I will be top dressing some areas in my yard this fall to promote growth of new seed (tall fescue) that will be planted at that time. I have been to some garden centers who sing the praises of mushroom soil (soil obtained from mushroom houses after they are done with it). I have heard others say that mushroom soil is basically spent since the growing of mushrooms would have taken the nutrients out of it. So, for my top dressing would you recommend regular old screened top soil or mushroom soil?
Cecil County Maryland
Mushrooms grown in compost use only a small portion of the many nutrients available. (See our publication on soil amendments: http://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG42_Soil_... ) A nutrient analysis of spent mushroom compost is 2.75-1.5-1.5, so it can be a good soil conditioner, however, it can have high soluble salt levels and should be fully incorporated into the soil and watered prior to planting. You would have to till it in before using it; it can't be used for top dressing. For top dressing, we recommend that you go with a regular screened top soil.
Thank you very much.....good info!