VYTAUTAS MAGNUS UNIVERSITY LITHUANIAN RESEARCH CENTRE FOR AGRICULTURE AND FORESTRY

Mykola KOCHIIERU

THE EFFECT OF CROP COVER AND WATER RETENTION ON PHYSICO-CHEMICAL AND BIOPHYSICAL QUALITY OF OF DIFFERENT ORIGIN

Scientific Doctoral Dissertation Agricultural Sciences, Agronomy (A 001)

Kaunas, 2020

The dissertation was prepared at Lithuanian Research Centre for Agriculture and Forestry in 2016-2020. The right of doctoral studies was granted to Vytautas Magnus University together with Lithuanian Research Centre for Agriculture and Forestry, on 22 February 2019, by decision No. V-160 of the Government of the Republic of Lithuania.

Scientific supervisor Dr. Virginijus Feiza (Lithuanian Research Centre for Agriculture and Forestry; Agricultural Sciences, Agronomy A 001). Scientific advisor Assoc. Prof. Dr. Jonas Volungevičius (Lithuanian Research Centre for Agriculture and Forestry; Physical sciences, Geography P 006).

The doctoral dissertation will be defended at the Council of Agronomy Sciences. Chairman Prof. Habil. Dr. Zenonas Dabkevičius (Lithuanian Research Centre for Agriculture and Forestry; Agricultural sciences, Agronomy A 001).

Members: Prof. Habil. Dr. Gediminas Staugaitis (Lithuanian Research Centre for Agriculture and Forestry, Agricultural sciences, Agronomy A 001); Prof. Habil. Dr. Andrzej Bieganowski (Institute of Agrophysics, Polish Academy of Sciences; Agricultural sciences, Agronomy A 001); Dr. Vita Tilvikienė (Lithuanian Research Centre for Agriculture and Forestry; Agricultural sciences, Agronomy A 001); Prof. Dr. Darijus Veteikis (Vilnius University; Natural sciences, Physical geography N 006).

The official defence of the dissertation will be held at 1 p.m. on December 10, 2020 at Lithuanian Research Centre for Agriculture and Forestry. Address: Instituto al. 1, Akademija, Kėdainiai distr.

The dissertation is available for viewing at Martynas Mažvydas National Library of Lithuania and the libraries of Lithuanian Research Centre for Agriculture and Forestry and Vytautas Magnus University. VYTAUTO DIDŽIOJO UNIVERSITETAS LIETUVOS AGRARINIŲ IR MIŠKŲ MOKSLŲ CENTRAS

Mykola KOCHIIERU

AUGALINĖS DANGOS IR VANDENTALPOS SAVYBIŲ ĮTAKA SKIRTINGOS GENEZĖS DIRVOŽEMIŲ FIZIKOCHEMINEI IR BIOFIZIKINEI KOKYBEI

Mokslo daktaro disertacija Žemės ūkio mokslai, Agronomija (A 001)

Kaunas, 2020

Mokslo daktaro disertacija rengta 2016–2020 m. Lietuvos agrarinių ir miškų mokslų centre pagal LR švietimo, mokslo ir sporto ministro 2019 m. vasario 22 d. įsakymu Nr. V-160 suteiktą doktorantūros teisę Vytauto Didžiojo universiteto ir Lietuvos agrarinių ir miškų mokslų centro institucijoms.

Mokslinis vadovas Dr. Virginijus Feiza (Lietuvos agrarinių ir miškų mokslų centras; Žemės ūkio mokslai, Agronomija A 001). Mokslinis konsultantas Doc. dr. Jonas Volungevičius (Lietuvos agrarinių ir miškų mokslų centras; Fiziniai mokslai, Geografija P 006).

Disertacija ginama Agronomijos mokslo krypties taryboje. Pirmininkas Prof. habil. dr. Zenonas Dabkevičius (Lietuvos agrarinių ir miškų mokslų centras; Žemės ūkio mokslai, Agronomija A 001).

Nariai: Prof. habil. dr. Gediminas Staugaitis (Lietuvos agrarinių ir miškų mokslų centras; Žemės ūkio mokslai, Agronomija A 001); Prof. habil. dr. Andrzej Bieganowski (Lenkijos mokslų akademijos Agrofizikos institutas; Žemės ūkio mokslai, Agronomija A 001); Dr. Vita Tilvikienė (Lietuvos agrarinių ir miškų mokslų centras; Žemės ūkio mokslai, Agronomija A 001); Prof. dr. Darijus Veteikis (Vilniaus universitetas; Gamtos mokslai, Fizinė geografija N 006).

Disertacija bus ginama viešame Agronomijos mokslo krypties tarybos posėdyje 2020 m. gruodžio 10 d. 13 val. Lietuvos agrarinių ir miškų mokslo centre. Adresas: Instituto al. 1, 58344 Akademija, Kėdainių r.

Disertacija galima peržiūrėti Lietuvos nacionalinėje Martyno Mažvydo bibliotekoje bei Lietuvos agrarinių ir miškų mokslų centro ir Vytauto Didžiojo universiteto bibliotekose.

CONTENTS

LIST OF PAPERS ...... 6 INTRODUCTION ...... 7 1. LITERATURE REVIEW ...... 11 1.1. The value of the soil in arable land and natural environment ...... 11 1.2. Soil agrophysical properties ...... 12 1.2.1. Soil pore structure ...... 14 1.2.2. Water aggregate stability ...... 16 1.3. Agrochemical soil properties ...... 17

1.4. dioxide (CO2) efflux ...... 19 1.5. Importance of cereal root development ...... 21 2. MATERIALS AND METHODS ...... 24 3. RESULTS ...... 26

3.1. Paper I: Effect of soil macroporosity, temperature and water content on CO2 efflux ...... 26 3.2. Paper II: Freezing-thawing impact on aggregate stability as affected by soil organic carbon ...... 27 3.3. Paper III: Effect of root network on soil macropores in Retisol ...... 27

3.4. Paper IV: Effect of environmental factors and root volume on CO2 efflux ...... 28 CONCLUSIONS ...... 30 LIST OF PUBLICATIONS ...... 31 ABOUT THE AUTHOR ...... 34 ACKNOWLEDGEMENTS ...... 35 REFERENCES ...... 36 SANTRAUKA ...... 51 APPENDIX ...... 65

5 LIST OF PAPERS

This doctoral thesis is based on the research contained in the following papers, referred to by Roman numerals in the text:

I. Kochiieru M., Lamorski K., Feiza V., Feizienė D., Volungevičius J. 2018. The effect of

soil macroporosity, temperature and water content on CO2 efflux in the soils of different genesis and land management. Zemdirbyste-Agriculture, 105 (4): 291–298.

II. Kochiieru M., Feiziene D., Feiza V., Volungevicius J., Velykis A., Slepetiene A., Deveikyte I., Seibutis V. 2020. Freezing-thawing impact on aggregate stability as affected by land management, soil genesis and soil chemical and physical quality. Soil and Tillage Research, 203: 1–11.

III. Kochiieru M., Lamorski K., Feiza V., Feizienė D., Volungevičius J. 2020. Quantification of the relationship between root parameters and soil macropore parameters under different land use systems in Retisol. International Agrophysics, 34 (3): 301–308.

IV. Kochiieru M., Feiza V., Feizienė D., Volungevičius J., Deveikytė I., Seibutis V.,

Pranaitienė S. 2021. The effect of environmental factors and root system on CO2 efflux in different types of the soil and land uses. Zemdirbyste-Agriculture, 108 (1): 1–12.

Papers I–IV are reproduced with the permission of the publisher.

6 INTRODUCTION

Soil is the most important part of successful agriculture and is the original source of the nutrients that we use to grow crops. Soil is formed as a result of mutual and interactive impacts of pedogenic processes. The geographical distribution of soils also differs in terms of variations in pedogenic factors, and consequently, different soils with variant properties are formed (Jafari and Sarmadian, 2008). Agricultural land productivity depends on , climate conditions and anthropogenic activity. predominate in the Central Lithuanian Lowland and Retisols are prevalent in the Western Lithuanian Upland (Galvonaitė et al., 2013). Preliminary estimates have shown that Retisols occupy 20.4% of Lithuania’s territory, Luvisols 21.0%, Cambisols 16.8%, Arenosols 11.9%, and 6.7%, mainly in forest areas, and 8.6% and 9.5% in the depressions (Staugaitis and Vaišvila, 2019). and crop species are important factors of soil use and management to improve soil fertility (Blanco-Canqui and Lal, 2007; Shluter et al., 2011). The processes which contribute to structure development are so complex that as, yet it is not possible to predict precisely the impact that a particular management option will have on soil structure. Common causes in degradation of soil structure include unsuitable tillage and decomposition of organic matter (Bronic and Lal, 2005; Lopez-Garrido et al., 2012). The influence of anthropogenic factors on the formation of soil structure is of great importance from the point of view of agronomy and the environment, therefore, soil cultivation (conventional and reduced tillage) as well as natural soil as the forest and the grassland was studied in this thesis. The concept of “” recognizes as an important attribute that has a great deal of control over many of the key . Soil quality is directly correlated with soil functions, such as providing a medium for plant growth, regulating water supply and storage of nutrients. Soil functions are an aggregation of several processes, such as organic matter decomposition, nutrient cycling, water retention and release, and . Soil fertility is determined by , heat, water and nutrient regime (Feiziene et al., 2008a; 2008b), organic matter content and soil management technologies used (Brevik et al., 2015). The interface between the earth, the air and the performs many vital functions: food and other biomass production, storage, filtration and transformation of many substances including water, carbon, nitrogen, phosphorus and potassium (Toth et al., 2007; Montanarella and Panagos, 2015). Quantity of soil organic matter is an integral component of soil management strategy, generally increasing with higher mean annual precipitation, lower mean annual temperature, higher content, higher crop residue inputs and cropping intensity (Majumder et al., 2007; Slepetiene et al., 2013) and native vegetation.

7 Soil evaporation, precipitation and the freezing-thawing processes occur under the climate conditions of Lithuania. Freezing-thawing processes have a great effect on the development of soil structure, that is, on the formation of aggregates within top (0–10 and 10– 25 cm soil depths) and sub-soil horizons (25–40 cm soil depth) in relation to different water content in the soil (air-dry soil, soil with water content at field capacity and soil near full saturation) at the time of freezing (Paper II). The amount of organic carbon in the soil is a driving factor of aggregation in the soil (Alagoz and Yilmaz, 2009; Paper II). In turn, water- stable aggregates are more resistant to the influence of the freezing-thawing process (Paper II).

Quantifying CO2 emissions in the soil is a key process for understanding the dynamics of carbon in various ecosystems. However, soil CO2 effluxes can change annually, as fluxes respond differently to changing environmental variables, such as nutrient availability, water content in the soil and soil temperature (Noh et al., 2010; Paper I), macroporosity (Paper I) and volume of roots (Paper IV). The effects of temperature on the exchange of CO2 efflux on the soil and atmosphere are mainly direct, and an increasing soil temperature leads to increased effluxes from the soil (Paper I), unless other factors are limiting. The effect of water content in the soil is more complex (Luo et al., 2012; Paper IV). Roots influence the creation of a macroporous network of the soil (Paper III), which leads to higher evaporation of water and CO2 (Paper IV) from the soil surface. Soil degradation in Lithuania occurs due to intensive agricultural and anthropogenic activity, therefore new investigations are necessary (Jankauskas, 1996). Soil capacity as well as the crop productivity directly depends on soil degradation and pollution, which determine declining of soil organic matter and biological diversity. The natural process of soil structure formation is slow, but vital for crop growing. If disregarded, the soils with poor structure will further exacerbate the problem (Blanco-Canqui and Lal, 2007; Galvonaitė et al., 2013; Palm et al., 2014). So far there has been a paucity of comprehensive research on how crop cover, long-term modern farming systems being managed on different types and textured soils exert influence upon morphological changes in different soil horizons, soil physico-chemical and biophysical changes and plant root growing environment. The data of research carried out on pedological changes taking place due to contrasting land use and soil management are gappy, while the problem itself is of significant scientific as well as practical relevance.

Research hypothesis

The study hypothesises that soil CO2 efflux and the content of water-stable aggregates can serve as indicators of fertility of soils differing in morphological origin ( and Retisol), which, in turn, demonstrates the contrasting physical, chemical and hydrophysical

8 properties of the soil under natural (grassland, forest) and different land uses and soil management conditions.

Research objective To investigate the influence of contrasting land use and tillage methods on soil carbon dioxide efflux, content of water-stable aggregates in different soil horizons and their relationship with physical and chemical properties and plant root parameters in the soils of different genesis.

Research tasks 1. To investigate physical soil properties within topsoil and layers in Cambisol and Retisol under natural and contrasting land use and soil management conditions.

2. To investigate CO2 efflux from topsoil layer of Cambisol and Retisol under natural and contrasting land use and soil management conditions. 3. To investigate chemical soil properties within topsoil and subsoil layers of Cambisol and Retisol under natural and contrasting land use conditions. 4. To investigate the changes in soil aggregate composition occurring after the freezing- thawing processes in Cambisol and Retisol under natural and contrasting land use and soil management conditions.

The statements of the thesis: 1. Soil temperature, volumetric water content and macroporosity are the dominant factors

affecting the CO2 efflux from Cambisol and Retisol (Papers I, IV). 2. Soil organic carbon is a driving factor contributing to aggregation depending on soil type and soil layer (Paper II). 3. Plant roots increase the volume of very fine macropores in Retisol (Paper III). 4. Soil carbon dioxide indicates root activity in Cambisol and Retisol (Paper IV).

