Annals of Arid Zone-16(2), 213-220, 1977

Water quality and soil properties: water_quality and itseffect on the properties of light textured soils

P. LAL AND F. LAL

Department of Soil Science and Agricultural Chemistry,College of Agriculture, Jobner, (Jaipur), Rajasthan.

(Received on 14.7.75)

ABSTRACT

Forty ,seven water samples and an equal number of corresponding soilsamples were ana lysed for different constituents. Almost all the soils were sandyor loamy sand in texture. Results show that the majority of waters belong tohigh salinity and high sodium category according to U.S. Salinity Laboratoryclassification. The potential salinity and residual sodium carbonate are also highas per limits suggested by Doneen (1966) for the former and Eaton (1950) forthe latter. Significant positive coefficients of correlations were found betweenboth EC and potential salinity of irrigation water and EC of saturation extractof the irrigated soils. Similarly, significant positive coefficients of correlationswere obtained between SAR and residual sodium carbonate of the water andESP of the irrigated soils as well as the boron content of waters and watersoluble boron in respective soils. The hydraulic conductivity of irrigated soilswas negatively correlated. with the permeability index of water. In general theEC of saturation extract and the water soluble boron in irrigated soils were63.6 and 60.0 per cent of the EC and boron content of water respectively.The need for working out the suitable standards for judging the suitability ofirrigation water for its use on light textured permeable soils has been emphasized.

INTRODUCTION

The area under observation (Jaipur tract) lies in the semi-arid region ofRajasthan receiving an average annual rainfall of about 50 em, mainly during theMonsoon season. The soils of this tract are light in texture varying from sandy tosanday loam. The main source of irrigation is wells, waters of which vary greatlyin quality and are unsuitable for irrigation purposes according to U.S. SalinityLaboratory classification (Richards, 1954) and many other standards but thesoils have not been markedly affected and the crops are being grown profitably(Singh et ai., 1967). The boron status of waters is relatively high to affect thesensitive crops (Scofield, 1935) but no toxicity symptoms on prevailing crops havebeen observed.

214 : P. LAL AND F. LAL

The effect of qualities of irrigation water on soils is modified by soil proper-ties, cultural practices and climate. It has been reported that the use of highsalinity waters can be made on light textured permeable soils and they are notcumulatively affected by the use of such waters (Kanwar, 1961; Lal and Singh,1.973, 1974). In view of the above observations it was thought worthwhile tostudy the properties of light textured soils as affected by the qualities of irrigationwater because this information will be valuable in deciding the cropping patternon the light textured soils of arid and semi-arid climate.

MATERIAL AND METHODS

Forty seven representative samples of irrigation waters were collected in themonth of March and April, 1972 from different wells of Jaipur district along withan equal number of soil samples from the fields irrigated by the correspondingwaters upto the depth of 30 em. They were analysed for different properties mostlyby following the methods as outlined in U.S.D.A. Hand Book 60 (Richards,1954). Permeability index and potential salinity of water were calculated by theformula of Doneen (1966). Saturation index of water and pHc values werecalculated by the formula of Langelier as quoted by Bower et aT. (1965) andBower and Wilcox (1965).

RESULTS AND DISCUSSION

It is apparent from the data in Table 1 that out of 47 waters, 10.6 per centhave EC values from 0.25 to 0.75 and 61.7 per cent from 0.76 to 2.25 mmhoslcmwhile 27.7 per cent waters have EC values more than 2.25 mmhos/cm. As re-gards sodium hazard, 23.4 per cent waters are in low category, 23.3 per cent inmedium, 21.3 per cent in high and 32.0 per cent in very high class. Thus themajority of waters are unsuitable for irrigation if rated on the basis of U.S.Salinity laboratory classification (Richards, 1954); but this classification is notfully applicable under our conditions. If judged on the basis of Eaton's concept(1950), 65.9 per cent water samples have more than 2.5 mell of residual sodiumcarbonate €R.S.C.), thus unsuitable for irrigation purpose. According to p0t ntialsalinity concept (Doneen, 1966) 34.0 per cent water samples are unsuitable forsemi tolerant crops if they are grown on open soils having deep percolation.

