Diagnosis of solonetzic process in virgin and agrogenically transformed soils of different regions

ISSN 1064�2293, Eurasian Soil Science, 2014, Vol. 47, No. 9, pp. 863–872. © Pleiades Publishing, Ltd., 2014.Original Russian Text © I.N. Lyubimova, V.V. Khan, I.A. Salpagarova, 2014, published in Pochvovedenie, 2014, No. 9, pp. 1046–1055.

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INTRODUCTION

Soils of solonetzic complexes are considered to beintricate natural phenomena; the genesis of thesecomplexes and the relationships between separate soilscomposing them remain insufficiently studied. In theSoviet Union, solonetzes were actively developed inthe 1970s–1980s. This necessitated evaluation of theefficiency of their reclamation. It was necessary tolearn to diagnose the development of solonetzic pro�cess in the reclaimed solonetzes. In particular, earlystages of the secondary development of solonetzicproperties in the soils of reclaimed solonetzic soilcomplexes had to be properly diagnosed. At present,there are many approaches to judge the developmentof solonetzic process and secondary solonetzization inthe reclaimed and irrigated soils. The following crite�ria are used: the exchangeable sodium content [1], theactivity of sodium ions at different soil�to�solutionratios [7, 10], the degree of illuviation in the soil pro�file [15], the sodium adsorption ratio (SAR) [3], theswelling kinetics of soils [6], and the calculated Bcharacteristic reflecting the physicochemical condi�tions of solonetzic process [19, 20].

Earlier, we compared two methods of the diagnosisof secondary solonetzization in the reclaimed solo�netzes and solonetzic soils of Volgograd oblast basedon the swelling kinetics of ground soil samples and onthe B characteristic of the physicochemical conditionsof solonetzic process [11, 12].

The aim of this work was to diagnose solonetzicprocess for a more diverse range of the agrogenically

transformed and virgin soils of solonetzic soil com�plexes in the chernozemic and chestnut soil zones ofEuropean Russia and Western Siberia. The approachesbased on the B characteristic of the physicochemicalconditions of solonetzic process and on the swellingkinetics indirectly related to the mineralogical compo�sition of the clay fraction and to the water�physicalproperties of the soils were applied. In addition, themorphological features of the soils were thoroughlycharacterized.

OBJECTS AND METHODS

We studied semihydromorphic and hydromorphicsoils of solonetzic complexes in the forest�steppe zoneof Western Siberia (Omsk and Novosibirsk oblasts)andin the forest�steppe and dry steppe zones of the Euro�pean part of Russia (Voronezh and Volgograd oblasts).The list of studied soils and their classification posi�tions are given in Table 1. Data on the content ofexchangeable sodium and total toxic salts in the soilsamples are presented in Table 2.

In Volgograd oblast, we studied soils of the KislovskIrrigation System in Bykovo and Nikolaevo districts.This is one of the largest irrigation systems with watersupply from the Volgograd water reservoir. The studiedplot is found within the marine plain of the Khvalyntransgression of the Caspian Sea. Its detailed charac�terization was given by Motuzov with coauthors [14].

In Voronezh oblast, soils were sampled byN.B. Khitrov in the Kamennaya Steppe (Talovsk dis�

Diagnosis of Solonetzic Process in Virgin and Agrogenically Transformed Soils of Different Regions

I. N. Lyubimovaa, V. V. Khana, and I. A. Salpagarovab

a Dokuchaev Soil Science Institute, per. Pyzhevskii 7, Moscow, 119017 Russiab Faculty of Soil Science, Moscow State University, Moscow, 119991 Russia

E�mail: [email protected] September 05, 2013

Abstract—To diagnose solonetzic process in virgin and agrogenically transformed soils of solonetzic soilcomplexes in the chernozemic and chestnut soil zones of European Russia and Western Siberia, their swellingkinetics and physicochemical characteristics were been studied. It was shown that a simultaneous applicationof these two approaches is more efficient than their separate use. The degree of manifestation of solonetzic processin the studied soils was determined. Swelling curves of sodic reclaimed solonetzes of Lyubinsk district of Omskoblast and of a virgin solonetz of the Baraba Lowland with a moderate content of adsorbed sodium proved to besimilar to those described for the vertic soils with a low infiltration capacity in the North Caucasus.

Keywords: agrogenically transformed solonetzes, diagnosis of solonetzic process, swelling kinetics, rate ofsolonetzic process, solonetzes of the European territory of Russia, solonetzes of Western Siberia

DOI: 10.1134/S1064229314070102

GENESIS AND GEOGRAPHY OF SOILS

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Table 1. Investigation objects

Pit number Land use

Classification, horizons

1977 [9] 2004 [8] WRB [13]

Nikolaevsk district of Volgograd oblast

1 Virgin land Virgin, high�sodium, shallow, strongly saline, chloride��sulfate, high�solon�chakous, semihydromorphic mead�ow�chestnut solonetz, AE�B1�B3k,g1�B32k�B33k,g

Light�colored medium solonetz SEL–BSN–BMK–BCAca,cs

Hyposalic Solonetz (Albic, Ruptic, Mag�nesic)

