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The most important component of agricultural system are soils as the basis for the growth of plants, accumulation of water, plant nutrients and organic matter. The main task of our research was to ascertain changes in soil organic carbon (SOC) and mobile humified carbon fractions in digestate-treated soils. We have performed three field experiments using the same design on two soil types in 2019–2020. We studied the fertilization effects of different phases of digestate on Retisol and Fluvisol. Fertilization treatments: control; separated liquid digestate 85 kg ha−1 N; and 170 kg ha−1 170 N; separated solid digestate 85 kg ha−1 N; and 170 kg ha−1 N. We have found a greater positive effect on the increase in SOC because of the use of the maximum recommended fertilization rate of the solid digestate. The content of mobile humic substances (MHS) tended to increase in grassland and crop rotation field in digestate-treated soil. In our experiment, maximum concentration of SOC was found in 0–10 cm soil layer, while in the deeper layers the amount of SOC, MHS and mobile humic acids proportionally decreased. We concluded, that long-term factors as soil type and land use strongly affected the humification level expressed as HD (%) in the soil and the highest HD was determined in the grassland soil in Fluvisol.

This paper analyses the effects of soil macropores, temperature and water content on soil carbon dioxide (CO 2) efflux behaviour, which could help understand the mechanism of CO 2 efflux as influenced by soil type and land use methods. The temporal dynamic changes of CO 2 efflux from the soil surface using a closed chamber method (LI-COR LI-8100A Automated Soil CO 2 Flux System) were measured. Soil CO 2 efflux was investigated at a topsoil depth of 0-5 cm in (1) arable land under conventional tillage on Cambisol (CM), (2) grassland on Cambisol, (3) park on Cambisol, (4) arable land under conventional tillage on Retisol (RT), (5) grassland on Retisol and (6) forest on Retisol. CO 2 emission was measured six times per growing season from May to September in 2017. Soil macropore network was researched by implementing an X-ray computed tomography and carried out at the laboratory of the Institute of Agrophysics, Polish Academy of Sciences in Lublin, Poland. Macropores resulting from soil pedogenesis and land use methods played an important role on soil water, temperature and gas transport. The type of soil vegetation cover and amount of soil macropores significantly influenced soil respiration rate. The efflux values were recorded ranging from 0.71 to 3.43 μmol CO 2 m-2 s-1 (Cambisol) and from 0.70 to 3.05 μmol CO 2 m-2 s-1 (Retisol) in the grassland, from 0.43 to 2.57 μmol CO 2 m-2 s-1 (Cambisol) in the park, from 0.44 to 2.52 μmol CO 2 m-2 s-1 (Retisol) in the forest, from 0.52 to 2.68 μmol CO 2 m-2 s-1 (Retisol) and from 0.09 to1.57 μmol CO 2 m-2 s-1 (Cambisol) in the conventional tillage. Computational tomography data revealed that the content of macropores amounted to 10.75% in the grassland site, 1.97% in the park and 1.21% in the conventional tillage within the soil depth of 3-8 cm of the Cambisol and 6.45% in the forest, 4.94% in the conventional tillage and 3.86% in the grassland at the same soil depth of the Retisol. Soil temperature, water content and macroporosity were the main factors exerting the influence on soil gas origination rate. The relationship between soil CO 2 efflux and volumetric water content at a 5 cm depth can be described by a linear regression model y = 0.0943x − 0.7651, R 2 = 0.53 (valid for volumetric water content from 22.5 to 27.0 vol.% on Retisol and from 16.8 to 24.4 vol.% on Cambisol). Also, linear regression model y = 0.1167x − 0.8214, R 2 = 0.65 showed the relationship between soil CO 2 efflux and soil macroporosity at the 3-8 cm depth. Soil CO 2 efflux displayed a typical polynomial relationship with soil temperature at the 5 cm depth; however, the relationship was very weak. Both soil type and land use methods had a noticeable influence on macroporosity, surface area and macropore range of soil pore-size distribution. The amount of macropores in macropore geometry was an important factor when dealing with CO 2 flow. Topsoil CO 2 efflux under contrasting vegetation cover and management conditions on Cambisol and Retisol was directly related to soil macroporosity and volumetric...

