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Physical indicators
Bulk density, water retention and transfer parameters and structural stability were chosen as basic physical soil characteristics and to study the effects of irrigation.
Soil bulk density (and porosity) varies according to soil texture, structure, and organic matter content, but within a given soil type, it can be used to monitor degree of soil compaction and puddling. Changes in bulk density affect other properties and processes that influence water and oxygen supply (Schoenholtz et al., 2000).
Water soil and transfer parameters are universally important for monitoring all soil functions. Available water holding capacity and saturated hydraulic conductivity are the two most frequently found in minimum data set (MDS) of physical soil quality indicators. Available water holding capacity measures the relative capacity of a soil to supply water and saturated hydraulic conductivity is both an indicator of drainage rate and water/air balance in soil (Schoenholtz et al., 2000).
Aggregate stability describes the ability of the soil to retain its arrangement of solid and void space when exposed to different stress (Kay, 1990). Structural stability of soil is an essential parameter, influencing many soil physical properties such as water filtration and water-air ratio, but also erodibility, biological activity and plant growth (Lynch and Bragg, 1985). Soil structure as such is not a plant-growth factor, but it influences practically all plant-growth factors: it determines the depth that roots can penetrate, the amount of water that can be stored in the soil (soil water distribution, movement and retention), availability of plant nutrients (nutrient recycling), aeration, movement of soil fauna and microbial activity (Hermawan and Cameron, 1993; Langemaack, 1999; Rampazzo et al., 1998; Pardo et al., 2000).
Stability characteristics are generally specific for a structural form and the type of stress being applied. A measure of aggregate stability could serve as a surrogate for soil structure, which is critical for development of root systems (Kay and Grant, 1996). To evaluate the impact of management practices on the soil environment it is necessary to quantify the modifications to the soil structure (Danielson and Sutherland, 1986). Since crop management systems generally have a strong influence on soil structural characteristics, aggregate stability is considered as a key indicator to assess soil structure (Six et al., 2000) and also soil quality (Albiach et al., 2001). The decline in soil structure is increasingly seen as a form of soil degradation (Chan et al., 2003) and it is often related to land use and soil/crop management practices.
Chemical indicators
Among chemical indicators for soil quality, soil reaction (pH) is obviously important in the case of liming. This basic factor is known to influence nutrient availability and microbiological activity.
Soil organic matter (SOM) is one of the most important parameter of soil quality for both scientists and farmers (Romig et al., 1995). Soil organic matter is a nutrient sink and source, enhances soil physical and chemical properties, and promotes biological activity (Doran and Parkin, 1994; Gregorich et al., 1994). The content of soil organic matter changes very slowly and many years are generally required to detect changes resulting from disturbance (Kandeler et al., 1993). It is well known that cultivation of the natural land resources induces SOM losses, which in turn directly affects the soil chemical, physical, and biological properties, and finally resulting in loss of crop production capacity (Stevenson and Cole, 1999). Soil organic carbon and total nitrogen are arguably the most significant single indicators of soil quality and productivity (Larson and Pierce, 1991; National Research Council, 1993; Cannell and Hawes, 1994).
Microbiological indicators
Soil organic matter (SOM) levels may vary within years, whilst active SOM-fractions like macro- and light fraction-organic matter, soil microbial biomass and microbial functions may change within shorter periods of time (Smith et al., 2000). Soil microorganisms have been shown to be potentially useful (early and sensitive) indicators of soil health, because they respond to soil management in time scales (month/years) that are relevant to land management (Torsvik et al., 1994; Hewitt and Sparling, 1998; Sparling and Schipper, 1999; Pankhurst et al., 1997; Kandeler et al., 1993). Soil microbiota, existing in extremely high density and diversity, rapidly modify the energetic performance and activity rates to changing environmental conditions (Schloter et al., 2003). Some biological measurements (such as enzymatic activities) are not useful measures of soil quality because they are too much affected by both seasonal and spatial variations (Nannipieri, 1994). National programs for monitoring soil quality are now generally based on microbial biomass and respiration measurements and are sometimes extended also to nitrogen mineralization, microbial diversity and functional groups of soil fauna (Bloem et al., 1998). One of the major difficulties in the use of soil organisms per se, or of soil processes mediated by soil organisms, as indicators of soil health has been methodological: what to measure, how and when to measure it, and how to interpret changes in term of soil function (Visser and Parkinson, 1992; Pankhurst et al., 1997; Kandeler et al., 1993; Sparling, 1997).
