MOBILITY OF EXCHANGEABLE CATIONS IN SOILS FROM LONG TERM FIELD EXPERIMENTS IN SKIERNIEWICE**

P O L I S H J O U R N A L O F S O I L S C I E N C E VOL. XLII/1 2009 PL ISSN 0079-2985 Soil Chemistry TERESA KOZANECKA, ZYGMUNT BROGOWSKI, MARCIN KISIEL, WOJCIECH STÊPIEÑ* MOBILITY OF EXCHANGEABLE CATIONS IN SOILS FROM LONG TERM FIELD EXPERIMENTS IN SKIERNIEWICE** Received February 27, 2009 Abstract. Taking advantage of the long term field stationary experiments in Skierniewice started at 1922 based on fixed mono-fertilization, the mobility of the exchangeable cations Ca, Mg, K, Na was studied for the whole soil profile up at a depth of 100 cm. Mobility was studied using an electrodialysis method to remove and determine cations in the cathode solutions. Calcium proved to be most mobile element and sodium the least mobile and the mobility ranking of exchangeable cations in the soil under investigation is as: Ca > K > Mg > Na. The genetic horizons of the soils showed differentiated mobility for individual cations. Cations in the surface horizons (up to 50 cm) are more mobile than in the deeper horizons with trace amounts of humus. A very long-term (multiyear) field experiment, dating started at back to 1922 year in Skierniewice, constitutes a unique object for all kinds of experiments in the field of agriculture in the broad sense. Our interest was directed towards changes taking place in the active part of the soil, i.e. in the sorption complex, as a result of long-term, one-sided fertilisation and specific types of crop rotation. In the present study, we concentrated not only on the quantitative relations among exchangeable cations in the sorption complex but also on the dynamics of their release over time. Long-term experimental studies into the physical-chemical soil properties in Skierniewice have been carried out systematically every few years; however, mainly on the arable-humus horizons [9, 11-16] up to a depth of cm. It seems that such a long period (85 years) of treating the soil in an identical way could put a *Asst. Prof. T. Kozanecka, DSc., Prof. Z. Brogowski, DSc., M. Kisiel, MSc., W. Stêpieñ, DSc.; Department of Soil Environment Sciences, Warsaw Agriculture University, Nowoursynowska 159, 02-776 Warsaw, Poland. **The studies were financed by the Ministry of Science and Higher Education, Poland, under the grant No. N 310 077 31/3167.

2 T. KOZANECKA et al. lasting mark on the whole soil profile up to a depth of at least 100 cm. Hence, the quantitative distribution of Ca, Mg, K and Na in the soil profile, and especially their binding energy with natural soil sorbents such as clay minerals and humus, could throw new light on the processes caused by mono-fertilisation [1-8, 10, 18-20] in the soil environment and the process of primary mineral weathering [17]. MATERIALS AND METHODS A vast amount of analytic-documentation material has been collected; however, the present study concentrates on three experimental combinations, namely: A a limed object without manure or mineral fertilization since 1922 with facultative crop rotations but without legumes plants; B a limed object fertilized with manure, without mineral fertilization since 1922, five crop rotation, with legumes plants; C an object with no liming and manure, fertilized with NPK, facultative crop rotation scheme, without legumes plants, nitrogen used in the form of ammonium sulphate. Soil samples from the above objects were collected from the following horizons: Ap ( cm), Eet ( cm), Bt ( cm) and C ( cm). After the samples had been air dried, they were crushed and sieved through a 1mm diameter mesh, then 50g portions were taken for electrodialysis. The soil sample was placed in a beaker between cathodes and anodes with especially pre-prepared middle hard filters according to method Maksimov [10]. The soil in the beaker was then inundated with 500 ml of re-distilled water. The voltage applied was similar to a root suction force of 100 V. Every three hours the anode and cathode solution were collected to the beakers. The content of these beakers was then evaporated at a volume of 100 cm 3, Ca and Mg content were determined in the cathode solution by means of the AAS atomic absorption spectrometry method, K and Na using the AES atomic emission spectrometry method. Electrodialysis was carried out until the conductivity of the electrodialyzed sample decreased below 5 ma. It was found that in soils with a similar grain size distribution (Table 1), 36 hours, consisting of 12 periods of 3 h, was enough for the full removal of the mobile cations. For the purpose of the present experiment, the sum of a given cation extracted during a 36 h period was assumed to be 100%, and removal of mobile cations was calculated as a percentage to make comparisons of the binding forces in sorption complexes of individual horizons studied possible. The physico-chemical properties of the studied objects were determined using methods generally accepted in the soil sciences and were presented in Table 1.

