Biologia 64/3: 550—554, 2009 Section Botany DOI: 10.2478/s11756-009-0095-6

Comparison of aggregate stability within six profiles under conventional tillage using various laboratory tests

Radka Kodešová1, Marcela Rohošková1& Anna Žigová2

1Department of Soil Science and Soil Protection, Czech University of Life Science, Prague, Kamýcká 129,CZ-16521 Prague, Czech Republic; e-mail: [email protected] 2Institute of Geology, Academy of Sciences of the Czech Republic, v.v.i., Rozvojová 269,CZ-16500 Prague, Czech Republic

Abstract: stability was studied in every diagnostic horizons of six soil types (Haplic Chernozem, Greyic Phaeozem, two Haplic Luvisols, Haplic Cambisol, Dystric Cambisol) using different techniques investigating various de- struction mechanisms of soil aggregates. Soil aggregate stability, assessed by the index of water stable aggregates (WSA), varied depending on the organic matter content, content and pHKCl . The presence of clay and organic matter coatings and fillings, and presence of oxides in some increased stability of soil aggregates. On the other hand periodical tillage apparently decreased aggregate stability in the Ap horizons. Coefficients of aggregate vulnerability resulting from fast wetting (KV1) and slow wetting (KV2) tests showed similar trends of the soil aggregate stability as the WSA index, when studied for soils developed on the similar parent material. There was found close correlation between the WSA index and the KV1 value, which depended also on the organic matter content, clay content and pHKCl . Less significant correlation was obtained between the WSA index and the KV2 value, which depended on the organic matter content and clay content. Coefficients of vulnerability resulting from the shaking after pre-wetting test (KV3) showed considerably different trends in comparison to the other tests due to the different factors affecting aggregate stability against the mechanical destruction. The KV3 value depended mostly on cation exchange capacity, pHKCl and organic matter content. Key words: fast wetting test; slow wetting test; shaking after pre-wetting test; wet sieving

Introduction rigation, and use of fertilizers can also lead to soil struc- ture degradation (Pagliai et al. 2003, 2004; Servadio et regime is highly affected by soil structure al. 2005). On the other hand, the soil aggregate stability and its stability. Various soil structure types may cause may be improved by adding (Valla et al. 2000; preferential flow or water immobilization. Soil struc- Fernandez et al. 2007; Tejada & Gonzales 2008). The ture breakdown may initiate a soil particle migration, soil particle arrangement into the structure elements formation of less permeable or even impermeable lay- (aggregates) has a significant impact on the soil pore ers and consequently decreased water fluxes within the system and consequently on the soil hydraulic proper- soil profile. Soil aggregation is under control of different ties (Kodešová et al. 2006, 2007, 2008). The degree of mechanisms in different soil types. Flocculated clay par- the soil aggregate stability (aggregate breakdown and ticles, or their complexes with humus (organo-mineral consequently changes of soil porous system) influences complexes) and act as main cement- water flux and solute transport within the soil profile ing agents in soil aggregates development. The cement- (Kodešová et al. 2009). ing effect of free Fe and Al oxides is important in soils The study presented here was performed to assess with low organic matter content (Six et al. 2002). Gen- stability of the soil structure within the soil profiles. erally, level of aggregation and stability of aggregates The main goals of this study were: 1) Evaluation of increases with increasing organic matter content, sur- soil structure stability using different methods to study face area of clay minerals and cation exchange capacity various destruction mechanisms, and 2) Assessment of (Bronick & Lal 2005). The low soil pH may also in- soil composition impact on soil structure stability. crease the aggregate stability due to the behaviour of acidoids prevailing in soils, which peptize at abundance of OH− (Valla et al. 2000). Beside impact of soil com- Material and methods ponents, has also very important in- Study was performed in six soil types (Table 1). A five year fluence on soil structure stability. By tillage, the topsoil rotation system with conventional tillage was used at all lo- is mixed and aggregates are exposed to different break- cations. Winter barley was planted at all areas when soil down mechanisms (Six et al. 1998). Soil processing at samples were taken from all horizons that were specified for improper soil moisture, crossing of heavy machinery, ir- each soil type. Particle size distribution, organic carbon con-

c 2009 Institute of Botany, Slovak Academy of Sciences Comparison of aggregate stability using various laboratory tests 551

Table 1. Soil aggregate stability within the soil profiles expressed as the index of water stable aggregates (WSA), the coefficient of vulnerability (KV1) to aggregate slaking due to the compression of entrapped air (the fast wetting test), the coefficient of vulnerability (KV2) to aggregate disintegration caused by the micro cracking due to the different swelling, and physico-chemical due to the osmotic stress (the slow wetting test), the coefficient of vulnerability (KV3) to the mechanical aggregate breakdown (the shaking after pre-wetting tests), and soil properties affecting aggregate stability. Soil aggregate stability increases with the increasing WSA index and decreasing KV values.

