Agronomic value of urban waste and the growth of ryegrass (Lolium perenne) in a calciorthid soil amended with this waste

The influence of the composting process on the agronomic value of urban waste (UW) from Murcia (south-eastern Spain) was studied. UW compost had a higher percentage of P, K and nitrate N than fresh UW, as well as a higher cation exchange capacity and a more stable organic matter. By contrast, total N content and values of extractable P/ total P × 100 ratio were lower. The addition of fresh UW to a calciorthid soil had an initially depressive effect on rxegrass (Lolium perenne) yield, which disappeared with time as this waste matured in the soil. No depressive effect was observed when composted UW was applied. When soil was amended with high doses of UW compost, yields were always significantly greater than the control. The uncomposted waste induced a large concentration of macroelements (except N) in the plants of the first harvest. Plants grown in amended soil had a higher concentration of Fe, Mn and Zn than the control.