Wood ash produced through cellulose manufacturing has agricultural uses due to its neutralizing power, like that of commercial products, in addition to providing key soil nutrients such as Ca, Mg, K, and P. However, this industrial waste can possess heavy metal(oid)s that bioaccumulate in the food chain. The objective of this study was to determine the effect of wood ash (WA) on the physicochemical properties of an Ultisol, the mobility of heavy metal(oid)s (As, Cd, Cr, Pb, and Ni) in the soil-plant-water system, and the nutritional response (N, P, and K) of ryegrass (Lolium perenne L.). The experiment was conducted in pots, under greenhouse conditions, using a completely randomized design. Ryegrass was grown in pots containing mixtures of WA plus soil at 7.5, 15, 30, and 75 g kg−1, commercial lime plus soil at 1.5 g kg−1, and unamended soil as a control. Heavy metal(oid)s were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES). All WA doses favored an increase in pH and the availability of P, Ca, Mg, Na, K, Cu, and Zn in soil and N, P, and K absorption in ryegrass. WA favored the availability and later absorption of heavy metal(oid)s by ryegrass (staying mainly in the roots). Heavy metal(oid)s mobility in the soil-plant-water system was as follows: Cr > Pb > Ni > As.