Effects of Mycorrhizae on Establishment and Performance of Forage Species in Mine Spoil1

Abstract

AbstractMine soil not containing topsoil usually lacks the normal endomycorrhizal fungi which improve the P uptake of many plants. The establishment of mycorrhizae might be useful for low‐cost, low‐maintenance revegetation of abandoned strip mines or other mineral wastes low in available P. The value of establishing endomycorrhizae to improve the growth of forage grasses and legumes on a low‐P strip mine spoil (Schlickig udispolent) was investigated using 1‐cm layers of field soil as mycorrhizal inoculum. In replicated l‐m2 field plots receiving lime but not fertilizer, yields of flatpea (Lathyrus sylvestris L.), crownvetch (Coronilla varia L.), and birdsfoot trefoil (Lotus corniculatus L.) after two seasons were 7, 13, and 18‐fold greater, respectively, in mycorrhizal treatments. Survival after two winters averaged 51 vs. 6% for nonmycorrhizal treatments. In 0.25 m2 plots receiving 0, 41, 81, and 162 kg/ha P or mycorrhizal inoculum at the two low rates of P, the yields of mycorrhizal and nonmycorrhizal plants converged as P was increased. The response of mycorrhizal trefoil improved over 2 years relative to nonmycorrhizal treatments receiving only initial applications of P. Growth of tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) in 600‐ml pots in the greenhouse was not significantly improved by mycorrhizae. Mycorrhizal fungi from different sources varied in their adaptation to low‐pH mine spoil. The establishment of mycorrhizae in mining wastes is useful if indigenous inoculum is absent or nonadapted, if available P is low, and if the plant species used for revegetation responds to mycorrhizae. Under these conditions, mycorrhizal plants are more persistant and less affected by the immobilization of fertilizer P.