Organic Cation Carbon Clay Exchange Soil Type Horizon Depth Content Content pHKCl Capacity WSA Index KV1 KV2 KV3 [cm] [%] [%] [–] [mmol+ (100g)−1] [–] [–] [–] [–]

Haplic Chernozem Ap1 0–20 1.91 25.3 6.28 24.5 0.46 11.15 5.68 2.72 on Loess Ap2 20–51 1.37 27.1 6.30 24.5 0.61 9.80 5.23 3.57 ACk 51–74 0.55 33.3 7.08 28.7 0.54 10.25 5.49 3.03 Ck 74–88 0.29 28.4 7.18 18.0 0.34 14.84 7.48 4.91

Greyic Phaeozem Ap 0–23 1.11 32.6 6.96 20.5 0.56 8.35 4.68 2.23 on Loess Bth 23–37 0.50 37.3 5.38 29.2 0.60 7.78 4.24 2.52 BCk 37–44 0.46 31.0 7.11 22.5 0.45 10.79 7.50 3.07 Ck 44–125 0.29 27.6 7.50 15.5 0.10 19.51 14.73 5.11

Haplic Luvisol 1 Ap1 0–29 1.11 24.4 4.52 14.0 0.48 11.58 6.76 2.93 on Loess Ap2 29–40 0.81 27.0 4.67 17.5 0.52 10.42 7.53 3.58 Bt1 40–75 0.49 34.6 4.58 21.3 0.61 10.06 5.40 2.96 Bt2 75–102 0.32 33.7 5.72 25.5 0.30 14.82 9.44 4.46 BC 102–120 0.31 28.9 6.80 19.0 0.34 17.25 11.42 5.56 Ck 120–145 0.16 24.0 7.04 16.5 0.05 20.40 15.64 7.86

Haplic Luvisol 2 Ap 0–29 1.49 18.7 4.84 12.7 0.65 6.63 4.68 2.64 on Loess Loam Bt1 29–51 0.38 27.1 4.30 12.0 0.46 12.72 12.44 5.52 Bt2 51–93 0.25 34.8 4.09 22.2 0.46 10.95 9.42 2.19 C 93–120 0.16 24.4 4.09 22.0 0.25 14.53 13.46 2.33

Haplic Cambisol Ap 0–29 1.77 15.0 4.09 14.2 0.75 3.80 2.94 1.94 on Paragneiss Bw 29–62 0.41 24.6 3.97 13.5 0.46 3.75 3.83 3.09 C 62–84 0.37 23.5 4.11 15.0 0.39 3.62 4.05 3.35

Dystric Cambisol Ap 0–20 2.08 18.1 4.49 19.0 0.64 2.99 2.57 1.35 on Orthogneiss Bw 20–43 0.46 19.7 4.12 10.7 0.28 3.24 2.77 1.77