Despite their small volume in soil (<0.5 %), microorganisms represent a very important component of soil organic matter (Paul and Clark, 1996; Sylvia et al., 1999). Soil microorganisms are involved in many biochemical processes and particularly C turnover (Buckley and Schmidt, 2003). They have an important role in soil fertility (especially decomposition of organic matter and recycling nutrients for plants) and decontamination of soils, especially degradation or bioaccumulation of toxic residues (Soulas and Lors, 1999). They also form symbiotic associations with roots, facilitating nitrogen fixation or phosphate uptake. They act as antagonists to pathogens, influence the weathering and solubilization of minerals (Silver et al., 1996) and contribute to soil structural stability (Emerson et al., 1986). Thereby, soil microorganisms and biological activity also affect water holding capacity, infiltration rate, crusting, erodibility, and susceptibility to compaction (Elliot et al., 1996).
These services are not only essential to the functioning of natural ecosystems, but also constitute an important resource for sustainable agricultural systems. Thus soil quality (or soil health) evaluations need to focus not only on chemical (fertility) considerations, but on the dynamic soil conditions as well. This supposes to consider a combination of physical, biological and chemical characteristics, which are directly affected by recent and current land use decisions and practices. The soil microbial biomass can be defined as organisms living in soils that are generally smaller than approximately 10µm. Most attention is given to fungi and bacteria and they are generally dominating within the biomass. These two groups of microbes are the most important with reference to energy flow and nutrient transfer in terrestrial ecosystems (Richards, 1987). It has been suggested that the microbial biomass content is an integrative signal of the microbial significance in soils because it is one of the few fractions in soil organic matter that is biologically meaningful, sensitive to management or pollution and finally measurable (Jenkinson & Powlson, 1996; Powlson, 1997). However, it must be also realized that between different soil samples different biomass may occur without direct correlation to soil quality (Martens, 1995; Dilly and Munch, 1998). Although microbial biomass is generally acknowledged to represent only a very small proportion of total carbon in the soil (0.1–5%), it is characterised by its rapid turnover compared to the other components of organic matter (Chaussod et al., 1988).
Soil microbial respiration, measured through carbon dioxide production is a direct indicator of microbial activity and indirectly reflects the bio-availability of organic matter (Parkin et al., 1996; Gomez et al., 2001). Soil microbial activity leads to the liberation of nutrients available for plants but also to the mineralization or mobilization of pollutants and xenobiotics. Thus microbial activity is of crucial importance in biogeochemical cycling. Microbial activities are mostly regulated by nutritional conditions, temperature, water availability, pH and oxygen supply (Schloter et al., 2003).
Soil pathogens. Microbial pathogens are widespread in the natural environment and diffuse pathogen pollution is chronic in rural environments. Soils and sediments are identified as having a critical role as transport pathways and reservoirs of pathogenic organisms. Despite this, important gaps remain in our knowledge of pathogens interactions with physically and biogeochemically heterogeneous soils environments. In particular, nonlinear and dynamic drivers of soil pathogen interaction and pathogen transport are under-researched because soils are complex and subsurface environments difficult to study (Centre for Sustainable Water Management, 2007-2008).
Pathogens that have the potential to infect humans can be divided into the categories of bacteria, protozoans, and viruses. Difficulties and expenses involved in the testing for specific pathogens, however, have generally led to the use of indicator organisms of enteric origin to estimate the persistence and fate of enteric pathogens in the environment (Crane et al., 1981). Faecal coliforms (FC) are the most commonly used indicator organisms. Escherichia coli are the most common FC and although most E. coli strains are non-pathogenic, some strains, such as E. coli O157:H7, pose a serious health risk to humans. Infectious viruses found in water systems include Enterovirus, Rotavius, Hepatitis A, and Retrovirus (USEPA, 2001).
