生物炭複合資材在不同質地土壤中的分解率與養分釋放及對小白菜產量之影響

生物炭搭配化肥或堆肥的使用，可改善生物炭自身肥力匱乏的缺點，並作為往後循環農業管理並增產的策略之一。本試驗選擇兩種台灣常見農業土壤(砂質土及黏質土)，將生物炭與蔗渣堆肥依不同比例製為四種粒狀複合資材，將四種複合資材置入茶包埋入土壤中孵育180天，評估各複合資材之分解速率及評估複合資材在作物產量上的變化。四種複合資材分別為生物炭：堆肥=1:3 (BC3)、生物炭：堆肥=1:1 (BC)、全生物炭 (B)及全蔗渣堆肥 (C)。本研究於孵育期間分別於1、3、7、14、28、56、120、180天時抽取土壤溶液分析無機氮(Inorganic N)、有效磷(Ava. P)及交換性鉀(Exc. K)含量評估各資材之養分釋放及兩期(第30天及第60天)作物產量的差異並進行土壤分析。研究結果顯示，兩試驗土壤中，各複合資材的分解率皆以C最高 (45-48%)，依序為BC3 (38-41%)、BC (35-39%)，最差為B (20-25%)；以砂土中之資材分解率較快。養分釋放方面， NH4+-N含量因硝化作用隨孵育時間減少，而NO3--N隨孵育時間增加。各資材處理間以C及BC3處理下土壤溶液中之NO3--N含量最高，分別為147-148 mg/kg及140-187 mg/kg，其中以砂土土壤溶液中的NO3--N含量最高，顯示硝化作用於砂土中較為顯著。鉀含量隨孵育時間而增加，以B處理較高以砂土土壤溶液最高為111 mg/kg。複合資材於有效磷釋放過程中，生物炭的存在可促進土壤磷的有效性，可能為自身提供的水溶性磷釋放或生物炭競爭土壤中有效磷的吸附位置所致。本研究僅於砂土溶液中可測得有效磷含量，而黏土中之有效磷於孵育期間多被固定於土壤上而緩慢釋放，可能導致短期作物缺磷。在作物產量表現上在第30天以C最高產量，依序為BC3、BC，最差為B；在第60天BC3及BC產量提高分別提高第30天的12-17%，則C降低30-64%。土壤分析結果在氮、磷、鉀含量在第30天C及BC3之間差距甚小(4-15%)，而到第60天BC3的土壤肥力超過C至少20-40%，所以BC3在養分供給上比C更具有緩釋效果，以提供長期養分供應。

關鍵字

生物炭；複合資材；養分釋放；作物產量；分解率

並列摘要

Combining biochar with chemical fertilizer or compost might not only improve fertility deficiency in biochar itself, but also control nutrient releasing to be a novel agricultural management strategy in future. In this study, we produced granular compound biochar fertilizers (gBCFs) by combining the biochar with bagasse compost, and then applied these into a sandy soil (Entisol) and a degraded red soil (Ultisol) to evaluate their effects on decomposition rate and nutrient releasing in soils. This study produced four gCBFs composed by different ratio of the biochar and the compost, which are biochar-compost (1:3, w/w) (BC3), biochar-compost (1:1) (BC), biochar only (B), and compost only (C), respectively. The results indicated that the highest decomposition rate (45-48%) of gBCFs was found in C-treated soil, and followed by treatments of BC3 (38-41%), BC (38-41%) and B (20-25%) after incubation, and decomposition rate was faster in sandy soil than in clayey soil. Regarding nutrient releasing dynamics, nitrification drove increases in NO3--N in soil solution after incubation in all treatments, and the highest contents were found in treatments of C and BC3. Nitrification was much more dominant in the sandy soil. The highest Exc. K contents in solution were in the treatments of B and BC indicating that biochar addition in soil could obviously increase Exc. K. During releasing process of available P (av. P) in this study, the presence of biochar certainly increased av. P contents in two studied soils. However, av. P could be only found in sandy soil solution, and nearly av. P contents were fixed in clayey soil, indicating P deficiency might be occurred in the clayey soil for short-term crop planting. In terms of crop yield performance, the highest yield of C was used in the first period, followed by BC3, BC, and the worst was B; in the second period, the yield of BC3 and BC increased by 12-17% of the first period, and C decreased. 30-64%. The results of soil analysis showed that the content of nitrogen, phosphorus, and potassium was close to between C and BC3 on the 30th day (4-15%), and the soil fertility of BC3 exceeded C by at least 20-40% by the 60th day, so the nutrients of BC3 slowed down. It has a slow-release effect than C to provide long-term nutrient supply.