Novelty of the research work 1. Soil environment under the influence of natural (grassland, forest) and contrasting anthropogenic (conventional and reduced tillage) activity of Cambisol and Retisol.

2. A new generation gas analyzer was used to measure soil CO2 efflux in Cambisol and Retisol. 3. Investigation of soil pore-size geometry and volumetric pore distribution and visualization in a 3D view by X-ray computed tomography. 4. The change in the composition of water-stable aggregates in two soil types was determined by the freezing-thawing method.

9 Originality of the research work The results obtained in the complex field and laboratory experiments provide new insights into how physical (moisture and temperature), chemical (pH, total P, total K, total N, organic C) properties of topsoil and subsoil of different types of soil, land uses and tillage intensity correlate with CO2 efflux, water-stable aggregates after freezing-thawing process and crop root development in different ecosystems.

Practical importance The results provide an opportunity to assess land use, agricultural systems in terms of long-term and sustainable management and create the preconditions for improving soil properties, crop production technologies, suggesting soil management tools that ensure the sustainability of agro-ecosystems.

The structure and volume of the thesis The volume of the PhD thesis is 50 pages. The thesis is written in English, based on 4 papers published in the journals with Impact Factor indexed in Clarivate Analytics Web of Science database. The thesis contains the following chapters: List of papers, Introduction, Literature review, Materials and Methods, Results, Conclusions, Acknowledgments, List of references (187 items), Summary (in Lithuanian), and Appendix with copies of 4 papers.

10 1. LITERATURE REVIEW

1.1. The value of the soil in arable land and natural environment

Soils are the fundamental resource supporting agriculture and forestry. Agricultural sustainability depends to a great extent upon the maintenance of soil fertility and crop productivity. There is no single measurement that can be made for its quantification although certain soil biophysical and chemical characteristics are found to be key potential indicators of (Dumanski and Pieri, 2000). Different soil quality parameters have been proposed to measure soil quality changes as a function of biophysical, chemical, economic and social indicators (Aparicio and Costa, 2007; Bender et al., 2016). It should be noted that most of them were derived from the data obtained from forest soils and soil of tropical and subtropical climate zones (Saggar et al., 2001). Soil quality changes have been investigated and soil quality parameter suitable for fertility evaluation of cultivated land in moderate climatic conditions has been described by Lithuanian scientists (Feiza et al., 2011). Management practices to sustain crop yields are also necessary to conserve or enhance soil fertility and its quality (Coulter et al., 2009). A difference in management practices often results in differences in biological, chemical and physical soil properties which in turn results in changes in functional ability of the soil (Toth et al., 2007; Brevik et al., 2015). Soil fertility has become a focal point for attempts to quantify modification in soil due to various soil management systems. According to Society of America, the soil quality is defined as the capacity of a specific soil to function, within natural or managed ecosystem boundaries, to sustain plant productivity, maintain or enhance water and air quality and support human health and habitation. These conditions can be accomplished by preserving or improving biological, chemical and physical properties of a soil by implementing sustainable agricultural management practices. Early warning signs about the problems of soils are crucial as they can be utilized to assess future capacity of soils (Lal, 2015). The effect of anthropogenic and environmental factors on soil structure formation is of great importance from the agronomic, environmental and climate change points of view. Lithuania belongs to the temperate climate region, which is one of the largest bio-geographical regions of Europe. We focused soil structure investigations in Cambisol and Retisol as the widely cultivated soils in the temperate climate zone (Galvonaitė et al., 2013; Putramentaite et al., 2014). Retisols which have originated on materials with low carbonate content and with deeply leached loamy deposits of marginal moraine origin, predominate in the Western Lithuanian Upland. Cambisols, whose parent materials are moraine , predominate in the Central Lithuanian Lowland.

11 Doran and Parkin (1994) defined: “The capacity of a soil to function, within ecosystem and land use boundaries, to sustain productivity, maintain environmental quality, and promote plant and animal health”. Others have identified it as the ability of the soil to support crop growth without causing soil degradation or otherwise harming the environment (Oliver et al., 2013). Soil quality is often perceived as an abstract characteristic of soils that cannot be determined because it depends on external factors, such as land use and soil management, the interaction of ecosystems and the environment, as well as socio-economic and political priorities (Pankhurst et al., 1997). Soil quality is assessed based on specific soil functions (Larson and Pierce, 1994). Soil quality is a combination of physical, chemical and biological properties of the soil, which are easily changed depending on the changes in soil conditions. Since the environments and the soil functions of interest are different, there is no methodology for characterizing quality of the soil based on a universal set of indicators (El-Ramady et al., 2014). The standard approach to assessing soil quality involves selecting soil properties that are ‘indicators’ of important soil processes and function (Lima et al., 2013). Effective monitoring of soil quality requires that indicator properties are sufficiently simple and robust for routine measurement and can provide meaningful insights into the state of a soil and any deterioration in soil functions over time (Gonzales-Quiñones et al., 2011).

1.2. Soil agrophysical properties

The physical properties of the soil determine the movement of air and water/dissolved chemicals through the soil, as well as the conditions affecting germination, root growth and erosion processes. The physical properties of the soil form the basis of several chemical and biological processes that can be further regulated by climate, landscape and land use. As a result, a number of physical characteristics of the soil when altered by the change of climate can cause a chain reaction that leads to a soil environment, which can significantly affect the growth and production of crops. Some key physical indicators of soil related to climate change include soil structure, water penetration, bulk density, rooting depth, and soil surface cover (Allen et al., 2011). Bulk density is usually estimated in agricultural systems to characterize the state of soil density in response to land use and management (Hakansson and Lipiec, 2000). It is considered a useful indicator for assessing soil conditions, taking into account soil functions such as aeration and infiltration (Dalal and Moloney, 2000; Pattison et al., 2008; Reynolds et al., 2009). Since bulk density generally negatively correlates with soil organic matter (SOM) or soil organic carbon (SOC) content (Weil and Magdoff, 2004), the loss of organic C due to increased

12 decomposition due to elevated temperatures (Davidson and Janssens, 2006) can increase density and, therefore, makes the soil more prone to compaction as a result of land management activities and stresses associated with climate change, for example, as a result of variable and intense rainfall and droughts (Birkas et al., 2009). The soil structure dictates the accumulation of organic carbon, the ability to penetrate, the movement and storage of gases, water and nutrients, the emergence of crops and root, as well as the activity of the microbial community. It can also be used to measure soil resistance to erosion and management changes, such as high-intensity rainfall and cultivation (Blanco-Canqui and Lal, 2004; Moebius et al., 2007; Rimal and Lal, 2009). Since nature and quality of the structure of a particular soil depend on the quantity and quality of the present organic matter, as well as on the inorganic components of the soil matrix and cultivation methods, a decrease in the level of organic matter in the soil that can occur under conditions of climate change can lead to a decrease in the stability of soil aggregates, an increase in susceptibility to compaction, lower infiltration rates, increased run-off, and hence an increased susceptibility to erosion (Jat et al., 2018). Soils with high clay content, especially with smectite mineralogy, have the potential to shrink when dry, which leads to the formation of large cracks and fissures. When the soil dries up, the cracks close. Drier climates are expected to increase the frequency and size of cracking. The increased drying of the soil will increase difficulty in the management of clayey agricultural soils with a high potential shrinkage-swelling. The importance of soil structure for future soil and water management, the movement of nutrients in soil and landscape are important aspects that must be considered in an environment under climate change (Allen et al., 2011). The degree of soil water infiltration is becoming increasingly important in modelling soil water (Dalal and Moloney, 2000), but it can change significantly with soil use, management, and time. The water available in the soil and its distribution can quickly respond to climate change, especially to the variable and intensity occurrences of the rainfall or drought, and thus management strategies such as soil conservation and the use of organic fertilizers that support or even enhance water infiltration and available water in the soil can help mitigate the effects of heavy rainfall and drought (Lal, 1995). Understanding soil function on a firm scientific basis is required to provide strategies and approaches for land resource managers and policy makers to promote long-term ecosystem sustainability (Dumanski and Pieri, 2000).

13 1.2.1. Soil pore structure Porosity, a measure of empty spaces in a material as a fraction (volume of voids to that of the total volume), and pore size distribution give a direct, quantitative assessment of the ability of a soil to store water and air in the root zone necessary for plant growth (Reynolds et al., 2002). Pore characteristics are closely related to the physical quality of the soil; bulk density and macroporosity are functions of pore volume, while soil porosity and water loss characteristics directly affect a number of soil physical parameters, including soil aeration ability, available plant capacity, and relative field capacity (Reynolds et al., 2009). Recent investigations for modelling soil water balance and ecosystem conditions under present-day and projected climatic scenarios use porosity as a model parameter (Porporato et al., 2005). Since root development and activity of soil enzymes are closely related to porosity of the soil and pore size distribution (Piglai and De Nobili, 1993) and also because future climate change scenarios

(e.g., increase in CO2 and temperature, as well as variable and extreme precipitation) can change the development of the roots and the biological activity of the soil, porosity of the soil and distribution of pore size and consequently soil functions are likely to be affected in unexpected directions; this aspect needs attention in future studies on the relationship between soil health and climate change. However, data on relationships between greenhouse gas emissions and soil porosity and pore size distribution in response to climate change are limited and hence urgently required to guide development of climate adaptive strategies (Dalal et al., 2003a; 2003b; 2008). New methods for investigation of soil physical properties are of great interest. Direct information on the deformation of the internal soil-pore architecture is typically missing. X–ray microtomography has turned into a standard technique to fill this gap and measure the three- dimensional internal structure of porous media (Ketcham and Carlson, 2001; Cnudde and Boone, 2013; Wildenschild and Sheppard, 2013). There is a huge variety of image processing and image analysis methods that are all tailored for the ultimate goal to quantify the complex, structural heterogeneity of the soil (Kaestner et al., 2008; Schlüter et al., 2014). Automated methods to detect deformation are usually based on digital volume correlation. The rationale of this method is to recover the displacement field by finding a geometric transformation of a deformed image that optimizes a correlation coefficient with the original, undeformed target image. The method usually comprises three steps: 1) the acquisition of X-ray microtomography image before and after the perturbation, 2) image registration of one image onto the other to obtain a discrete deformation vector field, and 3) calculation of the strain tensor field from the displacement vector field (Hall, 2010; Peth et al., 2010). Soil macropores are large voids in the soil. Roots of the plants use them as pathways for growth. Wormholes, soil cracks and voids between aggregates are often associated with a high

14 degree of variability in the transport of the gases, moisture (Helliwell et al., 2013) and solutes through the soil (Hu et al., 2010; 2016; 2019). Many investigations have shown that porosity and infiltration of the soil can be caused by roots of the plants (Li et al., 2009; Wu et al., 2017). Van Schaik (2009) found that soil macropores formed by roots of the plants are a major factor influencing downward water movement in pastures. A recent study has shown that the complexity of macropore network may be related to the age of the soil in the process (Musso et al., 2019). X-ray computed tomography is one of the newest methods for studying soil macropores (Dal Ferro et al., 2014; Zhang et al., 2017) and preferential water flow (Gunde et al., 2010; Sammartino et al., 2012). This method is more accurate and has higher resolution than traditional methods such as spectral analysis, dye tracking, and thin-section soil imaging. Recently, many studies related to the parameters of the structure of macropores (which include characterizations such as macroporosity, volume, distribution of macropore size, tortuosity and surface area) have been carried out using X-ray computed tomography for different types of soil, and different land use and management (Larsbo et al., 2014; Hu et al., 2015; Katuwal et al., 2015). Reconstruction, which is a quantitative assessment of networks of three-dimensional macropores and visualization of macropores, is important for correlating the parameters of macropores in soil with the physical functions of macropores, as well as for predicting their dynamics for different types of soils and land use (Paper I; Paper III). Different types of macropores function differently in relation to their specific geometric shapes (Luo et al., 2008). Types of the soil and land management are among the main factors affecting macropore parameters in the soil (Udawatta et al., 2008; Zhou et al., 2008; Luo et al., 2010). The characteristics of soil macropores are important for a wide range of essential soil properties, including looseness (Munkholm et al., 2012). Soil organic matter, soil structure and the porous system are key attributes of the regulation of water flow, nutrient supply, contaminants adsorption and desorption, and losses as well as gas emissions (Dexter, 2004; Clothier et al., 2008). Soil structure conditions influence the pore size distribution that can be described by means of the soil water retention curve. Pores draining up to the inflection point of the soil water retention curve are structural pores, whereas the remainder corresponds to textural pores, which are conditioned by soil microstructure (Dexter, 2004).