Soil quality index (SQI)
Assessment of complex soil quality and health requires a minimum data set of physical, chemical and biological parameters (Gregorich et al., 1994; Doran and Safely, 1997) which need to be aggregated to provide an overall index of soil quality (Burns et al., 2006). Comparison of individual indicators against reference sites is one way of assessing soil quality (Bucher, 2002; Carey et al., 2009; Nelson et al., 2009), but individual indicators are often interdependent or may show functional redundancy (Hunt and Wall, 2002), so combining them meaningfully into a single index may enhance the assessment (Bucher, 2002; Andrews et al., 2002). The values of the selected indicators need to be converted into scores before they are integrated into an index. This requires establishment of a functional relationship between the soil function in question and the indicators (Erkossa et al., 2007).
Agricultural practices and their impact on soil quality
Soil is under pressure and its quality is suspected to decrease. The European Commission (2002) recognized soil degradation in Europe as a serious problem which is driven by human activities such as inappropriate agricultural practices, urban and industrial sprawl, industrial activities, construction, and tourism. Alteration of soil characteristics by anthropogenic impact changes functional capacities of the soil. Agricultural technologies and current practices like monocropping, residue management, mineral fertilization, overuse of pesticides, heavy agricultural machinery, inadequate management practices of soil and irrigation, can significantly affect soil quality by changing physical, chemical, and biological properties (Fauci & Dick, 1994). Long-term human impact (e.g. sealing), as well as short-term soil management (e.g. irrigation) modifies material and energy flows. Erosion, a decline in organic matter content and biodiversity, contamination, sealing, compaction, salinization, and landslides were identified as the main soil threats (Andrews and Carroll, 2002; European Commission, 2002). Conventional horticultural cropping, due to continuous soil removal and intensive use of pesticides and fertilizers, is the main activity leading to deterioration of soil physical, chemical and biological properties (Albiach et al., 2000). These modifications result in transformation of the soil processes to smaller or greater extent. When these processes are traceable, controllable, soil-use and soil quality remains sustainable on the long run (Toth, 2008). It is important to be aware that soil is a finite and non-renewable resource, because regeneration of soil through chemical and biological weathering of underlying rock requires geological time (Huber et al., 2001).
In our study, some agricultural practices are involved in alteration of soil properties in different ways and levels. Preliminary mechanical interventions on soils such as terracing, land levelling and deep ploughing are the roughest and they change soil profiles from inherent to anthropogenic. These changes are leading to major landscape modifications and land degradation (Borselli et al., 2006). In addition, new management techniques with more intensive production are used after the abandonment of traditional practices (García-Ruiz et al., 1996; Zalidis et al., 2002). Heavy machines such as bulldozers are being used for large scale soil movements in order to create new terracing systems for vineyards and orchards. These movements are not always controlled by law or technical guidelines and are determined by the needs of the owner or the person on charge of the machinery. These works modify the soil surface characteristics, which influence the infiltration properties at the surface (Poesen et al., 1990; Léonard and Andrieux, 1998; Malet et al., 2003) and interact with other geomorphologic processes such as erosion (Lundekvam et al., 2003) and mass movements, mainly during extreme precipitation events (Abreu, 2005). The spatial variability created by all these operations leads to heterogeneous infiltration and runoff responses on hill-slopes. The soil redistribution also modifies the soil slope stability and the stability of the terraces, increasing the risk of surface mass movements. Some studies have pointed out the spatial variability of soil properties along hill-slopes (Agbenin and Tiessen, 1995; Bartoli et al., 1995) and with the slope degree (Janeau et al., 2003).