2 Postirrigation area

Postirrigation, strongly saline, sulfate (with gypsum), high�solonchakous, semihydromorphic meadow�chestnut solonetz, Ap1k�Ap2k�Ap3k�B3k1�B3k2

Carbonate, light�colored, solonetzic agrozem, P1ca–P2ca–P3ca–BCA1ca–BCca,s,cs

Endosalic Cambisol (Calcaric, Hyposodic, Humic)

3 Postirrigation area

Postirrigation medium�deep chestnut soil, Ap1 p�Ap2�B1�B2k�B3k

Textural calcareous agrozem P1ca–P2ca–CAT/Cca

Haplic Phaeozem (Calcaric)

Talovsk district of Voronezh oblast

4 Shelterbelt Postagrogenic, high�sodium, medi�um�deep, strongly saline, sulfate (with gypsum), and high�solonchakous semihydromorphic meadow�cher�nozemic solonetz, E�B1p1�B1p2 B1�B2g�B2k,g�B2g�B3k,g�BCk

Clay, crusty, solonchakous, gypsum�bearing, quasi�gley, postagrogenic, dark solonetz SEL–ASN1pa–ASN2pa–ASN3–AUcs,th–Bcs,th–BCAcs,q,i–BCA2nc,q,i–BD–ca,nc,mc,q

Mollic Stagnic Endo�hyposalic Solonetz (Magnesic? Humic, Clayic)

5 Plowland Postagrogenic, medium�humus, and medium�deep, ordinary chernozem, Ap1�Ap2�Ap3�AB�Bk1�Bk2

Deep�solonchakous, quasi�gleyed, segregation agrochernozem on brown covering clay PU1–PU2–PU3–AUb–BCAq,i–BCAnc,i,q

Haplic Phaeozem (Endohypo�sodic, Pachic, Clayic)

6 Fallow Medium�solonetzic, high�humus, medium�deep meadow�chernozemic soil of fallow land (pit t�0432), Asod�Ap1�Ap2�A1k�A2s�AB�B1g

Humus�stratified, postagrogenic, so�lonetzic, quasi�gley, dark�humus soil (pit t�0432) au,el–AUsn,pa,rh,pa–AUb,th,ca,nc–AUs–AUbsn–BIq

Luvic Stagnic Phae�ozem (Hyposodic, Pachic, Clayic, Novic)

7 Fallow Medium�solonetzic, high�humus, medium�deep meadow�chernozemic soil of fallow land (pit t�0434), Asod�Ap1�A p2(A1BkG)�Ap3�AB

Humus�stratified, postagrogenic, so�lonetzic, quasi�gley, and dark�humus soil (pit t�0434) au,el–AUsn,pa,rh–AU–BCAnc–Q–AUpa,sn–AUb,sn

Stagnic Phaeozem (Hyposodic, Pachic, Clayic, Novic)

8 Fallow Strongly�solonetzic and medium�deep meadow�chernozemic soil of fal�low land, A�Ap1�Ap2�B2g�B3g�Gk

Postagrogenic, solonetzic, humus–quasi�gley soil AUel–AUsn,pa–AUsn,pa–AUb,cs–BIq,cs–Qca,nc

Luvic StagnicPhaeozem(Hyposodic, Pachic, Clayic)


DIAGNOSIS OF SOLONETZIC PROCESS IN VIRGIN 865

Table 1. (Contd.)

Pit num�

berLand use

Classification, horizons

1977 [9] 2004 [8] WRB [13]

Omsk district, Omsk oblast

9 Virgin land Virgin, high�sodium, crusty, strong�ly�saline, soda�sulfate, high�solon�chakous, meadow�chernozemic, semihydromorphic solonetz, A1�B11�B2�B2�B3k

Dark solonetz AU–ASN1–ASN2–BMK–BCAnc

Mollic Hyposalic Solo�netz (Humic, Clayic)

10 Fallow Medium, strongly�saline, soda�sul�fate, solonchakous, meadow�cher�nozemic, semihydromorphic solo�netz of fallow land, Ap�B3�B3k�BCk

Dark solonetzic agrozem PU–BCA1nc–BCA2

Endohyposalic Phae�ozem (Sodic, Clayic)

11 Fallow Medium�sodium, medium, slight�ly�saline, sulfate�sodium, medium�solonchakous, meadow�cher�nozemic, semihydromorphic solo�netz of fallow land, Ap�B1�B2�B3k

Dark agrosolonetzPU–ASN–BMK–BCA

Mollic Hyposalic Solo�netz (Humic, Clayic)

Lyubinsk district, Omsk oblast

12 Experiment. Gyp�sum application in 1970; then, subsur�face tillage has been applied

Ameliorated, deep, strongly�saline, sodic, solonchakous, chernozemic�meadow, hydromorphic solonetz, Ap�B2k

Dark solonetzic agrozem PU–BCA

Endohyposolic Phae�ozem (Sodic, Clayic)

13 Experiment. Gyp�sum application in 1970 and 1985; then, subsurface tillage has been ap�plied

Ameliorated, deep, nonsaline, chernozemic�meadow, hydromor�phic solonetz, Ap�B2k


Endohyposolic Phae�ozem (Endohypo�sodic, Clayic)


