-1)Excellent (< 1.0) 51676 46Good (1.0-1.25) 1280 1Fair (1.25-2.0) 4797 4Poor (2.0-2.5) 3536 3Very poor (2.5-3.0) 4013 4Unsuitable (> 3.0) 47720 426 Potential salinity (meq L-1)Unsatisfactory (>15) 57103 51Satisfactory (<15) 55918 497 Permeability indexUnsatisfactory(>100) 16321 14Satisfactory (<100) 96701 8638Selvamani and DuraisamiSoluble sodium percentage (SSP)SSP of the irrigation water sample ranged from16 to 71 per cent in the study area with mean valueof 43 per cent and CV per cent of 30.5. InCoimbatore district the irrigation water samplesshowed SSP ranging from 16 to 71 per cent withthe mean of 43 per cent and CV per cent of 31.60.In Tiruppur district SSP of irrigation water samplesranged from 18 to 67 per cent and the mean was 42per cent with the CV per cent of 28.The SSP based irrigation water quality wasfound to be good in 1,09,544 ha area (97%),excellent in 2 per cent (2,771 ha), and fair in 0.6 percent (707 ha) of the coconut land cover.Residual sodium carbonate (RSC)RSC is an index used to determine thebicarbonate hazard as well as to distinguish betweenthe different water classes for irrigation purposes.RSC value of irrigation water samples in the studyarea ranged from -102.43 to 16.65 meq L-1 with themean value of 0.83 meq L-1. The CV per cent foundin the samples was very high (1615.48%). InCoimbatore district, RSC of irrigation water rangedbetween -28.54 to 16.65 meq L-1 with the mean valueof 3.81 meq L-1 and CV per cent of 199.44. The RSCof irrigation water samples of Tiruppur district rangedfrom -102.43 to 9.23 meq L-1 and the mean foundwas -5.23 meq L-1 with the CV per cent of 369.49.From the thematic map it was estimated thatirrigation water quality in terms of RSC wasexcellent in 46 per cent (51,676 ha), good in 1 percent (1,280 ha), fair in 4 per cent (4,797 ha), poor in3 per cent (3,536 ha) and very poor in 4 per cent(4,013 ha) area in the coconut land cover. Nearly42 per cent (47,720 ha) of the coconut land coverwas having irrigation water of unsuitable class basedon RSC. RSC gives an account of accumulation ofexcess carbonate and bicarbonate in the soil. Whenthe irrigation water containing CO3 + HCO3 higherthan Ca+Mg is used for irrigation, development ofalkali soils (saline or non-saline) may be expected(Eaton, 1950). Continuous use of water having RSCmore than 2.5 meq L-1 (45.77 % of the area) leads tosalt build up which may hinder the air and watermovement by clogging the soil pores and lead todegradation of the physical condition of soil.Irrigation water having RSC values ranging from2.5-4 meq L-1 can be used effectively with theaddition of gypsum.Potential salinity (PS)Potential salinity values in the study area rangedfrom 0.80 to 145.59 meq L-1 with the mean of 20.07meq L-1 and the CV per cent was 107.33. InCoimbatore district PS ranged from 0.80 to 105.30meq L-1 with the mean of 17.54 meq L-1 and CV percent of 107.33. It ranged from 1.77 to 145.59 meq L-1with the mean of 25.04 meq L-1 and CV per cent of107.33 in Tiruppur district.Around 50.52 per cent (57,103 ha) of thecoconut land cover of Coimbatore and Tiruppurdistricts were having irrigation water ofunsatisfactory quality based on PS. Hence, in theseareas the salts of chloride and sulphate ions in theirrigation water are sufficiently soluble to producesaline soil condition (Doneen, 1975).Permeability index (PI)In the study area, permeability index ofirrigation water samples ranged from 43.95 to429.74 with the mean value of 135.55 and CV percent of 47.81. In Coimbatore district permeabilityindex ranged between 51.02 to 429.74 with the meanvalue of 47.81 and CV per cent of 47.81. Permeabilityindex of irrigation water samples of Tiruppur districtranged from 43.95 to 325.98. The permeability indexof the irrigation water of 14 per cent (16,321 ha) ofthe coconut land cover of Coimbatore and