Abstract: [Objective] The agricultural waste-mushroom residue, which remains after the production of edible fungi, is widely available and cheap. And it is now gradually cognized as a potential alternative to the peat for seedling production. This study aimed to explore the mushroom residue compost as peat alternative substrate material for the feasibility of container seedlings and promote cyclic utilization of agricultural waste resources.[Method] This study was tested for feasibility as a component (0-75%) of a container medium for growing one-year-old Pinus tabulaeformis container seedlings in a greenhouse. The physical and chemical properties of different mediums and their effects on the growth of seedlings were studied.[Result] When the proportions of mushroom residue compost reaching to 30%, seedling germination percentage could achieve 80% production index requirements; seedling height, diameter, shoot biomass, and foliar biomass all did not exhibit significant changes compared with the peat treatment. Root morphology (except the fine root of 0<D ≤ 0.5mm) exhibit little changes compared with the control when the growing media contained less than 50% mushroom residue compost. However, as the composition of compost in the mixed medium increasing, the fine root morphology index (total root length, total root surface area and total root volume) firstly increased and then decreased, and it reached the highest when the compost reaching to 30%, which was significantly higher than the peat treatment. Adding mushroom residue compost could significantly promote the accumulation of N,P,K nutrients in seedlings, and N and K contents in seedling foliar increased significantly as the composition of compost was 30%, indicating that the medium could produce relatively high quality of seedlings which might be good for outplanting. The physical properties of all the treatments were suitable to grow seedlings. Density of medium gradually increased with the adding of compost but overall was still light. The water retention and air permeability of all treatments exhibit little changes. High pH value might be one of the important reasons to decrease the seedling quality when the composition of mushroom residue compost was higher than 40%, because it might affect the root system and its absorption of ions. Furthermore, higher EC value and available N, P, K nutrient levels of some treatments also might be another key reason to affect the seedling quality, including it might inhibit the growth of fine roots.[Conclusion] Thus, combined with the substrates materials cost and environmental factors, the best medium prescription is 30% mushroom residue compost, 25% perlite and 45% peat. This study provided a scientific basis for the evaluation of the application of the mushroom residue compost in the container seedling.

Key words: mushroom residue compost, Pinus tabulaeformis, root morphology, nutrient uptake