Features of the moisture regime of a model sod-podzolic soil when mulching with spruce litter

ISSN 0147�6874, Moscow University Soil Science Bulletin, 2014, Vol. 69, No. 2, pp. 78–83. © Allerton Press, Inc., 2014.Original Russian Text © M.A. Sidorova, E.O. Borisova, 2014, published in Vestnik Moskovskogo Universiteta. Pochvovedenie, 2014, No. 2, pp. 34–39.

78

INTRODUCTION

The most important aspect of regulating the soil�water regime is to find the optimal range of soil mois�ture for various species of plants and soils and its main�tenance during the growing season [14, 18]. The bor�ders of optimum moisture and their dynamics dependon how the soil is used, viz., as part of the habitat of acultural plant or as a decorative element of the recre�ational landscape, water protection of the territory, anarea of increased erosion activity, etc. There is a largeamount of experimental data on managing the hydro�logical regime of the soil [2, 3, 5, 17]. One of the tech�niques for agromeliorative water regulation is soil mulch�ing. Mulching considerably affects the soil moisture con�tent [1, 12, 13, 16], which, in turn, is an environmentalfactor that controls soil microorganisms [9]. The analysisof the available data shows, however, that the representa�tive data that were obtained on a single study object andthat allow determining the degree of influence of vari�ous types of mulch on the soil moisture regime are notsufficient.

Mulching materials can be divided into two largegroups. The first group includes compost and peat,which are actively processed by soil organisms andenrich the soil with nutrients. This mulch should beintroduced annually; it is quickly settled with wormsand the soil�structure improves. This group can alsoinclude agricultural (straw), cereal and oil (shucks,sunflower and buckwheat husks) by�products. Onemay mention even more exotic forms of mulch, suchas husks of cocoa bean and pine nuts. Sawmill waste(sawdust) may also be applied. However, one shouldremember that plants mulched with sawdust and strawrequire additional introduction of ammonia nitrogenfor binding with microflora. Acidophilic plants (ling,

Calluna vulgaris L., catawba rhododendron, Rhodo�dendron catawbiense Michx., panicled hydrangea,Hydrangea paniculata Sieb., Dutchman’s pipe, Aris�tolochia macrophylla L., etc.) respond well to mulch�ing with coniferous litter. Durable inert materials areincluded in the second group: crushed stone or finegravel, chips, etc. It is believed that the main purposeof inert mulch is decorative, since it almost does notaffect soil fertility. However, we should not forget thatthe chemical compositions of the materials (dolomitemarble, limestone, granite, etc.) are not the same.This may affect the chemical properties of the soilsolution, which in turn may affect the condition ofcrops [7].

In today’s cultural landscapes (parks, forest parks,and private areas), mulching is used as a decorativetechnique that enhances the aesthetic perception of artobjects (ornamental deciduous groups, flower beds,mixborders, etc.). The variety of mulching materialsrequires a systematic comparative analysis of behaviorin the soil environment, identifying both positive(reducing soil moisture loss by evaporation, reducingthe activity of weeds, etc.), and possible negative effects(violation of topsoil breathability). Research is alsoneeded in order to develop techniques for designingsoils and flower beds with specified characteristics.

In order to further develop the methodologicalframework to control the properties and regime of soilsin the art ecosystems, it is suggested to study the featuresof the moisture regime based on the example of a modelsod–podzolic soil in the case of mulching with fir litter.Identification of patterns in years with different precip�itation levels is becoming increasingly important inconnection with the issue of sustainable functioning ofart objects, including acidophilic plants.

SOILPHYSICS

Features of the Moisture Regime of a Model Sod–Podzolic Soil when Mulching with Spruce Litter

M. A. Sidorova and E. O. BorisovaDepartment of Soil Science, Moscow State University, Moscow, Russia

e�mail: [email protected] June 3, 2013

Abstract—During the dry growing seasons of 2011 and 2012, mulching of a sod–podzolic soil with coniferous lit�ter maintained the moisture of the upper soil layer at high and fairly stable levels. By varying the spruce litter thick�ness, it is possible to maintain optimum conditions for acidophilic plants characterized by varying responses to thesoil moisture content. In dry years (PER 0.5–0.8), the degree of influence of the mulch layer on the soil moisturecontent is closely related to the magnitude of the moisture deficit calculated for a warm season.