MOBILITY OF EXCHANGEABLE CATIONS IN SOILS 3 TABLE 1. GRAIN-SIZE DISTRIBUTION AND SOME OF THE SOIL PHYSICAL-CHEMICAL FEATURES OF THE LONG-TERM EXPERIMENTS IN SKIERNIEWICE Depth of sampling (cm) Genetic horizons % of grains with diameter in mm of Organic carbon (%) ph in KCl cmol(+)/kg 1-0.1 0.1-0.05 0.05-0.02 0.02-0.005 0.005-0.002 <0.002 S Hh T=S+Hh %V S 100 T A = Limed field, without manure or mineral fertilization since 1922 facultative crop rotation without legumes plants Ap Eet Bt C 69.0 67.0 53.0 53.0 11.0 10.0 11.0 13.0 7.0 5.0 5.0 3.0 B = Limed field, fertilized with manure without mineral fertilization since 1922 5-field crop rotation with papilionaceous plants 19.0 1 0.33 0.15 0.14 0.05 6.9 6.5 6.2 6.2 5.8 5.7 9.4 0.4 0.5 0.5 0.5 6.2 6.2 8.5 9.9 93.5 90.5 94.1 94.4 Ap Eet Bt C 6 6 55.0 59.0 11.0 10.0 10.0 10.0 9.0 5.0 C = Field without liming or manure fertilized with NPK since 1922 facultative crop rotation without legumes plants 19.0 1 0.71 0.29 0.19 0.06 6.2 5.9 5.3 7.8 7.0 5.8 6.2 9.2 1.0 0.7 0.9 0.5 6.5 7.1 9.7 87.5 89.2 87.3 94.8 Ap Eet Bt C 67.0 62.0 50.0 51.0 11.0 12.0 11.0 1 7.0 7.0 7.0 3.0 7.0 21.0 1 0.45 0.19 0.17 0.08 3.9 5.2 1.4 0.6 9.0 9.2 3.1 3.2 3.3 0.8 4.5 3.8 12.3 10.0 31.1 15.8 73.2 92.0