Ameliorated, deep, strongly�sa�line, sodic, solonchakous, cher�nozemic�meadow, hydromor�phic solonetz, Ap�B2k




Ameliorated, deep, strongly�saline, sulfate�sodic, solonchakous, cher�nozemic�meadow, hydromorphic solonetz, Ap�B2k



Ubinsk district, Novosibirsk oblast

16 Plowland Postagrogenic, medium�humus, thin meadow�chernozemic soil, Ap1�Ap2�AB�B1�B2k�B3k�BCk�Ck

Clay�illuvial agrochernozem PU1–PU2–AU–BI–BCA1–BCA2–Cca

Haplic Chernozem (Oxyaquic, Clayic)

17 Virgin land Medium�sodium, crusty, medium�saline, sodic, solonchakous, mead�ow�chernozemic, semihydromor�phic solonetz, A�B1�B2�B3k1�B3k2�BC

Crusty dark solonetzAU–ASN1–ASN2–BMK–BCA1–BCA2–BCA3

Mollic Solonetz (Oxyaquic, Clayic)

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Table 2. Some properties of the investigated soils

Horizon Depth, cmNaexch Total toxic salts Swelling lag, Δτ,

minType

of swelling curve B value%

Volgograd oblast (Khvalyn Plain)Pit 1. Virgin, high�sodium, chloride��sulfate, meadow�chestnut, semihydromorphic solonetz

AE 1–9 12.4 0.07 0 1 2B1 9–23 31.9 0.13 6 2A 4B3k,g1 23–40 48.2 0.76 <6 2A 1B3k2 30–42 48.1 0.58 <6 2A 2B3k,g3 40–67 28.5 0.98 0 1 0

Pit 2. Postirrigation, sulfate (with gypsum), meadow�chestnut, semihydromorphic solonetzAp1k 0–10(14) 1.8 0.02 0 1 0Ap2k 10(14)–23 4.8 0.06 0 1 1A p3k 23–32 14.0 0.09 0 1 2B3k 32–44 19.1 0.14 <6 2A 3

Pit 3. Postirrigation chestnut soilA p2 3–27 1.7 0.02 0 1 0B1 27–42 2.4 0.04 0 1 0B2k 42–56 2.6 0.04 0 1 0

Voronezh oblast (Kamennaya Steppe)Pit 4. Postagrogenic, high�sodium, sulfate (with gypsum), meadow�chernozemic, semihydromorphic solonetz

E 0–1 9.9 0.11 0 1 2B1p1 1–6 12.7 0.05 <6 2A 3

6–17 17.6 0.04 <6 2A 4B1p2 17–24 22.9 0.07 <6 2A 4B1 24–34 26.2 0.15 0 3 4–5B2g1 34–45 33.7 1.03 0 1 1B2k,g2 45–67 38.1 1.13 0 1 1B2g3 67–105 38.4 0.76 <6 2A 2B3k,g 105–130 37.0 – <6 2A 4

Pit 5. Postagrogenic ordinary chernozemAp2 11–22 0.4 0.01 0 1 0Ap3 22–30 0.5 0.01 0 1 0AB 30–50 1.6 0.01 0 1 0Bk2 82–100 13.0 0.10 <6 2A 3

Pit 6. Medium�solonetzic meadow�chernozemic soil of fallow landAsod 0–4 13.6 0.16 0 1 1Ap1 4–10 13.2 0.15 0 1 1–2

10–17 11.3 0.13 0 1 1–2Ap2 17–30 12.0 0.09 0 1 2

30–45 11.1 0.07 <6 2A 1–2Pit 7. Medium�solonetzic meadow�chernozemic soil of fallow land

Ap1 2–10 6.0 0.32 0 1 010–20 5.2 0.16 0 1 0

Ap3 50–60 4.2 0.10 0 1 0AB 60–70 4.0 0.08 <6 2A 3

Pit 8. Strongly solonetzic meadow�chernozemic soil of fallow landA 0–3 45.6 0.14 0 1 8–9Ap 3–7 47.6 0.50 0 1 8

7–20 47.2 0.84 <6 2A 6



Table 2. (Contd.)

Horizon Depth, cmNaexch Total toxic salts Swelling lag, Δτ,

minType

of swelling curve B value%

Omsk oblast, Omsk district

Pit 9. Virgin, high�sodium, crusty meadow�chernozemic, semihydromorphic solonetz

B1' 0–17(20) 26.6 0.09 <6 2A 5

B1'' 17(20)–34 46.3 0.26 152 2B 7

B2 34–48 51.9 0.46 76 2B 7

B3k 48–70 51.9 0.40 60 2B 8

Pit 10. Soda�sulfate, meadow�chernozemic, semihydromorphic solonetz of fallow land with destroyed solonetzic horizon

Ap 0–24 36.6 0.18 15 2A 0

B3 24–45 54.3 0.44 169 2B 8

B4k 45–90 52.0 0.29 65 2B 9–10

BCk 90–100 35.2 0.26 38 2A 7

Pit 11. Medium�sodium, sulfate�sodic, meadow�chernozemic, semihydromorphic solonetz of fallow land with preserved solonetzic horizon