15 1.2.2. Water aggregate stability Soil aggregation is an important parameter of soil quality because it increases porosity, and therefore infiltration and moisture retention, reduces runoff and erosion, and increases plant productivity (Barthes and Roose, 2002; Haydu-Houdeshell et al., 2018). Soil aggregates are often formed under the influence of physical forces, such as drying, shrinkage-swelling, root growth, and animal activity (Ghezzehei, 2012), but organic materials usually play an important role in stabilizing aggregates (Abiven et al., 2009; Paper II). The influence of organic substances is more pronounced in soils with a low content of clay (Haydu-Houdeshell et al., 2018). Stability of soil aggregates, i.e. their resistance to external energy such as high intensity precipitation and cultivation, is determined by structure of the soil, as well as a range of chemical and biological properties and management methods (Dalal and Moloney, 2000; Moebius et al., 2007). It is considered a useful indicator of soil health as it is involved in maintaining important ecosystem functions in the soil, including organic carbon storage, infiltration capacity, water movement and storage, and the activity of root and microbial communities; it can also be used to measure soil resistance to erosion and management changes (Lal, 1999; Blanco-Canqui and Lal, 2004; Weil and Magdoff, 2004). Since aggregate stability is measured in many different ways, a soil monitoring system requires standardized procedures within climate change scenarios (Dalal and Moloney, 2000; Salvador Sanchis et al., 2008). Concerns about deteriorating soil structure due to soil compaction, water erosion, or intensive tillage are expressed worldwide (Hamza and Anderson, 2005; Oldeman et al., 2017). Soil structure is one of the key factors of soil and environmental quality (Roger-Estrade et al., 2010; Garbout et al., 2013) and is one of the most important factors in the stabilization of organic carbon in the soil. In turn, organic carbon in soil is an important binding agent that binds mineral particles together into aggregates (Chaplot and Cooper, 2015; Rabbi et al., 2015). The physical protection of soil organic matter by aggregates is considered an important mechanism for stabilizing carbon in the soil. Water-stable aggregates (WSA) are important components of the soil that affect yield by affecting soil water, aeration, temperature and mechanical resistance. Freezing and thawing processes have a great influence on the development of soil structure, that is, on the formation of aggregates within horizon of the soil profile. These processes have not yet been widely studied in agricultural and forest soils in temperate climates. Ma et al. (2014) suggest that the abundance of WSA at the soil surface determines the potential for sheet erosion and formation of the crust. Oztas and Fayetorbay (2003) found that soils with dominant aggregates of 1–2 mm may remain more stable after freezing and thawing compared to soil aggregates more than 2 mm in size. It is also known that WSA increases with organic matter content in the soil and that soil management techniques such as reduced tillage with crop residue

16 retention can improve soil quality. In addition, and clay bind soil particles better than . The effects of freezing-thawing process on WSA can vary depending on soil texture, organic matter content, land use, soil type and depth, and soil water content during freezing (Oztas and Fayetorbay, 2003; Paper II). Research into WSA is becoming increasingly relevant because it can provide important information on soil conditions for different levels of water content (Bartlová et al., 2015). Cambisol and Retisol are predominant types of soil in Lithuania and are widely used for agricultural production. Under Lithuania’s temperate climate conditions, precipitation (soil wetting), evaporation (soil drying), and freeze-thaw processes occur. In the temperate regions, freezing-thawing leads to instability of aggregates of the soil. If soil aggregates enter the winter under relatively stable conditions, they can be weakened by the freeze-thaw process (Lehrsch, 1998). Due to the periodic changes of atmospheric temperature with seasons, soils in seasonally freezing and permafrost (frozen ground) regions are inevitably subjected to periodic freezing and thawing, with temperatures alternately rising above and falling below 0°C. Freeze-thaw cycling is a process of energy input and output in the soil (Li et al., 2002). During this process, water and salt transfer causes changes in soil structure, with the initial stable state of soil particles being changed through aggregation and fragmentation, causing changes in particle granularity. These changes may result in further variations in soil, including its composition, structure and characteristics, all of which can lead to ecological and engineering problems. From an ecological viewpoint, the changes in soil will affect its water-retention and nutrient- preservation capabilities, which will result in water loss, grassland degradation, desertification, etc. (Liang et al., 2005; Zhang and Zhao, 2009). The freeze-thaw cycle destroys the initial state of soil to generate a new state with updated composition, structure and properties through a complex process that evolves physical and chemical changes.

1.3. Agrochemical soil properties

Recently, soil quality has gained attention as a result of environmental issues related to soil degradation and production sustainability under different farming systems (Galantini and Rosell, 2006). It has been considered by previous researchers that the concentrations of soil nutrients (e.g., organic C, N, P, and K) are good indicators of soil quality and productivity because of their favourable effects on the physical, and chemical properties of soil (Cao et al., 2011). Soil pH affects the chemical reactions in soil (Zhao et al., 2011). Extremes of pH in soils, for example, will lead to a rapid increase in net negative surface charge and thus to increases in

17 the soil’s affinity for metal ions (Yang et al., 2006). Soil organic components, such as soil organic carbon (SOC) or total N (Ntotal) are the most critical indices of paddy soil fertility (Liu et al., 2011). Dynamics of SOC and Ntotal storage in agricultural soils drives microbial activity and nutrient cycles, promotes soil physical properties and water retention capacity, and reduces erosion (Manna et al., 2007). Moreover, it has been recognized that soil available nutrients (including N, P and K), coming from mineralization and available components of fertilizer, can be directly absorbed by plants, contributing greatly to the soil fertility (Vogeler et al., 2009).

Recognizing the importance of soil organic carbon (Corg) for sustaining soil quality and food production, the European Union (EU) considers the decline of soil Corg in European soils as one of the main drivers of soil degradation in its Thematic Strategy for Soil Protection (Commission of the European Communities, 2006; Nocita et al., 2014). Increasing human demands on soil-derived ecosystem services require reliable data on global soil resources for sustainable development (Jandl et al., 2014). Soil organic matter also has several environmental implications such as preventing risk of and reducing leaching of nutrients and pesticides to aquatic ecosystems (Jankauskas et al., 2007). Soil organic matter has an essential role in global C cycle, while C cycle together with changes of GHG concentration in the atmosphere is a significant part of global biochemical cycle (FAO, 2004; Heikkinen et al., 2013). Numerous studies have revealed that multiple cropping systems produced higher yields, had a positive effect on macrofauna activity in the soil as compared to continuous mono- cropping or with partial crop rotations (McGill et al., 1986; Collison et al., 2013; Crumsey et al., 2013). Multi-cropping systems improve soil quality and provide well documented economic and environmental benefits to agricultural producers (D’Hose et al., 2014; Eerd et al., 2014). Soil aggregation, soil organic matter, total N, soil pH, cation exchange capacity are particularly important indicators of dynamic of soil fertility because they are responsive to changes in soil management (Wander, 2004). A selected set of soil properties and their monitoring can serve as indicators on trends in soil fertility changes (Dumanski and Pieri, 2000; Aparicio and Costa, 2007). Soil organic carbon is increasingly viewed as a key indicator of soil quality (Liaudanskiene et al., 2013; Feiziene et al., 2018). It has been observed that forest soils generally have lower bulk density (BD), and higher SOC content, aggregate stability and saturated hydraulic conductivity as compared with the cultivated soils (Ayoubi et al., 2012). SOC content is essential to the formation for the WSA. It has been reported that soil management practices affect the content and quality of organic matter in the soil (Šimon et al., 2009), which is an important factor in the formation of WSA (Krol et al., 2013). Organic matter

18 of the soil and its labile fractions, clay minerals, and bacteria are important agents for the formation and stabilization of WSA (Wang et al., 2016). Soil organic matter affects the WSA by decreasing their moisture availability and increasing their mechanical strength (Onweremadu et al., 2007), and as a binding agent, organic matter of the soil can be retained in different size fractions of aggregates. Water-resistant aggregates retain more carbon compared with non- resistant ones. Eventually, the high WSA content has been indicated as an important contributor to the maintenance of soil resistance to physical degradation (Lehrsch, 1998). Soil carbon can be used as an indicator because it is directly related to ecosystem productivity and also has a “memory”, that is a change in time; but it cannot be a separate indicator of the soil quality, since it does not cover all attributes of an ecosystem (Janzen, 2005). While soil contains carbon in various forms and residence times, considerable research attention has focused on the form of the SOC, as it: 1) has been significantly altered as a result of human activity; 2) a decrease is expected with an increase in average global temperatures, which will adversely affect important functions and processes in the soil and its condition (Lal et al., 2007).

1.4. Soil carbon dioxide (CO2) efflux

Soil CO2 efflux is a physical process driven primarily by the CO2 concentration diffusion gradient between the upper soil layers and the atmosphere near the soil surface. Production of

CO2 in the soil is heavily influenced by the environmental factors, including soil temperature (Paper IV), water content (Paper I; Paper IV), and macroporosity (Paper I). The importance of macropores as preferential pathways of water, air and chemicals in the soil has been widely recognized (Lin et al., 2005; Jarvis, 2007; Hu et al., 2016). The efflux of CO2 from the soil is associated with many difficulties and therefore, is still not entirely understood. The influence of environmental factors on soil CO2 efflux is of great importance in terms of agronomy, environment, and climate change.

Soil CO2 efflux is the result of respiration of plant roots, microbial activity, the decay of organic matter, which depend on soil temperature and water content (Pumpanen et al., 2015).

CO2 emissions from the soil are mainly due to the temperature, water content, substrate input from plants, soil texture and root density (Zhou et al., 2016). Respiration from the soil is a measure of all the CO2 produced by underground processes, including heterotrophic and autotrophic respiration by roots and organisms of the soil. Soil respiration has become a recognized key component for assessing ecosystem potential within global budget of C and for predicting its change in global changes (Noh et al., 2010). Soil respiration is often used as a biological indicator of soil health, because it positively correlates with soil organic matter content (and often with microbial biomass and activity) and

19 can be defined as either CO2 production or O2 consumption, e.g., “soil” or “basal” respiration, using a range of in situ or laboratory methods (Arias et al., 2005; Haynes, 2008). Soil respiration, especially its temperature response, is widely recognized as a critical link between climate change and the global C cycle (Wixon and Balser, 2009), although the nature of this relationship is under scientific debate (Balser et al., 2006; Agren and Wetterstedt, 2007; Kuzyakov and Gavrichkova, 2010). Recent studies have also shown that respiration of the soil is relatively responsive to changes in seasonal rainfall patterns, which are projected to change in line with global and regional climate models (Chou et al., 2008). The characteristics of the pores in the soil are important for a wide range of the most important soil functions, such as colloidal, water and gas transport, the habitat of soil organisms, and the mechanical properties of the soil, such as soil loosening (Munkholm et al., 2012). Greenhouse gas (GHG) emissions from agricultural soils make a significant contribution to climate change (Smith et al., 2008); therefore, it is very important to develop agricultural practices that reduce GHG emissions from agricultural soils (Mangalassery et al., 2013). The regime of soil cultivation is considered one of the important factors affecting the efflux from the soils (Li et al., 2013). Management of the tillage can influence factors that control respiration of the soil, soil temperature, water content (Liu et al., 2006) and macroporosity (Paper I). and temperature are some of the most important factors controlling CO2 emissions from the soil (Lopes de Gerenyu et al., 2005; Ni et al., 2012). Higher water content in the soil usually causes an increase in soil respiration. But if water content in the soil is very high, the total CO2 efflux from the soil decreases due to limited oxygen diffusion and subsequent suppression of CO2 emission (Tavares et al., 2016). World soils contain an important pool of active carbon that plays a major role in the global carbon cycle. Soils store two or three times more carbon than that exists in the atmosphere as CO2 and from 2.5 to 3 times as much as that stored in plants (Lal, 2015). Farming systems have strong influence on soil properties, such as organic matter (OM) and major nutrients. Land use and soil management practices can significantly influence soil physical properties (Schlüter et al., 2011), water content (De Vita et al., 2007), soil organic carbon, carbon dioxide flux (Feizienė et al., 2011; 2015; Feiza et al., 2014) and also grain quality improvement (Chatskikh and Olesen, 2007; Velykis and Satkus, 2012). Soil physical properties, especially the porosity and water content, are also important because they affect the transport of gases in the soil (Salmawati et al., 2019).

Soil temperature is the best indicator of the dynamics of the CO2 flow rate. The high positive correlations between CO2 efflux in the soil and soil temperatures were found in natural

20 and agricultural ecosystems of the Russian taiga zone (Kudeyarov, Kurganova, 1998) and in the soil during the dry investigation period (Faimon and Lang, 2018). Researchers (Negassa et al., 2015; Dong et al., 2017) found similar relationships between soil temperature and soil CO2 emissions. Schaufler et al. (2010) found a non-linear increase of

CO2 effluxes in the soil with increasing soil temperature. Water content and groundwater level in the soil are important control factors, but their impact on the production of CO2 emission from the soil is more complex. Dong et al. (2017) estimated that the CO2 efflux in the soil slightly correlated with the soil water content. Soil saturation conditions have influence on soil CO2 production, which usually increases when the soil dries up till the optimum moisture content and then decreases with further drying. It has also been reported that CO2 emissions in the soil decrease with decreasing volumetric water content in the soil. The higher water content in the soil was associated with the intense release of CO2 into the soil in agricultural peatlands (Zeng and Gao, 2016).

In a high-latitude terrestrial ecosystem, it is also important to understand whether CO2 absorption by vegetation or CO2 emissions from soil, which control carbon balance and its response to climate change (Kim et al., 2013). According to Bortolotto et al. (2015), soil temperature is the variable that best explains the changes in CO2 effluxes in the soil, while water content in the soil is also an important factor for CO2 emission.