4 T. KOZANECKA et al. RESULTS Soil characteristics. The studied soils originated from light boulder loam transformed into sand loam in the upper part of the profile, i.e. up to 50 cm deep (Table 1). Bt illuviation horizons at depths of cm were clearly visible in these soils, with greater accumulation of the clay fraction <0.002 mm and grains particles below in diameter <0.02 mm being visible (Table 1). In all genetic horizons, grains of sand (1-0.1 mm) predominated and exceeded 50% of the soil mass. The silt fraction (0.1-0.02 mm) usually did not exceed 20%. Organic carbon at the Ap arable-humus horizons in all three experimental combinations studied was clearly differentiated. Its highest content was found in the combination with manure, liming and legumes plants, and the lowest in the combination with liming and without manure and with facultative crop-rotation (Table 1). Combinations with liming showed an alkaline reaction or close to alkaline; however, in the experimental combination with NPK without liming, the reaction was acidic or strongly acidic. Mobility of alkaline exchangeable cations. The application of the electrodialysis method for the removing of mobile (exchangeable) cations, using three-hour time intervals allowed a comprehensive observation of their mobility in the soils as well as their availability for plants. Due to the high amount of data collected, twelve three-hour periods constituting 36 h in total were treated jointly as four nine-hour periods by summing the cation content from each set of three three-hour periods. The above data, even though they are less detailed, allowed the determination of any trend in the phenomena, such as cation binding energy, taking place in the soils under the influence of the same type of fertilization-treatment taking place over a period of 85 years (Table 2). The exchangeable cation mobility in the present study was expressed as a percentage of the cations removed in individual electrodialysis periods (each lasting 9 h) compared to the sum obtained in the sum of 36 h period. Calcium was the predominant element among the alkaline exchangeable cations in the soils (Tables 2, 4, 5). In experimental combination A, calcium was the most mobile element in the first two genetic horizons, Ap and Eet, lying up to 50 cm deep. The sum of the exchangeable Ca removed during the first 9 h was 85% of the calcium removed during the 36 h period, while the remaining 15% was removed during the remaining 27 h. In the deeper horizons of the soil in combination A, only 22.9-30.9% Ca was removed during the first 9 h. In the a.m. horizons, calcium was bound more strongly and released uniformly during the whole electrodialysis period (Fig. 1). In object B, calcium was released very slowly and uniformly in the Ap, Eet and Bt horizons, lying at depths of up to 75 cm. In horizons C, i.e. the parent rock, lying at depths of up to cm, 86% of the total exchangeable calcium content was

MOBILITY OF EXCHANGEABLE CATIONS IN SOILS 5 TABLE 2. CONTENT OF EXCHANGEABLE CATIONS (Ca AND Mg) REMOVED FROM THE SOIL BY ELECTRODIALYSIS (mg kg -1 ) Depth of sampling (cm) Time to remove Ca from the soil (h) Time to remove Mg from the soil (h) Weight Ca Mg 0-9 0-19 18-27 27-36 0-36 0-9 0-19 18-27 27-36 0-36 ratio A = Limed field, without manure or mineral fertilization since 1922 facultative crop rotation without legumes plants 732.8 721.2 443.2 105.2 61.5 61.7 392.0 182.4 34.4 35.1 277.0 87.6 35.9 35.2 321.4 83.7 964.6 853.2 1433.6 458.9 49.5 49.2 7.3 7.4 19.5 21.6 8.1 8.5 8.8 11.5 6.4 8.9 8.6 9.5 14.1 7.7 86.4 91.8 35.4 32.5 10.0 9.3 39.9 14.1 B = Limed field, fertilized with manure without mineral fertilization since 1922 5 field crop rotation with papilionaceous plants 418.9 319.7 276.5 1 266.9 353.3 278.1 291.0 134.1 268.2 201.3 282.9 45.1 107.4 169.3 263.7 24.4 1147.4 968.4 111 1470.5 9.6 11.8 7.8 99.1 11.9 15.8 6.9 30.3 2 14.5 8.2 15.0 21.3 9.1 7.5 10.8 66.8 51.2 30.4 155.2 17.2 18.9 36.6 9.5 C = Field without liming or manure fertilized with NPK since 1922 facultative crop rotation without legumes plants 110.6 19.6 1 341.8 781.8 8.4 3.6 25.0 385.8 7.1 1.2 10.5 224.2 1.4 1.0 5.5 164.2 126.5 25.4 1388.6 155 7.2 1.9 89.9 7.8 1.7 0.5 19.9 23.8 1.8 0.1 6.9 41.6 0.3 0.2 4.2 29.6 11.0 2.9 120.9 100.8 11.5 8.7 11.5 15.4