Ap 10–20 6.1 0.02 <6 2A 2

B1 20–50 24.8 0.08 40 2A 5

B2 50–70 30.8 0.19 150 2B 6

B3k 70–90 32.3 0.23 12 2A 6

Omsk oblast, Lyubinsk district

Pit 12. Control variant

Ap 0–20 28.5 0.16 <6 2A 6

B2k 20–40 61.6 0.35 0 3 13

Pit 13. Repeated gypsum application, 32 t/ha

Ap 0–20 0.6 0.02 0 1 0

B2k 20–40 5.0 0.06 0 1 1–2


Ap 0–20 19.4 0.16 0 1 4

B2k 20–40 56.3 0.37 0 3 11


Ap 0–20 30.5 0.20 0 3 6

B2k 20–40 74.4 0.49 0 3 14

Novosibirsk oblast, Ubinsk district

Pit 16. Virgin, medium�sodium, crusty, sodic, medium�chernozemic, semihydromorphic solonetz

B1' 1–8 18.7 0.10 0 1 1

B1'' 8–15 32.1 0.18 <6 2A 5–6

B2 15–25 43.0 0.24 <6 2A 8

B3'k 25–31 47.0 0.29 0 3 9

B3''k 31–42 46.9 0.26 0 3 9

BC 42–52 40.7 0.21 0 3 8

Pit 17. Meadow�chernozemic postagrogenic soil

Ap1 0–10 1.5 0.01 0 1 0

Ap2 10–22 2.1 0.01 0 1 0

AC 22–35 5.5 0.01 0 1 2

B1 35–56 4.3 0.03 <6 2A 1

Sum of toxic salts is given according to the results of the analysis of soil water extracts; the total content of salts is given according to theresults of the analysis of water�saturated pastes.

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trict) on experimental sites 1 and 2 allocated to thecentral part of the Bityug–Khoper interfluve. Adetailed description of this object is given in [17].

In Omsk oblast, we studied sodic solonetzes andsolonetzic soils of the forest�steppe zone in Omsk andLyubinsk districts. In Lyubinsk district, the soils weresampled at the Golubkovsk Experimental Station onreclamation of crusty high�sodium sulfate–sodicmeadow�chernozemic solonetzes. The field experi�ment was set in 1970 by L.V. Berezin, Z.I. Voropaeva,and V.E. Kushnarenko [18]. Gypsum was applied atthe rate of 32 t/ha by disking into upper 10�cm�thicklayer. In 1985, gypsum was repeatedly applied at therates of 8, 16, and 32 t/ha. A trial with a single applica�tion of gypsum in 1970 (32 t/ha) was used as a control.These objects were characterized by Trotsenko [18].

In Novosibirsk oblast, soils of the Baraba Lowlandnear the village of Kozhurla were studied. The sampleswere taken by T.N. Elizarova from the Institute of SoilScience and Agricultural Chemistry of the RussianAcademy of Sciences. A detailed characterization ofthese objects is presented in the guidebook for fieldexcursions of the IV Congress of the Dokuchaev SoilScience Society [16].

Methods. Morphological descriptions of soils weremade according to the manual for field soil descrip�tions [2]. The composition of soluble salts was deter�mined in the soil water (1 : 5) extract. Exchangeablebases were determined by Pfeffer’s method in modifi�cation by Molodtsova and Ignatova; the pH of watersuspensions (1 : 2.5 and 1 : 5) were determined by thepotentiometric method [4]; the content of carbonates(CO2), by the acidimetric method of Kozlovskii; andthe gypsum content, according to Khitrov [21]. Elec�trical conductivity (EC) was determined with anEkspert�002 conductometer in filtrates from thewater�saturated soil pastes. Swelling kinetics wasdetermined by the approach elaborated by Grachevand Kornblyum [6]; the development of solonetzicprocess was estimated according to Khitrov [19, 20].

RESULTS AND DISCUSSION

Khitrov [20] determined swelling kinetics in thesoils of North Caucasus in order to distinguishbetween solonetzic and vertic soils and specified fourmain types of swelling curves. The first type is charac�terized by a rapid increase in the volume (height) ofthe sample in the first 30–60 min with a subsequentplateau�type curve. It is typical of the upper soil hori�zons and of the horizons containing gypsum.

The second type of swelling curves is typical of the mid�dle�profile horizons with the high content of exchangeablesodium (>10–20%) and relatively low salinity. The swell�ing lag is seen within the first 0.5–1.5 hrs. This type ofswelling curves was first described by V.A. Grachev andE.A. Kornblyum for solonetzes in the chestnut soil zone.

Gypsum�free vertic lower horizons are character�ized by the third type of swelling curves with a long (2–6 hrs.) gentle part beginning within 5–10 min aftermoistening; thus, an increase in the volume (height) ofthe sample is very slow at the beginning, which isrelated to a sharp decrease in the water permeability ofthe sample.