Keywords: mulching, soil moisture content, spruce litter, sod�podzolic soil.

DOI: 10.3103/S0147687414020069

MOSCOW UNIVERSITY SOIL SCIENCE BULLETIN Vol. 69 No. 2 2014

FEATURES OF THE MOISTURE REGIME OF A MODEL SOD–PODZOLIC SOIL 79

MATERIALS AND METHODS

The experiment was carried out in an area that was8.5 m2 and 1.6 m in depth, which was located 100 mfrom the Meteorological Observatory of the MoscowState University in the territory of the soil stationary.The studied soil is model middle�loamy sod—pod�zolic; some of it physical and water properties are pre�sented in Table 1 [10].

The spruce litter was placed on the soil surface inlayers of 2 and 5 cm. In some versions of the experi�ment the soil surface was previously covered with thenonwoven material “agrospan” (herein the symbol“+agr.”), which significantly reduces the activity ofweeds, and then with a layer of spruce litter; the otherversion had no agrospan. A soil under bare fallowserved as the control. The experimental studies werecarried out during the growing seasons of 2011 and2012. The data on precipitation, temperature, and rel�ative air humidity obtained by the MeteorologicalObservatory of the Moscow State University were usedas the main meteorological parameters (Table 2).

The climatic parameters of both the growing sea�sons significantly differed from long�term averages.While the average long�term total precipitation (Pr)for warm months (May–September) was 389 mm,total precipitation in 2011 and 2012 was lower by 23and 16%, respectively.

In 2011 and 2012, the average daily air tempera�tures during the warm period (t) reached, respectively,17.8° and 16.1°, that is, were above the long�term aver�age by 2.6° and 0.9°. It should be noted that the warmperiod of 2011 was cooler than the same period ofextremely hot 2010 (t = 19.4°) only by 1.6°.

The maximum evapotranspiration (Et) of the twoexperimental years was marked in the warm period of2011 (582.6 mm), the amplitude of oscillation reached32% of the long�term average evapotranspiration

equal to 442.2 mm. During the warm period of 2012,Et was lower than the average long�term sum by 20%.

In terms of the existing climatic zoning [8], theMoscow oblast belongs to the zone of sufficient mois�ture: the average long�term precipitation–evaporationratio during the warm period is 1.05. The assessment ofclimatic conditions in terms this parameter indicatesthat both the years of research were dry (PER did notexceed 0.62–0.63). However, the analysis of climaticparameters in terms of individual months showed thatthe studied warm periods of these years significantlydiffered among each other. Thus, if one summarizesthe monthly amounts of the moisture deficit (Et–Pr)over the growing season, the maximum experimentalperiod (307.8 mm) will be 2011, and the minimum(207.6 mm)—2012. For comparison, let us providethe total moisture deficit in extremely hot 2010, viz.,420 mm. May–August, that is, 4 months of the warmperiod in 2011, were dry with PER 0.2–0.5 (0.29,0.45, 0.45, and 0.46, respectively), and September wasexcessively wet (PER 1.47). In 2012, May and Julywere dry, June and August were rather humid (PER0.8–1.0), and September was dry (PER 0.5–0.8).

The soil moisture was determined by the gravimet�ric method. The statistical processing of the results ofthe research was carried out by conventional methods[6] and the significance of the difference in the ver�sions was estimated by the Student’s t�test.

RESULTS AND DISCUSSION

During the growing seasons, all the versions weremonitored for the soil moisture (W) at a 10 cm depth(figure). In the dry growing season of 2011 with a hightotal moisture deficit, W of the soil under bare fallow(control) ranged from 15.4 (W, close to the wiltingmoisture, WM = 11.1%) to 22.4% (figure, left, a). Thesoil moisture in the control was higher in 2012 than in

Table 1. Physical and water properties of the model sod–podzolic soil (according to [10])

Horizon, depth, cm Solid phase density, g/cm3

Density,g/cm3

Porosity,% by volume

Moisture content, % by weight

MH WM FMC

Aarable + A2 0–10 2.63 1.19 54.9 6.8 11.1 29.1

10–20 1.24 53.0 24.6

B1 20–30 2.66 1.47 44.7 7.8 10.6 21.5

30–40 1.56 41.4 19.9

40–50 1.54 42.1 20.1

B2 50–60 2.65 1.57 40.7 9.2 12.6 20.7

70–80 1.59 40.0 22.2

90–100 1.60 39.6 22.2

110–120 2.69 1.61 40.1 9.5 12.8 23.0

130–140 1.61 40.1 22.6

MH, maximum hygroscopic moisture; WM, wilting moisture; FMC, field moisture capacity.