6 T. KOZANECKA et al. Depth of sampling (cm) TABLE 3. Exchangeable cations content (K and Na) removed from the soil by electrodialysis (mg kg -1 ) Time to remove K from the soil (h) Time to remove Na from the soil (h) Weight K 0-9 0-19 18-27 27-36 0-36 0-9 0-19 18-27 27-36 0-36 Na ratio A = Limed field, without manure or mineral fertilization since 1922 facultative crop rotation without legumes plants 46.5 8 11.9 10.1 13.3 11.5 12.0 9.7 11.2 13.6 12.8 10.9 10.6 10.8 13.9 9.7 131.6 123.9 50.6 40.4 B = Limed field, fertilized with manure without mineral fertilization since 1922 5 field crop rotation with papilionaceous plants 36.1 36.7 30.9 12.3 27.9 15.0 22.0 7.1 16.1 18.4 19.3 7.2 14.6 14.8 22.1 3.3 94.7 84.9 94.3 29.9 1.4 1.5 0.5 1.4 118.7 43.2 13.6 59.0 20.4 19.1 13.3 10.8 16.1 14.7 13.6 10.2 12.0 13.3 11.6 9.8 167.2 90.3 52.1 89.8 C = Field without liming or manure fertilized with NPK since 1922 facultative crop rotation without legumes plants 29.5 23.4 17.1 55.2 15.8 13.6 12.2 9.1 14.6 12.2 12.6 7.7 12.0 10.4 10.2 7.5 71.9 59.6 52.1 79.5 2.3 1.5 1.0 1.1 141.6 107.5 241.1 3 25.4 19.4 21.6 21.4 22.8 15.8 14.4 20.4 23.5 15.2 14.2 18.3 213.3 157.9 291.3 96.1 12.8 10.9 42.0 33.7 6.1 3.3 11.1 18.7 6.1 4.1 9.7 16.4 5.8 12.6 1 30.8 22.3 75.4 82.8 6.9 7.1 3.9 1.2

MOBILITY OF EXCHANGEABLE CATIONS IN SOILS 7 TABLE 4. EXCHANGEABLE CATIONS CONTENT REMOVED FROM THE SOIL BY ELECTRODIALYSIS OVER A 36 H PROCESS AND THEIR PERCENTAGE SHARE [MMOL (+)] IN THE SORPTION COMPLEX (mg kg -1 ) Depth of sampling (cm) Genetic horizons cmol(+)/kg soil Percentage of cations in the total Ca Mg K Na Sum= 100% Ca + Mg K + Na Ca Mg K Na (Ca+Mg) (K+Na) A = Limed field, without manure or mineral fertilization since 1922 facultative crop rotation without legumes plants Ap Eet Bt C 43.2 42.7 71.2 22.9 7.2 7.6 3.0 2.7 3.4 3.2 1.3 1.0 4.1 3.7 4.1 1.3 57.9 57.2 79.6 27.9 B = Limed field, fertilized with manure without mineral fertilization since 1922 5-field crop rotation with papilionaceous plants 6.7 7.3 13.7 11.0 74.6 74.6 89.4 82.1 12.4 13.3 3.8 9.7 5.9 5.6 1.6 3.6 7.1 6.5 5.2 4.6 87.0 87.9 93.2 91.8 13.0 12.1 6.8 8.2 Ap Eet Bt C 57.4 48.4 55.7 73.5 5.6 4.3 2.5 12.9 4.3 2.3 1.3 2.3 3.1 2.6 2.3 3.5 70.4 57.6 61.8 92.2 C = Field without liming or manure fertilized with NPK since 1922 facultative crop rotation without legumes plants 8.5 10.7 16.2 15.0 81.5 8 90.1 79.7 7.9 7.5 4.1 1 6.1 2.1 2.5 4.5 4.5 3.7 3.8 89.4 91.5 94.2 93.7 10.6 8.5 5.8 6.3 Ap Eet Bt C 6.4 1.3 68.9 77.8 0.9 0.2 10.1 8.4 5.5 7.5 2.5 1.3 1.0 3.3 3.6 14.1 6.5 89.8 92.3 1.1 0.3 7.3 14.2 45.4 20.0 76.7 84.3 6.4 3.1 11.2 9.1 39.0 61.5 8.4 2.7 9.2 15.4 3.7 3.9 51.8 23.1 87.9 93.4 48.2 76.9 12.1 6.6

8 T. KOZANECKA et al. % of mobile cation release in time % of mobile cation release in time Fig. 1. Mobility of exchangable cations in limed soil but withouth manured and mineral fertilizer since 1922. Facultative plant rotation without legume plants. (Total sum of exchangeable cations removed during 36 h electrodialisis duration from separate genetic horizons = 100%).