Deep layers without gypsum and with the highalkalinity of extracts from water�saturated soil pastesare described by a combination of the second and thirdtypes of swelling curves (the fourth type). Within thefirst 2–6 hrs., swelling corresponds to the third type;then, a long period of an almost complete absence ofthe increase in the sample height begins. After thisperiod, swelling is continued.

According to [5, 6], swelling curves of the secondand fourth types correspond to solonetzic horizons ofchestnut and chernozemic soils, respectively. Thus, wehave combined these two types into one (second) typeof curves. The second type of curves as described byKhitrov is designated as 2A, and the fourth type of curvesaccording to Khitrov is designated as 2B (figure).

In order to assess the degree of manifestation ofsolonetzic process according to Khitrov [20], weexamined two groups of characteristics: the morpho�logical features of solonetzic process and the index ofits physicochemical characteristics B. In the soils withpronounced morphological features of the solonetzichorizon, the modern development of solonetzic pro�cess is predicted, if B > 4; if B <4, its probability is low.Solonetzic process is absent in the soils without defi�nite morphological features of solonetzes and with B = 0.As a rule, B = 0 in the soils that contain no solublesalts, or in the saline soils with a predominance ofbivalent cations (calcium and magnesium) [19].

The study of soil samples has shown that the high�sodium virgin solonetz on the Khvalyn Plain is charac�terized by platy structure in the above�solonetzic hori�zon; distinct morphological features of solonetzic pro�cess are absent. The exchangeable sodium content is12.4%; the horizon is not saline, B is equal to 2, andthe swelling curve is of the first type. Thus, it may be

1 3

2А 2B

T i m e

Sw

el

li

ng

Types of swelling curves of crushed samples: numbers cor�respond to those of curve types.



concluded that solonetzic process is absent in thishorizon (Table 2).

The solonetzic (B1) horizon in this soil is specifiedby the compound prismatic structure, high density andhardness, and distinct dark�brown illuviation coat�ings. The content of exchangeable sodium reaches31.9%. The horizon is slightly saline. Well�pro�nounced morphological features of solonetzic processin this horizon and B equal to 4 allow us to concludeabout the activity of solonetzic process. This is confirmedby specific features of swelling kinetics: the swelling curveis of type 2B and the swelling lag is 6 min.

In the B3k,g horizon, the morphological featuresof solonetzicity are absent. At the same time, the con�tent of exchangeable sodium is high (48.2%), andsalinity (chloride–sulfate) is very strong. The B valueis equal to 1, and the swelling kinetics is assigned totype 2A. The swelling lag is less than 6 min. This atteststo the potential possibility of the development of solo�netzic horizon.

In the B3k,g3 horizon, the morphological featuresof solonetzization are absent, B is equal to 0, and theswelling curve is of the first type.

In postirrigation solonetzes, the solonetzic horizonwas destroyed during surface leveling operations; itwas mixed with the above and lower layers and partiallytransported to the areas of other soils of the solonetzicsoil complex. There are rare fragments of solonetzichorizon in the plow layer, and humus�clay cutans arenot developed. That is to say, the morphological fea�tures of restoration of the solonetzic process areabsent. The B value varies from 0 to 2, and the swellingcurve is of the first type. It can be concluded that con�ditions for the modern development of solonetzic pro�cess are absent in this horizon.

The B3k (subplow) horizon is characterized by theblocky–prismatic structure and by the absence of illu�viation cutans. The content of exchangeable sodium is19.1%, and the horizon is slightly saline. The B valueis equal to 3, which attests to favorable conditions forthe development of solonetzic process. This is alsoconfirmed by data on swelling kinetics with a short(<6 min) swelling lag.

In the chestnut postirrigation soil, the morpholog�ical features of solonetzic process (the specific multi�level structure and illuviation cutans) are absent. Thelag in swelling is absent in all the horizons (the curvesare assigned to the first type), and B is equal to 0 in allthe horizons.

The study of soils in the Kamennaya Steppe hasshown that the E horizon of the high�sodium postirri�gation solonetz is characterized by the granular struc�ture, B equal to 2, and the swelling curve is assigned tothe first type. In the B1p1 and B1p2 plowed solonetzichorizons and the preserved B1 solonetzic horizon,there are abundant humus�clay cutans, and B is 4, 4,and 4–5, respectively. This points to pronounced solo�netzic process. These conclusions are confirmed by

data on swelling kinetics of the soil samples. In theplowed solonetzic horizons, swelling curves corre�spond to type 2A. In the preserved B1 solonetzic hori�zon, they correspond to the third type typical of verticsoils. Morphological features typical of vertic soilshave already been described in some soils of theKamennaya Steppe by Khitrov [18].