tent, pHKCl and cation exchange capacity were measured wetting tests was utilized to study the mechanical aggregate using the standard laboratory techniques (Dane & Topp breakdown. Four grams of air dry soil aggregates of the size 2002; Sparks 1996) (Table 1). In addition micromorpho- of 2–5 mm were pretreated according to each test methodol- logical study on thin soil sections was performed to assess ogy: 1. fast wetted in 50 cm3 of distilled water (10 minutes), aggregate compositions. 2. slowly wetted on the saturation pan (up to aggregate sat- The aggregate stability was studied using two different uration), 3. wetted in 50 cm3 of ethanol (10 minutes), then approaches. The indexes of water stable aggregates were inserted into 50 cm3 of distilled weather and shaken (20 determined using the procedure presented by Nimmo & times). Then aggregates were removed from the liquids or Perkins (2002). Four grams of air-dry soil aggregates of the saturation pan and sieved for 6 minutes in ethanol (sieve size of 2–5 mm were sieved for 3 minutes in distilled water 0.25 mm). Finally, the distribution of particular aggregate (sieve 0.25 mm). Aggregates remaining on the sieve were size fractions (< 0.25, 0.25–0.5, 0.5–1.0, 1.0–2.0 and 2.0–5.0 next sieved in hexametaphoshate until only mm) was measured. The coefficient of vulnerability, KV [–], particles remained on the sieve. The index of water stable was then determined as: aggregates, WSA [–], was then determined as: IMWD KV WDS = FMWD (2) WSA= (1) WDS+ WDW where IMWD [L] is the initial mean weight diameter where WDS [M] is the weight of aggregates dispersed in dis- of aggregates (in this case 3.5 mm), and FMWD [L] is persing solution and WDW [M] is the weight of aggregates the final mean weight diameter of aggregates after their dispersed in distilled water. disintegration. The three methods proposed by Le Bissonnais (1996) were also used to study various destruction mechanisms. Results and discussion The fast wetting test was applied to study aggregate slak- ing due to the compression of the entrapped air (mechanism WSA similar to the WSA test). The slow wetting test was used The resulting indexes within all soil profiles are to evaluate aggregate disintegration caused by the micro shown in Table 1. Soil aggregate stability increases with cracking due to the different swelling, and physico-chemical the increasing WSA index. Soil aggregate stability was dispersion due to the osmotic stress. The shaking after pre- generally in the A horizons higher than in the 552 R. Kodešová et al.

measured physical and chemical soil properties) were in the Bt2 horizons only slightly less favorable to aggre- gate stability then those in the Bt1 horizon. In the case of Greyic Phaeozem, the aggregate stability decreased in the Ap horizon due to the tillage and increased in the Bth horizon due to the presence of clay-organic mater coatings as in the Bt2 horizon of Haplic Luvisol 1. The multiple linear regressions were used to evalu- ate a relationship between the WSA index and mea- sured physical and chemical soil properties (Fig. 1). Regression analysis showed that the WSA index was mainly affected by the organic carbon content, clay con- tent and pHKCl, and may be described using the follow- ing equation: Fig. 1. Micromorphological images of the soil samples character- izing the Ap horizon in Haplic Cambisol. A – pores, B – small rock fragments. WSA =0.131 + 0.260 Org.Carbon [% ] + + 0.0165 Clay [% ] − 0.0589pHKCl (3)

(B, C) in both Cambisol and the Haplic Luvisol 2 pro- Order of soil parameters in this equation reflects files due to the higher organic carbon content. High ag- the statistical significance of the variables. Equation (3) gregate stability was found in both Cambisols despite explained 70.2% of the variability in the WSA index. that the micromorphological images have shown weakly The standard deviation of the residuals was 0.102. It developed soil aggregates (Fig. 1). This was probably is evident that other factors discussed above, like con- caused also by the presence of free iron oxides in these figuration of clay particles, presence of iron oxides and soils. In the case of Haplic Chernozem and Haplic Lu- tillage, had to have a significant impact on the aggre- visol 1, soil aggregates stability increased in the Ap2 gate stability. Especially formation of aggregate coat- horizon in comparison with Ap1 horizon even if the or- ings and fillings consisting of clay particles and organic ganic carbon content was lower. This might be due to matter noticeably increased aggregate stability due to the higher content of clay under exclusion of tillage ef- the cementation effect as well as due to the consider- fects in the Ap2 horizon. In the case of Haplic Luvisol 1, able reduction of a water flow through the coatings and the most stable aggregates were found in the Bt1 hori- consequently slower wetting of the soil aggregates. The zon, presumably because of the presence of aggregate composition and permeability of aggregate coatings was coatings and fillings consisting of clay particles and or- studied by Ellerbrock & Gerke (2004), and Gerke & ganic matter in this horizon. The impact of soil particle K¨ohne (2002). The water repellency of aggregates con- composition can be seen by comparing results for the taining organic matter and temporal protection of soil Bt1 and Bt2 horizons. While aggregates, their coatings aggregates against disintegration may be another fac- and fillings are extensively developed in the Bt1 horizon tor affecting aggregate stability. Water repellency of (Fig. 2, left), a relatively homogeneous matrix structure soils containing organic matter was recently investi- with separated pores affected by coatings is present in gated by Hurrass & Schaumann (2006, 2007), Lichner the Bt2 horizon (Fig. 2, right). Different composition et al. (2007), and Orfánus et al. (2008). resulted in considerably different values of the WSA in- The evaluated KV values within all soil profiles dex despite that soil conditions (described by values of are shown in Table 1. Soil aggregate stability increases

