生物炭、有機質與棘孢木黴菌TA對土壤改良及樟樹苗生長之影響

Abstract

都市樹木為人類社會帶來許多效益，然而其生長環境是否適宜卻經常被忽視。樹木生長環境不佳會導致生長勢下降，營養吸收不良，亦降低對病原菌的抵抗力。臺灣都市樹木病害以褐根病 (brown root rot disease) 為大宗，造成樹木腐朽死亡或倒塌，連帶造成生命財產損失。樟樹 (Camphora officinarum) 為國內都市林常見樹種及褐根病感病樹種，本研究以樟樹苗為實驗材料，以稻殼炭、禽畜糞堆肥、泥炭土與晶曜石等資材與壤土和黏壤土混合，開發樹穴土壤改良配方，提供樹木根系良好的生長環境以提升樹勢。另以具拮抗褐根病菌 (Phellinus noxius) 能力之棘孢木黴菌TA (Trichoderma asperellum TA) 進行澆灌，探討其促進樟樹苗生長之潛力。為期84天的2次溫室盆栽獨立試驗結果顯示，經過改良的壤土與黏壤土其總體密度顯著降低、酸鹼值和電導度增加，且在壤土處理中顯著提升樟樹苗之根系投影面積、樹基徑、葉綠素SPAD值；澆灌T. asperellum TA則對樟樹苗的生長無顯著差異。T. asperellum TA施用後，在各處理組均能維持穩定的族群至少42天，且在壤土的族群量高於黏壤土，顯示對所測試之不同土壤條件均具有良好的適應力。從短期試驗篩選具潛力配方，加入晶曜石為測試資材，進行234天以壤土為基土的長期溫室盆栽試驗。結果顯示「10%稻殼炭 + 5%堆肥 + 10%泥炭土」(體積比) 為最佳配方，與對照組相比顯著提升樹基徑37%、根系投影面積99%、葉綠素SPAD值25%、地上部乾重59%及地下部乾重27%。以晶曜石取代稻殼炭、配合堆肥及泥炭土一起施用，可以與最佳配方達到類似效果，但在根系投影面積增加率顯著較低。每42天澆灌一次T. asperellum TA並未顯著促進樹苗生長。本研究從市售常見資材中評估適合壤土的土壤改良配方，確認能有效促進樟樹苗生長，期望提供更精準且具經濟效益的方式改善樹木棲地，促進都市林之健康管理。

Urban trees provide numerous benefits to human society, yet their growth environment is often overlooked. Poor soil conditions can weaken tree vigor, impair nutrient uptake, and reduce resistance to pathogens. In Taiwan, brown root rot disease caused by Phellinus noxius is the most predominant disease affecting urban trees, leading to tree decay, collapse, and associated risks to human life and properties. Camphor trees (Camphora officinarum), a common urban tree species in Taiwan, are particularly susceptible to brown root rot disease. Aiming to improve tree growth conditions and enhance tree vigor, this study used camphor tree seedlings as experimental material to develop soil amendment formulations by incorporating rice husk biochar, poultry manure compost, peat, and expanded obsidian into loam and clay loam soils. In addition, Trichoderma asperellum TA, which has the ability to antagonize P. noxius, was used to evaluate its potential in promoting the growth of camphor seedlings. Results from two 84-day greenhouse pot trials showed that both amended loam and clay loam soils had significantly reduced bulk density and increased pH and electrical conductivity (EC). In loam soil, the amendments significantly improved root area, basal diameter, and SPAD chlorophyll values of the camphor seedlings. Drenching with T. asperellum TA did not significantly enhance seedling growth. The applied T. asperellum TA maintained a stable population in all treatments for at least 42 days, with higher abundance observed in loam soil compared to clay loam, indicating good adaptability across different soil conditions. Based on the 84-day results, a promising formulation was selected and further tested with expanded obsidian in a 234-day long-term greenhouse trial using loam soil. The optimal formulation—10% rice husk biochar, 5% compost, and 10% peat (v/v)—significantly increased basal diameter by 37%, root projected area by 99%, SPAD values by 25%, aboveground dry weight by 59%, and underground dry weight by 27%, compared to the control. Replacing biochar with expanded obsidian achieved similar effects on most plant growth parameters, but resulted in a significantly lower increase in root projected area. Soil drenching with T. asperellum TA every 42 days did not significantly improve seedling growth in the long-term trial. Overall, this study identified an effective and practical soil amendment formulation using readily available materials for loam soil, confirming its potential to enhance camphor seedling growth. The findings provide a precise and economically feasible approach to improving urban tree habitats and supporting healthy urban forest management.