Annals of Arid Zone~18 (3), 174-180, 1979 Studies on potassium fixation and its relationship with chemical characteristics of some desertic soils of western Rajasthan R.K. AGGARWAL, V.K. SHARMA and R.P. DHIR Central Arid Zone Research Institute, Jodhpur (Received 3-2-1978) ABSTRACT Potassium fixation in some soil groups of Jodhpur and Nagaur districts of arid Rajasthan has been studied. The K-fixation capacities of grey brown loam, light brown loam, Luni alluvium and hard pan soils, on an average were: 0.535, 0.451, 0.180 and 0.140 meq/ioog soil respectively. Sub-surface soils showed higher K-fixation capacities. K-fixation capacity was found to bear a significant positive relationship with organic matter content, fixed K and non-exchangeable K. Highly significant correlation was found between K-fixation capacity and CEC and clay content of soil. Organic matter in soil was found to have depressing effect on K-fixation capacity when regressed along with CEC of soil. In these soils, either CEC or clay content can be an important indicator in determining the extent of K-fixation capacity. INTRODUCTION Potassium fixation has a great relevance in the potassium nutrition of plants as it regulates the equilibrium amongst different potassium fractions in soil and thus the supply of available K. The fixation of applied potassium m soil mainly depends on the amount and nature of clay minerals, degree of weathering and chemical and mechanical composition of soils. Thus, the knowledge of potassium fixation capacity and its relationship with chemical composition of soils and various forms of soil potassium is essential to work out the potassium-supplying capacity of soil and recommending potassium fertilizers. Information of these aspects for soils of arid Rajasthan is scanty. The present investigation has, therefore, been undertaken to study the potassium fixing capacity of different soils of Jodhpur and Nagaur districts and its relationship with various forms of soil potassium, cation exchange capacity and organic matter content.
K. FIXATION IN W. RAJASTHAN 175 EXPERIMENTAL Twenty two surface and subsurface samples were collected from different sites representing major soil groups of Jodhpur and Nagaur districts of Western Rajasthan and their physico-chemical characteristics are shown in Table 1. ph and E. C. were measured in 1:2.5 soil water ratio using glass electrodes and solu bridge respectively. Organic carbon was estimated by the method of Walkley and Black (1934). Cation exchange capacity was determined by sodium-acetate method (Jackson, 1967). Potassium fixing capacity, exchangeable potassium and fixed potassium were determined as per the methods described by Jackson (1967). Non-exchangeable potassium in the soil was estimated by substracting the exchangeable potassium from the fixed potassium. RESUL TS AND DISCUSSION Potassium fixation capacity: The data presented in Table 2 reveal that K fixation capacity of the soils under study varied to a great extent and it ranged from 0.06 to 0.90 meq/ioo g. Further it was observed that the surface soil, in general, had low K-fixation capacity than the sub-surface soils. Among different soil groups, highest K-fixation was observed in grey brown loam (0.535 meq/ioog) while the low.est in the Luni alluvium (0.18 meq/100g) and hard pan soils of Bap (0.14 meq/loog). Light brown loam soils showed medium fixation of K (0.451 meq/hlog). Bishnoi and Khatri (1974) also reported high K-fixation capacity in medium black soils of Mewar. These variations in K-fixation capacities amongst different soil groups and between two depths can be due to the variations in soil CEC which is a function of amount and nature of clay in soil. As these soils are mostly dominated by iilitic and montmorillonite type of clay minerals, so the variation in amount of clay seems to be more influencing factor of the CEC. A perusal of the data in Table 1 showed that these soils vary widely in their clay content. The mean per cent clay content in surface and sub-surface of different soil groups were : 18.0 and 24.0 in grey brown loam; 10.6 and 18.3 in light brown loam; and 6.1 and 10.8 in light textured Luni alluvium and hard pan soils, respectively. A comparison of CEC values of soils showed a positive association with the per cent clay content. The statistical analysis of the data' showed a highly significant positive relationship of K-fixation capacity with CEC ( r = 0.753**) and clay content ( r = 0.825-*) and the regression equation were obtained as follows :
