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The ability of light-textured soils to retain nutrients and water is small. In agriculture such soils pose a risk of nutrient leaching when amended with fertilizers. This study investigated the effects of the incorporation of activated carbon (AC) into the soil to determine (i) if it would decrease leaching of major nutrient ions and (ii) if its effect on leaching is influenced by fertilizer use. Nitrate nitrogen (NO 3 − -N), ammonium nitrogen (NH 4 + -N), phosphorus (P) and potassium (K) leaching through two substrates (sandy loam soil (S) and a sandy loam soil mixed with activated carbon (S + AC), which were unfertilized (NF or control) or fertilized with inorganic fertilizer (F), pig slurry (PS), pig slurry digestate (PD) or sewage sludge digestate (SD) was studied using mini-lysimeters. In soil enriched with AC mark K-835, water percolation and NO 3 − -N and P leaching were significantly reduced, and K leaching was increased. Ammonium nitrogen leaching was not influenced by the AC amendment. The impact of AC on NO 3 − -N and P leaching and water percolation did not change during the two-year period, from which it is concluded that AC mark K-835 prevents the leaching of NO 3 − -N and P and increases soil water retention ability, and thus it is beneficial for light-textured soils.

Although fertilization has a positive effect on agricultural productivity, its negative side effect can be the leaching of plant nutrients. Our objectives were to study the impact of fertilizer type and nitrogen application rate on the nitrogen and potassium leaching from grassland during and after the vegetative period. Within three years (2008-2011) mini-lysimeters experiment was conducted on grassland swards receiving mineral NPK, mineral PK, cattle slurry and sewage sludge based on nitrogen rate 0, 60, 120 and 180 kg ha -1 year -1 . Nitrogen and potassium leaching was measured monthly throughout the experimental period. From our results it can be concluded that nitrogen leaching is lower with the use of mineral NPK, because it increases the sward yield most efficiently. Potassium leaching in grassland can be reduced when using nitrogen containing fertilizers, as the fertilizer N:K ratio has a great effect on its leaching potential. Fertilizers are not the only N and K leaching source. It can be high also from unfertilized soil at the expense of soil reserves. Injection of slurry at rational amounts can be an effective method for the reduction of nitrogen leaching in grassland.

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 filled 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.

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