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SIDOROVA, BORISOVA

2011 and varied over a fairly wide range (from 18.8 to29.1%, approaching in some periods to field moisturecapacity (FMC) of 29.1%) (figure, right, a).

The form of soil moisture was evaluated by themain hydro�physical characteristics [10] using themethod of secants according to A.D. Voronin [4]. Ifone takes the number of moisture measurements overthe entire growing season as 100%, then in 2011 in50% of cases the moisture in the control version wasfilm and in another 50%, film�capillary. This moistureis insufficient for normal development of the majorityof mesophytic plant species, and, of course, hygro�phytes. To resolve water scarcity in such years, it isnecessary to employ irrigation or mulching, oftenreferred to as “dry irrigation.” In 2012, in most cases(71%) the moisture in the control was assessed as film�capillary, in 18% as film, and in 7% and 4% as bothcapillary and gravitational respectively. Thus, in 2012,over quite a long period of time the plants were notprovided with easily accessible moisture.

Under the influence of mulching with spruce litter,the soil moisture in 2011 significantly (significancelevel α = 0.05) increased as compared with the controlby 7.7–9.7% (figure, left, b–f). The effect of mulchingin 2012, which, as noted above, was characterized bythe smaller humidification shortage, was weaker (fig�ure, right, b–f; Table 3). The soil moisture increasedby 1.9–8.0% relative to the control. The significanceof the differences (at α = 0.05) was confirmed in com�parison with the control in all the versions but one, a2�cm layer of mulch without agrospan substrate, inwhich the excess of the soil moisture was only 1.9%.

Under the influence of a spruce litter that was only2 cm thick, regardless of the presence or absence of the

agrospan substrate, the ratio of the soil moisture formschanged in the warm period of 2011. The gravita�tional, capillary and film�capillary moisture was regis�tered in 60, 30, and 10% of cases, respectively. In thegrowing season of 2012, the agrospan substrate underthe 2�cm layer of mulch influenced the forms of mois�ture: in 71% of cases it was gravitational and in 29%capillary. In the version without agrospan, it was cap�illary and film�capillary (each in 46% of cases), andonly in 8% of cases it was gravitational.

The mulch that was placed in a 5�cm layer signifi�cantly altered the percentage of occurrences of variousforms of moisture. In 2011, in the experimental ver�sions with and without the agrospan substrate, thegravitational moisture occurred, respectively, in 80and 70% of the cases, for the capillary, 10 and 20%,and for film�capillary it occurred in 10% of the casesin both the versions. In 2012, the number of cases withgravitational moisture increased to 82–86% and cap�illary increased to 14–18%. Let us note that the exper�iments were carried out without plants. It can beassumed that the proportion of gravitational moisturewould be significantly reduced due to plant transpira�tion. According to some studies [15], the proportion oftranspiration in evapotranspiration can be high andrange from 24 to 49%. It should also be noted that themoisture of the upper layer of soil can be reduced dueto the capillary resorption into the underlying layers.It is known that in the case of moisture transpirationfrom aerial organs the moisture capacity in themdecreases. This is the reason for the movement ofwater from the soil to the plant, which compensates forlosses for transpiration and thereby prevents its exces�sive dehydration. To maintain sufficiently high levels

Table 2. Meteorological conditions of growing seasons of 2011 and 2012 (according to the data of the MeteorologicalObservatory of the Moscow State University)

