Objective   Means to utilize coffee peel waste and improve quality of ground soil at coffee plantations were investigated.

  Method  The soil at a 56-year-old coffee plantation was used as the base material for the pot experiment. Aside from CK using 100% plantation soil, treatments applied the mass fractions of acid soil conditioner (TL) and fermented coffee peels (CP) including TL1 (2% TL), TL2 (4% TL), TL3 (6% TL), TL4 (8% TL), CP1 (4% CP), and CP2 (8% CP) were added to the potting soil. Leaf photosynthetic properties, and RuBP activity, growth indicators, and dry biomass accumulation of the seedlings, as well as nutrient content, pH, and activities of acid phosphatase (S-ACP), alkaline phosphatase (S-ALP), catalase (S-CAT), and urease (S-UE) in soil were determined.

  Result  The addition of TL raised 0.8-1.6 on the soil pH, while CP increased it at first, then decreased, and became 0.50 lower than CK after 6 months. The available K and exchangeable Ca and Mg in soil were significantly increased with increasing TL or CP. But the available P significantly dropped by the added TL which, at TL4, was 69.34% lower than CK. The total N, alkaline N, and available P were significantly higher with CP than other treatments. TL2 and TL3 showed the greatest effects on RuBP enzyme activity with significantly 101.16% and 135.30%, respectively, and on net photosynthesis (Pn) 81.71% and 80.35%, respectively, higher than CK. And those were followed by the treatments of CP1 and CP2. All enzyme activities in the soils treated by TL and CP were higher than CK, except ACP, which was similar to CK. The S-ALP activities in the treatment soils were 2.05 to 3.71 times higher than CK. The S-CAT activities were higher than CK by 109.62%-18.60% in the order of CP2＞CP1＞TL4＞TL3＞TL2. The S-UE activities were 18.70%-5.37% higher than CK with the highest showing under CP2 and CP1 followed by TL1 and TL4. The TL2, TL3, CP1, and CP2 treatments promoted the growth and dry matter accumulation of coffee seedlings with plant height and stem diameter increases by 25.09%-81.29% and total and dry weights of leaves, roots, and stems by 1.65-5.02 times over CK. Among them, CP1 delivered the greatest rises.

  Conclusion   Application of TL and CP improved the soil microbial environment, increased the availability of soil nutrients, and promoted the coffee seedling growth. However, excessive TL could bring about high exchangeable Ca inducing P fixation, and with CP addition, the mineralization of organic N would lower the pH in soil. Consequently, the appropriate use of TL and CP was expected to achieve the goal of improving acid soil quality, utilizing coffee waste, and enhancing coffee cultivation at the plantations.