Irrigation
Irrigation is one of the most common agricultural practices in orchards and its positive effect on crop production is well known. The benefits of irrigation may include: better and improved crop (apple) quality, earlier crop production, greater yields, efficient nutrient distribution, less plant stress and reduced yield variability (Cetin et al., 2004). Although irrigated agriculture has some benefits such as yield increase (Bilgehan, 1998), it brings about some problems such as increased drainage rates, salinisation-alkalinization and degradation of soil structure (Çullu et al., 2002). Irrigation is directly linked with soil water conditions what could potentially affect soil structure and thus soil water-air ratio, plant nutrition, soil microbial biomass and activity. Inappropriate production technologies have resulted in soil quality deterioration, leading to soil organic matter losses and structure degradation, affecting water, air and nutrient flows, and consequently plant growth (Golchin et al., 1995). Other externalities such as crusting, runoff, surface- and groundwater pollution and increased CO2 emissions are also influenced by irrigation. Species biodiversity can also be affected by management practices: generally high-input agricultural practices decrease biodiversity (Munyanziza et al., 1997; Lupwayi et al., 2001). The effects of freshwater irrigation on soil are primarily physical, including increased drainage and nutrient transport. Wastewater irrigation can have more significant chemical and biological effects on soil properties. Among the potential risks associated with irrigation with waste treated water is degradation of soil structure, e.g. aggregate stability deterioration, a decrease in soil hydraulic conductivity, surface sealing, runoff and soil erosion problems, soil compaction, and a decrease in soil aeration (Bhardwaj et al., 2007). In addition to the impact of irrigation heterogeneity on the distribution of percolation in the field, it is often believed that intensive irrigation leads to rapid movement of nitrate below the root zone (Endelman et al., 1974) since nitrate is carried down through the profile with the percolating water.
It can be concluded that, depending on various parameters such as water quality, soil, agricultural techniques, fertilization and other chemical treatments, crop and climate, irrigation may sometimes severely damage the soil (Miller and Donahue, 1995; Tedeschi and Dell’Aquilla, 2005). The initial increase in crop yields becomes unsustainable, and in some circumstances severe chemical, physical, and biological fertility problems appear (Sun et al., 2003), which can eventually compromise the agricultural activity itself (Porta et al., 1994). The question is whether irrigation is capable of continuing the high level of agricultural production in the longer term without damaging the environment (Pereira et al., 1996). There are several examples of large areas in the world that formerly were very productive and now are almost abandoned (Nunes et al., 2007).
The primary sustainability goal for soil is the maintenance of productivity. Irrigation should be managed so that it has minimal adverse effects on the quality of the soil. This will ensure that the soil is healthy and remains productive in years to come. Proper management of irrigation water and wastewater as fertiliser can result in enhanced productivity. By using the correct indicators of soil productivity, the effects of irrigation can be gauged, and thus optimised. Soil productivity is affected directly and indirectly by the type of crop, management practices and soil quality, which in turn is affected by moisture, pH, organic matter, heavy metal content etc. Many of these soil characteristics are interdependent – changes in one characteristic result in changes in another. This means that monitoring a subset should highlight any changes in soil productivity. The effect of some agricultural practices such as irrigation on soil structure will depend both on the soil natural properties (particle-size distribution, organic matter content, etc.) and the intensity of agricultural practices (Virto et al., 2005).
Irrigation with wastewater raises, however, sanitary problems: risk of viral and bacterial infection both for farmers and crops as well as other problems due to the presence of toxic substances. Many studies have been conducted to point out the effects of the biological depuration process on the microbiological quality of these waters and on crop pollution by pathogens (Wolter and Kandiah, 1997).