Fig. 2. Micromorphological images of the soil samples characterizing the Bt1 (left) and Bt2 (right) horizons in Haplic Luvisol 1. A – pores, B – aggregates, C – clay and organic matter coatings and fillings. Comparison of aggregate stability using various laboratory tests 553

25.00 25.00 KV1 = -19.639 WSA + 19.189 KV1 = -21.290 WSA + 21.530 2 R2 = 0.462 R = 0.909 20.00 KV2 = -16.755 WSA + 14.776 20.00 KV2 = -19.022 WSA + 16.628 2 R2 = 0.559 R = 0.797 KV3 = -5.596 WSA + 5.926 KV3 = -6.130 WSA + 6.383 15.00 15.00 2 R2 = 0.413 R = 0.479

10.00 10.00

5.00 5.00 Coefficient ofVulnerability KV1,2,3 - Coefficient of Vulnerability - KV1,2,3 - Vulnerability of Coefficient 0.00 0.00 0.00 0.20 0.40 0.60 0.80 0.00 0.20 0.40 0.60 0.80 Index of Water Stable Aggregates Index of Water Stable Aggregates

KV1 KV2 KV3 LR (KV1) LR (KV2) LR (KV3) KV1 KV2 KV3 LR (KV1) LR (KV2) LR (KV3)

Fig. 3. Relationships between the index of water stable aggregates (WSA) and the coefficients of vulnerability (KV1, KV2, KV3), and evaluated linear regression (LR) for all soil types’ data (left) and excluding the data for Cambisols (right).

20.00 20.00 KV2 = 0.7023 KV1 - 0.0265 KV2 = 0.8436 KV1 - 1.9939 R2 = 0.8192 R2 = 0.7811

15.00 KV3 = 0.2347 KV1 + 0.9798 15.00 KV3 = 0.3202 KV1 - 0.2133 R2 = 0.6062 R2 = 0.6514 KV3 = 0.2905 KV2 + 1.3069 KV3 = 0.289 KV2 + 1.304 2 2 10.00 R = 0.559 10.00 R = 0.4836

5.00 5.00 Coefficient of Vulnerability - KV2,3 - Vulnerability of Coefficient 0.00 KV2,3 - Vulnerability of Coefficient 0.00 0.00 5.00 10.00 15.00 20.00 25.00 0.00 5.00 10.00 15.00 20.00 25.00 Coefficient of Vulnerability - KV1,2 Coefficient of Vulnerability - KV1,2 KV1-KV2 KV1-KV3 KV2-KV3 KV1-KV2 KV1-KV3 KV2-KV3 LR(KV1-KV-2) LR(KV1-KV3) LR(KV2-KV3) LR(KV1-KV-2) LR(KV1-KV3) LR(KV2-KV3)

Fig. 4. Relationships between the coefficients of vulnerability (KV1, KV2, KV3), and evaluated linear regression (LR) for all soil types’ data (left) and excluding the data for Cambisols (right).