00 N tr)n tr) N '<1" '-C 00 '" N \0 00 -- NN N o 0 000000 0 co 00 0 '<1" OIO'Dor,N O...o~r-O - _NOO CO 0000 '<1" \0'0 '<1"\0 \0 0000000 00 \0 N N.!--tr) \0 00-0 '<1"00 00 0 0 --00000-0000 0 000000000 ~ ~ ~ ~ ~ 0... o ~ ~ 0 ~ "': tr)'<1"0 \00\ 0 Ntr) tr)tr) "': Cl Z cx5 00 00 00 cx5 00 r.: r.: 00 cx500 00 00 00 0..., O'l\ONN ~NC""\""'M 0000000 N ' ō C?\0 0\ 00 0 'c; r-- M '<1"!--!-- M\0 '<1" M 0\ 00 ffi N '<1" cx5.n 0 or) -.r _ 0\ r...:...ol --N NN-N-N '<1"\O<'">O\\OM!-- -.rr...:o\i.cln N '" 0 tr) Otr) 0 tr)0 on Oon Otr) 0 N onn "'N tr) Non N tr)n tr)n on I 0 I I I I 0 I J I I I I I o on0 or,0 tr) 010 0 ono 100 on N ("'I N N N N N <r. 0 IOV"'IO 100 (,~V"'INNonNon I I I I I I J OIOOOor,Oor, N N N E u..c:: u I o.~ VJ ~..c:: 0... 0.. ;::l o... 01J o r.f:j E..s '" c ::: o....0.....c::.~...:l E '"o c.s ~ (J o...:l
K FIXATION IN W. RAJASTHAN 177 Table 2. K-fixation capacity and forms of K in different soil groups Location Depth K-fixation Forms of potassium (meqf100 g) (em) capacity Exchangeable Non- Fixed (meq/100 g) exchangeable NAGAUR Degana 0-25 0.19 0.22 2.24 2.46 25-50 0.54 0.13 2.64 2.77 Gotan 0-25 0.19 0.10 1.23 1.33 25-50 0.45 0.08 1.51 1.59 Tabta II 0-25 0.54 0.12 1.88 2.00 (North of 25-50 0.90 0.18 2.54 2.72 Borunda) Tabta I 0-25 0.22 0.14 1.50 1.64 (South of 25-50 0.58 0.10 2.62 2.72 Harsar) Dodyana 0-25 0.38 0.30 3.70 4.00 25-50 0.77 0.15 3.75 3.90 Silgaon 0-25 0.19 0.53 3.43 3.95 25-50 0.41 0.33 3.05 3.38 Dhanelas 0-25 0.32 0.51 3.44 3.95 25-50 0.71 0.35 2.37 2.72 JODHPUR Gajsinghpura 0-25 0.83 0.61 2.88 3.49 25-50 0.67 0.49 0.84 3.33 Bhavi 0-25 -0.19* 0.09 1.04 1.13 Bhavi 0-25 0.06 0.31 2.77 3.08 25-50 0.31 0.44 2.75 3.18 Bap 0-25 0.06 0.24 1.76 2.00 25-50 0.23 0.20 1.59 1.79 * Negative fixation.
178 R.K. AGGARWAL et aj. Y = 0.028 + 0.0277 x Y = -0.15+ 0.033 XI Where, Y = K-fixation capacity meq/ I 00 g X = CEC meq/ioo g soil Xl = Percent clay content. Mehta and Shah (1956) and Chaudhary and Pareek (1976) also reported an increase in K-fixation capacity with the increase in CEC of soil. Thus, the high amount of K-fixation in grey brown loam soils may be due to high content of clay as revealed by their high CEC values also. Similarly, the low K-fixation capacity of Luni alluvium and hard pan soils may be attributed to the low CEC of these soils. The negative K-fixation in surface soil of Luni alluvium seems to be due to very low CEC and clay content of soil. Prasad et a/. (1967) also reported negative K-fixation in Ranchi soil of Bihar. Relationship between K-fixation capacity and forms of soil potassium: The various forms of K in the soil are given in Table 2. The data reveal that the exchangeable K varied from 0.09 to 0.61 meqjloog soil and the mean values in grey brown loam, light brown loam, Luni alluvium and hard pan soils were 0.41, 0.13, 0.31, and 0.22 meq/l00g soil. respectively. On the basis of the standard fixed by JARl and other soil testing laboratories in India, the soils belonging to light brown loam can be categorised as low in available K. The exchangeable K had significant positive correlation with the non-exchangeable and fixed-k but had no correlation with K-fixation capacity (Table 3). Similar results were reported by Bhatnagar et a/. (1973). The non-exchangeable K of these soils varied from I. 04 to 3.75 meq/ioo g soil. The grey brown loam soils contained the highest amount of non-exchangeable K with the mean value of 3. I 8 meq/ioog while the hard pan soils had its lowest content with a mean value of 1.67 meq/ioo g. This form of K was found to have significant positive correlation with K-fixation capacity and highly significant positive correlation with exchangeable and fixed K. The amount of fixed K present in these soils varied from 1.13 to 4.0 meq/ioog. The grey brown loam soils were found to contain the maximum content of this fraction and the least was observed in hard pan soils. Fixed K had a significant positive correlation with K-fixation capacity and highly significant correlation with exchangeable and non-exchangeable K of soil. These findings revealed the maintenance of equilibrium between different forms of K in these soils.