It is very important to estimate the benefit of irrigation, based on appropriate soil analysis, before building an irrigation system, so as to be able to monitor the effects of irrigation on soil properties, as long as irrigation is used. For adequate water management, the proper use of these irrigation systems is important as well to avoid soil degradation and water contamination. The irrigation water should be regularly monitored chemically and biologically. The sanitary aspect of irrigation water in food safety should not be underestimated: there might be a possibility of crop pollution via irrigating water. Recent environmental investigations indicated pollution of surface or underground irrigation water with several faecal pathogens, which can also contaminate the apple harvest and have potential effects on public health. To analyse irrigation water quality on presence of pesticide, metals, salts or even pathogens, is rather an exception than a rule in Slovenia. It also has to be kept in mind that improper irrigation can cause severe damages to the environment (Miller and Donahue, 1995; Tedeschi and Dell’Aquilla, 2005).
In general, irrigation systems in Slovenia are technically more or less well prepared (Slovenian Irrigation Project, 1998), but not enough attention is devoted to soil conditions (before, during and after irrigation). Fruit or vegetable producers should not only focus on yields (here the benefit of irrigation is already well known), but also be aware of the irrigation consequences in soil conditions. In northern-east Slovenia, many orchards lay on hilly terrains, so technical specificity on different slopes and possibility of erosion should be take into consideration. Under the same weather conditions and very heterogeneous parent material, different soils will not react in the same way, either chemically or physically. According to specific physical, chemical and biological properties of each soil type, irrigation can have many advantages and also disadvantages. So far, in Slovenia there is still no serious study on irrigation effects on soil properties, especially soil microflora and soil structure.
Organic amendments
Application of organic fertilizers is linked to soil organic carbon and nitrogen pools, which consequently change microbial parameters and plant nutrition.
Maintenance of soil organic matter is important for the long-term productivity of agroecosystems. Soil application of organic amendments is a management strategy to counteract the progressive loss of organic matter (Marinari et al., 2000; Tejada et al., 2008). The addition of organic amendments may improve soil physico-chemical, biochemical and microbiological properties involved in biogeochemical cycles and thus positively influences plant productivity parameters. The organic amendments are a source of slow-releasing nutrients and available energy for soil microorganisms (Gomez et al., 2006). Among the main benefits attributed to the use of organic amendments are an improved soil aggregation and reduced bulk density, a greater water holding capacity, stabilization of pH, an increased CEC (Sasal et al., 2000; Tejada et al., 2008). Less nutrient potential loss and particularly a reduction in the loss of nitrate are also quoted as positive effects of organic farming. As this could also promote plant health, it seems possible to obtain equivalent or even higher yields in organic production than with conventional farming (Bulluck et al., 2002; Courtney and Mullen, 2008).
Swiss researchers (Fließbach et al., 2007) concluded that organic farming with composted manure is the only agricultural practice that limits the decrease of carbon content in the soil. They show that organic farming is the best agricultural practice for sustainable land management, in particular through the enhancement of soil microbial activity, leading to increased mineral exchange between plants and soil. The use of amendments has been reported previously to increase soil organic matter, provide nutrients and improve microbial activity (Lee et al., 2004). The results are conditioned by the composition of amendments, the rate of application and the soil type (Albiach et al., 2001; Tejada and Gonzalez, 2003). Furthermore, as soils are the basis of food production, preserving their quality with manure and low chemical use is essential for sustainable land management, even if these farming systems are not the most productive.
Less understood, however, are the effects of organic amendments on soil food webs, which contain the biotic assemblages responsible for decomposition and generation of soluble nutrients for plant uptake. Soil food webs also contain parasitic organisms, such as plant-parasitic nematodes, whose densities are influenced by the presence of host plants, the soil environment, and regulation by predators and pathogens (all factors that are potentially influenced by organic amendments). Maximizing the efficacy of organic amendments towards improving soil health requires an understanding of how this practice affects the entire soil food web (beneficial and pathogenic/parasitic components), and how these effects are mitigated by other agricultural practices, such as tillage. However, tillage can also be used to incorporate amendments into the soil, and therefore should expand their effect into deeper soil layers (Treonis et al., 2010).
