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Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/6178

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Sirvi Artiklid Märksõna "aggregate stability" järgi

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  • Pisipilt
    Kirje
    Effect of crop residue decomposition on soil aggregate stability
    (MDPI, 2020) Stegarescu, Gheorghe; Escuer-Gatius, Jordi; Soosaar, Kaido; Kauer, Karin; Tõnutare, Tõnu; Astover, Alar; Reintam, Endla; Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences
    The decomposition of fresh crop residues added to soil for agricultural purposes is complex. This is due to di erent factors that influence the decomposition process. In field conditions, the incorporation of crop residues into soil does not always have a positive e ect on aggregate stability. The aim of this study was to investigate the decomposition e ects of residues from two di erent cover crops (Brassica napus var. oleifera and Secale cereale) and one main crop (wheat straw) on soil aggregate stability. A 105-day incubation experiment was conducted in which crop residues were mixed with sandy loam soil at a rate of 6 g C kg􀀀1 of soil. During the incubation, there were five water additions. The decomposition e ects of organic matter on soil conditions during incubation were evaluated by determining the soil functional groups; carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions; soil microbial biomass carbon (MBC); and water-stable aggregates (WSA). The functional groups of the plant residues and the soil were analyzed using Fourier transform infrared spectroscopy (FTIR) and a double exponential model was used to estimate the decomposition rates. The results show that the decomposition rate of fresh organic materials was correlated with the soil functional groups and the C/N ratio. Oilseed rape and rye, with lower C/N ratios than wheat straw residues, had faster decomposition rates and higher CO2 and N2O emissions than wheat straw. The CO2 and N2O flush at the start of the experiment corresponded to a decrease of soil aggregate stability (from Day 3 to Day 10 for CO2 and from Day 19 to Day 28 for N2O emissions), which was linked to higher decomposition rates of the labile fraction. The lower decomposition rates contributed to higher remaining C (carbon) and higher soil aggregate stability. The results also show that changes in the soil functional groups due to crop residue incorporation did not significantly influence aggregate stability. Soil moisture (SM) negatively influenced the aggregate stability and greenhouse gas emissions (GHG) in all treatments (oilseed rape, rye, wheat straw, and control). Irrespective of the water addition procedure, rye and wheat straw residues had a positive e ect on water-stable aggregates more frequently than oilseed rape during the incubation period. The results presented here may contribute to a better understanding of decomposition processes after the incorporation of fresh crop residues from cover crops. A future field study investigating the influence of incorporation rates of di erent crop residues on soil aggregate stability would be of great interest.
  • Pisipilt
    Kirje
    Water satability of soil aggregates in a 50-year-old soil formation experiment on calcareous glacial till
    (Pleiades Publishing, Ltd., 2020) Are, Mihkel; Kauer, Karin; Kaart, Tanel; Selge, Are; Astover, Alar; Reintam, Endla; Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences; Institute of Veterinary Medicine and Animal Sciences. Estonian University of Life Sciences,
    Soil formation on the human time scale is immensely time consuming, although it can be significantly accelerated through the effects of vegetation. The content of water-stable aggregates (WSAs) is a useful indicator for determining both the soil development level and the soil quality. However, in severely degraded soils, especially in the Baltic pedoclimatic region, the effects of vegetation on the aggregate stability have been poorly studied. Therefore, to obtain more knowledge about the impact of vegetation on WSA, and thereby knowing how to improve it, this study was conducted on a long-term soil formation experiment in Estonia near Tartu. In 1964, the initial soil from an area of 20 × 8 m down to 100 cm depth was replaced with a sandy loam calcareous glacial till. The experiment started on April 26, 1965, when plants were sown on the plot. The topsoil (0–20 cm) samples were analyzed in 1966, 2000, 2007, and 2014. The study indicated that perennial grasses (meadow fescue and common meadow-grass) fertilized with P40K75, compared to N150P40K75, decreased the WSA content, as well at the accumulation rate of soil organic carbon (SOC) and the total nitrogen content (Ntot). The hybrid alfalfa treatment resulted in the significantly highest SOC and Ntot accumulation, but not in the overall highest WSA content. Under barley, manure positively affected the WSA and SOC, though many other physical properties were not improved. Compared to the initial till under bare fallow, the SOC and Ntot contents were significantly higher under grown crops, but the WSA content remained the same. In addition, regardless of the grown crops, the WSA of larger (0.25–2 mm) aggregates was substantially higher than that of smaller (0.25–1 mm) aggregates. Also, as the relationship between WSA and SOC in the study was linear, the soil was far from C saturation and still in development. Overall, it can be concluded that the cultivation of perennial grasses and hybrid alfalfa on the severely eroded soil is the most rational option to improve the water stability of aggregates and increase the SOC and Ntot contents. However, because of the complexity of the aggregation process, further research is still needed.