Year ParameterMonth Average (t, PER)

or sum (Pr, Et)V VI VII VIII IX

Average long�term

t 12.9 16.8 18.6 16.7 11.1 15.2

Pr 53.8 93.2 97.6 70.2 74.6 389.0

Et 106.7 102.9 96.3 81.6 54.0 442.2

PER 0.63 1.01 1.12 0.92 1.56 1.05

2011 t 14.9 19.4 23.6 19.1 12.1 17.8

Pr 33.0 61.6 71.6 57.5 75.1 298.8

Et 112.8 137.0 157.9 123.8 51.1 582.6

PER 0.29 0.45 0.45 0.46 1.47 0.62

2012 t 15.5 17.0 19.4 15.5 13.2 16.1

Pr 49.4 89.2 61.8 79.2 45.6 325.2

Et 118.6 104.8 143.2 91.8 74.4 532.8

PER 0.85 0.85 0.43 0.86 0.61 0.63

Pr, precipitation, mm.Wg; t, average daily air temperature, °C; Et, evaporability, mm.Wg: Et = 0.0018(25 + t)2(100 – A), where A is therelative air humidity, %; PER is the precipitation�evaporation ratio: PER = Pr/Et.



of hydration of the plant tissues and photosynthesis,one should provide an environment in which even aslight decrease in the capacity of moisture in the plantwill create the potential gradient that is required forpractically complete recovery of the costs for transpi�ration. One of the methods that provides this opportu�nity is to increase the soil moisture capacity to highvalues and, consequently, to the high humidity of thesoil. However, one obstacle with this method is thelack of soil aeration with low permeability of aquifersor large inefficient water consumption for vertical fil�

tering with their high permeability. Therefore, the soil�moisture capacity should be lower than the values atwhich the majority of the large capillary pores is filledwith gravitational moisture that rapidly flows underthe influence of gravity, but at the same time higherthan the values at which the rate of transpiration sub�stantially (greater than 20%) decreases. The upperlimit is most often the capillary sorption capacityequal to –5 kPa, which corresponds to the moisturecontent of the soil under study of 32.5% by weight. The“critical” capillary sorption capacity at which the rel�

32

Jul, 10 Jul, 20 Jul, 30 Aug, 09 Aug, 19Date

22

(f)

3 4

32

22

(e)

1 2

32

22

(d)

2

32

22

(c)

3 1

24

14

(b)

30

0

(a)

4

W, % of weight

10

20Precipitation, mm

tav, °C2011

35

25

15

5

34

Jun, 10 Jul, 10 Jul, 20 Aug, 10 Aug, 20Date

24

(f)

34

Sep, 10

30

20

(e)2 1

35

25

(d)

2

4

30

20

(c) 3

1

25

15

(b)

10

0

(a)

35

2012Precipitation, mm

tav, °C

20

30

W, % of weight

35

25

15

5

Dynamics of climatic parameters (precipitation in columns, average daily air temperature on the curve) (a) and humidity (W) ofa sod–podzolic soil at a depth of 10 cm in the control (b) in different versions of the experiment under the spruce litter (c–f);influence on W of the mulch thickness (l): (c) without agrospan, (d) with agrospan; influence on W of agrospan at l = 2 cm (e);l = 5 cm (f); without agrospan substrate: 1, l = 2 cm; 3, l = 5 cm; with agrospan substrate: 2, l = 2 cm; 4, l = 5 cm.

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ative transpiration for plants–hygrophytes on loamysoils begins to decline, is –10 kPa, which correspondsto the humidity of the model sod–podzolic soil of28.5% [10, 14]. Similar results were obtained innumerous experiments by many foreign researchers,which were generalized by S.A. Teylor [18].

During the studies, there were attempts to evaluatethe significance of differences in the soil moisture inthe versions with the mulch layers of 2 and 5 cm (Table 4).The differences were significant at the 0.05 level of sig�nificance in the versions without agrospan in 2011 andwith its substrate in 2012. However, the trend to anincrease in the soil moisture under the influence of theincreasing mulch thickness can be traced in all the ver�sions and is 1.1–4.5%. The growth of the soil moistureunder the influence of the increasing thickness ofmulch is defined by further reduction of nonproduc�tive moisture consumption due to evaporation fromthe soil surface [2, 3, 5, 11, 14, 16]. The use ofagrospan as a substrate under a layer of mulch in threecases out of four possible increased the soil moistureby 0.3–5.0%; and in only one case (version of 2012, amulch thickness of 2 cm) significantly (Table 5).It should be noted that clarification of the degree ofinfluence of agrospan on evaporation of moisture fromthe soil requires further study.