with decreasing KV values. Values of KV1, KV2 and is affected by the chemical and physical forces inside KV3 represent the coefficients of vulnerability resulted the aggregates (as result, aggregates are less vulnerable from the fast wetting, slow wetting and shaking after to mechanic breakdown). In addition, in the top humic pre-wetting tests, respectively. The KV1 and KV2 val- horizons, organisms like fungi and plant roots stabilize ues show similar trends as the WSA indexes except for soil structure and soil microorganism excretions influ- both Cambisols. The parent material of studied Cam- ence physical and chemical processes. bisols was either ortogneiss or paragneiss. Therefore There no considerable correlation between the those soils contained higher contents of sand particles WSA index and the KV values (Fig. 3, left) was found, (Fig. 1), which are excluded in the WSA test. Sand as was presented by Rohošková & Valla (2004), because considerably decreased the KV values and illusorily in- of the significant variation of the parent materials of our creased the aggregate stability compared to that in the investigated soils. Excluding the data for both Cam- other soils on loess or loess loam. The KV3 values of bisols (which were developed on considerably different the top humic horizons are always lower then these of material then the other studied soils), a close correla- the subsurface horizons except for the Bt2 and C hori- tion between the WSA index and the KV1 value was zons of Haplic Luvisol 2, where significantly low KV3 obtained (Fig. 3, right). Less significant correlation was values were obtained. Different trends of the mechan- observed between the WSA index and the KV2 value ical aggregate breakdown compare to the other aggre- and poor correlation was found between the WSA index gate disintegration trends (e.g. the lower vulnerability and the KV3 value. As expected, a higher correlation of the top horizon aggregates to the mechanical destruc- was found between the various KV values compared tion compare to that of the subsurface horizons affected to the correlation between WSA index and KV values by the clay and organic matter coatings) are caused by (Fig. 4). However, low correlation was found again be- different major stabilization factors in various horizons. tween the KV3 value and the other two KV values. While aggregates of subsurface horizons are mainly pro- The multiple linear regressions relating different tected by the clay and organic matter coatings (that three KV values to the measured physical and chem- may be mechanically cracked along the oriented soil ical properties for all soils did not provide significant particles planes), the stability of the topsoil aggregates relationships between the variables (not shown). The 554 R. Kodešová et al. following equations relating KV values to measured soil Ellerbrock R.H. & Gerke H.H. 2004. Characterizing organic mat- properties (excluding Cambisol data) were obtained us- ter of soil agregate coatings and biopores by Fourier transform infrared spectroscopy. Eur. J. Soil Sci. 55: 219–228. ing the multiple linear regressions: Fernandez H.M.T., Mataix-Solera J., Lichner Ľ., Štekauerová V. Zaujec A. & Garcia Izquierdo C. 2007. Assessing the micro- KV1 =21.032 − 5.736 Org.Carbon [% ] − bial, biochemical, soil-physical and hydrobiological effects of 62: − 0.417 Clay [% ] + 1.234 pH amelioration of degraded soils in semiarid Spain. Biologia KCl 542–546. Gerke H.H & K¨ohne M. 2002. Estimating hydraulic properties of KV2 =25.875 − 6.229 Org.Carbon [% ] − soil aggregate skins from sorptivity and water retention. Soil. − 0.461 Clay [% ] Sci. Soc. of Am. J. 66: 26–36. Hurrass J. & Schaumann G.E. 2006. Properties of soil organic matter and aqueous extracts of actually water repellent and −1 132: KV3 =4.177 − 0.149 CEC [mmol (100g) ]+ wetted soil samples. Geoderma 222–239. +0.592 pH − 1.259 Org.Carbon [% ] (4) Hurrass J. & Schaumann G.E. 2007. Hydration kinetics of wet- KCl table and water-repelent soils. Soil Sci. Soc. Am. J. 71(2): 280–288. Order of soil parameters in these equations reflects Kodešová R., Kodeš V., Žigová A. & Šimůnek J. 2006. Impact of plant roots and soil organisms on soil micromorphology and the statistical significance of the variables. Equations 61 (Supl. 19): KV hydraulic properties. Biologia S339–S343. (4) explained 69.2 % of the variability in the 1 value, Kodešová R., Pavlů L., Kodeš V., Žigová A. & Nikodem A. 2007. 