Annals of Arid Zone - 21 (3), 199-205, 1982

Soil factors affecting forms of potassium and potassiumfixation in some arid soils

D. C. JOSHI, B. S. GUPTA AND B. K. DUTTACentral Arid Zone Research Institute, Jodhpur-342003

ABSTRACT

Differen\. forms of potassium and potassium fixation capacity in relationto soil characteristics in dominant arid soils of Rajasthan have been reported.Mean values of HCI soluble, N HNO. soluble, fixed and available forms indune and interdunal sand, light brown sandy and brown light loam soils werelow than the grey brown soils. The potassium fixation capacity of differentsoils decreased in the order: Grey brown loam> brown light loam> lightbrown sandy > dune and interdunal sand. The dune and interdunal soilsbecause of very low clay content showed negative potassium fixation. Theclay, silt and organic carbon content of soils significantly affected the rela-tionship between fixed potassium and potassium fixation capacity. Differentsoil parameters studied accounted for 44.9, 49.6, 53.4 and 72.6 per cent vari-ability in HCI ~oluble, N HNO. soluble, fixed and available potassium andpotassium fixation capacity, respectively. Potassium fixation capacity can bebest predicted by the regression equation arrived at as it gives 72.6 per centvariability.

INTRODUCTION

Potassium availability in soils is re-gulated by the equilibrium between theforms of potassium and potassium fixa-tion capacity which is further conditionedby the soil characteristics like clay, silt,Olganic matter, pH and nature of the ex-change complex. The nature and amountof the clay minerals dominate fixationwhile the potassium bearing primaryminerals regulate release. Though somereports on the forms of potassium in Raj-asthan soils have appeared (Dhawanet al., 1968; Joshi et al., 1978; Choudhariand Jain, 1979; Aggarwaletal., 1979)·nocomprehensive information is availablefor arid soils. Looking to the wide vari-ability in these soils systematic work hasbeen taken up and in this paper relation-

ship between forms and fixation capacityof potassium and soil characteristics fordominant arid soils are reported.

EXPERIMENTAL'

Thirty two surface soil samples frommajor soil groups (Dhir, 1976), viz.,dune and interdunal sand, light brownsandy, brown light loam and grey brownloam occurring in Jaisalmer, Barmer,Jodhpur and Nagaur district were takenfor the study. These soils were analysedfor different forms of potassium, viz.,.total (semi micro diges~on; Jackson,1967), HCI soluble (AEA provis\onalmethod; Piper, 1950), N HN03 soluble(by boiling the soil in 1: 10 soil to acidratio for ten minutes; Jackson, 1967) andavailable by extracting the soil with 1 Nammonium acetate (Muhr et al., 1963).

200 : D. C. JOSHI et al.

Potassium in all the extracts was deter-mined with the help of an EEL flamephotometer. The fixed potassium wascalculated as the difference betweenNHN03 soluble and available. Potassiumfixation capacity was determined accord-ing to the method of Volk as describedby Jackson (1967). The soil samples werealso analysed for different physico-chemi-cal characteristics by the standardmethods (Piper, 1950; Jackson, 1967).The multiple correlations and regressionanalysis was done with the help of HCLmicro computer.

RESULTS AND DISCUSSION

The soils under study are from therainfall zone of 100 to 400 mm with highevaporation. The vast area is sandy plaininterspersed with dunes and hummocks.Medium to fine textured alluvium occursin the south eastern part of the Jodhpurand Nagaur districts. The dune and inter-dunal sand and light brown sandy soilswere very low in organic matter (TableI) and clay content mostly ranged fromJ.3 to 9.8 per cent. The grey brown loamsoils were high in clay content mostlyfrom 11.9 to 32.8 per cent. CaC03 con-tent in all these soils was appreciably low«2%) except in few samples, whereit ranged from 5.9 to 9.2 per cent.

Total potassium content in differentarid soils varied from 0.63 to 1.67 percent and the mean values for dune and in-terdunal sand, light brown sandy, brownlight loam and grey brown loam soils were1.16, 1.00, 0.97 and 0.94 per cent, res-pectively. These values were slightly lowerthan those reported for Punjab (1.4 to2.7%; Kanwar and Grewal, 1966) andUttar Pradesh (1.45 to 3.20%; Mehrotra

et al., 1973) soils. Total potassium con-tent was not related with any of the soilcharacteristics studied and also with otherforms, perhaps due to low weathering ofthe potash bearing minerals. All thesesoil parameters together accounted foronly 18.2 per cent variability in totalpotassium.