In the B2g and the B3k,g subsolonetzic horizons ofpostagrogenic solonetzes, B is equal to 1, which pointsto the low potential danger of solonetzization. Theswelling lag typical of solonetzic horizons is absent. Inthe B3g horizon, the morphological features of solo�netzic process are absent. The content of exchange�able sodium is 38.4%, and the sulfate�type salinizationis strong. The B value is equal to 2, the swelling curveis of type 2A, and the swelling lag is less than 6 min�utes. This attests to the possibility of the developmentof solonetzic process. In the postagrogenic ordinarychernozem (Table 2), the morphological features ofsolonetzic process in the Ap1, the Ap2, and the Ap3horizons and in the AB (subplow) horizon are absent.The B value in all the horizons is equal to 0. The swell�ing lag is absent. It can be concluded that solonetzicprocess in the plow and subplow horizons is not devel�oped. In the Bk2 horizon, the morphological featuresof solonetzization are not pronounced; B is equal to 3,and the swelling lag is up 6 min. This attests to thepotential possibility of the development of solonetzicprocess (Table 2).

In the meadow�chernozemic medium�solonetzicsoil of the fallow (soil pit t�0432), B in the plow layervaries from 1 to 2 (to a depth of 45 cm). In the Ap2horizon, the swelling curve is assigned to type 2A (theswelling lag is less than 6 minutes), which points topossible development of solonetzic process in thishorizon (Table 2).

In the meadow�chernozemic medium�solonetzicsoil of the fallow described in pit t�0434, the morphol�ogy of the topsoil is strongly destroyed, and the solo�netzic horizon cannot be definitely diagnosed. In allthe horizons to the depth of 60 cm, B is equal to 0, andthe curve for swelling kinetics is assigned to the firsttype. This points to the absence of solonetzic process inthe plow layer. In the AB horizon (60–70 cm), B = 3.Physicochemical conditions for the development ofsolonetzic process are formed here, which is con�firmed by the swelling curve of the second type withthe swelling lag of less than 6 minutes (Table 2).

In the meadow�chernozemic strongly solonetzicsoil of the fallow, the morphological features of solo�netzization in the Ap subhorizon (0–3 cm) are absent,B = 8–9, and the swelling curve is assigned to the firsttype. It can be supposed that there are physicochemi�cal conditions for solonetzic process in this horizon,but the process is not developed. In the Ap subhorizon(7–20 cm), black clay cutans are seen, and B = 6,which attests to the strongly pronounced solonetzicprocess. This is confirmed by data on the swelling

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kinetics: the swelling curves are of type 2A (the swell�ing lag is less than 6 min) (Table 2).

A comparative analysis of soils in Omsk district ofOmsk oblast (Table 2) has shown that the developmentof solonetzic is predetermined by the high content ofexchangeable sodium against the background of a rel�atively low content of soluble salts. In the B1' prismaticsolonetzic nonsaline horizon of the virgin high�sodium solonetz, the content of exchangeable sodiumis 26.6%, B = 5, and the swelling curve is assigned totype 2A (the swelling lag is less than 6 minutes). Thisattests to the strong manifestation of solonetzic pro�cess. In the B1''(second solonetzic) dense horizonwith a blocky structure (Naexch = 46.3%) and in the B2and B3k subsolonetzic horizons, B = 7–8. The swell�ing curves are assigned to type 2B. The solonetzic pro�cess in the second solonetzic horizon is also well pro�nounced.

In solonetzes of the fallow land with destroyedsolonetzic horizon, solonetzic features are absent inthe Ap horizon. The B value is equal to 6. The swellingcurve is assigned to type 2A (the swelling lag is 5 min).Thus, both approaches allow us to conclude that solo�netzic process is developed in the plow layer. In the B3,the B3k, and the BCk horizons, the physicochemicalconditions favor the development of solonetzic pro�cess (B = 8, 9–10, and 7, respectively). The dataobtained by the approach developed Grachev andKornblyum confirm the presence of solonetzic pro�cess: the swelling curves are of type 2B in the B3 hori�zon (the swelling lag is 169 min) and in the B3k hori�zon (the swelling lag is 65 min) and of type 2A in theBCk horizon (the swelling lag is 38 min).

In the plow layer of the medium�sodium solonetzof the fallow land with preserved solonetzic horizon, Bis equal to 2, which points to the danger of solonetzicprocess. It is characterized by the swelling curve oftype 2A with the swelling lag of less than 6 min, whichconfirms the development of solonetzic process.

In the preserved B1 prismatic solonetzic horizonwith abundant illuviation cutans, the degree of devel�opment of the solonetzic process is high; B = 6. Thecontent of exchangeable sodium is 24.8%. Swellingkinetics also points to intensive solonetzic process: theswelling curve is of type 2A (the swelling lag is 40 min).

In the B2 and the B3k subsolonetzic horizons, B =6. The swelling curve is of type 2B (the swelling lag is150 min) in the B2 subsolonetzic horizon and oftype 2A (the swelling lag is 12 min) in the B3k horizon.

Swelling curves of type 2A are most often revealedin solonetzic horizons of virgin and agrogenicallytransformed solonetzes and in the plow horizons ofagrogenically transformed solonetzes. It should bementioned that swelling curves of this type in the soilsof Omsk district are difficultly diagnosed, becausesteppes of the curve are not well pronounced and theiredges are leveled.

Investigation data of the Golubkovsk ExperimentalStation are of considerable interest (Table 2). Initialsoil horizons were destroyed during soil reclamationworks, and there are no morphological features ofsolonetzic horizon. The content of exchangeablesodium in the plow layer varies from 0.6 to 74.4%.Ameliorated soils are characterized by the soda type ofsalinization, except for the variant with repeated gyp�sum application at the rate of 32 t/ha.

