Abstract:

To find out the effects of edible (medicinal) fungus residues under different carbon-nitrogen ratios on soil aggregates, an indoor constant temperature culture experiment was used to study the effects of adding Lentinus edodes residues, Grifola frondosa residues, and Agaricus bisporus residues on the composition and properties of water-stable aggregates in sandy loam soils. The results showed that the three tested fungi residues could effectively increase the average weight diameter of sandy loam soil aggregates, and the increase range was Lentinus edodes residues (206.8%) > Agaricus bisporus residues (81.8%) > Grifola frondosa residues (54.5%), the adding of Lentinus edodes residues improved the soil aggregate property rating from good to excellent. The aggregate properties treated by Lentinus edodes residues were significantly improved with the adding amount and cultivation time, and the increase of aggregate property index was mainly related to the transform of aggregates < 0.25 mm into large aggregates through agglomeration. The increase of the aggregate property index in Grifola frondosa residues’ treatment was mainly related to the aggregates of <0.25 mm forming larger aggregates in a short time under the entanglement of the fungal mycelium, but the newly formed aggregates had poor stability. While in the treatment of Agaricus bisporus residues, the transformation of 0.25-1 mm aggregates to 3-5 mm aggregates played an important role in the improvement of aggregate property index. The ability of different edible (medicinal) fungus residues to improve the properties of sandy loam aggregates was very different, and the carbon-nitrogen ratio of fungus residues was an important factor that affecting the improvement of soil aggregate properties. Too high carbon-nitrogen ratio of the fungus residues resulted in only a short-acting mechanism for improving the properties of the aggregates, and the aggregates formed did not have long-term stability. However, if the carbon-nitrogen ratio of the fungus residues was too low, the amount of fungus residues added to achieve the improvement effect was greatly increased, and the improvement effect was very slowly. When the carbon-nitrogen ratio of fungus residues was about twice the suitable carbon-nitrogen ratio for microbial activity (50:1), it was more cost-effective for improving sandy loam aggregates, and a long-term mechanism of action could be obtained.

Key words: Lentinus edodes residues, Grifola frondosa residues, Agaricus bisporus residues, sandy loam soils, water stable aggregates, carbon-nitrogen ratio