MOBILITY OF EXCHANGEABLE CATIONS IN SOILS 9 released in the first 9 hours (Fig. 2). It should be assumed that part of the mobile Ca was leached down from the horizons lying above C horizons. Hence, in these horizons, calcium was more loosely bound with the clay minerals than in the horizons from which labile calcium was taken up by plants, especially legumes plants. Soil from object C, without manure and liming and fertilized with NPK, is clearly different. Exchangeable Ca mobility, despite its low amount (Fig. 3), is enormous. During the first 9 h, 50 to 97% of all exchangeable calcium was removed from all genetic horizons (Fig. 3). It can be concluded that the mineral fertilisers applied, cause from 39.0 to 61.5 % of potassium share in the soil sorption capacity in the two upper horizons, Ap and Eet, caused almost total removing of this element from the soil by its leaching down to deeper horizons (Table 4). Hence, calcium, with its trace amounts, cannot be bound by the soil sorptive complex becouse its surface was almost fully saturated by potassium. Magnesium occurs in the soil in lower amounts than calcium, its content usually not exceeding 10% of the exchangeable Ca content in the soils studied (Tables 2, 4 and 5). Despite its trace amounts, the highest mobility of Mg was found in the soil in the combination fertilized with NPK (Figs 1-3). The results clearly showed that Mg was more strongly bound than Ca in the soils. Similar results were obtained by other researchers, such as Brogowski [2-4] and Musierowicz [17, 18], for various kind and soil types. In the present study the results obtained using electrodialysis contradicted the usual theory of cation binding in the soil sorptive complex, which states that the binding energy depends on the cation valence and atomic mass for all cations except hydrogen. A theory that seems to match the results better is that of ionic potential, which states that the binding energy of exchangeable cations in the soil depends on the valence divided by the ionic radius of the cation. In some cases, a higher amount of Mg was releazed in later periods of electrodialysis than in the initial stage (Figs 1 and 3). As follows from studies by Musierowicz [17, 18] and Brogowski [2-4], the later release of Mg may take place when chlorite minerals and saponite from the montmorillonite group occur in the soils. Potassium by far exceeded, quantitatively, the magnesium content in the soils of the objects studied (Tables 3-5). Potassium mobility slightly exceeded magnesium mobility, although it was lower than that of calcium (Figs 1-3). Potassium mobility in the soil of objects A and C was similar but different to the soil of object B, where manure had been applied together with liming and legumes plants. Potassium mobility in this combination was clearly higher than that of Ca, Mg or even Na, especially during the first 9 hours of electrodialysis when 4 to 71.0 % of K was released. The horizon in the parent rock, lying at a depth of cm, was an exception as Ca, Mg, K and Na expressed the same or a similar mobility at this horizon (Fig. 2).

10 T. KOZANECKA et al. % of mobile cation release in time % of mobile cation release in time Fig. 2. Mobility of exchangable cations in soil with manured but without mineral fertilizer since 1922. Five plant rotation with legume plants. Explanations as on Fig. 1.

MOBILITY OF EXCHANGEABLE CATIONS IN SOILS 11 % of mobile cation release in time % of mobile cation release in time Fig. 3. Mobility of exchangable cations in soil without lime and manured but with fertilizer since 1922. Facultative plant rotation without legume plants. Explanations as on Fig. 1.