1.5. Importance of cereal root development

The plant growth is directly dependent on soil functions. Organic materials are the storehouse of all essential soil and plant nutrients in the soil and they are important components of soil fertility, which are associated with a variety of other important soil physical, chemical and biological characteristics. The use of organic materials in soil management will be a good way to improve and maintain soil quality and soil fertility rehabilitation under agricultural production (Garcia-Pausas et al., 2008; Rumpel and Kogel-Knabner, 2011). Plants help to aggregate soil particles in a variety of ways. The most important one probably is the excretion of gelatinous organic compounds from the roots which serve as links between inorganic substances. The roots perform many functions for the plant, including fixing and obtaining vital nutrients and water necessary for growth. The plant roots and soil are a dynamic area in which numerous biogeochemical processes occur due to physical activity and various chemicals released by the plant roots and mediated by soil microorganisms. In turn, the processes taking place in this region control many reactions that regulate the carbon cycle and other elements that support plant growth and have a huge impact on the functions and structure of the plant

21 community and microorganisms, which significantly affect various processes at the ecosystem level (Wardle et al., 2004; Van der Heijden et al., 2008; Berg and Smalla, 2009). Root hairs make the soil particles cling together. Dehydration of the soil by the roots causes strains in the soil due to shrinkage that may result in cracks and subsequently in aggregate formation. Plant tops and residues keep the soil shaded and protect it from extreme and sudden temperature and moisture changes and from raindrop impact. Plant residues, roots and tops, serve as food supply for microbes, the prime aggregate builders. New and biologically active organic matter is continuously required for this purpose. Plant residues also serve as insulating material between soil cracks (Kohnke, 1968). The various plant compartments colonized by microbes do not provide a constant environment, but differ depending on the stage of plant development or as a result of environmental factors, including temperature, water content (Tardieu, 2013), or nutrient availability (Kowalchuk et al., 2002; Tuteja and Sopory, 2008; Philippot et al., 2013). The importance of environmental factors, as factors affecting the plant phenotype, has been confirmed in many studies in which the same plant genotype developed different phenotypes in response to different environmental conditions (Schlichting, 1986; Sultan, 2000; Valladares et al., 2007). However, most of these studies were conducted in greenhouse conditions, where the key factors affecting plant productivity were maintained in optimal conditions, and only one factor was changed. Land use intensity strongly affects a range of environmental factors, including the quantity and quality of nutrients, soil structure, and the overall picture of biodiversity (Birkhofer et al., 2012). Thus, land use intensification is a typical example of a driving force causing multifactorial changes in a given plant phenotype (Kirkham et al., 1996; Wedin and Tilman, 1996). The depth of rooting is considered an important indicator of the state of the soil, since changes in this property probably affect the available plant capacity, , SOC content or other properties, which indicates physicochemical limitations in the soil profile (Dalal and Moloney, 2000; Arias et al., 2005; Birkas et al., 2009). In conditions of prolonged drought, the influence of subsoil use factors such as salinity and high chloride concentrations (Dang et al., 2008; Rengasamy, 2010) is likely to be greater on the water available to plants and, therefore, on its productivity. In addition, Birkas et al. (2009) included rooting depth as a parameter of soil health for monitoring soil conditions and plant growth under severe drought and variable rainfall to indicate the ability to adapt and mitigate climatic pressures by varying the rooting depth. Roots contribute to the formation of well-connected channels (macropores), which usually grow into rigid pores broader than their own diameters (Logsdon and Allmaras, 1991).

22 Plant roots are a major contributor to matrix flow mechanics as they create spatial voids that can be used as matrix flow pathways (Gish et al., 1998). Root channels are the void biopores formed by plant roots. Water flow in the root channels is an important mechanism for soil infiltration and is crucial for the prediction of runoff formation and groundwater recharge (Weiler and Naef, 2003). Macropores formed by the root systems of vegetation are important channels for moving water down pastures. Root channels generate macroporosity of the soil, which leads to higher infiltration than expected, based solely on the textural properties of the surface soil layer (Van Schaik, 2009). The flow from the root canals can create a lateral component of the flow and lead to rapid seepage into groundwater and the flow of the stream after precipitation. This process can affect erosion processes and the transport of solutes and pollution (Van Schaik, 2009). In Lithuania, there is a shortage of complex, long-term studies aimed at determining how sustainable agricultural systems affect physico-chemical soil properties, CO2 emissions, and root development in soils with different genesis. Such research will contribute to solving problems related to the impact of long-term use of agronomic practices on soil productivity and resilience.

23 2. MATERIALS AND METHODS

Soils and experimental sites (Papers I–IV) Soil types involved in this work are classified according to WRB (2015) as Endocalcaric Endogleyic Cambisol (Loamic, Drainic) in Akademija (55°23′38″ N, 23°51′35″ E), Kėdainiai district (Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry), Central Lithuanian Lowland, and as Dystric Retisol (Loamic, Bathygleyic), near Bijotai (55°31′12″ N, 22°36′55″ E), Šilalė district, on hilly landscape of Western Lithuania. Four land uses were investigated on Cambisol: 1) conventional tillage; 2) reduced tillage; 3) grassland; 4) park (forest) area. Four land uses were investigated on Retisol: 1) conventional tillage; 2) reduced tillage; 3) grassland; 4) forest.

Measurement of soil macropore network (Papers I, III) Soil monoliths (soil cylinder – 46 mm in diameter and 50 mm in length) were sampled from each treatment. Laboratory investigation of the soil macropore networks was conducted at the Institute of Agrophysics, Polish Academy of Sciences, by X-ray Computed Tomography. A reconstruction was conducted using the software DatosX 2.0 (GE Sensing & Inspection Technologies GmbH). As a result, 16 bit grey-level 3D images were generated. An image analysis was performed using VG Studio Max 2.0 (Volume Graphics GmbH, Germany), Fiji (National Institutes of Health, USA) and software Avizo 9 (Field Electron and Ion Company, USA). Thresholding was implemented using the IsoData algorithm (Ridler and Calvard, 1978) with a thorough inspection of the thresholder images. After that, the labelling of the detected pores was performed. Any group of voxels connected by at least one voxel face was treated as an individual pore. As a result of this labelling, the volumes, surface and equivalent diameters of the individual macropores were determined.

Measurement of agrochemical soil properties (Paper II) Soil pH was determined by a potentiometric method in 1 M KCl. The content of soil organic carbon was determined by a spectrophotometric procedure at a wavelength of 590 nm using glucose as a standard after wet combustion according to Nikitin (1999). Total nitrogen content was determined by the Kjeldahl method. The content of soil total potassium was determined using atomic absorption spectrometry by analyst (Perkin Elmer) after wet digestion with sulphuric acid. The content of total soil phosphorus was quantified spectrophotometrically at a wavelength of 430 nm on a Cary 50 UV-vis (Varian Inc., USA).

24 Measurement of soil CO2 efflux (Papers I, IV) -2 -1 The soil CO2 efflux (µmol m s ) was measured using a closed chamber LI-8100A (LI-

COR Inc., USA). Three soil collars were positioned randomly in each plot. Soil CO2 efflux was measured 6 times per growing season in 2017 and 2018 at the same time of the day, from 10 a.m. to 5 p.m.

Measurement of the environmental factors (Papers I, IV)

Soil temperature (°C) and volumetric water content (%) were measured during soil CO2 efflux measurement. The soil temperature and volumetric water content were measured at 5 cm depth with a portable sensor HH2 WET (Delta-T Devices Ltd, England).

Investigation of water-stable aggregates after freezing-thawing process (Paper II) Undisturbed soil monolith samples (5 cm in diameter) for determination of water-stable aggregates after freezing-thawing cycles, were taken from each treatment at the 0–40 cm soil depth. The intact soil cores were adjusted to the three contrasting levels of water content: 1) air- dry soil; 2) soil at field capacity, and 3) soil saturated at 90–95% water holding capacity. Soil monoliths with different water contents were subjected to three temperature cycles. For freezing-thawing cycle, the soil monoliths were frozen at −5°C for 48 h and after that they were thawed at 5°C for 48 h. The duration for change from −5°C to 5°C or from 5°C to −5°C was 24 h. The duration of a single freezing-thawing cycle was 5 days. The freezer was fixed at a temperature of –5°C for slow freezing of the soil, which allowed the redistribution of water during freezing. Water-stable aggregates after freezing-thawing cycles were determined for the 0–10, 10– 25 and 25–40 cm depths by using a wet sieving apparatus (Eijkelkamp Agrisearch Equipment, The Netherlands). Four replications of 4 g of air-dried soil aggregates (1–2 mm size) were wet sieved (0.25 mm mesh size) in distilled water and then stable aggregates were destroyed by 0.2% NaOH solution, oven-dried at 105°C for 24 h and weighed.

Investigation of root system (Papers III, IV) Monoliths of the soil 10 × 10 × 10 cm from two topsoil (0–10 and 10–20 cm) layers were taken from each land use treatment. Samples (three replications) were taken at the flowering stage of plants (BBCH 61–65) from different land uses according to Lapinskienė (1993) method. An analysis of the root length density, the volume of the root and also the mean root diameter was conducted using the software WinRhizo.

25 3. RESULTS

3.1. Paper I: Effect of soil macroporosity, temperature and water content on CO2 efflux

The aim of the work was to quantify the effect of soil macroporosity, soil temperature and soil water content on soil CO2 efflux in different land uses of Cambisol and Retisol. The average values of CO2 efflux, temperature, volumetric water content and macroporosity are shown in Table 1.

Table 1. The effect of land uses on CO2 efflux, soil temperature (T-soil), volumetric water content (VWC) at the 5 cm depth averaged across dates of measurement and macroporosity at the 3–8 cm depth

CO2 efflux T-soil VWC Macroporosity Land use μmol m-2 s-1 °C % % Cambisol Retisol Cambisol Retisol Cambisol Retisol Cambisol Retisol Conventional tillage 0.68 c 1.44 ab 19.3 a 18.4 a 16.8 c 22.5 b 1.21 4.94 Grassland 2.11 a 1.75 a 19.2 a 17.1 b 24.4 a 27.0 a 10.75 3.86 Forest – 1.23 b – 15.4 c – 26.2 ab – 6.45 Park 1.13 b – 15.4 c – 20.2 b – 1.97 – Average 1.31 1.47 18.0 16.9 20.4 25.2 4.64 5.08 Note. CO2 efflux, T-soil and VWC data followed by the same letters are not significantly different at P < 0.05.

Average soil CO2 efflux in Cambisol was 11% lower than in Retisol. Volumetric water content in Retisol was profoundly higher than that in Cambisol. The grassland of Cambisol had the greatest macroporosity (10.75%), while the conventional tillage of Cambisol had the lowest macroporosity (1.21%). Volumetric water content ((R2 = 0.53 (valid for volumetric water content from 16.8 to 27.0%), P < 0.05)) and volume of macropores ((R2 = 0.65 (valid for volume of macropores from 1.21 to 10.75%), P < 0.05)) were dominant factors enhancing soil

CO2 efflux (Fig. 1).

2.5 2.5 -1

2.0 s 2.0

-2 -2

-1

s -2 -2 1.5 1.5

1.0 1.0

y = 0.0943x - 0.7651 efflux µmol m 2 y = 0.1167x + 0.8214

efflux µmol m 2

2 2

R = 0.53 CO 0.5 R = 0.65

CO 0.5

0.0 0.0 15 17 19 21 23 25 27 29 0 2 4 6 8 10 12 Volumetric water content % a) b) Volume of macropores %

Figure 1. The relationships between: CO2 efflux and volumetric water content at the 5 cm depth (a) and

CO2 efflux and volume of macropores at the 3–8 cm depth (b) under different soil types and land uses

During the whole growing season, correlation analyses showed poor relationship between soil CO2 efflux and soil temperature at the 5 cm depth (P > 0.05). 26 3.2. Paper II: Freezing-thawing impact on aggregate stability as affected by soil organic carbon

The aim of this study was to determine the effect of soil freezing-thawing processes on the formation of water-stable aggregates in the 0–10, 10–25 and 25–40 cm depths of the Cambisol and Retisol in relation to the contrasting levels of water content, organic matter content and type of land use. Average values of water-stable aggregates (WSA) in relation to water content at soil freezing, soil organic carbon and their correlation matrix in Cambisol and Retisol are presented in Table 2.

Table 2. Soil quality indices and their correlation matrix in Cambisol and Retisol Cambisol Retisol Index CT RT Forest WSAFC WSAAD WSANS CT RT Forest WSAFC WSAAD WSANS Depth 0–10 cm WSAFC 22.25 41.34 80.24 29.67 77.81 95.58 WSAAD 14.45 39.92 97.53 1.00** 42.2 84.56 95.95 1.00** WSANS 28.55 36.41 97.24 0.86** 0.87** 23.03 52.39 92.48 0.84** 0.83** SOC 12.20 12.10 37.80 0.94** 0.95** 0.88** 8.10 16.60 27.50 0.95** 0.92** 0.87** Depth 10–25 cm WSAFC 24.40 30.56 53.46 30.27 84.18 77.72 WSAAD 10.66 33.34 80.31 0.98** 40.2 86.91 90.95 0.98** WSANS 20.89 26.92 82.53 0.98** 0.97** 34.93 80.69 69.63 0.99** 0.95** SOC 13.00 10.70 11.30 –0.45* –0.56* -0.35 9.70 14.20 17.80 0.84** 0.93** 0.77* Depth 25–40 cm WSAFC 28.84 23.44 45.68 41.52 31.88 40.97 WSAAD 37.97 23.08 34.21 0.42* 39.06 44.77 76.75 0.32 WSANS 24.98 27.60 27.62 0.40* 0.06 22.59 20.31 53.36 0.44* 0.87** SOC 2.80 4.80 5.60 0.51* –0.46* 0.36 1.80 7.80 2.00 –0.99** –0.35 –0.46* *and ** – statistically significant at P < 0.05 and P < 0.01, respectively; CT – conventional tillage, RT – reduced tillage, WSAAD – air–dry WSA (n = 12), WSAFC – WSA at field capacity (n = 12), WSANS – WSA near full saturation (n = 12), SOC – soil organic carbon (n = 3)

The content of WSA in Retisol was significantly higher than in Cambisol at all water contents at soil freezing. Soil organic carbon content acted as a direct factor for three water contents at soil freezing in the 0–10 cm depth of Cambisol and Retisol.