It is known that the lower limit of the optimumrange of humidity naturally increases with the increas�ing intensity of hygrophytic properties of plants, theincreasing content of large size fractions of soil, andevaporability [14]. Thus, in the same soil and climaticconditions, by varying the mulch thickness and usingagrospan in some cases as a substrate under mulch,one can significantly affect the root�zone soil mois�ture, thereby creating the best conditions for humidi�fication of plants�hygrophytes, hygromesophytes, andmesophytes in the decorative�recreational landscapeof the Nonchernozem region. It should be recognizedthat the amount of moisture deficit of the warm sea�son, even with the same coefficient of moisture, isreflected in the degree of soil moisture under themulch and on the control.

CONCLUSIONS

The spruce litter that is used as mulch in art objectswith acidophilic plants not only plays a decorativerole, but also significantly changes parameters of thehydrological regime of the model sod–podzolic loamysoil.

The extent to which a layer of mulch influences thesoil moisture is closely related to the value of moisturedeficiency in the warm season (Et–Pr). In the dry veg�etation periods, under the influence of the spruce lit�

Table 3. Significance of the differences in soil moisture in the control and in the versions with mulch

Experimental version, mulch

thickness

Statistical parameters

Xav, % by weight Sx av d Sd t hypothesis

Control 20.1/22.4 0.7/0.7

2 cm 28.0/24.3 0.8/0.6 7.9/1.9 1.1/1.0 7.3/1.8 H0/H1

5 cm 29.3/28.8 0.8/0.5 9.2/6.4 1.1/1.0 8.7/6.7 H0/H0

2 cm + agr. 27.8/29.9 0.8/0.5 7.7/7.5 1.1/1.0 7.1/7.8 H0/H0

5 cm + agr. 29.8/30.4 0.9/0.7 9.7/8.0 0.9/1.1 2.6/7.3 H0/H0

Numerator—data of 2011 (t0.05 = 2.10 at ν = 18), denominator is the data of 2012 (t0.05 = 2.06 at ν = 26, where ν is the number of degreesof freedom); hypothesis: H0, if t > t0.05, then the differences are significant; H1, if t < t0.05, then the differences are insignificant, Xav is theaverage of measurements for the experimental versions and control; Sx av is the error of the average for the versions, d is the difference ofthe averages, Sd is the estimate of the difference of the averages, t is the Student’s test (here and in Tables 4 and 5).

Table 4. The significance of the differences in soil moisture in the versions with mulch thicknesses of 2 and 5 cm


thickness



2 cm 28.1/24.3 0.6/0.6 1.4/4.5 0.8/0.8 1.8/5.4 H1/H0

5 cm 29.5/28.8 0.5/0.5

2 cm + agr. 27.6/29.3 0.6/0.5 2.2/1.1 0.9/0.9 2.6/1.1 H0/H1

5 cm + agr. 29.8/30.4 0.6/0.7

The numerator is the data of 2011 (t0.05 = 2.04, with ν = 38), the denominator is 2012 (t0.05 = 2.06, with ν = 26) (here and in Table 5).



ter, the soil moisture (W) at a depth of 10 cm signifi�cantly increased by 7.7–9.7% (2011, moisture deficit308 mm) and 6.4–8.0% (2012, moisture deficit208 mm). In only one of the experimental versions of2012 (the 2�cm mulch thickness with no agrospansubstrate), the excess in the soil moisture relative tothe control was not significant at a significance level ofα = 0.05 and was only 1.9%.

With the increasing mulch thickness from 2 to 5 cm,the soil moisture increased significantly in two casesout of four possible ones by 2.2–4.5%, while in twoother cases W increased by 1.1–1.4%.

The nonwoven fabric agrospan that was placed onthe soil surface under the mulch layer reduced theactivity of weeds and increased W in three cases out offour possible ones by 0.3–5.0%, in one case signifi�cantly.

REFERENCES

1. Andersen, R.L. and Kosolap, R., Plant residues andweed control in No�till technique, Zerno, 2008, no. 4.

2. Brutsaert, W., Evaporation into the Atmosphere: Theory,History and Applications (Environmental Fluid Mechan�ics), Kluwer Acad. Print on Demand, 1982.

