Field evaluation of starter N and delayed inoculation of Lespedeza cuneata grown in minesoil

A field study was conducted on freshly reclaimed surface-mined area to determine response of sericea lespedeza (Lespedeza cuneata [Dumont] G. Don.) to delayed rhizobial inoculation. Soybeans (Glycine max L.) were used as a control legume. Plots were inoculated with spray applications of rhizobial suspensions at seeding, cotyledon stage or second trifoliate leaf stage, or not inoculated. Starter N at 0, 10 or 20 kg ha⁻¹ was applied preplant in a factorial arrangement with inoculation timings. G. max. was grown for 92 days and L. cuneata for 121 days. Starter N increased plant growth and total shoot N in both species. However, % shoot N was found to increase only in L. cuneata. Delaying inoculation had no significant effect upon total shoot N or % shoot N accumulation in L. cuneata. Inoculation of G. max at planting produced greater plant growth and N accumulation than delayed inoculation treatments. Application of inoculum as a surface spray appeared to be an effective method for delayed inoculation as evidenced by nodule formation. Lack of increased plant growth, regardless of time of inoculation, suggests that delayed inoculation does not improve establishment and growth of L. cuneata in minesoil.