3.3. Paper III: Effect of root network on soil macropores in Retisol

The research aimed to quantify the effect of root parameters on soil macropores in Retisol. The results of correlation analyses comparing the volumes of different pores and root parameters for different land uses and soil depths of Retisol are shown in Table 3.

27 Table 3. Correlation matrix among volumes of different-sized macropores and root parameters for different land uses and soil depths in Retisol Range Correlation matrix mean Properties very macro- root from to coarse medium fine root fine porosity volume diameter Coarse (%) 0.00 1.41 1.00 Medium (%) 0.47 3.02 0.47* 1.00 Fine (%) 0.47 2.56 –0.30 0.38 1.00 Very fine (%) 0.17 1.19 –0.71* –0.63** 0.34 1.00 Macroporosity 1.91 6.45 0.36 0.89** 0.71** –0.29 1.00 (%) Mean root 0.23 0.72 –0.34 –0.26 0.10 0.18 –0.17 1.00 diameter (mm) Root 0.51 9.83 –0.56* –0.16 0.61** 0.68** 0.14 0.67** 1.00 volume (cm3) Root length density 84.6 1517.3 –0.49* –0.43 0.35 0.91** –0.10 0.21 0.75** (km m-3) * and ** – statistically significant at P < 0.05 and P < 0.01, respectively

The grassland had the greatest root volume (9.83 cm3), while the conventional tillage had the lowest (0.51 cm3) one. Root volume increased the volume of very fine macroporosity in all land uses, within the entire 0–20 cm depth of the soil.

3.4. Paper IV: Effect of environmental factors and root volume on CO2 efflux

The objective of this investigation was to establish the effect of soil temperature, volumetric water content and root volume on soil CO2 efflux in different land uses of Cambisol and Retisol. Average values of CO2 efflux, soil temperature, volumetric water content and root volume are presented in Table 4.

Table 4. The influence of land use on soil CO2 efflux, soil temperature (T-soil), volumetric water content (VWC) at the 5 cm depth averaged across dates of measurement and root volume in the 0–10 cm depth

CO2 efflux T-soil VWC Root volume Land use μmol m-2 s-1 °C % cm3 Cambisol Retisol Cambisol Retisol Cambisol Retisol Cambisol Retisol Conventional tillage 1.40 b 1.71 ab 27.6 a 24.2 a 12.2 b 18.8 a 0.89 b 1.08 b Grassland 2.64 a 1.97 a 21.6 b 20.3 b 22.5 a 25.6 a 4.85 a 5.54 a Forest 1.77 b 1.43 b 19.4 b 18.9 b 21.6 a 27.2 a 4.04 a 2.93 ab Average 1.94 1.70 22.8 21.1 18.7 23.9 3.26 3.18

Note. CO2 efflux, T-soil, VWC and root volume data followed by the same letters are not significantly different at P < 0.05.

The average soil CO2 efflux in Cambisol was 12% higher than in Retisol. In the conventional tillage treatments, the highest soil temperature (27.6°C) was recorded in Cambisol,

28 while the lowest soil temperature (18.9°C) was determined in Retisol. The volumetric water content in Retisol was profoundly higher than that in Cambisol. The greatest root volume (5.54 cm3) was found in grassland in Retisol, while the lowest root volume (0.89 cm3) was determined in the conventional tillage treatments in Cambisol. Soil temperature (R2 = 0.58 (valid for soil temperature from 13.6°C to 27.3°C), P < 0.05) and volumetric water content (R2 = 0.63 (valid for volumetric water content from 6.3% to 39.8%), P < 0.05) were the main factors limiting the rate of CO2 efflux from the soil (Fig. 2).

3.0 3.0 y = -0.02x2 + 0.88x - 7.32 y = -0.01x2 + 0.20x + 0.17 R2 = 0.58 R² = 0.63

2.5 2.5

)

-1

)

-1

s

-2 s

-2 2.0 2.0

1.5 1.5

1.0 1.0

efflux (µmol m

2

efflux (µmol m

2 CO CO 0.5 0.5

0.0 0.0 10 15 20 25 30 0 10 20 30 40 50 a) Soil temperature (oC) Volumetric water content (%) b)

Figure 2. The relationships between: CO2 efflux and soil temperature at the 5 cm depth (a); CO2 efflux and volumetric water content at the 5 cm depth (b) under different land uses and types of soil

2 Root volume had a positive effect on soil CO2 efflux (R = 0.58 (valid for root volume from 0.89 to 5.54 cm3), P < 0.05, Fig. 3).

4.0 y = 0.33x + 0.83 3.5 R2 = 0.58

) 3.0

-1 s -2 2.5

2.0

1.5 efflux (µmol m

2 1.0

CO 0.5

0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 3 Root volume (cm )

Figure 3. The relationship between soil CO2 efflux and root volume at the 0–10 cm depth under different land uses and types of soil

29 CONCLUSIONS

1. Topsoil CO2 effluxes under contrasting vegetation cover, land use and management conditions in Cambisol and Retisol were directly related to soil temperature and

volumetric water content. Dry and hot weather conditions increased CO2 emissions from

the soil. With increasing soil volumetric water content, soil CO2 efflux increased. However, when the volumetric water content was higher than 20%, the relationship was

negative. A soil temperature of up to 25°C increased CO2 emission, while with further

soil temperature increase, CO2 efflux in Cambisol and Retisol decreased. 2. Average volume of macropores in Retisol was 9% higher than in Cambisol. The volume

of macropores increased soil CO2 efflux. The soil pore network was a dominant factor

enhancing CO2 under different soil types and land uses. 3. Plant roots were concentrated in the 0–10 cm soil layer in the arable land under conventional tillage, grassland and forest and their volume was higher than in the 10–20 cm soil layer. Roots increased the volume of very fine macropores within the entire 0–20 cm soil layer in all land uses. The decreases in the root volume and the root length density were dependent on land use in the following order: grassland > forest > arable land under conventional tillage. 4. The response of soil water-stable aggregates (WSA) to freezing-thawing processes depended on many factors, including soil texture, soil organic carbon content and water content during freezing process and agronomic practices. In Cambisol and Retisol, soil organic carbon content had a positive direct effect on the formation of WSA. The potential of Retisol to increase the content of water-stable aggregates within the whole 0–40 cm soil layer was found to be higher than that of Cambisol. The content of WSA, averaged across soil types, land uses and soil layers, tended to decrease in the following

order: WSAAD – air-dry soil > WSAFC – soil with water content at field capacity >

WSANS – soil near full saturation.

30 LIST OF PUBLICATIONS

Articles in journals with an impact factor in Clarivate Analytics Web of Science database: I. Kochiieru M., Lamorski K., Feiza V., Feizienė D., Volungevičius J. 2018. The effect of

soil macroporosity, temperature and water content on CO2 efflux in the soils of different genesis and land management. Zemdirbyste-Agriculture, 105 (4): 291–298. IF – 1.02 (doi:10.13080/z-a.2018.105.037) II. Kochiieru M., Feiziene D., Feiza V., Volungevicius J., Velykis A., Slepetiene A., Deveikyte I., Seibutis V. 2020. Freezing-thawing impact on aggregate stability as affected by land management, soil genesis and soil chemical and physical quality. Soil and Tillage Research, 203: 1–11. IF – 4.601 (doi.org/10.1016/j.still.2020.104705) III. Kochiieru M., Lamorski K., Feiza V., Feizienė D., Volungevičius J. 2020. Quantification of the relationship between root parameters and soil macropore parameters under different land use systems in Retisol. International Agrophysics, 34 (3): 301–308. IF – 1.655 (doi.org/10.31545/intagr/123266) IV. Kochiieru M., Feiza V., Feizienė D., Volungevičius J., Deveikytė I., Seibutis V.,

Pranaitienė S. 2021. The effect of environmental factors and root system on CO2 efflux in different types of the soil and land uses. Zemdirbyste-Agriculture, 108 (1): 1–12. IF – 0.833. (doi:10.13080/z-a.2021.108.001)

Articles in popular periodical publications: 1. Feiza V., Volungevičius J., Feizienė D., Veršulienė A., Kochiieru M. 2017. Tvarus dirvožemių naudojimas skirtingose agroekosistemose. Ūkininko patarėjas. Specialus leidinys, 2017 m. birželis, p. 40.

Recommendations: 1. Feiza V., Feizienė D., Liaudanskienė I., Šlepetienė A., Deveikytė I., Pranaitienė S., Gaurilčikaitė R., Amalevičiūtė-Volunge K., Veršulienė (Putramentaitė) A., Jokubauskaitė I., Bunevičiutė L., Kochiieru M., Boguzas V., Marcinkevičienė A., Aleinikovienė J., Butkevičienė L., Sinkevičienė A., Vaisvalavičius R., Steponavičienė V., Volungevičius J., Ambrazaitienė D., Karčauskienė D., Skuodienė R., Velykis A., Satkus A., 2019. Tvarus skirtingos genezės dirvožemių naudojimas / Sustainable use of soils of different genesis. Naujausios rekomendacijos žemės ir miškų ūkiui / Recent recommendations for

31 agriculture and forestry. Lietuvos agrarinių ir miškų mokslų centras / Lithuanian Research Centre for Agriculture and Forestry. Akademija, Kėdainių r. p. 4–8.

Conference proceedings: 1. Volungevičius J., Amalevičiūtė K., Vaisvalavičius R., Veršulienė A., Feizienė D., Feiza V., Šlepetienė A., Kochiieru M. 2017. Transformation of Retisols properties in the Lithuania due to agrogenization. 2nd International symposium of . Abstracts book. Zabrze, Poland, p. 35–36.

2. Kochiieru M., Feiza V., Volungevičius J., Feizienė D. 2018. CO2 efflux from the soil as influenced by the contrasting vegetation cover and management conditions in Cambisol. 3rd International symposium of soil physics. Abstracts book. Krakow, Poland, p. 22.

1. Kochiieru M., Feiza V., Feizienė D., Šlepetienė A., Volungevičius J. 2018. CO2 efflux from the soil as influenced by the contrasting vegetation cover and management conditions in Retisol. 26th NJF Congress: Agriculture for the Next 100 Years, Programme and summaries of presentations. Akademija, Kaunas, Lithuania, p. 84. 3. Feiza V., Feizienė D., Velykis A., Karčauskienė D., Volungevičius J., Satkus A., Kochiieru M. 2018. Capability of tillage practices for waterlogging risk reduction in two soil types of glacial genesis. 26th NJF Congress: Agriculture for the next 100 years. Programme and summaries of presentations. Akademija, Kaunas, Lithuania, p. 34. 4. Kochiieru M., Feiza V., Šlepetienė A., Velykis A., Volungevičius J. 2018. Stability of soil aggregates after freezing-thawing processes in Retisol and their relationship with organic carbon. International scientific conference AGROECO 2018. Programme and abstracts. Akademija, Kaunas, Lithuania, p. 22. 5. Feizienė D., Feiza V., Veršulienė A., Kochiieru M., Deveikytė I., Seibutis V., Volungevičius J., Janušauskaitė D. 2018. Consequence of long-term contrasting soil management: soil properties and wheat roots distribution. International scientific conference AGROECO 2018, Programme and abstracts. Akademija, Kaunas, Lithuania, p. 34. 6. Kochiieru M. 2018. The effect of humus content on water stability of soil aggregates after freezing-thawing processes in Cambisol. Conference of young scientists and PhD students Young Scientists for Advance in Agriculture. Abstracts book. Vilnius, Lithuania, p. 23. 7. Kochiieru M., Lamorski K., Feiza V., Feizienė D., Volungevičius J. 2019. The effect of macropore network on plant root length in Retisol of Western Lithuania. 4th International symposium of soil physics. Abstracts book. Lublin, Poland, p. 25.

32 8. Volungevičius J., Kochiieru M., Feiza V., Liaudanskienė I., Vaisvalavičius R., Amalevičiūtė-Volungė K., Šlepetienė A., Skridlaitė G., Žaludienė G. 2019. Some aspects of SEM application in the research of soil weathering and clay mineral formation. 4th International symposium of soil physics. Abstracts book. Lublin, Poland, p. 20–24. 9. Kochiieru M., Feiza V., Volungevičius J. 2019. The effect of soil temperature and water

content on CO2 efflux on arable land of Cambisol. “Young Scientists for Advance in Agriculture”. Abstracts book. Vilnius, Lithuania, p. 14.