In the upper 20 cm of the variant with a single gyp�sum application (32 t/ha) in 1970 taken as a control,the swelling curve of type 2A was revealed (the swellinglag was less than 6 min), which is typical of solonetzichorizons. The B value is equal to 6, which points to thefavorable physicochemical conditions for solonetzicprocess.

In the variant with repeated gypsum application atmaximum rate (32 t/ha), the conditions for solonetzicprocess in the upper 20 cm are absent: the swellingcurve is of the first type, and B = 0 (Table 2). In thesubplow layer, B rises up to 2 pointing to the low prob�ability of solonetzic process, and the swelling curve isalso of the first type. Similar data were obtained for theupper 20 cm of the soil with repeated phosphogypsumapplication at the rate of 16 t/ha. These data confirmthe fact that application of the high phosphogypsumrates (32 t/ha) to solonetzes is an efficient method tostop the development of solonetzic process for a longtime.

In the upper 20 cm of the variant with repeatedgypsum application at the rate of 8 t/ha and in the layerof 20–40 cm of the control variant and of the variantswith repeated phosphogypsum application at the ratesof 8 and 16 t/ha, B is high (from 6 to 14). This atteststo the high probability of the development of solo�netzic process. The swelling curve is of the third type.

Let us discuss the data on the virgin medium�sodium solonetz and meadow�chernozemic postagro�genic soil of the Ubinsk district in Novosibirsk oblast.The content of exchangeable sodium in the B1' (uppersolonetzic) prismatic horizon of the virgin solonetz is18.7%. The horizon is slightly saline, and soda pre�dominates among soluble salts. The B value equals 1,which attests to the probability of solonetzic process.The swelling curve is of the first type. In the B1'' (sec�ond solonetzic) horizon, the danger of solonetzic pro�cess increases (B = 4–5). The swelling kinetics isdescribed by the curve of the second type. In theB2 horizon, the danger of solonetzic process develop�ment is even higher, B = 8, and swelling curve is of thetype 2A. In the B3'k and the B3''k subsolonetzic hori�zons and in the BC horizon, the danger of solonetzicprocess is high, B = 9, 9, and 8, respectively. However,the swelling curves belong to the third type.

In the meadow�chernozemic postagrogenic soil,the physicochemical conditions for solonetzic processare absent in the Ap1, e Ap2, and AB (subplow) hori�zons. No solonetzic features were diagnosed, andswelling curves did not have any steppes. The curves



belonged to type 2A., though the B value was low (B = 1).This points to the possible development of solonetzicprocess in this horizon.

CONCLUSIONS

Two different methods for assessing the degree ofdevelopment of solonetzic process in the studied virginand agrogenically modified soils gave similar results in84% of studied cases. The solonetzic process isstrongly pronounced in virgin solonetzes on the Khva�lyn Plain in Volgograd oblast, on the Om’–Irtyshinterfluve in Omsk oblast, and in the Baraba Lowland(Novosibirsk oblast) and in the high�sodium postagro�genic solonetz in the central part of the Bityug–Khoper interfluve (the Kamennaya Steppe in Voron�ezh oblast). The swelling curves of these soils are char�acterized by the swelling lag in the solonetzic horizon(the swelling curve of the second type), and the B valueexceeds 4.

A potential danger of the development of solo�netzic is identified in the postirrigation solonetz of theKhvalyn Plain in Volgograd oblast), the ordinary post�agrogenic chernozem, the meadow�chernozemicsolonetzic soils of fallow land in the central part of theBityug–Khoper interfluve in Voronezh oblast, themeadow�chernozemic postagrogenic soil of theBaraba Lowland (Novosibirsk oblast), the agrogeni�cally transformed soils of the Om’–Irtysh interfluve(Omsk oblast), and the soda�saline ameliorated solo�netzes of the Ishim–Irtysh interfluve (Omsk oblast).The swelling curve of the solonetzic type in these soilsis combined with B value of 2–3.

The solonetzic process is not pronounced in thevirgin and postirrigated chestnut soils of the KhvalynPlain (Volgograd oblast), where B = 0, and the swellingcurve is of the first type.

It should be mentioned that the swelling curve isassigned to the first (not the second) type in some soilswith well pronounced solonetzic horizon, while B var�ies from 4 to 9. This is the case for the meadow�cher�nozemic strongly solonetzic soil in Voronezh oblast(the content of exchangeable sodium is 45–46%, andthe content of toxic salts is 0.18–0.5%) and for the soilsubjected to repeated gypsum application at the rate of16 t/ha (0–20 cm) at the Golubkovsk ExperimentalStation (Omsk oblast) with the exchangeable sodiumcontent of 18% and the content of toxic salts of 0.18%.In some case, an opposite situation is observed. Thus,in the Ap horizon of the postagrogenic solonetz withdestroyed solonetzic horizon (Omsk oblast), the swell�ing curve is assigned to the second type, while B = 0.The content of exchangeable sodium in this sample is36.6%, and the content of toxic salts is 0.18%. It canbe supposed that the first case is typical of the soilswith favorable physicochemical conditions for thedevelopment of solonetzic process and, at the sametime, without clearly pronounced features of this pro�cess because of some reasons. This confirms the neces�

sity of application of both investigation approaches forassessing the degree of manifestation of solonetzicprocess.

