ISSN 1392-3196 Zemdirbyste-Agriculture Vol. 101, No. 4 (2014) 389 ISSN 1392-3196 / e-ISSN 2335-8947 Zemdirbyste-Agriculture, vol. 101, No. 4 (2014), p. 389−394 DOI 10.13080/z-a.2014.101.049 Effects of sward botanical composition on nitrogen and potassium leaching in cut grassland Mailiis TAMPERE, Karin KAUER, Indrek KERES, Evelin LOIT, Are SELGE, Rein VIIRALT, Henn RAAVE Estonian University of Life Sciences, Institute of Agricultural and Environmental Sciences Kreutzwaldi 5, 51014 Tartu, Estonia E-mail: mailiis.tampere@emu.ee Abstract The leaching of nutrients in regions where annual precipitation considerably exceeds evaporation needs to be minimised. Our objective was to study the dependence of leached nitrogen and potassium on botanical composition of grassland sward. Mini-lysimeters illed with loamy sand were embedded in three swards (a mixture of three grass species, grasses mixed with white clover and grasses mixed with lucerne). Annual nitrogen application rates (0, 60, 120 and 180 kg ha -1 ) in conjunction with three fertilizers (mineral fertilizer, cattle slurry and sewage sludge) were applied. The nitrogen and potassium leaching was measured monthly during three years. We concluded that nitrogen and potassium leaching are affected by sward botanical composition. The leaching of both elements was the lowest from grass-clover sward. Key words: leaching, nitrogen, potassium, sward type, water percolation, yield. Introduction Nutrient leaching has become a major concern worldwide, mainly due to the intensiication of agricultural production involving the application of fertilizers and organic wastes (Di, Cameron, 2002). Leaching of fertilizer NO 3 - -N through the soil proile can contribute to eutrophication of streams and lakes, contaminate surface and groundwater resources (Mašauskas et al., 2006) and cause several health problems to humans (Di, Cameron, 2002). Nutrient leaching is a problem in regions where precipitation exceeds evaporation considerably. Estonia is located in a moderately cold and humid region, where total annual precipitation exceeds evaporation by 1.5–2 times; hence weather conditions for nutrient leaching are favourable. Concerning the grasslands it has been found that nutrient leaching is high only from pastures, in cut grassland it is often estimated to be low (Eriksen, Vinther, 2002). Although nutrient leaching from grassland is lower than from arable land it is still important to ind opportunities for its reduction. Under the conditions of climate change the risk of nutrient leaching is expected to become more favourable also from grasslands (Olesen et al., 2011). So far the research work in grassland has paid only little attention on the identiication of relationships between nutrient leaching and sward species composition. Studies have shown that the ability of grasses to take up nitrogen (N) varies in great extent (Zemenchik, Albrecht, 2002). Therefore it can be presumed that N leaching at the same N application rate in swards with different botanical composition can be different. The study of Bouman et al. (2010) showed that NO 3 - -N leaching is affected by the compositional diversity of the sward. In their experiment NO 3 - -N leaching decreased in a treatment with bluegrass (Poa pratensis L.), while the number of grasses did not affect leaching. Due to the decreasing amount of resources in agricultural production it has been suggested that the targeted use of biodiversity, especially grass-legume mixtures, could play a role (Peyraud et al., 2009). According to several current studies, livestock production systems based on legumes are more sustainable than those based on mineral fertilizers (Thomas, 1992; Jarvis et al., 1996). The use of legumes in seed mixtures is an eficient strategy to reduce the external N-input on farms (Pötsch et al., 2013). But the impact of legumes on N leaching is not so clear. The amount of N ixed by legumes depends on their proportion in the sward and on environmental conditions, which may vary greatly (Frame, 1992). Bouman et al. (2010) showed that in midsummer when the percentage of white clover in the sward is high, N leaching also increases. Eriksen et al. (2004) have reported that less leaching occurs from unfertilized grassland containing white clover than from fertilized grass-only grassland. Low and Armitage (1970) studies have demonstrated increased leaching in the swards with reduced legume content. Most research so far has focused only on N leaching (Eriksen et al., 2004; Mašauskas et al., 2006; Bouman et al., 2010). The leaching of potassium (K), which is also a very mobile element in the soil, but which does not cause eutrophication (Alfaro et al., 2004) or lower the quality of groundwater (Kayser, Isselstein, 2005) has received less attention. Potassium is a very important nutrient for the growth of grasses and the reduction of its