Contribution of organic matter and clay to the cation exchange capacity of the Rajasthan Canal Soils

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1 Annals of Arid Zon-I6(4), , 1977 Contribution of organic matter and clay to the cation exchange capacity of the Rajasthan Canal Soils R.S. BHATNAGAR,S C. ATRI, G.S. MATHUR AND R.S. CHOUDHARY Agriculture Chemistry Section, Agriculture Department, Bikaner. (Received on ) ABSTRICT Cation exchange capacity of the Rajasthan Canal Soils has been recognised in close corre lation with clay, silt and organic matter coments respectively. The contribution of clay was dominant to the C.E.C. followed by O.M. and silt contnls. Multiple regression equation relating clay and O.M. content. (C.E.C.=O.75J clay + 5.6!t \1) with the C E.C. of soils was found more suitable than that including silt content, and can be used precisely, for prediction of C.E C. of these soils. INTRODUCTION Significant simple correlation co-efficient between soil C.E.C. and loss in weight on ignition; 8il C.E.C. and 8.M. content has bien reported by Oland (1955); and Kamprath t ai. (1962) respectivdy. While Williams (1932) had recognised a close correlation of mil C.E C. with clay and O.M. content. Similar relationship has been reported by Hallsworth and WIlkinson (1958), Lavit et at. (1969) and including the silt content by Mohamad and Gohar (1955); Lavti et ai. (1969). The C.E.C. of either clay or orgujic fraction is obtained directly from the regression co-efficients. Helling et al. (1964) have discussed the merits of using multiple regression analysis of the above parameters. Lavti et ai. (1969) bave concluded that it is likely that universal applicability of any such correlation is not expected, because when applying the regression equation, it must be noted that they are accurate in predicting C.E.C. only with a limited geographic and climatic zone, since it is assumed that the composition of the clay and organic fractions are essentially homogeneous from one sample to another and that the soil3 vary only in the amounts of the components present. Therefore, an attempt has been made in the present study to find out the relationship of C.E.C. with the different size particles of the Rajasthan Canal Area soils and its organic matter content; and also tested he validity of the previous proposed regression equations.

2 434 R. S. BHATNAGAR et al. EXPERIMENT AL Fifty one representative soil profile, augered textural depthwise, of Rajasthan Canal Area comprising in all one hundred and hfly samples were collected. They widely varied in ph, texture, CaC 3 and M. contents. The processed soil samples were analysed for CaCo 3 by acid titration and particle size distribution by International Pipette Method (Piper, 195); ph in 1:2 Boilwater ratio, O.M. content and C.E.C. were determined as suggested by Richards (1954). Statistical analyses were carried out for simple correlation and multiple regression as suggested by Panse and Sukhatme (1967). The suitability of the multiple regression equation was tested on the basis of percentage of variation for the observed G.E.C. values. RESULTS AND DISCUSSION Results of soils analysis are given in Table 1 showing the ranges in their characteristics along with mean and standard deviations. b is seen that all the soil samples are in the alkaline range and C.E C. varies widely. Most of the soils are poor in organic matter contents. Table 1. General Characteristics of the Soils ph Clay Silt O.M. C.E.C. % ;" % m.e.fioo gm. Range Mean S.D Simple coorrelation co efficients (r) given in Table 2 clearly shows that cation exchange capacity is significantly correlated with clay, silt and M. but clay has a higher co-efficient of correlation (r=.97) than silt (r=o. 719); which clearly shows that the finer fractions have a higher C.E.C. values than the coarser fractiom. It has been reported in U.N D P. report (1971) that these soils are dominantly illite type. The G.E.C. of illite type clay increases as the particle size decreases as pointed out by Grim and Bray (1936). Soil C.E.C. is also significantly correlated with organic matler (r= +.435), but the degree

3 CATION EXCHANGE IN RAJASTHAN CANAL SOILS: 435 of predictability is quite low (r2= 192%). This may be due to the fact that the C.E.C. of the organo-clay complexes is slightly lower, as has been demonstrated by Mattson (1932), than the sum of the C E.C. of the two components. Table 2. Co-efficients of correlation of C.E.C. with soil constituents Fa ctors r r2 Clay % Silt % OM.% A multiple regression line was found out on the basis of significant correlation of clay, silt, and a.m. content with the C.E.C. of soils (C.E.C.=.67 clay +.25 silt a.m.) called equation (1). This equation showed lesser variation (18.93%) than those so far proposed. There was no significant difference in the percent vanatlon between predicted and observed values of C.E.C., in the soil profiles under study, with the increase of depth, though C.E.C. generally increases in the sub soil, probably due to the accumulation of clay size particles. This suggests that the mineralogical make up is probably uniform, which is reflected in the low degree of variation between the observed and the calculated values. The increase in C.E.C. of the clay in the sub soil progressively increases with decrease in the drainage classes are consistent with the clay minerology of these soils. The multiple regression equation between soil C.E.C. with clay and a.m. content (C.E.C.=.751 clay a.m.) called equation (2) have a still more lower variation (16.%.) between the observed and calculated values. By substituting of a.m. and clay means in equation No.1 and 2, it was computed that the latter gives higher contribution i.e and 81.22% of the C.E.C. while the former gives only 6.23% and 72.46% respectively, including 2.23% by the silt. The agreement is shown in Fig. 1 and a highly significant correlation (r=.911) at.1 % level of probability between the predicted and observed value, has been observed, which can be expressed by the equation Y = x where x is the calculated and y is the observed value of C.E.C.