K. FIXATION IN W. RAJASTHAN 179 Table 3. Correlation coefficient of potassium fixing capacity with potassium fractions and other chemical characteristics of soils Organic Fixed Non-exch. Exch. matter CEC K K K K - fixation capacity 0.485* 0.753** 0.423* o 443* 0.1 56 Exch.-K 0.491 * 0.579 0.686** 0.573* Non-exch.-K 0.6611<* 0.634* 0.989** Fixed K 0.671 ** 0.665** * Significant at 5% level. ** Significan tat 1% level. Relationship of K-fixafion capacity with organic matter of soil: The correlation coefficient values presented in Table 3 reveal that K-fixation capacity had a significant positive correlation with the organic matter content of soil at 5 per cent level only. Verma and Verma (1971) also observed positive and significant relationship of K-fixation capacity with organic matter in soils of Madhya Pradesh. The studies further elucidated that when organic matter is regressed on K-fixation capacity of soil along with the factor CEC, it showed a depressing effect as revealed by the following multiple regression equation having a prediction value of 56%. Where, 0.0372 + 0.0285 Xl - 0.0436 X2 K-fixation capacity meq/l00 g soil CEC meq{100 g soil Per cent organic matter Walker and Sturgin (1940), Zolotarev and Boktor (1973) also reported a depressing effect of organic matter on K-fixation capacity of soil as a result of adsorption of organic polyanions in the interlayer exchange sites of expanding clays. It appears from these studies that one could use the criterion of per eent clay or CEC values to predict the K -fixation capacity of these soils.
180 R.K. AGGARWAL et al. ACKNOWLEDGEMENTS The authors owe their sincere thanks to Dr. H. S. Mann and Dr. A.N. Lahiri, Director and Head, Division of Soil-Water-Plant Relationship. respectively of Central Arid Zone Research Institute, Jodhpur, for providing necessary facilities and guidance in the course of these studies. The valuable help rendered by Dr. H.P. Singh, Soil Physicist, Dry Land Agriculture Centre is duly acknowledged. REFERENCES Bhatnagar, R. K., Nathani, G. P., Chouhan, S. S. and Seth, S. P. 1973. Potassium fractions and fixing capacity of medium black soils of Rajasthan. J. Indian Soc. Soil Sci. 21 (4) : 429-432. Bishnoi, S. R. and Khatri, P. B. 1974. Potassium fixation in Mewar soils. J. Indian Soc. Soil Sci. 22 (4) : 329-332. Choudhari, J. S. and Pareek, B. L. 1976. Exchangeable reserve potassium in soils of Rajasthan. J. Indian Soc. Soil Sci. 24 (1): 57-61. Jackson, M. L. 1967. Soil Chemical Analysis. Prentice Hall of India Pvt. Ltd., New Delhi. Mehta, B. V. and Shah, C. C. 1956. Potassium status of soils in western Rajasthan. 2. Fixation of potassium. Indian J. agric. Sci. 26: 267-27&. Prasad, R. N., Sinha, H. and MandaI, S. C. 1967. Fractions of potassium in Bihar soils. J. Indian Soc. Soil Sci. 15 (3) : 173-179. Verma, O. P. and Verma, G.P. 1971. Potassium fixation in soils of Madhya Pradesh. JNKVV Research Journal 4 : 22-24. Walker, R. K. and Sturgin, M. B. 1940. Effect of wetting, drying and treatments on the availability of potassium in soils. Assoc. South Agr. Workers Proc. 41 : 79. Walkley, A. and Black, I. A. 1934. Estimation of soil organic carbon by the chromic acid titration method. Soil Sci. 47 : 29-38. Zolotarev, S. A. and Boktor, S. 1973. Potassium fixation by the clay fraction of Ukranian Chernozemic soils. Pochvovedenic No.2, pp. 129-134.