WATER QUALITY AND SOIL PROPERTIES 215

Table 1. Characteriatics of irrigation waters

PercentageS. No. Characteristics Range of samples Average

in the range

1. pR 8.3-8.7 21.3 8.58.8-9.2 78.7 9.0

2. EC (mmhosjcm) 0.25 - 0.75 10.6 0.590.76 - 2.25 61.7 1.58

> 2.25 27.7 4.42

3. Sodium adsorption <10.0 42.6 6.2ratio ]0.0 -·18.0 42.6 12.3

>18.0 23.3 23.7

4. Permeability index 48.0 - 70.0 17.0 60.670.] - 100.00 61.7 89.8

> 100.0 21.3 106.8

5. Residual Na2C03 0.0 - 1.13 27.7 0.1(meqjl) 1.4 - 2.5 6.4 1.8

> 2.5 65.9 7.2

6. Potent ial sal inity 1.0 - 10.0 65.9 4.5(meqjl) >10.0 34.1 23.3

7. Boron (ppm) < 0.5 10.6 0.410.5 - 1.2 89.4 0.74

8. a) Negative saturation -1.21 to 0.0 82.9 -0.57index(pRc values) (8.76-10.11) (82.9) (9.48)

b) Positive saturation 0.0 - 0.53 ]7.1 0.32index(pRc values) (7.87 - 8.69) (17.]) (8.37)

The boron content of waters varies from 0.57 to 1.19 ppm. Except two watersamples, boron content of water is less than 1.0 ppm. On the basis of permeabilityindex of waters, only 17.0 per cent waters are good for irrigating the soils of highpermeability. The classification of waters for salinity hazard as suggested byBhumbla and Abrol (1972) puts 6.0 and 8.0 mmhosjcm as the upper permissiblelimits of EC of waters for the safe use for irrigating semi tolerant and tolerantcrops respectively grown on light textured soils having clay contents of less than10 per cent and excellent internal and surface drainage. On this basis all the waters

216 : P. LAL AND F. LAL

except one can be used on sandy and loamy sand soils. The saturation index ofirrigation waters varied from -1.21 to +0.53. Out of 47 waters, 39 have thenegative values of saturation index indicating that water will dissolve CaC0

3while

8 samples have positive values of saturation index indicating the precipitation ofCaC03 from them. The pHc values of waters with a negative saturation indexare from 8.76 to 10.11, indicating that the CaC03 is likely to be dissolved bythem.

Table 2. Characteristics of irrigated soils

Average

12.882.94.3

100.0 6.6

6.4 4.293.6 6.5

83.0 8.117.0 8.868.1 0.729.8 1.42.1 5.2

93.6 1.626.4 5.4

61.7 10.138.3 22.4

48.9 0.3851.1 0.51

Percentageof samplein the range

Range

l. Texture SandyLoamy sandSandy loam

2. Clay (%) 4.5 -- 9.03. Hydraulic conductivity 2.8 - 5.0

(cmjhr) > 5.04. pH 7.5 - 8.5

> 8.5

5. Calcium carbonate < l.0(%) 1.0 - 2.0

;::. 2.0

6. ECe (mmhosjcm) 0.5 - 4.0> 4.0

7. Exchangeable sodium 1.8 - 15.0percentage >150

8. Water soluble boron < 0.5(ppm) 0.5 - 1.0

S. No. Characteristics

It is evident from the data presented in Table 2 that texturally all the soilsbelong to sandy or loamy sand category except two samples which are sandy loam,but the clay content is less than 10 per cent. Out of 47 soil samples, only threesoil samples which have ECe more than 4.0 mmhosjcm at 25°C may be con-sidered as saline while others are nons aline soils. Only 17.0 per cent soil samples

WATER QUALITY AND SOIL PROPERTIES : 217

have pH greater than 8.5 and 38.3 per cent soil samples cross the limit of ESP 15for sodic soils. Calcium carbonate is not more than 2 per cent in any soil excflPtone. None of the soils have boron in quantities harmful to plants. It is verystriking that the boron content of all the soil samples is less than that of the cor-responding waters in spite of their use for decades.

