Browsing by Subject "Soil organic matter (SOM)"

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  • Salonen, Anna-Reetta (Helsingin yliopisto, 2020)
    Applying organic amendments to agricultural soils holds a potential to mitigate climate change by increasing soil carbon stock. It may also provide other benefits, such as enhanced nutrient cycling along with improved soil quality and fertility. Aim of this study was to determine whether utilizing organic soil amendments has effects on soil aggregates and root-associated fungi, both of which are associated to increasing soil carbon stocks. Soil and oat (Avena sativa L.) samples were obtained from a field experiment established in Parainen, South-West Finland in 2016 on a clay (54 % clay) soil. Studied treatments included four organic soil amendments (two wood-based biochars and two fibrous by-products of paper industry), mineral fertilization control soil and untreated control soil. Sampling was done two years after the amendment application, in 2018. Soil sampling was done after the harvest and plant sampling at three timepoints (June, July and August). Soil aggregates were separated from the bulk soil by wet sieving to determine their stability and size distribution. Carbon content of aggregates, as well as topsoil (0-5 cm) carbon stocks were quantified. Oat roots were stained and colonisation rate of different intra-root structures formed by root-associated fungi (arbuscular mycorrhizal fungi and dark septate endophytes) determined with microscope. Studied organic soil amendments did not affect soil aggregate structure or carbon content of aggregates. Nevertheless, C/N-ratio of some of the studied samples as well as larger soil carbon stock imply that other one of the studied biochars could have increased soil carbon content. When observing fungal data by month for between treatment differences, AM arbuscules were found to be most common in untreated control soil in August. When monthly fungal structure observations from all the studied treatments were combined, clear change in intra-root structures was detected (likely due to seasonal dynamics of fungi); AM arbuscules were more common in June and July, whereas DSE structures predominated in August. Large variation in the field together with methodological constraints might hide some effects of organic amendments and to verify their impacts, more research is needed. Based on the results gained in this study, effect of organic soil amendments seemed to be neutral on both soil aggregates and root-associated fungi. Since no adverse effects were detected, studied soil organic amendments could be utilized as recycled fertilizers.
  • Miajee, Md. Jahidul Hasan (Helsingin yliopisto, 2020)
    The agricultural management of soil organic carbon (SOC) is highly important to build a climate-smart and eco-friendly agricultural system. For this reason, our study was conducted to test the hypothesis that the effect of different treatments consisting of soil textures and crop varieties on SOC stock has a major influence on any loss or accumulation of SOC storage. We also test the hypothesis that equivalent soil mass (ESM) is more consistent than fixed depth (FD) in estimating SOC content. In our study, the results were not found statistically significant but they showed minor differences in the SOC estimation. The difference was not clearly observed between ESM and FD methods. The influence of soil textures and crop varieties on SOC content was not significantly different. However, the cultivation of grass in fine-textured soils slightly increased the SOC stock compared with that in coarse-textured soils probably due to enhanced grass root growth and aggregation in fine-textured soils that protects soil organic matter from microbial oxidation.