71.9 % of the variability in the KV2 value, and 57.8 % Impact of spruce forest and grass vegetation cover on soil of the variability in the KV3 value. The standard de- micromorphology and hydraulic properties of organic matter horizon. Biologia 62: 565–568. viation of the residuals was 2.36, 2.08 and 1.10 for Kodešová R., Kočárek M., Kodeš V., Šimůnek J. & Kozák J. 2008. the KV1, KV2 and KV3 values, respectively. Equations Impact of soil micromorphological features on water flow and show that, while the KV1 values depended similarly herbicide transport in soils. Vadose Zone J. 7(2): 798–809. to the WSA indexes on the organic carbon content, Kodešová R., Vignozzi N., Rohošková M., Hájková T., Kočárek M., Pagliai M., Kozák J. & Šimůnek J. 2009. Impact of vary- clay content, and pHKCl,theKV2 values did not de- ing soil structure on transport processes in different diag- pendedonpHKCl due to the dominant affect of clay nostic horizons of three soil types. J. Contam. Hydrol.104: content and organic matter. Different trends of KV3 107–125. KV WSA Le Bissonnais Y. 1996. Aggregate stability and assessment of soil values compared to other values and indexes crustability and erodibility: Theory and methodology. Eur. J. resulted in considerably different regression equation. Soil Sci. 47: 425–437. The KV3 values depended on the cation exchange ca- Lichner L., Hallett P.D., Feeney D.S., Ďurová O., Šír M. & Tesař M. 2007. Field measurement of soil water repellency and its pacity, pHKCl and organic carbon content. Regression impact on water flow under different vegetation. Biologia 62: analysis proved low impact of clay particles. As for the 537–541. WSA index, it is apparent that also other factors af- Nimmo J.R. & Perkins K.S. 2002. Aggregate stability and size fected soil aggregate stability as indicated by the dif- distribution, pp. 317–328. In: Dane J. H. & Topp G.C. (eds), Methods of Soil Analysis, Part 4 – Physical Methods. Soil ferent wetting tests. Science Society of America, Inc. Madison, USA. Our study showed that the WSA test provides data Orfánus T., Bedrna Z., Lichner Ľ., Hallett P.D., Kňava K. & that may be used to asses different aspects of aggregate Sebíň M. 2008. Spatial variability of water repellency in pine forest soil. Soil Water Res. 3 (Suppl. 1): S123–S129. stability within and between various soil profiles. The Pagliai M., Marsili A., Servadio P., Vignozzi N. & Pellegrini S. KV tests allow studying aggregate decay due to vari- 2003. Changes in some physical properties of clay soil in cen- ous destruction mechanisms. However, results of those tral Italy following the passage of rubber tracked and wheeled tractors of medium power. Soil Till. Res. 73: 119–129. tests are also considerably affected by the presence of Pagliai M., Vignozzi N. & Pellegrini, S. 2004. Soil structure and large amounts of sand particles. Therefore these meth- the effect of management practices. Soil Till. Res. 79: 131– ods are less suitable for aggregate stability assessment 143. in soil containing high fraction of large sand particles Rohošková M. & Valla M. 2004. Comparison of two methods for aggregate stability measurement – a review. Plant Soil Envi- and consequently they are not appropriate for compar- ron. 50: 279–382. ison of soil structure stability of soils developed on var- Servadio P., Marsili A., Vignozzi N., Pellegrini S. & Pagliai, M. ious parent materials. 2005. Effect on some qualities in central Italy following the passage of four wheel drive tractor fitted with single and dual tires. Soil Till. Res. 84: 87–100. Six J., Elliott E.T., Paustian K. & Doran J.W. 1998. Aggregation Acknowledgements and soil organic matter accumulation in cultivated and native grassland soils. Soil Sci. Soc. Am. J. 62: 1367–1377. Authors acknowledge the financial support of the Grant Six J., Feller C., Denef K. & Ogle S.M. 2002. Soil organic matter, Agency of the Czech Republic (grant No. GA CR 526/08/ biota and aggregation in temperate and tropical soils – Effect 22: 0434) and the Ministry of Education, Youth and Sports of no-tillage. Agronomie 755–775. Sparks D.L. (ed.) 1996. Methods of Soil Analysis, Part 3 – Chem- (grant No. MSM 6046070901). ical Methods. Soil Sci. Soc. of America, Inc. Madison, USA. Tejada M. & Gonzalez J.L. 2008. Influence of two organic amend- ments on the soil physical properties, soil losses, sediments References and runoff water quality. Geoderma 145(3–4): 325–334. Valla M., Kozák J. & Ondráček V. 2000. Vulnerability of ag- gregate separated from selected Antroposoils developed on Bronick C.J. & Lal R. 2005. Soil structure and management: a 46(12): review. Geoderma 124: 3–22. reclaimed dumpsites. Plant Production 563–568. Dane J.H. & Topp C.T. (eds) 2002. Methods of Soil Analysis, Received October 2, 2008 Part 4 – Physical Methods. Soil Science Society of America, Inc. Madison, USA. Accepted January 22, 2009