Browsing by Subject "kaasun diffuusio"

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  • Gustafsson, Markus (Helsingfors universitet, 2013)
    Soil compaction is a long known phenomenon in agriculture affecting several soil functions, crop yield and environment. Soil compaction is caused e.g. by natural processes and field traffic. In the agriculture soil compaction is often defined as reduced soil air porosity caused by field traffic in wet soil conditions. Ever increasing weight of agricultural machines can cause stress propagation in deep soil layers which increases the risk of subsoil compaction. Subsoil compaction can alter soil pore volume and continuity, deteriorate soil air conditions and air permeability and also increase water surface runoff and gaseous nitrous oxide emissions to the atmosphere due to denitrification. Effects of subsoil compaction on soil properties have been reported to be very long-term and to remain measurable for decades. This work was carried out as a part of the Nordic Poseidon project, investigating the arable soil compaction effects on soil functions and the environment. The objectives of this study were to design and implement a measurement program for soil sample gas diffusion coefficient measurements and secondly to analyze the continuous measurement data of soil moisture and temperature determined in situ (in the defined position) on a long term soil compaction experimental site in Southern Finland, Jokioinen. In the measurement program the accuracy of gas diffusion coefficient calculation process was confirmed by demonstration measurements. The measurement program eased the usage of gas diffusion measurement equipment and also enabled wider studies than in the past. In the Jokioinen experimental site soil temperature and moisture were found to vary from year to year depending on the weather conditions and the amount of rainfall. On the rainy summer 2011 the moisture level was higher in compacted soil than in uncompacted soil. The difference between the compacted and uncompacted soils was possibly caused by weakened hydraulic conductivity in the compacted subsoil. In addition the compaction treatment increased temperature variation during the day in the upper 15 cm layer possibly due to higher thermal diffusivity of the soil.