3. Budagovskii, A.I., Soil water evaporation, in Fizikapochvennykh vod (Soil Water Physics), Moscow, 1981.

4. Voronin, A.D., Osnovy fiziki pochv (Foundation of SoilWater Physics), Moscow, 1986.

5. Gusev, E.M., Water evaporation by drying soil, Poch�vovedenie, 1998, no. 8.

6. Dospekhov, B.A., Metodika polevogo opyta (FieldExperiment Methods), Moscow, 1985.

7. Drozdova, I.V., Accumulation features for macro� andmicroelements by Polar Ural plants of different ecolog�ical groups, Tr. Vseros. konf. “Fundamental’nye iprikladnye problemy botaniki v nachale XXI veka”(Proc. All�Russian Conf. “Fundamental and AppliedBotanical Problems at the Beginning of 21st Century”),Petrozavodsk, 2008.

8. Lektsii po sel’skokhozyaistvennoi meteorologii (Lectureson Agricultural Meteorology), Kulik, M.S. andSinel’shchikov, V.V., Eds., Leningrad, 1973.

9. Manucharova, N.A., Yaroslavtsev, A.M., Stepanov, A.L.,et al., Specificity of soil hydrolytically microbial com�plex under different moisture conditions, Moscow Univ.Soil Sci. Bull., 2012, vol. 67, no. 1, p. 25.

10. Optimizatsiya vodnogo i azotnogo rezhimov pochvy (TheWay to Optimize Water and Nitrogen Modes of Soil),Sudnitsyn, I.I. and Umarov, M.M., Eds., Moscow,1988.

11. Sidorova, M.A. and Chernova, A.D., Decorativemulching as an efficient regulator of soil water evapora�tion, Tr. Mezhdunar. nauch.�prakt. konf. “Nauchnyeosnovy ekologii, melioratsii i estetiki landshaftov” (Proc.Int. Sci.�Pract. Conf. “Scientific Foundations of Ecol�ogy, Melioration and Landscape Esthetics”), Moscow,2010.

12. Sidorova, M.A. and Chernova, A.D., Mulching byorganic materials as an efficient agro�reclamationmethod for sod�podzol soil under conditions ofdestructive growing seasons, Tr. Mezhdunar. konf.“Tendentsiya razvitiya agrofiziki v usloviyakh izmenyay�ushchegosya klimata (k 60�letiyu Agrofizicheskogo NII)”(Proc. Int. Conf. “Development Trends for Agrophys�ics under Climate Change (to 60th Anniversary of Agri�cultural Scientific�Research Institute)”), St. Peters�burg, 2012.

13. Smolin, N.V., Mul’chirovanie pochvy v zernovoi sistemezemledeliya (Soil Mulching in Grain Farming System),Saransk, 1997.

14. Sudnitsyn, I.I., Egorov, Yu.V., and Sidorova, M.A., Theway to optimize soil water conditions, Dokl. Akad.Nauk SSSR. Biol. Nauki, 1977, no. 11.

15. Shumova, N.A., Mulching effect onto summary evapo�ration from summer wheat fields at the Russian Planesouth, Meteorol. Gidrol., 2010, no. 2.

16. Massee, T. and Cary, J., Potential for reducing evapora�tion during summer fallow, J. Soil Water Concerv., 1978,vol. 33, no. 3.

17. Steiner, J.L., Tillage and surface effects on evaporationfrom soils, Soil Sci. Soc. Am. J., 1989, vol. 53, no. 3.

18. Taylor, S.A., Physical Edaphology, San Francisco, 1972.Translated by K. Lazarev

Table 5. The significance of the differences in soil moisture in the versions with and without the agrospan substrate


thickness



2 cm 28.1/24.3 0.6/0.6 0.5/5.0 0.8/0.8 0.6/6.0 H1/H0

2 cm + agr. 27.6/29.3 0.6/0.5

5 cm 29.5/28.8 0.5/0.5 0.3/1.6 0.8/0.9 0.3/1.8 H1/H1

5 cm + agr. 29.8/30.4 0.6/0.7

The numerator is the data of 2011 (t0.05 = 2.04, with ν = 38), the denominator is 2012 (t0.05 = 2.06, with ν = 26) (here and in Table 5).

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Features of the moisture regime of a model sod-podzolic soil when mulching with spruce litter