Organic fruit production in Slovenia has steadily increased in recent years due to the excellent returns for growers. In 2011, almost 3 % of Slovene farmers were registered as organic producers. Slovenia still has convenient natural conditions for organic farming; so small farmers in this trend see a good or even the only solution for surviving (mostly in combination with so called “eco-tourism”). Organic farming in Slovenia is a part of Agro-environmental programme. Slovenian farmers are supported by The Institute for Sustainable Development, they are well organised in their own union and they have their own trademark (« Biodar »).
Offer of organic products in Slovenia still does not follow the demand, consequently resulting in prices which are 20-40 % higher, on average, compared with conventional agricultural products. Organic products are mostly sold on special organic markets or on farms, as a part of tourist offer. Most people see organic food as something pure and healthy, but there is also another point of view, which is less known: some consumers have doubts concerning about food safety in organic production, because soils which have received material (like organic fertilisers and irrigation water, as in our case), can be potential pathogen sources. This view of food safety linked with organic production is very interesting and requires further studies, because it can also help people to be acquainted with healthy nourishment.
Liming
Liming is a traditional agricultural practice to counteract soil acidification and improving calcium and magnesium supply, with effects on crops and soil quality (including physical and biological aspects). In spite of the extended lime application, the investigation of liming effects on organic matter remained restricted to C content, mass ratio of carbon to nitrogen (C/N ratio) and carbon storage (Derome et al., 1986; Persson et al., 1995). The following observations gave rise to the expectation that liming may also influence the chemical composition of soil organic matter (SOM). The C/N ratio of the organic surface layer material usually decrease (Belkacem and Nys, 1995; Marschner and Wilczynski, 1991) after lime application. Tree growth may be inhibited (Derome et al., 1986) by liming, presumably as a consequence of the growth stimulation of ground (weeds) vegetation (Rodenkirchen, 1998). The soil fauna populations are usually influenced by liming and, in general, resemble that of nutrient-rich soils (Persson, 1988). Soil microbial biomass (Smolander and Mälkönen, 1994; Badalucco et al., 1992), microbial activity (Anderson, 1998) and the potential for nitrification and nitrate leaching (Neale et al., 1997; De Boer et al., 1993) may increase after liming. Root growth in the organic layer may be stimulated (Raspe and Haug, 1998) or inhibited (Helmisaari and Hallbäcken, 1999) by liming.
Table of contents :
General introduction
Chapter 1: Literature review
I. Definition of soil quality and soil health
II. Indicators of soil quality and soil health
II.1 Physical indicators
II.2 Chemical indicators
II.3 Microbiological indicators
II.4 Soil quality index (SQI)
III. Agricultural practices and their impact on soil quality
III.1 Irrigation
III.2 Organic amendments
III.3 Liming
IV. Research aims
Chapter 2: Materials and methods
I.Study sites
I.1 General presentation
I.1.1 Geology
I.1.2 Climate
I.2 Detailed presentation of studied sites
I.2.1 Location Gačnik
I.2.1.1 Soils
I.2.1.2 Application of treatments
Irrigation
Fertilising and mulching
Application of pesticides
I.2.2 Location Pohorski dvor
I.2.2.1 Soils
I.2.2.2 Application of treatments
Organic fertilising
Liming
Application of pesticides
Mechanical applications
I.2.3 Pohorski dvor and Gačnik: similarities and differences
II. Methods
II.1 Soil and water sampling
II.1.1 Location Gačnik
II.1.2 Location Pohorski dvor
II.2 Soil and water regime characterization
II.2.1 Soil characterization
II.2.2 Water regime characterization
II.2.2.1 Water retention curves
II.2.2.2 Tensiometers