Table 3 gives the relationship between different constituents of irrigationwaters and those of soils continuously irrigated by them for years together. Ahighly significant positive coefficient of correlation (r = + 0.912) between ECof water and ECe was observed. A close relationship between the salt content of

Table 3. Relationship between different constituents in irrigationwaters and irrigated soils

S. No. Relation between Value of 'r' Regr::ssion equation

1. EC of irrigation waters(X)and EC of Saturation extractof soils (Y) + 0.912*** Y = 0.381 + 0.636X***

2. Potential salinity of water (X)and EC of saturationextract (Y) + 0.929*** Y = 0.91 + 0.084X***

3. S.A.R. of irrigation waters(X) and ESP of soils (Y) + 0.836*** Y = 2.323 + 0.962X***

4. Residual sodium carbonateof water (X) and ESP ofsoils (Y) + 0.353* Y = 9.96 + 0.782X*

5. Permeability index of water(X) and hydraulic conduc-tivity of soils (Y) - 0.323* Y = 7.943 - 0.0184X*

6. Residual sodium carbonatein water'(X) and calciumcarbonate in soil (Y) + 0.437** Y = 0.628 + 0.08IX**

7. Boron in water (X) andwater soluble boron insoil (X) + 0.854*** Y = 0.024 + O.EOOX***

* Significant at 5%, ** at 1% and *** at 0.1% level of probability.

218 : P. LAL AND F. LAL

the soil and salt content of irrigation water was also reported by Singh andBhumbla (1968). The regression equation shows that in general ECe of soils is63.6 per cent of the EC of irrigation waters. Inspite of their long use, the magnitudeof impact of irrigation waters is not pronounced due to high hydraulic conductivityand sandy nature of the soils which permit free percolation of water.

A stilI higher coefficient of correlation (r = +0.929) between potential salinityof waters and ECe was observed. A highly significant coefficient of regression as in-dicated by the regression equation shows that the potential salinity of waters is also agood index for predicting the salinity status of the irrigated soils. However, thismethod of salinity appraisal of water needs further testing for different types ofwater qualities and soils under different climatic conditions.

SAR and RSC of irrigation waters were also correlated with ESP' of soilbut the relationship between RSC of waters and ESP of soils was of low order(r = + 0.353). This shows that the SAR of these waters is a better index ofalkali hazard. The regression equation indicates that each unit rise in SAR ofirrigation waters increases the ESP of soils by 0.96 units. Highly significant posi-tive correlation between SAR of irrigation waters and ESP of soils was also re-ported by Singh and Bhumbla (1968). Although 18 soil samples cross the limitof 15 ESP, no marked effect is seen on the hydraulic conductivity of soils becauseof low clay content in them. A weak negative correlation (r = -0.323) althoughsignificant at, 5 per cent level of probability was found to exist between the per-meability index of waters and hydraulic conductivity of soils. This low correla-tion may be attributed to the sandy nature of the soils.

Saturation index of majority of waters is negative indicating that the waterwill dissolve CaC03• The data on pHc values .of irrigation waters alsoshow that majority of waters are likely to dissolve CaC03• as indicatedby Bower and Wilcox ( 1965) . This fact is also substantiated by thelow value of coefficient of correlation between RSC of water and CaC03 of soils(r = + 0.437). The value of coefficient of determination (100 r2) comes to19.09 i.e. the variability in CaC03 content of light textured soils controlled byRSC of water is only 19.09 per cent which is not very high. The correlation of loworder may be due to sandy nature of soils where every irrigation is a leachingprocess. Wilcox et at. (1954) and Pratt et at. (1960) also indicated that the extentof carbonate precipitation from irrigation waters is highly variable depending up-on water composition and leaching percentage and in no case approaches quantita-tiveness.