The HCI soluble potassium fraction lindifferent arid soils varied from 40 to232.5 mg/lOOg and the mean valueswere low in dune and interdunal sand,light brown sandy and brown light loam(83.2 to 91.5 mg/100 g) where as greybrown loam and playa soils containedhigher amounts (160 to 174.5 mg/100g).The low content of this form of potas-sium in comparison to Punjab andmedium black soils of Rajasthan (200-770 mg/100g; Bhatnagar et aI., 1973)appears to be due to their low clay con-tents. Out of the total, HCl soluble potas-sium accounted for 7 to 9 per cent indune and interdunal sand and light brownsandy soils and 10 to 18 per cent inbrown light loam and grey brown loamsoils. Kanwar and Grewal (1966) couldrecover 30 per cent of the total K in theHCI extract of punjab soils. This formof potassium was significantly relatedwith clay, silt, organic carbon, CaC03 andpH (0.484, 0.606, 0.457,0.624, 0.454).Multiple regression analysis of these soilparameters on the HCI soluble potassiumis given by the followling equation:

HCI soluble K=192.3+32.2 pH+35.77,org. carbon+3.86 silt-1.38 c1ay+6.63·CaC03 (R2=0.449)

The content of N HN03 soluble andfixed potassium in different soils rangedfrom 17.5 to 110 and 10.5 to 97.5mg/lOOg; respectively. Though both these

POTASSIUM IN ARID SOILS : 201

Table 1. Physico chemical -;:haracteristics of the arid soils

S. No. Location Rainfall pH CaCO. Organic Clay Silt Texture(mm) ('Yo) carbon ('Yo) ('Yo)

t. Dune and interdunesand

Longewale 100-200 8.7 5.87 0.05 5.7 0.5 Fs

Ja isalmer 8.5 1.40 0.05 3.1 4.1

Devikot 8.3 0.03 0.03 2.4 0.0

Kelnor 200-300 8.5 0.75 0.09 6.9 0.8

Chohtan 8.2 0.07 0.02 3.6 0.0

Dechu 8.8 1.08 0.07 2.9 2.6

Shergarh 8.2 1.65 0.07 4.5 4.7

Gudlai 8.6 0.54 0.09 1.3 3.7

Chirai 8.1 0.05 0.09 5.2 2.9

Titari 8.2 0.00 0.05 3.7 1.3

Kaolesar 8.0 1.21 0.15 8.8 4.2 ..Molasar 300-400 8.4 0.27 0.13 6.2 2.1

II. Light brown sandyShiva ]00-200 8.5 1.07 0.07 5.3 0.0 Fs

Manaklav 300-400 8.4 1.28 0.16 6.5 1.6 ..Tiwari 8.3 0.32 0.]9 7.8 5.4

Guda 8.1 1.11 0.]6 9.6 8.3 Ls

Bhagwanpura 8.2 0.13 0.12 6.2 2.1 Fs

Mithari " 8.5 0.42 0.14 6.2 2.1

III.Brown light loamJodhpur I 300-400 8.3 0.04 0.]6 ] 1.9 7.1 SI

Jodhpur II 8.2 0.04 0.16 6.5 0.5 Fs

Bhopalgarh 8.4 0.43 0.08 6.9 2.9 Ls

Katoti .. 7.8 0.1>8 0.13 11.0 4.3

Katiasani 8.2 0.70 0.29 10.9 8.3

Bilu 400-500 7.5 0.0] 0.17 8.9 5.2

Parbatsar 7.7 0.14 0.31 14'6 12.5 L

V. Grey brown loamPipad 300-400 8.4 1.19 0.18 11.9 ] 1.2 SI

Asop I 8.9 7.40 0.31 20.2 20.3 CI

Asop II 9.2 4.54 0.31 17.8 . 18.7

Ren " 8.3 9.18 0.20 32.8 19.0

Kankray 8.0 1.00 0.38 16.3 22.1 L

V. Playa soilPokaran 100-200 8.7 1.03 0.05 7.3 3.3 Cs

Pacb'padra 200-300 8.8 6.01 0.23 5.6 7.3 Fs

Fs-Fine sand, Ls-Loamy sand, SI-Sandy loam, L-Loam, CI-Clay loam, Cs-Coarse sand.