33 ABOUT THE AUTHOR

Mykola Kochiieru was born on the 1st of July 1988 in Vinnitsa, Ukraine. In 2006, he finished school No. 1 in Kherson city and entered the Kherson State Agricultural University, Ukraine. In 2010, he graduated with a bachelor’s degree and in 2011, a master’s degree in Civil and Construction Engineering. From 2011 to 2012 he served in the Ukrainian Army. From 2012 to August 2016 he was working as an engineer of the 2nd category at Architectural and Construction Department of Public Joint Stock Company “Ukrainian Institute for Design of Refining and Petrochemical Plants “Ukrnaftokhimproect”. During 2016–2020, he did PhD studies at Lithuanian Research Centre for Agriculture and Forestry. Since 2016 he has been employed as a junior researcher at the Department of Soil and Crop Management of Institute of Agriculture, LAMMC.

34 ACKNOWLEDGEMENTS

Undertaking this PhD was an exciting experience for me. This work would not have been accomplished without the co-operation and support by the community of the Institute of Agriculture of Lithuanian Research Centre for Agriculture and Forestry. I would like to say a huge thank to my supervisor Dr. Virginijus Feiza for all the support and encouragement he gave me in my research. Also, many thanks to Assoc. Prof. Dr. Jonas Volungevičius and Dr. Dalia Feizienė for assisting in developing the research ideas and methodology. Without guidance, discussions and constant feedback from them, this PhD would not have been achieved. My deep appreciation goes out to the researchers’ team and technical staff of the Department of Soil and Crop Management. I wholeheartedly thank a group of people without whom I would not have achieved the goals of the dissertation and the many experimental tasks I have undertaken. My personal thanks go to Dr. Bronislava Butkutė, Dr. Krzysztof Lamorski (Institute of Agrophysics, Polish Academy of Sciences), Dr. Alvyra Šlepetienė and Dr. Aleksandras Velykis. Many thanks to the Lithuanian and Polish Academies of Science for the opportunity to do internships and perform soil research by computed tomography at the Institute of Agrophysics, Poland. I would like to say a heartful thanks to my wife and son for their full support I received when working on my PhD.

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50 SANTRAUKA

ĮVADAS

Dirvožemis yra svarbus žemės ūkio veiklos pagrindas ir maisto medžiagų mitybos šaltinis. Dirvožemis yra daugiafunkcinio pedogenezės proceso pasekmė. Geografinis dirvožemio pasiskirstymas įvairuoja. Kadangi jį formuoja įvairūs aplinkos veiksniai, tad dirvožemio savybės taip pat įvairuoja (Jafari, Sarmadian, 2008). Dirvožemio derlingumas priklauso nuo jo tipo, klimato sąlygų ir antropogeninės veiklos. Vidutinio klimato zonos Vidurio Lietuvos lygumoje vyrauja rudžemiai, o vakarų Lietuvoje – balkšvažemiai (Galvonaitė et al., 2013). Preliminarūs skaičiavimai parodė, Lietuvos teritorijos 20,4 % sudaro balkšvažemiai, 21 % – išplautžemiai; rudžemiai (16,8 %), smėlžemiai (11,9 %) ir jauražemiai (6,7 %) yra paplitę miškuose, o šlynžemiai (8,6 %) ir durpžemiai (9,5 %) – žemumose (Staugaitis, Vaišvila, 2019). Dirvožemio struktūra ir augalo rūšis yra svarbūs veiksniai žemdirbystėje, siekiant didinti dirvožemio derlingumą (Blanco-Canqui, Lal, 2007; Schlüter et al., 2011). Dirvožemio struktūrą lemia įvairiapusiai procesai, todėl labai sudėtinga iš jų visumos išskirti vieną. Netinkamas žemės dirbimas yra vienas dažniausiai minimų dirvožemio struktūrą bloginančių ir organinės medžiagos kiekį mažinančių veiksnių (Bronic, Lal, 2005, Lopez- Garrido et al., 2012). Dirvožemio struktūros formavimui labai svarbi yra antropogeninė veikla. Agronomine bei aplinkosaugine prasme taip pat yra svarbi ir augalų geba lemti dirvožemio struktūrą. Atžvelgiant į tai, dirvožemio struktūros tyrimai buvo vykdomi dirbamoje dirvoje (tradicinis ir supaprastintas žemės dirbimas), taip pat natūraliose gamtinės aplinkos fonuose – miško bei žolynų dirvožemiuose. Sąvoka „dirvožemio kokybė“ apima ir dirvožemio organinę medžiagą, kuri turi didelę reikšmę pagrindinėms dirvožemio funkcijoms. Dirvožemio kokybė tiesiogiai lemia augalų augimą, jų aprūpinimą vandeniu bei maisto medžiagomis ir dirvožemio kvėpavimą. Dirvožemio derlingumą apibūdina jo granuliometrinė sudėtis, šilumos režimas, drėgmė ir augalų aprūpinimas maisto elementais (Feiziene et al., 2008 a; Feizienė et al., 2008 b), organinės medžiagos kiekis ir taikomos žemės dirbimo technologijos (Brevik et al., 2015). Sąveika tarp dirvožemio, oro ir vandens atlieka gyvybiškai svarbias funkcijas: augina maistą ir kitą biomasę, saugo, transformuoja bei filtruoja įvairias chemines medžiagas (Toth et al., 2007; Montanarella, Panagos, 2015). Organinės medžiagos kiekis didėja didėjant vidutiniam metiniam kritulių ir fizinio molio, augalinių liekanų bei augalinės dangos kiekiams, bet mažėja

51 intensyvinant žemės dirbimą (Majumder et al., 2007; Slepetiene et al., 2013). Taigi, dirvožemio organinė medžiaga yra svarbi sudedamoji žemdirbystės strategijos dalis. Lietuvos klimato sąlygomis vyksta drėgmės garavimas, iškrinta nemažas metinis kiekis kritulių, dirvožemyje vyksta įšalimo ir atitirpimo procesai. Įšalimo ir atitirpimo procesas turi didelę įtaką dirvožemio struktūrai – vandenyje patvarių agregatų (grumstelių) armenyje (0– 25 cm sluoksnyje) ir podirvyje (25–40 cm sluoksnyje) susidarymui. Drėgmės kiekis (orasausis, drėgmė, artima lauko drėgmės kiekiui, ir dirvožemis, pilnai prisotintas vandeniu) yra itin svarbus dirvožemio įšalimo veiksnys (žr. II publikaciją). Organinės medžiagos kiekis yra lemiamas dirvožemio agregatų susidarymo veiksnys (Alagoz, Yilmaz, 2009; žr. II publikaciją). Pažymėtina, jog vandenyje patvarūs agregatai yra atsparesni įšalimo ir atitirpimo procesui (žr. II publikaciją).

Kiekybinis CO2 emisijos nustatymas yra svarbus veikslnys, siekinat įvertinti anglies dinamiką įvairiose ekosistemose. Tačiau CO2 emisija kasmet gali kisti, priklausomai nuo pokyčių aplinkoje, pavyzdžiui, augalams reikalingų maisto medžiagų pasiekiamumo, vandens kiekio ir oro temperatūros (Noh et al., 2010; žr. I publikaciją), makroporingumo (žr.

I publikaciją) ir šaknų tūrio (žr. IV publikaciją). Dirvožemio CO2 emisijai tiesioginės įtakos turi temperatūra. Temperatūros didėjimas didina ir CO2 išsiskyrimą iš dirvožemio (žr. I publikaciją), nors kiti veiksniai emisiją limituoja. Dirvožemio drėgmė turi komplikuotesnę ir sudėtingesnę įtaką (Luo et al., 2012; žr. IV publikaciją). Augalų šaknys turi įtakos makroporų susidarymui dirvožemyje (žr. III publikaciją) – didina vandens garavimą iš dirvožemio ir CO2 emisiją iš jo viršutinio (0–10 cm) sluoksnio (žr. IV publikaciją). Lietuvoje dirvožemio degradacija vyksta dėl intensyvios žemdirbystės ir aktyvios antropogeninės veiklos. Dirvožemio našumas ir derlingumas siejamas su organinės medžiagos kiekiu, dirvožemio fizikine bei agrochemine kokybe ir biologine įvairove (Jankauskas, 1996). Dirvožemyje vykstantys procesai yra lėti, bet gyvybiškai svarbūs (Blanco-Canqui, Lal, 2007; Galvonaitė et al., 2013; Palm et al., 2014). Jei į juos nebus atkreiptas dėmesys šiandien, ateityje dirvožemio degradacija (o ypač struktūra) kels kur kas daugiau problemų. Iki šiol trūko išsamių tyrimų apie ilgalaikių modernių žemdirbystės sistemų taikymo įtaką skirtingos granuliometrinės sudėties ir tipų dirvožemiuose, vertinant morfologinius pokyčius skirtinguose dirvožemio horizontuose, tiriant jo fizikines, chemines bei biofizikines savybes ir vienamečių (dirbamų dirvų bei pievų) bei daugiamečių sumedėjusių augalų šaknų vystymąsi. Tyrimų duomenys apie pedologinius pokyčius, vykstančius taikant ilgalaikes skirtingo intensyvumo žemės dirbimo sistemas ir įvairias žemėnaudas, turi svarbią praktinę reikšmę.

52 Tyrimo hipotezė

Dirvožemio CO2 emisija ir vandenyje patvarių agregatų kiekis yra indikatoriai, rodantys skirtingos morfologinės kilmės dirvožemių (rudžemių ir balkšvažemių) derlingumą, kurie turi jiems būdingas fizikines, chemines ir hidrofizikines savybes, taikant natūralią (pieva, miškas) ir antropogeninę (dirbama žemė) žemėnaudą ir skirtingo intensyvumo žemės dirbimą.

Tyrimo tikslas

Ištirti kontrastingų žemėnaudų ir žemės dirbimo būdų įtaką CO2 emisijai, vandenyje patvarių agregatų kiekiui skirtingose dirvožemio profilio genetiniuose horizontuose ir jų sąveiką su dirvožemio fizikinėmis bei cheminėmis ir augalų šaknų savybėmis skirtingos genezės dirvožemiuose.

Tyrimo uždaviniai 1. Nustatyti dirvožemio fizikines savybes rudžemio bei balkšvažemio armenyje ir podirvyje esant natūraliai ir antropogeninei žemėnaudai ir skirtingo intensyvumo žemės dirbimui.

2. Įvertinti CO2 emisiją iš rudžemio bei balkšvažemio viršutinio sluoksnio esant natūraliai ir antropogeninei žemėnaudai ir skirtingo intensyvumo žemės dirbimui.

3. Nustatyti rudžemio ir balkšvažemio chemines savybes esant natūraliai ir antropogeninei žemėnaudai ir skirtingo intensyvumo žemės dirbimui.

4. Ištirti vandenyje patvarių agregatų sudėties pokyčius vykstant įšalimo ir atitirpimo procesams rudžemyje bei balkšvažemyje esant natūraliai ir antropogeninei žemėnaudai ir skirtingo intensyvumo žemės dirbimui.

Disertacijos teiginiai: 1. Dirvožemio temperatūra, tūrinis vandens kiekis ir makroporingumas yra dominuojantys

veiksniai, lemiantys CO2 kiekį rudžemyje ir balkšvažemyje (žr. I ir IV publikacijas).

2. Organinė medžiaga yra vandenyje patvarių agregatų formavimąsi lemiantis veiksnys, priklausomai nuo jos buvimo gylio ir dirvožemio tipo (žr. II publikaciją).

3. Augalų šaknys didina mažųjų makroporų tūrį balkšvažemyje (žr. III publikaciją).

4. Anglies dioksido emisija atskleidžia šaknų aktyvumą rudžemyje ir balkšvažemyje (žr. IV publikaciją).

53

Darbo naujumas 1. Dirvožemio aplinka yra veikiama natūralios (pieva, miškas) ir kontrastingos antropogeninės (tradicinis bei supaprastintas žemės dirbimas) veiklos rudžemyje ir balkšvažemyje.

2. Tiriant CO2 emisiją rudžemyje ir balkšvažemyje buvo panaudotas naujos kartos dujų analizatorius.

3. Dirvožemio porų dydžio, jų išsidėstymo ir tūrinio vandens kiekio pasiskirstymas ir jų vizualizacija 3D formatu analizuota taikant kompiuterinę tomografiją.

4. Vandenyje patvarių agregatų pokyčiai skirtingo tipo dirvožemiuose buvo tirti užšalimo ir atšilimo metodu.

Darbo originalumas Kompleksiniai tyrimo rezultatai, gauti laboratorijose ir lauko eksperimentuose, suteikia naujų mokslo žinių apie fizikinių (drėgmės ir temperatūros), cheminių (pH, suminių P, K ir N, organinės C) dirvožemio savybių armenyje bei poarmeniniame sluoksnyje, nustatytų skirtingo tipo dirvožemiuose su įvairia žemėnauda bei žemės dirbimo intensyvumu, tarpusavio ryšius su

CO2 emisija, vandenyje patvarių agregatų kiekio kitimą veikiant įšalimo ir atitirpimo procesams dirvožemyje ir augalų šaknų vystymusi skirtingose ekosistemose.

Darbo praktinė reikšmė Gauti rezultatai sudaro galimybę įvertinti žemėnaudos, žemdirbystės sistemų ilgalaikį, tvarų naudojimą ir sukurti sąlygas gerinti dirvožemio savybes, augalų auginimo technologijas, pasiūlant žemės dirbimą, kuris laiduotų agroekosistemų tvarumą.

