Browsing by Subject "astiakokeet"

The ambition of the agricultural environmental programme is to reduce nutrient load, because greater part of the diffuse loading of phosphorus is caused by agriculture. A eutrophic influence of the phosphorus in water systems tends to be limited inter alia by constructed wetlands. Their main task is to allow sedimentation of eroded soil into the bottom of the wetlands. There is ambiguity on the findings of the functionality and the importance of the prevention of water loading among scientific research in Finland. The aim of this study is to examine by utilizing soil analyses what happens to the basin water eroded phosphorus in the wetland sediment and wether the sedimentary constituent of the soil be suitable for a substratum of plant production. Comparing the samples of basin soil and wetland sediments revealed that the eroded constituent of the basin soil got assorted on wetlands. The samples collected from the wetlands contained 48 % more clay than the samples collected from the basin soil. The growth of the clay concentration increased the reactive area of the sediment. In consequence, it contained 45 % more hydroxides of aluminium and iron in the samples of the sediment than the samples of the basin soil. Because of the hydroxides, the phosphorus sorption capacity was 52 % higher than in the samples of the basin soil. However, the degree of phosphorus saturation was equal in the sediment and basin soil, because the oxidized sediment contained 50 % more phosphorus extracted from hydroxides of aluminium and iron. At the time of sampling the sediment was in reduced state and the amount of its water extracable phosphorus was significantly higher compared to the oxidized sediment. Correspondingly, when the sediment became oxidized the sorption capacity for phosphorus increased significantly, therefore the phosphorus was desorbed from reduced sediment to the wetlands water. This was also proven in a pot experiment, where rye-grass that grew in the sediment suffered from a severe shortage of phosphorus. In contrast, rye-grass grown in the basin soil didn’t suffer from the deficiency of phosphorus at the same fertilization levels. After threefold extra fertilization of phosphorus, the dry matter yield, concentration of phosphorus and uptake of phosphorus on the second yield grown in sediment were equal to the results of the first yield grown in basin soil. According to the results of the pot experiment, the sediment in reduced state is weakly suitable for the substratum of plant production, because the sorption capacity of phosphorus is high. Instead, sediment suits well to be utilized in the areas wherein the soil includes plenty of easy soluble phosphorus, such as for the material of subgrade for the corral of livestock, because the sediment reduces the load of phosphorus directed to the environment.