Tiruppurdistricts were found to be unsatisfactory. This highvalue of permeability index indicates the lowpermeability of water into soil (Doneen, 1975).ConclusionThe most important quality parameter whichlimits the irrigation water quality in the study areawas found to be SAR and it is poor or very poor in40.43 per cent area which expresses alkalinityhazard and may develop permeability andinfiltration related hazard in the soil. The poorirrigation water quality is due to high salt contentespecially sodium followed by chloride andsulphates. Hence the spatial information generatedin the thematic maps especially on SAR followedby RSC and PS may help in the irrigation water39Mapping irrigation water quality of coconut grovesmanagement, thereby protect soil health fromhazards of long term use of poor quality irrigationwater in the study area.ReferencesA.O.A.C. 1950. Official and Tentative Methods of Analysis ofthe Association of Official Agricultural Chemists.Washington, D.C., USA. 539p.Balachandar, D, Sundararaj, P., Rutharvel Murthy, K. andKumaraswamy, K. 2010. An investigation of groundwaterquality and its suitability to irrigated agriculture inCoimbatore District, Tamil Nadu, India – A GISApproach. International Journal of EnvironmentalSciences (1): 2.Boumans, J.H., Van Hoorn, J.W., Kruseman, G.P. and Tanwar,B.S. 1988. Water table control, reuse and disposal ofdrainage water in Haryana. Agricultural WaterManagement 14: 537-545.CDB, 2011. Coconut Statistics 20010-11. CoconutDevelopment Board. http://coconut board.nic.in/ stat.htmDiehl, C., Goetz, H.  and Hach, C.C. 1950.  The versenatetitration for total hardness.  American Water WorksAssociation Journal 42: 40-48.Doneen, L.D. 1975. Water quality for irrigated agriculture. In:Plants in Saline Environments (Eds.)  A. Poljakoff-Mayberand J. Gale, Springer-Verlag, New York. pp: 56-76.Eaton, F.M. 1950. Significance of carbonates in irrigationwater.  Soil Science 69: 123-133.Kamra, S.K., Khajanchi Lal, Singh, O.P. and Boonstra, J. 2002.Effect of pumping on temporal changes in groundwaterquality.  Agricultural Water Management 56: 169-178.Mahendran, P.P. and Arunachalam, G. 2002. An assessmentof chemical parameters of well waters in the coastalbelt of Radhapuram taluk, Tirunelveli district, TamilNadu. Journal of the Indian Society of Soil Science50(2): 230-231.Minakshi, Deepak Mehra, Sharma, P.K., Tur, N.S.,Harpinder Singh and Kang, G.S. 2006. Assessment,management and spatial distribution of ground waterfor irrigation in Rupnagar district of Punjab (India).Journal of Environmental Science and Engineering478(42): 9216-9363.Pradhan, S., Chadrasekharan, H., Jain, N. and Yadav, B.R.2011. Characterization of groundwater quality forirrigation in ‘Gohana’ Block of Sonepat District,Haryana. Journal of Agricultural Physics 11: 63-70.Reetz, H.F. Jr. and Fixen, P.E. 2000. Strategic approach tosite-specific systems. In: Site-Specific ManagementGuidelines Series. Potash and Phosphate Institute (PPI),SSMG. 28pp.Richards, L.A. 1954. Diagnosis and improvement of salineand alkali soils. In: Agriculture Handbook, 60, USDA,Washington. D.C., USA. 160p.Stanford, S. and English, L. 1949. Use of flame photometer inrapid soil tests of potassium and calcium. AgronomyJournal 41: 446-447.Tandon, H.L.S. 1995. Methods of Analysis of Soils, Plants,Water and Fertilizers. Fertilizer Development andConsultation Organisation, New Delhi. pp. 84-90.

Characterization and mapping irrigation water quality of coconut groves in Coimbatore and Tiruppur districts of Tamil Nadu, India

https://updatepublishing.com/journal/index.php/JPC/article/download/5542/4904/

Characterization and mapping irrigation water quality of coconut groves in Coimbatore and Tiruppur districts of Tamil Nadu, India

Abstract

Similar works

Full text

Available Versions

Update Publishing (E-Journals)