WATER QUALITY AND SOIL PROPERTIES : 219

A highly significant posItIve correlation (r = +0.854) between boron inwater and water soluble boron in soils indicates that the accumulation of boron insandy soils depends on the boron content of irrigation waters to a large extent.Paliwal and Mehta (1973) also reported that boron accumulated more with anincrease in its content in irrig~.tion waters. The data reveal a very important factthat the quantity of water soluble boron in soils is considerably less than that ofwater in spite of their continued use. In general, the content of water solubleborn in soils is 60 per cent of the boron content in water. So it can be inferredthat the permissible limits of boron in waters can be safely raised for their useon highly permeable light textured soils.

ACKNOWLEDGEMENTS

The authors are thankful to Dr. R.M. Singh, Associate Dean and Dr. K. S.Singh, Head, Department of Agricultural Chemistry and Soil Science, College of .Agriculture, Jobner for providing the facilities for this work and to Mr. R. C.Gupta for his advisory help in the statistical analysis of the data.

REFERENCES

Bhumbla, D.R. and Abrol, J.P. 1972. Is your water suitable for irrigation. IndianFmg.22 (4): 15-16.

Bower, C.A. and Wilcox, L.V. 1965. Precipitation and solution of calcium car-bonate in irrigation operations. Proc. Soil Sci. Soc. Am. 29: 93-94.

Bower, c.A., Wilcox, L.V.,_Akin, G.W. and Keyes, M.G. 1965. An index of thetendency of CaC03 to precipitate from irrigation waters. Proc. Soil Sci. Soc.Am. 29: 91-92.

Doneen, L.D. 1966. Water quality requirements for agriculture. Proc. NationalSymp. on Quality Standards for National Waters. School of Public Health,Univ. of Michigan, p. 213-218.

Eaton, F.M. 1950. Significance of carbonates in irrigation waters. Soil Sci. 69:123-133.

Kanwar, J.S. 1961. Quality of irrigation water as an index of its suitability forirrigation purpose. Potash Rev. (Sept.) Sub. 24: 1-13.

Lal, P. and Singh, K.S. 1973. Effect of qualities of irrigation waters andfertilizers on soil properties, yield and nutrient uptake by wheat. IndianJ. agric. Sci. 43(4): 392-400.

Lal, P. and Singh, K.S. 1974. A comparative study of the effect of qualities ofirrigation water on different soils. J. Indian Soc. Soil Sci. 22 (1): 19-25.

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Paliwal, K.V. and Mehta, K.K. 1973. Boron status of some SOilS irrigated withsaline waters of Kota and Bhilwara regions of Rajasthan. Indian J. agric.Sci. 43 (8): 766-772.

Pratt, P.P., Branson, R.L. and Chapman, H.D. 1960. Effect of crop, fertilizerand leaching on carbonate precipitation and sodium accumulation in soilirrigated with water containing bicarbonate. Trans. Intern. Soil Sci. Soc.COflg. 7th, Madison, 2: 185-192.

Richards, I.A. (Ed.) 1954. Diagnosis and Improvement of Saline and Alkali Soils.U.S. Dept. Agric. Hand Book. 60.

Scofield, C.S. 1935. The salinity of irrigation water. Smithson. Inst. Ann. Rept:275-287.

Singh, B. and Bhumbla, D.R. 1968. Effect of quality of irrigation water on soilproperties. J. Res. Ludhiana. 5: 166-171.

Singh, K.S., Lal, P. and Lal, P. 1967. Preliminary studies on the effect of irriga-tion waters on the properties of soils of Jobner Tract, Jaipur, Rajasthan.J. Indian Soc. Soil Sci. 15: 35-39.

Wilcox, L.V., Blair, George, Y., and Bower, C.A. 1954. Effect of bicarbonate onsuitability of water for irrigation. Soil Sci. 77: 259-266.