Case Study Site 6: Ljubljana, Central Slovenia

Responsible partner: 13 - UL

1. Geographical description
The Case study in Slovenia is located on the Ljubljansko polje (Figure 8), the twenty-kilometre long and six-kilometre wide plain in the central part of Slovenia on the fertile plains of Sava river basin (300 m altitude, 1431' E, 463' N) which has a moderate continental and sub-alpine humid climate (mean air temperature 10 °C, annual precipitation 1400 mm). Most of the highly fertile arable land in Slovenia is located in plains above shallow groundwater recharge zones, which are country’s most important sources of drinking water (Zupanc et al, 2011). Mean annual water balance is positive (600 mm), and with the highly permeable soils and subsoils, there is a high risk of N leaching and ground water pollution, leading to a confrontation of drinking water resource protection and agricultural production interests.

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Figure 8. Case study site location (red dot) of Ljubljansko polje in the central part of Slovenia on the alluvial plains of the river Sava and its tributaries.

2. Main farming systems and typical agricultural management activities in the study area
More than 60% of Slovenia is covered by forests, and a quarter of the land (480,000 ha) is used for agriculture (permanent meadows, pastures: 281,000 ha, arable land: 172,000 ha). The field crops are grown most intensively in the valleys, where a predominately flat surface enables the use of modern farm machinery. The gravel plains of Ljubljansko polje are traditionally agricultural, although the city of Ljubljana has been expanding substantially. According to CORINE land cover data, arable land covers 20.6%, meadows 14.7% and pastures 1.2%. Small family farms are typical for the central-west part of Slovenia. The average farm has 10 ha of farm land. Farms are mixed and produce cash crops (wheat, barley, potato, canola, maize, field vegetables), as well as fodder crops for animals, including second crops in the same year established after the harvest of winter cereals (fodder kale, oil radish, fodder rape, grass-clover mixtures). The cattle farming is quite intensive, consequently, silage maize is grown in 40% of fields in a crop rotation.

3. Characteristic soils and soil quality monitoring practice
Almost 80% of the soils of these flat areas were formed on fluvio-glacial deposits of sand and gravel, and these soils represent >50% of all tilled fields. In the west of Slovenia, in the river basin of Sava, the parent material is rich in bases, so the soil complexes are saturated with bases. The older, deeper, weathered brown soils are formed above conglomerate or breccia. This type of soil is acid, mostly covered with pine or mixed forests. Predominant soils are gleyic Fluvisols and endogleyic Fluvisols with heterogeneous soil texture, mainly loam and sandy loam, with gravel appearing either on surface or below the ploughing layer. Some alluvial soil in the study area is classified as silty clay to silty clay loam with a moderately-gleyed layer between 30 cm and 70 cm below the surface of the soil and gravel material underneath. The soil is locally artificially drained by sub-surface drains.

4. Ongoing research and innovation actions on soil improvement and monitoring
High soil quality provides s buffer zone for the retention of possible pollutants, enabling better nutrient and water use efficiency. A suitable soil management system is essential for preservation of soil and water resources.

Tillage experiment: Effect of 12 years of minimum tillage system (MT) showed positive influence on soil quality, namely increased microbial biomass and soil organic carbon in the upper soil layer, increased aggregate stability, soil water retention properties and water infiltration rate compared to conventional tillage (Kaurin et al., 2013; Žigon, 2013). Plant available P, K, N and DOC showed greater stratification in the soil profile under minimum tillage. Minimum tillage also increased aggregate stability. The effect of organic amendments (straw, compost from separately collected biogenic waste (Turk and Mihelič, 2013)) was also monitored.

Grassland experiment: Although it is a typical long-term experiment there are some useful results obtained after the three experimental years: (i) the influence of fertilizer application on botanical composition of the treated sward was significant in the first three years, (ii) the fertilizer application had also a major effect on herbage dry matter yield, and (iii) the impact of cutting regimes on the botanical composition of the sward and on the herbage DM yield was considerably lower than that of fertilization application. In general, increased amounts of nutrients, especially nitrogen, in the grassland ecosystem increased herbage dry matter yield mainly due to increased yield of the grass component. In the fourth experimental year (2014), the measures of forage quality parameters, abundance and structure of AM fungi and balance of mineral nutrients will also be included.

5. Stakeholders to be included in the research
The main stakeholders are Ministry for Agriculture and Environment (Ministrstvo za kmetijstvo in okolje), Chamber of Agriculture and Forestry of Slovenia (Kmetijsko gozdarska zbornica Slovenije), Municipality of Ljubljana (MOL), and farmers.

6. References
Kaurin A, Mihelič R, Kastelec D, Grčman H, Suhadolc M. 2013. Soil quality and microbial community changes after a decade of different tillage at two Slovenian sites with different pedo-climatic conditions. In: 12th Symposium on Bacterial Genetics and Ecology, 9-13 June 2013, Ljubljana, Slovenia. Mandić-Mulec I (ed.). Networking and plasticity of microbial communities: the secret to success. BAGECO 12. Jena: Conventus Congressmanagement & Marketing, 2013.
Turk A, Mihelič R. 2013. Wheat straw decomposition, N-mineralization and microbial biomass after 5 years of conservation tillage in Gleysol field. Acta Agriculturae Slovenica 101: 69-75.
Žigon P. 2013. Nutrient availability as a function of soil tillage intensity: MSc. thesis, Biotechnical Faculty, University of Ljubljana.
Čop J, Lavrenčič A, Košmelj K. 2009. Morphological development and nutritive value of herbage in five temperate grass species during primary growth: analysis of time dynamics. Grass and Forage Science 64: 122-131.
Čop J, Vidrih M, Hacin J. 2009. Influence of cutting regime and fertilizer application on the botanical composition, yield and nutritive value of herbage of wet grasslands in Central Europe. Grass and Forage science 64: 454-465.