202 : D. C. JOSHI et ai.

forms showed wide variations, theirmean values were low (50.6 to 60 mg;36.5 to 42.8 mg) in dune and interdunalsand, light brown sandy and brown lightloam than the grey brown loam (82.1 and70.3 mg/100g). The fixed potassiumcontent in arid soils was quite low whencompared with the ,medium black soilsof Rajasthan (110 mg/100g; Bhatnagaret ai., 1973), 'punjab (117.6 mg/100g;Kanwar and Grewal, 1966) and Bihar(134.3 mg; Tiwari et ai., 1967). Clay,silt and organic carbon contents were ,s·ignificantlyrelated with N HN03 soluble(0.428, 0.623, 0.692) and fixed (0.403,0.635, 0.736) forms of potassium. Thecombined effect of all the soil parameterstogether accounted for variability to theextent of 49.6 per cent in N HN03soluble and 53.4 per cent in fixed formsof potassium. The regression of soil para-meters on these forms of potassium can 'be given by the following equations:

N HN03 soluble K=114.38-8.9 pH+151.'27 org. carbon +1.11 silt-1.95 clay+3.85 CaCOa (R2=O.496)

Fixed K=102.62-8.62 pH+133.46 orgcarbon + 1.89 silt-I. 79 clay+O.90 •CaCOa (R2=O.534)

Available potas~ium content variedwidely in different arid soils but the meanvalues for different soil groups were not·much different (7.9 to 11.8 mg/100g)except the playa soils which containedhigher amount. When' viewed from thelimits suggested by Muhr et at. (1963),68.8 per cent samples were medium and28 per cent samples high in availabb r

potassium content. The significant corre-lation of available potassium with pH(0.396) and CaC03 (r = 0.626) sug-

gested that soil reaction appears to domi-nate the regulation of available pool. Allthe soil parameters together accountedfor 48.8 per cent variability in the avail-able potassium content and regression ofthese soil parameters can be given bythe following equations:

Available K=11.77-0.30 pH+) 7.79org. carbon-O.7! silt-O.16 clay-t-2.94CaCOa (R2=0.488)

The significant correlations betweendifferent forms of potassium, viz., totalwith available (0.469); HCI soluble withN HN03 soluble, exchangeable and fixed(0.616,0.458,0.494); N HN03 solublewith fixed (0.948) lends support to theconcept of equilibrium between differentforms of potassium and their contribu-tion to the available pool.

Potassium fixation

Potassium fixation capacity of differentarid soils varied widely (Table 2). Thegrey brown loam soils showed higl,lerpotassium fixation capacity (16 to 37mg/100g) followed by brown light loam(3 to 37mg/100g) and light brown sandysoils (0 to 16mgj100g). The dune andinterdunal sand and playa soils showednegative potassium fixation capacitywhich ranged from 0 to -21 mg/100g.This negative potasslium fixation, i,e.,release of K instead of fixation can beattnibuted to their very low clay contentand -higher potassium bearing mineralslike weathering feldspars in the sandfraction. Similar negative potassium fixa-tion has also been observed by Aggarwalet ai. (1979) for arid soils and Prasadet ai. (1967) for Ranchi soils. Potassiumfixation capacity of these soils was verylow when compared with medium black

POTASSIUM-IN ARID SOILS: 203

Table 2. Forms of potassium and potassium fixation capacity of the arid solis

S. No. Location Total K HCl soluble N HNO. Fixed Available K fixation('Yo) K soluble K K K capacity

mg/IOO g

I. Dune and interdunesandLogewale 1.57 127.5 788 44.3 34.5 -ISJaisalmer 0.99 102.5 43.8 34.8 9.0 - 5Devikot 0.88 65.0 37.0 20.5 16.5 -13Kelnor 1.00 127.5 61.3 43.8 17.5 - 6Chohtan 1.35 27.5 27.5 18.5 9.0 -13Oechu 0.97 58.8 45.8

)"'.

