The research recognized the effect of various doses sewage and ash and peat and ash mixtures on the yield and the contents of P, Ca, Mg, K and Na in a grass mixture with bird’ s foot trefoil. The investigations were conducted as a pot experiment on mineral soil, with addition of ash and sewage and ash and peat mixtures in doses of 1-30% in relation to total soil mass. The yield was diversified and depended on the treatment and year, ranging within 9.61-135.38 g DM·pot⁻¹. The highest yield was obtained in the third year while the smallest in the first. A significant decline in yield was registered on treatments where solely ash, peat or their mixtures were used. A supplement of ash and sewage mixtures significantly increased the yield, whereas ash and peat mixture decreased it. Macroelement content in grass mixture was diversified, depending on the variant and date of harvest and ranged within: 2.32-5.58 g P; 1.35-5.65 g Ca; 1.66-3.85 g Mg; 12.83-24.19 g K; 0.10-2.63 g Na·kg⁻¹ DM. It was stated that with increasing percentage of sludge and ash mixtures P, Ca, Mg, K and Na contents in plant mixture increased.