In the samples from reclaimed sodic solonetzes ofthe Golubkovsk Experimental Station on the Ishim–Irtysh interfluve (Omsk oblast) and from the medium�sodium virgin solonetz of the Baraba Lowland(Novosibirsk oblast), B is high (from 6 to 10), while theswelling curves are similar to those described byKhitrov for vertic soils of the Ciscaucasian region [19,20]. At the same time. there are no published data onthe presence of slickensides typical of vertic soil inthese particular soils. This points to the fact that swell�ing curves of the third type may be typical not only ofvertic soils but also of other heavy�textured soils withlow water permeability.

REFERENCES

1. I. N. Antipov�Karataev and A. Ya. Mamaeva, “The role ofadsorbed magnesium in soil solonetzicity,” in Ameliorationof Solonetzes (Pochv. Inst. im. V.V. Dokuchaeva, Moscow,1966), pp. 152–158 [in Russian].

2. Basic Scales of the Properties of Morphological Elementsof Soils. Methodological Handbook for Field SoilDescription (Pochv. Inst. im. V.V. Dokuchaeva, Mos�cow, 1982) [in Russian].

3. E. Bresler, B. L. McNeal, and D. L. Carter, Saline andSodic Soils (Springer�Verlag, Berlin–Heidelberg–NewYork, 1982).

4. L. A. Vorob’eva, Chemical Analysis of Soils (Izd. Mosk.Gos. Univ., Moscow, 1998) [in Russian].

5. V. A. Grachev, O. Yu. Baranova, and V. A. Isaev, “Swell�ing kinetics and solonetzicity of hydromorphic soils,”Vestn. Ross. Akad. Sel’skokhoz. Nauk, No. 3, 40–43(1992).

6. V. A. Grachev and E. A. Kornblyum, “Swelling kineticsand swelling capacity of the soils of solonetzic com�plexes and solods of the Transvolga region,” Poch�vovedenie, No. 2, 55–66 (1982).

7. N. G. Zyrin and D. S. Orlov, “Methods of determina�tion of the activity of sodium ions in soils and soil solu�tions,” Vestn. Mosk. Gos. Univ., No. 1, 71–80 (1958).

8. Classification and Diagnostic System of Russian Soils(Oikumena, Smolensk, 2004) [in Russian].

9. Classification and Diagnostics of Soils of the USSR(Kolos, Moscow, 1977) [in Russian].

10. N. V. Knyazeva, “Soil peptization of activity of sodiumions in soil suspensions,” Pochvovedenie, No. 8, 52–60(1981).

11. I. N. Lyubimova, A. V. Gorobets, A. V. Aksenov, andV. V. Khan, “Comparison of two approaches for assess�ing solonetzic process in the virgin and human�trans�formed soils of the dry steppe zone,” Eur. Soil Sci. 45(5), 532–538 (2012).

12. I. N. Lyubimova, Extended Abstract of Doctoral Dis�sertation in Agriculture (Moscow, 2003).

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14. V. Ya. Motuzov, I. N. Lyubimova, and A. G. Bondarev,“Salt regime of post�irrigated soils at the Kislovsk irri�gation system (Volgograd oblast),” Eur. Soil Sci. 41 (5),523–530 (2009).

15. A. V. Novikova and P. G. Kovalivnich, “Correlativerelationship between the degrees of solonetzicity andilluviation in solonetzic soils of the Sivash area inCrimea,” in Mater. All�Union Workshop on Reclamationof Solonetzes in Kustanai (Moscow, 1968), pp. 216–227[in Russian].

16. Guide on Field Excursions of the IV Congress of theDokuchaev Soil Science Society (Novosibirsk, 2004) [inRussian].

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18. I. A. Trotsenko, “Changes in the properties of high�sodium solonetzes of the forest�steppe zone on theIshim–Irtysh interfluve upon the first and repeatedgypsum application,” in Reports of the Omsk Branch ofthe International Academy of Ecology and Life Safety (St.Petersburg–Omsk, 2009), Vol. 8, No. 2 (15), 69–82 [inRussian].

19. N. B. Khitrov, “The choice of diagnostic criteria tojudge the development of the solonetzic process insoils,” Eur. Soil Sci. 37 (1), 12–23 2004).

20. N. B. Khitrov, Genesis, Diagnosis, and Functioning ofClayey Swelling Soils of the Central Cis�Caucasus (Mos�cow, 2003) [in Russian].

21. N. B. Khitrov and A. A. Ponizovskii, Handbook on Lab�oratory Methods of Studying Ion�Salt Composition ofNeutral and Alkaline Mineral Soils (Pochv. inst.im. V.V. Dokuchaeva, Moscow, 1990) [in Russian].

Translated by I. Bel’chenko

Documents

Diagnosis of solonetzic process in virgin and agrogenically transformed soils of different regions