13.0 -1577.5Shergaril 0.S8 105.0 37.5 31.0 6.S -10Gudlai 0.70 47.5 45.0 40.0 5.0 6Chirai 1.25 97.5 67.5 56.0 II.S 0Titari 1.10 40.0 43.0 38.6 4.4 0Koalesar 1.36 46'3 5\.0 44.7 6.3 0Molasar 1.25 85.0 58.8 S1.8 7.0 -5

11. Light brown sandy7.0 jShiva 1.25 87.5 17.5 10.5 9

Manaklav 0.80 52.5 500 42.6 7.4 16Tiwari 0.54 900 62.5 54.0 .; : 8.5" 14Guda 1.15 1175 65.0 57.2 7.8 4Bhagwanpura 0.99 75.0 58.8 51.3 7.5 22Mithari 0.99 92.5 50.0 42.0 8.0 9

III. Brown light loamJodhpur I 0.70 72.5 47.5 41.4 6.1 15Jodhpur II 0.63 70.0 45.0 39.7 5.3 3Bhopalgarh 1.03 70.0 58.8 51.3 7.S 3Katoti 0.91 162.5 45.0 34.0 11.0 32Katiasani \.13 550 50.5 42.4 8.1 19Bilu 0.96 52.5 65.0 60.3 .- 4.7 24Parbatsar 1-23 111.3 107.0 94.0 12.9 37

V. Grey brown loamPipad 1.07 182.5 86.3 80.3 6.0 16Asop I 0.95 232.5 110.0 97.5 12.5 25Asop II 0.83 300.0 77.5 66.0 11.5 20Ren 0.85 120.0 50.0 30.6 19.4 37Kankray 1.17 137.5 37.0 77.2 9.8 25

V. Playa soilPokaran 0.90 117.5 32.5 20.0' 17.5 -21Pachpadra 1.60 202.5 87.5 58.5 29.0 -7

Mean 1.04 103.13 58.23 47.36 10.87 6.69

204 : D. C. JOSHI et al.

(2.5 to 15 mg/l00g; Bhatnagar et al.,1973) and Mewar (32.6 to 115 mg/lOOg; Bishnoi and Khatri, 1974) soils.Significant positJive correlation of potas-sium fixation capacity with clay, silt andorganic carbon content (0.727, 0.640,0.717) and negative correlation with pH(r = - 0.367) suggested that potassiumfixation is the function of finer fractionand the nature of the exchange complex.Similar relationship has also been ob-served for other Indian soils (Ramana-than and Krishnamoorthy, 1976; Grewaland Kanwar, 1967). All the soil para-meters together accounted for 72.1 percent variability in the potassium fixationcapacity of arid soils. The regression ofall these soil parameters on the potassiumfixation capacity can be given by theequation:

K fixation capacity = 87.26 - 12.21 pH+ 73.34 org. carbon - 0.32 silt + 1.65clay - 1.25 CaCOa (R2=0.726)

This equation was a reliable predictor ofpotassium fixation capacity because theparameters involved accounted for 72.6per cent of the variability.

Among different forms potasSlium fixa-tion capacity was significantly rehtedonly with fixed (r = 0.506) andN HN03 soluble (r = 0.404) forms ofpotassium. All the forms of potassiumtogether accounted for 48.3 per centvariation in potassium fixation capacity.The regression of different forms on pota-ssium fixation capacity can be given bythe equation:

K fixation capacity = - 4.74 - 3.87total K+O.04 HCl K-4483.30 NHNO

3

K+4482.4 available K + 4483.7 fixed K{R2=0.483)

Thus the clay, silt and organiccarbon content of these soils appearedto be the dominating factor affecting re-serve pool of potassium and potassiumfixation capacity whereas pH and CaC03

content of the soil affected the availablepool.

ACKNOWLEDGEMENTS

Authors are grateful to Dr. H.S. Mann,Director, Dr. K.A. Shankarnarayan,Head, Division of Basic ResourcesSurvey and Dr. R.P. Dhir, Soil ScientJist,CAZRI, Jodhpur, for their guidanceand encouragement.

REFERENCES

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Bhatnagar, R.K., Nathani, G.P.,Chouhan, S.S. and Seth, S.P. 1973.Potassium fractions and fixing capa··city of medium black soils of Raj-asthan. J. Indian Soc. Soil Sci. 21:429-432.

Bishnoi, S.R. and Khatri, P.B. 1974.Potassium fixation in Mewar soils.J. Indian Soc. Soil Sci. 22: 329-332.

Choudhari, J. S. and Jain, S. V. 1979.Forms of potassium and K fixingcapacity of soils in different agroclimatic regions of Rajasthan. J.Indian Soc. Soil Sci. 27 : 132-138.

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Kanwar, J.S. and Grewal, J.S. 1966.Forms of potassium in Punjab soils.J. Indian Soc. Soil Sci. 14: 63-67.

Mehrotra, C.L., Gulab Singh and Pandey,R. K. 1973. Relationship between

POT ASSlUM IN ARID SOILS : 205

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