12 T. KOZANECKA et al. Exchangeable sodium showed similar or slightly higher contents than exchangeable magnesium (Tables 3-5). Its mobility in the soils of combination A was uniform for all electrodialysis periods and clearly lower in the Ap and Eet horizons as compared to the mobility of calcium, magnesium or potassium (Fig. 1). In combination B, sodium mobility was similar to that of Ca and Mg; however, it was markedly different from that of potassium (Fig. 2). On the other hand, in the soil of combination C (fertilization with NPK), sodium mobility was the lowest in compared to all remaining exchangeable cations (Fig. 3), and it could be concluded that sodium was blocked in the soil by potassium, the content of which in the soil sorption complex was the highest, especially in the Ap and Eet horizons lying at depths of 0-50 cm (Fig. 3). DISCUSSION Summing up, it is worth stressing that the soils studied in individual experimental fertilization-treatment clearly differ in the quantitative content of exchangeable cations and in their mobility. The most significant changes in the relations between exchangeable cations took place as a result of treatment in the soil sorption complex in the soil treatment with mineral NPK fertilizers without liming. A high of acidification took place in this with only trace amounts of exchangeable Ca and Mg occuring in the Ap and Eet horizons. Considerable amounts of exchangeable potassium accumulated together with a clear increase in the mobility of the remaining Ca and Mg as well as other cations. Deeper horizons of the soil fertilized with NPK did not undergo changes or were enriched to a low extent by Ca and Mg, probably as a result of their leaching down from the upper Ap and Eet horizons to the Bt and C horizons. Hence, in the soil of object A (methodology), Ca. Mg and K mobility decreased in the genetic horizons in the following order: Ap > Eet > Bt > C The deeper in the soil profile, the higher cations binding energy and the lower it mobility. Sodium mobility was as follows in the respective horizons: Eet > C > Ap > Bt In this last combination, the mobility of the cations decreased according to the following ranking: Ca > K > Mg > Na This last ranking follows the theory that the energy of exchangeable cations binding in the soil depends on the valence and atomic mass of the element. Similarly, it also follows a second theory where the cation binding energy in the

MOBILITY OF EXCHANGEABLE CATIONS IN SOILS 13 soil depends on the ionic potential of the element. The question now is whether identical long-term soil treatments could influence the binding energy of the individual exchangeable cations in the soil sorption complex? This phenomenon is difficult to interpret and requires further investigaton. In the soil of object B, the mobility of exchangeable Ca, Mg and Na decreased in the horizons in the following order: C > Ap > Eet > Bt For potassium the ranking was as follows: Ap > C > Eet > Bt In this last combination, the mobility of the cations decreased according to the following ranking: Ca > K > Na > Mg This is similar to the experimental combination A with the exception of the Na shift from fourth to third place, and the Mg shift to fourth place. In the soil of object C, the decreasing rank of cation mobility in the genetic horizons is as follows: for Ca = Bt > Ap > Eet > C This is similar to exchangeable Mg. For exchangeable potassium, the decreasing mobility in the genetic horizons is as: K = Bt > Eet > Ap > C A similar ranking occurred for sodium. In the above mentioned combination, the mobility of the cations studied in the soil was: Ca > K > Mg > Na This is similar to that of experimental combination A. As mentioned earlier, the binding energy of the exchangeable cations in these soils, which were under long-term anthropogenic pressure, bears no relation to the theories applied in this problem and hence the problem requires further study. Summing up, the following conclusions can be assumed based on the studies into the cations mobility in soils from multi-year field experiments carried out in the experimental fields of SGGW (Warsaw Agriculture University) in Skierniewice. CONCLUSIONS 1. The mobility of exchangeable cations was clearly differentiated in the soils. Calcium proved to be the most mobile element and sodium the least mobile, in the all combinations observed. Therefore, generally speaking, the decreasing mobility ranking of exchangeable cations studied is as: Ca > K > Mg > Na. 2. The genetic horizons of the soils showed differentiated mobility level for individual elements. Generally speaking, the cations were more loosely bound in the surface horizons (up to 50 cm) enriched for humus.

