Browsing by Author "Baarman, Axel"

Nitrogen leaching is the main cause of nitrogen loss from Finnish agricultural soils. Nitrogen leaching can exceed 20 kg/ha/year. The Finnish waters and the Baltic Sea are affected by nitrogen leaching due to that nitrogen increases algae blooming. Studies have shown that the loss of nitrogen can be decreased by cultivating catch crops. Nitrogen leaching can in some cases be decreased by up to 90 %. In Finland catch crops are seldom grown. Catch crops are thought to be too costly and time consuming. The aim of this study was to investigate how efficiently winter wheat, rye and winter turnip rape function as catch crops and what effect the preceding crops of fallow, barley and peas have on autumn sown crops, with regard to nitrogen levels. A three year-long field experiment was established in 2010 at Viikki research farm in Helsinki. Winter wheat, rye and winter turnip rape were cultivated as catch crops; the preceding crops were fallow in 2010-2011 and barley and pea in 2011-2012. In 2012 winter wheat, rye and winter turnip rape were cultivated with fallow, peas and barley as preceding crops. In this study the soil’s mineral nitrogen content was measured before sowing in autumn and in spring. In 2010-2011 the soil’s mineral nitrogen content was also measured after harvest. The nitrogen content of the plants was measured in autumn. The seed quality and the seed yield were also measured. In autumn 2011 the mineral nitrogen content of the soil was higher after barley than after peas. However, there was more mineral nitrogen after cultivating fallow, compared to peas and barley in autumn 2012. The loss of mineral nitrogen between autumn 2010 and spring 2011 was slight. The nitrogen loss was greatest where winter turnip rape was cultivated, due to the plant’s high nitrogen assimilation. Winter turnip rape accumulated much more nitrogen than rye and winter wheat, whereas rye accumulated more nitrogen than winter wheat in 2010 and 2011. Mineral nitrogen loss between autumn 2011 and spring 2012 was high, over 80 % of the nitrogen was lost due to heavy rainfall and a mild winter.