Disertacijos apimtis ir struktūra Daktaro disertacijos apimtis – 50 puslapių. Disertacija parašyta anglų kalba. Darbas remiasi 4 straipsniais, išspausdintais leidiniuose, referuojamuose ir turinčiuose citavimo indeksą duomenų bazėje Clarivate Analytics Web of Science. Disertaciją sudaro šie skyriai: Publikacijų sąrašas, kurių duomenimis remiasi disertacija, Įvadas, Literatūros apžvalga, Medžiagos ir Metodai, Rezultatai, Išvados, Padėka, Literatūros sąrašas (187 šaltiniai), Santrauka (lietuvių kalba) ir Priedas su 4 straipsnių kopijomis.

54 MEDŽIAGOS IR METODAI

Dirvožemiai ir tyrimų vietos (I–IV straipsniai) Šiame darbe tirti dirvožemio tipai klasifikuojami pagal WRB (2015) kaip giliau karbonatingas giliau glėjiškas rudžemis (priemolio, drenuotas), Akademija (55°23′38″ N, 23°51′35″ E), Kėdainių r. (Lietuvos agrarinių ir miškų mokslų centro Žemdirbystės institutas), Vidurio Lietuvos lyguma, ir kaip nepasotintasis balkšvažemis (priemolio, giliau glėjiškasis), Bijotai (55°31′12″ N, 22°36′55″ E), Šilalės r., kalvotas-banguotas reljefas, Vakarų Lietuva. Keturi žemėnaudos tipai buvo tirti rudžemyje: 1) tradicinis žemės dirbimas, 2) supaprastintas žemės dirbimas, 3) pieva ir 4) parkas (miškas). Keturi žemėnaudos tipai tirti balkšvažemyje: 1) tradicinis žemės dirbimas, 2) supaprastintas žemės dirbimas, 3) pieva ir 4) miškas.

Dirvožemio makroporų išsidėstymas (I, III straipsniai) Dirvožemio monolitai (dirvožemio cilindrai – skersmuo 46 mm, aukštis – 50 mm) buvo paimti iš kiekvieno varianto. Dirvožemio makroporų tyrimas laboratorijoje atliktas kompiuterinės tomografijos metodu Lenkijos mokslų akademijos Agrofizikos institute. Naudota programa DatosX 2.0 (GE Sensing & Inspection Technologies GmbH). Buvo gauti 16 bitų pilkos spalvos 3D vaizdai. Vaizdas buvo perduodamas į vaizdų analizatorius VG Studio Max 2.0 (Volume Graphics GmbH, Germany), Fiji (National Institutes of Health, USA) ir program Avizo 9 (Field Electron and Ion Company, USA). Vaizdo apdorojimui naudotas IsoData algoritmas (Ridler, Calvard, 1978). Po to nustatytos poros buvo pažymėtos. Bet kuri vokselio grupė, turinti sąryšį su kitu vokseliu, buvo žymima kaip individuali pora. Po to buvo nustatytas individualios poros tūris, jos paviršiaus plotas ir ekvivalentinis skersmuo.

Dirvožemio agrocheminių savybių tyrimas (II straipsnis) Dirvožemio pH nustatytas potenciometriniu metodu 1 M KCl. Dirvožemio organinės anglies kiekis nustatytas spektrofotometriu metodu, bangos ilgiui esant 590 nm, naudojant gliukozę kaip standartą po šlapio deginimo pagal Nikitiną (1999). Suminio azoto kiekis nustatytas Kjeldahl metodu. Suminio kalio kiekis nustatytas atominės absorbcijos spektrometrijos metodu, naudojant analizatorių (Perkin Elmer) po šlapio apdorojimo sieros rūgštimi. Suminis fosforo kiekis nustatytas spektrofotometriniu metodu, bangos ilgiui esant 430 nm, naudojant Cary 50 UV (Varian Inc., USA).

55 Dirvožemio CO2 emisijos tyrimai (I, IV straipsnis) -2 -1 Dirvožemio CO2 emisija (µmol m s ) matuota uždaro tipo gaubtu, naudojant aparatą LI–8100A (LI-COR Inc., USA). Trys dirvožemio žiedai buvo įterpti į atsitiktinę vietą visuose tyrimų laukeliuose. Dirvožemio CO2 emisija matuota 6 kartus per augalų vegetaciją 2017 ir 2018 m. tuo pačiu paros metu – nuo 10 iki 17 val.

Aplinkos veiksnių matavimai (I, IV straipsnis) Dirvožemio temperatūra (°C) ir dirvožemio drėgmės kiekis (% pagal tūrį) tirti tuo pačiu metu, kaip ir CO2 emisijos matavimas. Dirvožemio temperatūra ir dirvožemio drėgmė matuoti 5 cm gylyje nešiojamu aparatu HH2 WET (Delta-T Devices Ltd, England).

Vandenyje patvarių agregatų tyrimas po užšalimo ir atšilimo proceso (II straipsnis) Nesuardytos struktūros dirvožemio monolitai (5 cm skersmens) vandenyje patvarių agregatų tyrimui buvo paimti iš visų variantų dirvožemio 0–40 cm gylio. Nesuardytos struktūros ėminiai buvo tirti trijuose drėgmės lygiuose: 1) orasausis dirvožemis, 2) dirvožemis, sukaupęs lauko drėgmės vandens kiekį ir 3) dirvožemis, sukaupęs 90–95 % vandens kiekį nuo pilno vandens imlumo. Monolitai buvo šaldomi esant trims skirtingiems temperatūrų ciklams: –5 °C temperatūroje laikomi 48 h ir po to atitirpinami esant 5 °C 48 h. Laikotarpis nuo –5 °C iki 5 °C ir nuo 5 °C iki –5 °C truko 24 h. Atskiro užšalimo ir atitirpimo ciklo trukmė buvo 5 dienos. Šaldytuvas buvo nustatytas −5 °C lėtam užšalimui, kad dirvožemyje vanduo pasiskirstytų tolygiai. Vandenyje patvarūs agregatai užšalimo ir atitirpimo procese buvo panaudoti iš dirvožemio 0−10, 10−25 ir 25−40 cm sluoksnių, atlikus jų šlapią sijojimą (Eijkelkamp Agrisearch Equipment, the Netherlands). Keturių gramų (1−2 mm dydžio agregatai) orasausis dirvožemis buvo sijotas šlapiuoju būdu (sieto akučių skersmuo 0,25 mm) keturiais pakartojimais distiliuotame vandenyje. Agregatams suirus, jie dar buvo apdoroti 0,2 % NaOH, 24 h išdžiovinti termostate 105° C temperatūroje ir pasverti.

Šaknų tyrimai (III, IV straipsnis) Monolitai (10 × 10 × 10 cm) iš dirvožemio viršutinio (0–10 ir 10–20 cm) sluoksnio buvo paimti iš visų žemėnaudos variantų. Monolitų mėginiai paimti trimis pakartojimais augalų žydėjimo metu (BBCH 61–65) (Lapinskienė, 1993). Šaknų ilgis, tankumas ir vidutinis skersmuo nustatyti kompiuterine programa WinRhizo.

56 REZULTATAI I straipsnis:

Makroporingumo, temperatūros ir drėgmės kiekio įtaka CO2 emisijai Tyrimo tikslas buvo nustatyti makroporingumo, temperatūros ir drėgmės kiekio įtaką dirvožemio CO2 emisijai taikant skirtingas žemėnaudas rudžemyje ir balkšvažemyje. CO2 emisijos, temperatūros, tūrinio vandens ir makroporų kiekio vidutiniai duomenys pateikti 1 lentelėje.

1 lentelė. Skirtingos žemėnaudos įtaka CO2 emisijai, dirvožemio temperatūrai (T-dirv.) ir dirvožemio drėgmės kiekiui pagal tūrį (DKT) 5 cm sluoksnyje, išvedus vidurkį tarp matavimo datų ir makroporingumo dirvožemio 3–8 cm sluoksnyje

CO2 emisija T-dirv. DKT Makroporingumas Žemėnauda μmol m-2 s-1 °C % % RD JI RD JI RD JI RD JI Tradicinis žemės 0,68 c 1,44 ab 19,3 a 18,4 a 16,8 c 22,5 b 1,21 4,94 dirbimas Pieva 2,11 a 1,75 a 19,2 a 17,0 b 24,4 a 27,0 a 10,75 3,86 Miškas – 1,23 b – 15,0 c – 26,2 ab – 6,45 Parkas 1,13 b – 15,4 c – 20,2 b – 1,97 – Vidurkis 1,31 1,47 18,0 16,9 20,4 25,2 4,64 5,08

Pastaba. CO2 emisija, T-dirv. ir DKT, pažymėti ta pačia raide, reiškia, kad esminių skirtumų nėra esant P < 0,05 tikimybės lygiui; RD – rudžemis, JI – balkšvažemis.

Vidutinė dirvožemio CO2 emisija rudžemyje buvo 11 % mažesnė nei balkšvažemyje. Drėgmės kiekis pagal tūrį balkšvažemyje visuose variantuose buvo didesnis nei rudžemyje. Rudžemio pievoje makroporingumas buvo didesnis (10,75 %) nei žemę dirbant tradiciškai. Mažiausias makropoingumas rudžemyje buvo žemę dirbant tradiciškai – 1,21 %.

Dominuojantys veiksniai, didinantys dirvožemio CO2 emisiją, buvo drėgmės kiekis pagal tūrį (R2 = 0,53 (galioja nuo 16,8 iki 27,0 %), P < 0,05) ir makroporų tūris (R2 = 0,65 (galioja nuo 1,21 iki 10,75 %), P < 0,05) (1 paveikslas).

57

2.5 2.5 -1

2.0 s 2.0

-2 -2

-1

s -2 -2 1.5 1.5

1.0 y = 0,0943x - 0,7651 1.0

emisija µmol m y = 0,1167x + 0,8214 2 2 2 emisija µmol m R = 0,53

2 R = 0,65

0.5 CO 0.5 CO

0.0 0.0 15 17 19 21 23 25 27 29 0 2 4 6 8 10 12 Drėgmes kiekis pagal tūris % a) b) Makroporų tūris %

1 paveikslas. Ryšys tarp: CO2 emisijos ir drėgmės kiekio pagal tūrį 5 cm gylyje (a); CO2 emisijos ir makroporų tūrio 3–8 cm sluoksnyje (b) skirtingo tipo dirvožemiuose ir žemėnaudose

Vegetacijos laikotarpiu dirvožemio CO2 emisijos ir dirvožemio temperatūros 5 cm gylyje tarpusavio ryšys buvo silpnas (P > 0,05).

II straipsnis: Įšalimo ir atitirpimo įtaka vandenyje agregatų patvarumui dėl dirvožemio organinės anglies įtakos

Tyrimo tikslas buvo nustatyti įšalimo ir atitirpimo poveikį vandenyje patvarių agregatų susidarymui dėl dirvožemio organinės anglies įtakos 0–10, 10–25 bei 25–40 cm sluoksniuose esant skirtingam drėgmės bei organinės medžiagos kiekiui skirtingo tipo dirvožemiuose ir žemėnaudose. Vandenyje patvarių agregatų (VPA) tarpusavio sąveikos su drėgmės kiekiu dirvožemio užšalimo metu ir organinės anglies kiekiu rudžemyje bei balkšvažemyje vidutiniai duomenys pateikti 2 lentelėje.

2 lentelė. Dirvožemio kokybiniai rodikliai ir jų tarpusavio sąveika rudžemyje bei balkšvažemyje Rudžemis Balkšvažemis Rodiklis TD SD Miškas VPALD VPAOR VPAPVI TD SD Miškas VPALD VPAOR VPAPVI 0–10 cm sluoksnis

VPALD 22,25 41,34 80,24 29,67 77,81 95,58

VPAOR 14,45 39,92 97,53 1,00** 42,2 84,56 95,95 1,00**

VPAPVI 28,55 36,41 97,24 0,86** 0,87** 23,03 52,39 92,48 0,84** 0,83** DOA 12,20 12,10 37,80 0,94** 0,95** 0,88** 8,10 16,60 27,50 0,95** 0,92** 0,87** 10–25 cm sluoksnis

VPALD 24,40 30,56 53,46 30,27 84,18 77,72

VPAOR 10,66 33,34 80,31 0,98** 40,2 86,91 90,95 0,98**

VPAPVI 20,89 26,92 82,53 0,98** 0,97** 34,93 80,69 69,63 0,99** 0,95** DOA 13,00 10,70 11,30 –0,45* –0,56* –0,35 9,70 14,20 17,80 0,84** 0,93** 0,77*

58 Rudžemis Balkšvažemis Rodiklis TD SD Miškas VPALD VPAOR VPAPVI TD SD Miškas VPALD VPAOR VPAPVI 25–40 cm sluoksnis

VPALD 28,84 23,44 45,68 41,52 31,88 40,97

VPAOR 37,97 23,08 34,21 0,42* 39,06 44,77 76,75 0,32

VPAPVI 24,98 27,60 27,62 0,40* 0,06 22,59 20,31 53,36 0,44* 0,87** DOA 2,80 4,80 5,60 0,51* –0,46* 0,36 1,80 7,80 2,00 –0,99** –0,35 –0,46*

*ir ** – esminis esant P < 0,05 ir P < 0,01 tikimybės lygiui; VPAOR – orasausis dirvožemis (n = 12), VPALD – dirvožemis, sukaupęs lauko drėgmės vandens kiekį (n = 12), VPAPVI – dirvožemis, sukaupęs 90–95 % vandens kiekį nuo pilno vandens imlumo (n = 12), DOA – dirvožemio organinė anglis (n = 3); TD – tradicinis žemės dirbimas, SD – supaprastintas žemės dirbimas

VPA balkšvažemyje buvo esmingai didesnis nei rudžemyje visose drėgmės kiekio lygiuose bei užšalimo ir atitirpimo tyrimuose. Dirvožemio organinės anglies kiekis buvo tiesioginis veiksnys visose drėgmės kiekio lygiuose 0–10 cm sluoksnyje rudžemyje bei balkšvažemyje.

