Objective   Effects of returning mushroom discards to the field on soil and quality and yield of off-season cultivated yams were investigated.

  Method  In a field experimentation Nahuai No. 1 yams were planted off-season on lots added with mushroom discards (T1), an organic fertilizer (T2), mushroom discards + an organic fertilizer (T3), or blank control (CK) to determine the quality and yield of the yams grown on them.

  Result  The treatments significantly increased the tuber yield over CK with T3 delivered the greatest at 39,328.63 kg·hm⁻², which was significantly higher than other treatments—T1 increased by 15.53%, T2 by 17.92%, and T3 by 26.53%. The starch content in the tubers increased with T3 producing the significantly highest at 30.84%; the amino acids ranged between 2.38% and 2.47%; the highest soluble sugars came from yams grown on T2; the highest saponin among all at 0.46 mg·g⁻¹; and the leaf chlorophyll heightened in 10-160d after emergence with the highest peak value and the slowest on declining under T3. The treatments, especially T3, also altered the soil nutrients increasing the available nitrogen, phosphorus, potassium, and organic matters, while balanced the pH.

  Conclusion  By returning mushroom discards with added organic fertilizer to the soil, T3 significantly improved the yield and quality of the yams grown on the treated land.