II.3 Analytical methods for soils and water characterization
II.3.1 Chemical methods
II.3.1.1 Analytical methods for determining C, N and δ13C in each size fraction
II.3.2 Analytical methods of physical soil properties characterization
II.3.2.1 Bulk density (γb)
II.3.2.2 Gravimetric water content (W)
II.3.2.3 Clods porosity
II.3.2.4 Structural stability
II.3.2.5 Organic matter grain size fractionation
II.3.3 Analytical methods of microbiological soil and water properties
II.3.3.1 Soil microbial biomass
II.3.3.2 Labile organic matter pool
II.3.3.3 Carbon mineralization (respiration of soil microbes)
II.3.3.4 Enumeration of bacteria and fungi present in soil and water samples
II.3.3.5 Detection of enteroviruses in soils and water
Isolation of enteroviruses in water
Isolation of enteroviruses in soil
II.3.3.6 Qualitative analysis of HEV and Rotavirus with dotblot assay
II.4 Statistical analysis
Chapter 3: Results in Gačnik
I. Soil morphology
I.1 Soil profiles
I.1.1 Upslope soil profile
I.1.2 Downslope soil profile
I.1.3 Comparison of soils from different water regime and slope positions
II. Soil water regime and quality of irrigation water
II.1 Water retention curves
II.2 Soil water regime in 2004 and 2005
II.2.1 Evolution of soil water potential along 2004 summer
II.2.2 Evolution of soil water potential along 2005 summer
II.2.3 Comparison summers 2004 and 2005
II.3 Quality of irrigation water
III. Physico-chemical soil characteristics
II.1 General soil characteristics
III.1.1 Results
III.1.2 Discussion
II.2 Spatial distribution of organic carbon and calcium carbonate
II.2.1 Distribution of Corg and CaCO3 through soil profile
II.2.2 Distribution of Corg and CaCO3 along the slope in the soil surface
II.2.3 Discussion
IV. Pore space characterization
IV.1 Downslope position
IV.1.1 Bulk density
IV.1.2 Clods void ratio
IV.2 Variations along the slope
IV.3 Discussion
V. Organic matter characterization and origin
V. 1 Characterization of the grain size fractions
V.1.1 Grain size fractions abundance
V.1.2 Total carbonates content
V.1.3 Organic carbon content
V.1.4 C/N ratio
V.1.5 Isotopic signature of organic carbon: δ13C
V.2 Discussion
VI. Microbiological soil characteristics
VI.1 Soil physico-chemical characteristics and wetness at the sampling periods
VI.1.1 Organic carbon and nitrogen, C/N and exch. Cu
VI.1.2 Gravimetric water content
VI.2 Spatio-temporal variation of the biological parameters
VI.2.1 May 2004
VI.2.2 September 2004
VI.2.3 May 2005
VI.2.4 September 2005
VI.3 Discussion
VII. Structural stability of soil aggregates
VII.1 Variations of structural stability according to seasons
VII.1.1 October 2004
VII.1.2 May 2005
VII.2 Discussion
VIII. Discussion and conclusions – Gačnik site
Chapter 4: Results in Pohorski Dvor
I. Soil morphology
II. Physico-chemical soil characteristics
II.1 General soil characteristics
II.1.1 Comparison among blocks
II.1.2 Comparison between treatments
II.2 Soil pH evolution according treatment and year
II.3 Discussion
III. Physical soil characteristics
III.1 Soil water characteristics
III.1.1 Soil water retention curve (SWRC)
III.1.2 Soil water potential measurements
III.2 Evolution of gravimetric water content according to treatment and year
III.3 Discussion
IV. Microbiological soil parameters evolution according to treatments and seasons
IV.1 May 2004
IV.2 September 2004
IV.3 May 2005
IV.4 September 2005
IV.5 Discussion
V. Discussion and conclusions – Pohorski dvor site
Chapter 5: Pathogenic microbes in soil
I Gačnik site: effect of irrigation
I.1 Summary of previous results
I.2 Specific microbes characterization
I.2.1 Enumeration of Fungi
I.2.2 Enumeration of Bacteria
I.2.3 Presence of viruses
I.3 Discussion
II Pohorski dvor site: effect of organic fertiliser and lime
II.1 Summary of previous results
II.2 Specific microbes characterization
II.2.1 Fungi enumeration
II.2.2 Bacteria enumeration
II.2.3 Presence of viruses
II.3 Discussion
III. Short conclusion for both locations
General discussion and conclusions
References
Annexes