III straipsnis: Šaknų sistemos įtaka makroporingumui balkšvažemyje

Tyrimo tikslas buvo nustatyti šaknų rodiklių įtaką dirvožemio makroporingumui balkšvažemyje. Skirtingų tūrio porų makroporų ir šaknų rodiklių tarpusavio sąveika skirtingo tipo dirvožemiuose bei žemėnaudose ir dirvožemio gyliuose pateikta 3 lentelėje.

3 lentelė. Koreliacinė matrica tarp skirtingo tūrio porų, makroporų ir šaknų rodiklių skirtingose žemėnaudose balkšvažemyje Ribos Koreliacinė matrica vidutinis Savybės labai makro- šaknies nuo iki stambios vidutinės smulkios šaknies smulkios poringumas tūris skersmuo Stambus (%) 0,00 1,41 1,00 Vidutinis (%) 0,47 3,02 0,47* 1,00 Smulkios (%) 0,47 2,56 –0,30 0,38 1,00 Labai smulkios (%) 0,17 1,19 –0,71* –0,63** 0,34 1,00 Makro- 1,91 6,45 0,36 0,89** 0,71** –0,29 1,00 poringumas (%) Vidutinis šaknies 0,23 0,72 –0,34 –0,26 0,10 0,18 –0,17 1,00 skersmuo (mm) Šaknies tūris 0,51 9,83 –0,56* –0,16 0,61** 0,68** 0,14 0,67** 1,00 (cm3) Šaknies ilgio 84,6 1517,3 –0,49* –0,43 0,35 0,91** –0,10 0,21 0,75** tankis (km m-3) * ir ** – esminis esant P < 0,05 ir P < 0,01 tikimybės lygiui

59 Pievoje nustatytas didžiausias šaknų tūris (9,83 cm3), o tradiciškai dirbant žemę šaknų tūris buvo mažiausias – 0,51 cm3. Šaknų tūris didino labai smulkių porų tūrį visose žemėnaudose dirvožemio 0–20 cm sluoksnyje.

IV straipsnis:

Aplinkos veiksnių įtaka šaknų tūriui ir CO2 emisijai

Tyrimo tikslas buvo nustatyti dirvožemio temperatūros, tūrinio vandens kiekio ir šaknų tūrio įtaką dirvožemio CO2 emisijai skirtingose žemėnaudose rudžemyje ir balkšvažemyje. CO2 emisijos, temperatūros, tūrinio vandens kiekio ir šaknų tūrio vidutiniai duomenys pateikti 4 lentelėje.

4 lentelė. Skirtingos žemėnaudos įtaka CO2 emisijai, dirvožemio temperatūrai (T-dirv.) ir dirvožemio drėgmės kiekiui pagal tūrį (DKT) 5 cm sluoksnyje, išvedus vidurkį tarp matavimo datų bei šaknų tūrio dirvožemio 0–10 cm sluoksnyje skirtingose žemėnaudose rudžemyje ir balkšvažemyje

CO2 emisija T-dirv. DKT Šaknų tūris Žemėnauda μmol m-2 s-1 °C % cm3 RD JI RD JI RD JI RD JI Tradicinis žemės 1,40 b 1,71 ab 27,6 a 24,2 a 12,2 b 18,8 a 0,89 b 1,08 b dirbimas Pieva 2,64 a 1,97 a 21,6 b 20,3 b 22,5 a 25,6 a 4,85 a 5,54 a Miškas 1,77 b 1,43 b 19,4 b 18,9 b 21,6 a 27,2 a 4,04 a 2,93 ab Vidutiniškai 1,94 1,70 22,8 21,1 18,7 23,9 3,26 3,18 Pastaba. CO2 emisija, T-dirv., DKT ir šaknų tūris, pažymėti ta pačia raide, reiškia, kad esminių skirtumų nėra esant P < 0,05 tikimybės lygiui; RD – rudžemis, JI – balkšvažemis.

Vidutinė CO2 emisija rudžemyje buvo 12 % didesnė nei balkšvažemyje. Aukščiausia dirvožemio temperatūra (27,6° C) buvo žemę dirbant tradiciškai rudžemyje, mažiausia (18,9 °C) – miško balkšvažemyje. Dirvožemio drėgmės kiekis pagal tūrį visose tirtose žemėnaudose balkšvažemyje buvo didesnis nei rudžemyje. Šaknų tūris didžiausias (5,54 cm3) buvo pievoje balkšvažemyje, mažiausias nustatytas žemę dirbant tradiciškai rudžemyje.

Pagrindiniai veiksniai, mažinantys dirvožemio CO2 emisiją, buvo dirvožemio temperatūra (R2 = 0,58 (galioja nuo 13,6 iki 27,3 °C), P < 0,05) ir drėgmės kiekis pagal tūrį (R2 = 0,63 (galioja nuo 6,3 iki 39,8 %), P < 0,05) (2 paveikslas).

60 3.0 3.0 y = -0,02x2 + 0,88x - 7,32 y = -0,01x2 + 0,20x + 0,17 R2 = 0,58 R² = 0,63

2.5 ) 2.5

-1

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s

-1

-2 s

-2 2.0 2.0

1.5 1.5

1.0 (µmol m emisija 1.0

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emisija (µmol m emisija

2 CO

CO 0.5 0.5

0.0 0.0 10 15 20 25 30 0 10 20 30 40 50 a) Dirvožemio temperatūra (oC) b) Drėgmes kiekis pagal tūris (%)

2 paveikslas. Ryšys tarp CO2 emisijos ir dirvožemio temperatūros (a), CO2 emisijos ir tūrinio drėgmės kiekio (b) 5 cm gylyje taikant skirtingas žemėnaudas rudžemyje ir balkšvažemyje

2 Didėjant šaknų tūriui, dirvožemio CO2 emisija taip pat didėjo (R = 0,58 (galioja nuo 0,89 iki 5,54 cm3), P < 0,05) (3 paveikslas).

4.0 y = 0,33x + 0,83 3.5 R2 = 0,58

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-1 s -2 2.5

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µmol µmol m (

1.5 emisija emisija

2 1.0

CO 0.5

0.0 0 1 2 3 4 5 6 3 Šaknų tūris (cm )

3 paveikslas. Ryšys tarp CO2 emisijos ir šaknų tūrio dirvožemio 0–10 cm sluoksnyje taikant skirtingas žemėnaudas rudžemyje ir balkšvažemyje

61 IŠVADOS

1. CO2 emisija iš dirvožemio viršutinio sluoksnio esant skirtingai augalų dangai ir žemės dirbimo sistemai rudžemyje bei balkšvažemyje buvo tiesiogiai susijusi su temperatūra ir

tūriniu vandens kiekiu. Sausringos meteorologinės sąlygos didino CO2 emisiją iš

dirvožemio. Didėjant tūriniam vandens kiekiui CO2 emisija taip pat didėjo, bet kai vandens kiekis buvo didesnis nei 20 %, emisijos ir drėgmės tarpusavio ryšys buvo

neigiamas. Dirvos temperatūrai didėjant iki 25 °C, CO2 emisija didėjo, tačiau tolesnis jos kilimas mažino dirvožemio kvėpavimą ir rudžemyje, ir balkšvažemyje. 2. Vidutinis makroporų tūris balkšvažemyje buvo 9 % didesnis nei rudžemyje. Didėjant

makroporų tūriui dirvožemio CO2 emisija taip pat didėjo. Porų tūris buvo dominuojantis

veiksnys, didinantis dirvožemio CO2 emisiją skirtingo tipo dirvožemiuose ir žemėnaudose. 3. Augalų šaknys buvo sutelktos dirvožemio ariamajame 0–10 cm sluoksnyje žemę dirbant tradiciškai pievoje ir miške, o jų tūris buvo didesnis nei dirvožemio 10–20 cm sluoksnyje. Šaknys didino mažųjų makroporų tūrį skirtingose žemėnaudose visame dirvožemio 0–20 cm sluoksnyje. Šaknies tūrio ir šaknų ilgio tankio sumažėjimas nuo žemės naudojimo būdo priklausė tokia seka: pieva > miškas > tradicinis žemės dirbimas. 4. Dirvožemio vandenyje patvarių agregatų formavimasis dėl įšalimo ir atšilimo poroceso priklausė nuo daugelio veiksnių: dirvožemio granuliometrinės sudėties, organinės anglies kiekio, vandens kiekio jų įšalimo metu, žemėnaudos ir žemės dirbimo būdo. Rudžemyje ir balkšvažemyje dirvožemio organinės anglies kiekis turėjo tiesioginę teigiamą įtaką vandenyje patvarių agregatų formavimuisi. Didesnis vandenyje patvarių agregatų susiformavimo potencialas visame dirvožemio 0–40 cm sluoksnyje nustatytas balkšvažemyje, palyginus su rudžemiu. Vidutinis vandenyje patvarių agregatų kiekis tirtuose dirvožemio tipuose, žemėnaudose ir dirvožemių gyliuose mažėjo tokia seka: orasausis dirvožemis > dirvožemis, sukaupęs lauko drėgmės vandens kiekį > dirvožemis, sukaupęs 90–95 % vandens kiekį nuo pilno imlumo.

62 APIE AUTORIŲ

Mykola Kochiieru gimė 1988 m. liepos 1 d. Vinicoje, Ukrainoje. 2006 m. baigė Chersono mokyklą Nr. 1 ir įstojo į Chersono valstybinį žemės ūkio universitetą. 2010 m. jį baigė ir įgijo bakalauro ir civilinės bei konstrukcinės inžinerijos magistro laipsnį. 2011–2012 m. tarnavo Ukrainos karinėse pajėgose. Nuo 2012 iki 2016 m. dirbo antros kategorijos inžinieriumi UAB Ukrainos dizaino, rafinavimo ir lengvųjų degalų gamyklos instituto (Ukrnaftokhimproect) Architektūros bei konstrukcijos skyriuje. 2016–2020 m. studijavo Lietuvos agrarinių ir miškų mokslų centro (LAMMC) doktorantūroje. Nuo 2016 m. dirba jaunesniuoju mokslo darbuotoju LAMMC Žemdirbystės instituto Dirvožemio ir augalininkystės skyriuje.

63 PADĖKA

Doktorantūros studijos man buvo įdomi patirtis. Šis darbas būtų buvęs neįmanomas be Lietuvos agrarinių ir miškų mokslų centro Žemdirbystės instituto mokslo bendruomenės pagalbos ir bendradarbiavimo. Norėčiau padėkoti darbo vadovui dr. Virginijui Feizai už visokeriopą pagalbą ir skatinimą studijuoti doktorantūroje. Dėkoju konsultantui doc. dr. Jonui Volungevičiui (LAMMC ŽI Dirvožemio ir augalininkystės skyrius) ir LAMMC ŽI Augalų mitybos ir agroekologijos skyriaus vedėjai dr. Daliai Feizienei už vertingas idėjas, metodinius ir konkrečius praktinius patarimus. Be jų nuolatinės pagalbos, patarimų ir diskusijų šis darbas būtų buvęs neįmanomas. Esu dėkingas ir visiems Dirvožemio ir augalininkystės skyriaus mokslo darbuotojams bei techniniam personalui už bendradarbiavimą ir pagalbą. Esu dėkingas ir kitiems asmenims, su kuriais teko bendrauti rengiant disertaciją. Dėkoju dr. Bronislavai Butkutei, dr. Krzysztof Lamorski (Agrofizikos institutas, Lenkija), dr. Alvyrai Šlepetienei (LAMMC ŽI Cheminių tyrimų laboratorijos vedėjai) ir dr. Aleksandrui Velykiui (LAMMC Joniškėlio bandymų stoties vyresniajam mokslo darbuotojui). Esu dėkingas Lietuvos ir Lenkijos mokslų akademijoms už sudarytą galimybę stažuotis bei atlikti dirvožemio tyrimus kompiuterinės tomografijos metodu Agrofizikos institute Lenkijoje. Dėkoju savo žmonai ir sūnui už supratimą ir palaikymą per visą doktorantūros laikotarpį.

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APPENDIX

PAPER I I STRAIPSNIS

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PAPER II II STRAIPSNIS

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PAPER III III STRAIPSNIS

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84 PAPER IV IV STRAIPSNIS

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Mykola KOCHIIERU

THE EFFECT OF CROP COVER AND SOIL WATER RETENTION ON PHYSICO-CHEMICAL AND BIOPHYSICAL QUALITY OF SOILS OF DIFFERENT ORIGIN

Scientific Doctoral Dissertation

Language editors: Dangira Šidlauskienė (English) Daiva Puidokienė (Lithuanian)

Spausdino – Vytauto Didžiojo universitetas K. Donelaičio g. 58, LT-44248 Kaunas Užsakymo Nr. K 20-098. Tiražas 15 egz. 2020 10 12 Nemokamai.