Publikasjoner

Sammendrag

Spent mushroom substrate (SMS) is used by the turf industry in the northeastern United States for soil improvement. When tilled into soil at high rates, some turfgrass managers claim that SMS inhibits turf seed germination. Our objectives were 1) to determine if fresh SMS inhibits turf seed germination and, if so, which species are most adversely affected; 2) to evaluate whether any inhibition caused by SMS is due to osmotic effects or toxicity of compounds in SMS extracts; 3) to determine if any negative effect of SMS on germination can be eliminated by leaching the SMS-amended soil before seeding; and 4) to assess the performance of SMS on seedling emergence in the field. Germination of nine turfgrass species was evaluated in mixtures made from fresh SMS [electrical conductivity of saturated paste extract (ECe) = 11.9 dS m-1] and a loamy sand soil. Germination inhibition due to SMS was most pronounced in the following order: Colonial bentgrass (Agrostis capillaris L.) > sheep fescue (Festuca ovina L. ssp. hirtula [Hackel ex Travis] Wilkinson) > Kentucky bluegrass (Poa pratensis L.) > hard fescue (Festuca trachyphylla [Hackel] Krajina]) > creeping bentgrass (Agrostis stolonifera L.) > Chewings fescue (Festuca rubra L. sp. commutata [Thuill.] Nyman) = strong creeping red fescue (Festuca rubra L. ssp. rubra Gaud.) > slender creeping red fescue (Festuca rubra L. sp. litoralis [Meyer] Auquier) > perennial ryegrass (Lolium perenne L.). SMS had a stronger negative effect on germination rates (GRs) than on final germination percentages (FGPs). Germination of perennial ryegrass and Kentucky bluegrass on blotter paper moisted with SMS-extracts or polyethylene glycol of equivalent osmotic potentials showed that the inhibition was primarily due to osmotic effects. In an experiment with a 50% soil / 50% SMS (v/v) mixture, Kentucky bluegrass germinated better in pots that had been watered with 133 or 167% of the evaporation rate for ten days prior to seeding than in unleached pots. Although the negative effect of SMS on seed germination was not confirmed in a field study where ECe values never exceeded 4.1 dS m-1, we conclude that incorporation of high rates of SMS represents a potential problem for turfgrass establishment.