Carbon dioxide (CO 2 ) efflux from 0-5 cm topsoil layer in conventional tillage plots, in grassland and forest Retisol (in West Lithuania in a hilly terrain) and Cambisol (in Central Lithuania in a plane terrain) was investigated using a closed chamber method. The soil CO 2 efflux was measured six times per growing season from April to August in 2018. Soil temperature and the volumetric water content were recorded at 5 cm depth at the same time as soil CO 2 efflux measurements. Small soil monoliths were collected for the measurements of plant root parameters within 0-10 cm layer and were investigated later in the laboratory. In Cambisol, the efflux values ranged from 0.20 to 2.67 μmol CO 2 m -2 s -1 under conventional tillage, from 1.10 to 3.41 μmol CO 2 m -2 s -1 in grassland and from 0.89 to 2.28 μmol CO 2 m -2 s -1 in forestland. In Retisol, the efflux values varied from 0.81 to 3.54 μmol CO 2 m -2 s -1 under conventional tillage, from 1.23 to 2.69 μmol CO 2 m -2 s -1 in grassland and from 0.88 to 2.06 μmol CO 2 m -2 s -1 in forestland. The soil temperature varied from 11.5°C to 33.6°C during the experimental period and averaged 22.8°C and 21.1°C at 5 cm depth in Cambisol and Retisol, respectively. The volumetric water content at 5 cm depth averaged 18.7% and 23.9% in Cambisol and Retisol, respectively. The volumetric water content in Cambisol was markedly lower than in Retisol during the whole experimental period. The maximum root volume within 0-10 cm depth was determined in grassland Retisol. Root volume under conventional tillage in Cambisol was 6.2-fold lower, in Retisol -5.1-fold lower, in forest Retisol -1.9-fold lower, in forest Cambisol -1.4-fold lower and in grassland Cambisol -1.1-fold lower compared to grassland Retisol. Average CO 2 efflux from Retisol was 12% lower than that from Cambisol. Soil CO 2 emission decreased in the following order: Cambisol -grassland > forestland > conventional tillage plots and Retisol -grassland > conventional tillage plots > forestland. Volumetric water content was found to increase soil CO 2 efflux; however, at the content higher than 20%, efflux decreased. A soil temperature of up to 25°C increased soil CO 2 emission. However, with a further increase in soil temperature, soil respiration decreased in both soil types investigated. The decrease in root volume and root length density depended on the land use: grassland > forestland > conventional tillage plots.

The study aimed to quantify the relationship between root parameters and soil macropore characteristics in two soil layers of Retisol from a hilly landscape in Western Lithuania, as influenced by different land use systems. The decreases in root volume and root length density were dependent on land use and soil depth. The values of root length density and root volume at 0-20 cm depth tended to decrease in the following order: grassland > forest > arable land under conventional tillage. The highest volume in the framework of macropores was recorded for medium-size pores under arable land (3.02%), for fine pores (2.56%) in forest soil and very fine pores in grassland soil (below 1.19%) at the 0-10 cm soil depth, while at 10-20 cm soil depth, the coarse macropores dominated in the arable land system (below 1.41%). Root length density, root volume and the volume of very fine macropores had close relationships (p < 0.01, r = 0.91 and r = 0.68, respectively) under different land use at 0-20 cm depth. In Retisol, the roots were concentrated at 0-10 cm soil depth, and their volume was higher compared to the 10-20 cm depth. Plant roots increased the volume of very fine macropores in all land use systems, within the entire 0-20 cm soil depth. K e y w o r d s: plough layer, porosity, root length, root volume, tillage, X-ray computed tomography