4 436 :R. S. BHATNAGAR et al....,. -.., C'l \ Cl'l.g d d- u-i d... C'l co < c<).,,* If) c<)... c<) c<) ';:; " <Xl a:; Ol - < < O'l O'l - - a 1- ;.. <ii t\l.c.".c." " " " ---." C'l " "." c<) C C C." :a :a O'l "."." " u -.c " " c c :: c."."." '"." '" '" '".. a c.!! 1-..!:l.c.".c.".. 'Z -5-5 <ii ;> u ;>." <'S ::l ::l ::r:...:l...:l <: <: :> If) \ \ O'l O'l O'l.,; s=.sl -; ::s d ' If) :i '" ci d s= + d.!2 C'l co Cl'l.. \ W'" o-i 1- oo:t< ClO '" u.. c<) :i ,. If) C'l + < + + e-i ci..... "C.. u + '".- '" O'l <Xl + '" II") If) <Xl C'l C'l < C. If) c<) III c<) II").. "i3 + oo:t< "i3 d III d d c ec') (:of < >... d ;>. d lis C III III <'S t\l t\l s= "i3.!2.!2 "i3 + "i3 + "i3 "i3 "i3 -; III If)... <... If) If) ::s ::s c<) < c<) If)... "'! <ii " d d ci d d >, 1/ H U II U cr; d d d d d d d tl:j u d d d : t\l fool "

5 CAnON EXCHANGE IN RAJASTHAN CANAL SOILS ; 437 o :5 CEC Calc. Fig, I. Rlationship belween observed and calculated values of colio,n IllC honge capacity. The comparative predictability of earlier equation with those proposed herewith was clearly brought out in Table 3. The variation noted in the, com}.lutationaccording to the earlier equations including Lavti et al. (199), for Rajasthan Canal Soils are higher th,m proposed in the pre!ent study. Therefore. it may be concluded that the C.E.C. of Rajasthan Canal Soils can be obtained with the data of particle size distribution and a.m. content with a more precise degree of accuracy inspite of the wide variation in their physico-chemical characteristics. I ACKNOWLEDGEMENT Authors are thankful to Shri P.O. Bhargava, Project Director. Agricult.- ure Department, Bikaner for providii g facilitiesand guidance. REFERENCES Anonymous V.N.D.P. Tech. Rep. Rome, AGL SF/IND. 24,1.2. Grime, R E. and Bray, R.H The mineral constitution of various ceramio clay. J.Am. Ceram. 19: Halhworth, E.C. and Wilkinson, G.K The contribution of clay and Organic matter to tbe cation excbange ji : 1-3. capacity of the soil. J Agric. sa.

6 438 : R. S. BHATNAGAR eta/. Helling, C.S., Ghester, G. and Corey, R.B Contribution of Organic matter and clay to soil calion exchange capacity as affected by the ph of the saturating solution. Soil. Sci. Soc. Am. Proc. 28 : Kamprath, E J. and Welch, C.D Retention and Cation Exchange properties of Organic matter in coastal plain soils. Soil. Sci. Soc. Am. Proc. 26 : Lavti, D.L., Gandhi, A.P. and Paliwal, K.P Contribution of clay and Organic matter in the cation exchange capacity of Rajasthan Soils. J. India Soc. Soil. Sci. 17 : Mohamad, M.K. and Gohar, A.A.I Contribution of clay silt and organic matter to the potential fertility of Egyptian soils as measured by their Cation Exchange Capacity. Abst. in Soil and Fert. 24 : 7. Mattson, S The laws of Soil colloidal behaviour. VII. Protein and proteinated complexes. Soil. Sci. 23 : Olandl K Ek sempler pa Naeringstil stan Den i Jord Etter Ulike Gjodslinger ( Abst.) Soil and Fert. 18 : 294. Pause, V.G. gand Sukhatme, P.V Statistical Methods for Agricultural Worker".. I.C. A.R. Publication, New Delhi. P Piper, C.S Soils and Plant Analysis. Adelaide, Australia. Richards, LA. (Ed.) Diagnosis and Improvement of Saline and Alkaline Soil. V.S.D.A. Hand book No. 6. William, S.R The contribution of clay and Organic matter to the base exchange capacity of Soils. J. Agrj. Sci. 22 :