14 T. KOZANECKA et al. 3. The exit rankings of individual exchangeable cations in the soils did not follow any recognized theories. 4. Due to problems in explaining the reasons behind such differences in the exchangeable cations mobility in the soils, it appears necessary to deeper studies of the clay materials of these soils. REFERENCES [1] B a l l o u E. V.: J. Colloid Sci., 10, 450, 1955. [2] B r o g o w s k i Z.: Roczn. Glebozn., 10(2), 680, 1961. [3] B r o g o w s k i Z.: Zesz. Probl. Post. Nauk Roln., 40a, 103, 1963. [4] B r o g o w s k i Z.: Wyd. SGGW, 68, 1967 (rozprawa habilitacyjna). [5] B r o g o w s k i Z., K o z a n e c k a T.: Zeszyty Naukowe 2001. Wy sza Szko³a Ekonomiczno- Humanistyczna in Skierniewice, 1, 77, 2001. [6] H y d e S. J., M o r t l a n d M. M: Soil Sci. Society Am. Proc., 23, 4, 273, 1956. [7] K o z a n e c k a T., B r o g o w s k i Z., W a g n e r J., J e s k e K.: Polish J. Soil Sci., 34(2), 21, 2001. [8] L e n a r t S., M e r c i k S., a b ê t o w i c z J., M a z u r T., U r b a n o w s k i S: Fragmenta Agronomica, 1, 161, 2005. [9] L o w P. F: Soil Sci. Am. Proc., 22, 395, 1958. [10] M a k s i m o w A.: Roczn. Nauk Roln. Leœnych, 34, 27, 1966. [11] M e r c i k S., N e m e t h K.: Plant and Soil., 83, 151, 1985. [12] M e r c i k S.: Annals of Warsaw Agric. University of Agriculture, 19, 3, 1986. [13] M e r c i k S., S t ê p i e ñ W.: Fragmenta Agronomica, 1, 189, 2005. [14] M e r c i k S., S t ê p i e ñ W., a b ê t o w i c z J.: Folia Universitatis Agriculturea Agric., 84, 317, 2000. [15] M e r c i k S., S t ê p i e ñ W., G ê b s k i M.: Zesz. Probl. Post. Nauk Roln., 465, 3, 1999. [16] M e r c i k S., N o w o s i e l s k i O., P a u l M.: Zesz. Nauk. AR w Krakowie, 277, 85, 1993. [17] M o r t l a n d M. M., L a w t o n K., U e h a r a G.: Soil Sci., 82(6), 477, 1956. [18] M u s i e r o w i c z A., B r o g o w s k i Z.: Roczn. Glebozn., 13(1), 3, 1963. [19] M u s i e r o w i c z A., B r o g o w s k i Z.: Zesz. Probl. Post. Nauk Roln., 50a, 3, 1964. [20] N o r m a n A., C l a r k H., H u m f e l d A., A l f e n A.: Soil Sci., 24, 291, 1927. MOBILNOŒÆ KATIONÓW WYMIENNYCH W GLEBACH Z WIELOLETNICH DOŒWIADCZEÑ POLOWYCH W SKIERNIEWICACH Korzystaj¹c z d³ugoterminowych polowych badañ doœwiadczalnych w Skierniewicach rozpoczêtych w 1922 roku, opartych na jednakowym nawo eniu, zbadano ruchliwoœæ kationów wymiennych Ca, Mg, K, Na dla ca³ego profilu glebowego do g³êbokoœci 100 cm. Ruchliwoœæ badano przy u yciu elektrodializy dla usuniêcia i okreœlenia kationów w roztworach katodowych. Czas elektrodializy trwa³ 36 godzin, aby mieæ pewnoœæ, e wszystkie kationy wymienne zosta³y usuniête. Na ogó³ wapñ okaza³ siê najbardziej ruchliwym pierwiastkiem, a sód najmniej. Kolejnoœæ ruchliwoœci kationów wymiennych w badanej glebie jest nastêpuj¹ca: Ca>K>Mg>Na. Poziomy genetyczne gleb wykazywa³y zró nicowanie ruchliwoœci poszczególnych kationów. Kationy w poziomach powierzchniowych (do 50 cm) s¹ bardziej ruchliwe od g³êbszych poziomów ze œladow¹ zawartoœci¹ próchnicy.