Lettuce (Lactuca sativa L.), tomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativus L.), and marigold (Tagetes patula L.) transplants were grown from seed in leached and unleached media containing 0%, 25%, or 50% (by volume) peat and/or fresh or aged spent mushroom compost with 50% vermiculite. Reduced growth and symptoms of ammonium toxicity were seen in transplants grown in fresh spent mushroom compost. Transplants grown in 0% or 25% compost were larger than those grown in 50%, probably due to high salinity in 50% compost. Leaching reduced media soluble salts and generally improved plant yields. K and Ca were higher and P and Mg were lower in the tissue of transplants grown in spent mushroom compost than of those in the peat-lite control mix. High quality transplants were produced in 25%, aged spent mushroom compost, while acceptable plants of slightly reduced quality were produced in 50%, aged compost.
Spent mushroom compost (SMC) was used as a soil amendment for field-grown vegetables. Four rates (0, 2, 10, or 20 kg/m2) of SMC were applied to a fine sandy loam in 1981 and 1982. SMC application decreased bulk density and increased the percentage of small pore space, pH, and electrical conductivity. Yields of cucumber and snap bean increased and yield of onion decreased, as the rate of SMC increased in 1981. Yields of cabbage, radish, and tomato were not affected significantly by the addition of SMC. Tomato yield was maximum at 10 kg/m2, then declined as SMC was increased to 20 kg/m2 in 1982. Yield responses of cucumber, fall-planted radish, spinach, and mustard were similar to that of tomato. Salt sensitive crops, such as snap bean, onion, and spring-planted radish, suffered severely reduced plant stands and, consequently, decreased yields. Yield of cabbage, a relatively salt tolerant crop, was not affected by SMC. Concentrations of K in all leaf tissues increased significantly as the level of SMC increased. Mg content in leaf tissue decreased.