Effects of rice hull biochar on the yield, nutrient uptake, and antioxidant properties of purple leaf Ipomoea batatas

生物炭為生質在高溫裂解所得之副產物，在此條件下將物質縮合，可視為儲存碳的一種方式，並能減少溫室氣體散逸到空氣中。將其施加於土壤中，可為土壤改良劑，研究已證實可因此而增加土壤通氣性、減少溫室氣體散逸、改善pH值等。然製作溫度、環境、原料等不同皆會造成生成之生物炭性質有所差異，故研究也顯示不同之生物炭之效果有所差異。生物體內自由基為氧分子接受自由電子而成，過多自由基會造成DNA斷裂、細胞死亡，導致疾病。紫色葉肉甘藷葉對環境之適應力強且生長期短，研究顯示施加肥料、石灰、土壤改良劑或環境改變對於各種作物對花青素影響結果不一。本研究之目的在探討兩種不同溫度生成之稻殼生物炭 (350℃與800℃) 加入土壤中後種植紫色葉用甘藷葉，對產量、養分吸收和抗氧化物質之影響。本試驗取自稻殼於350℃ (B1) 與800℃ (B2) 裂解生成之生物炭，所設定的處理分別為控制組 (Cont)、施化學肥料組 (Chem-F)、添加石灰改善pH值後施加化學肥料 (LEF)、施有機質肥料 (Org-F) 與分別添加20 g kg-1和50 g kg-1之生物炭 (B1-2、B1-5、B2-2及B2-5)，又分為再添加化學肥料 (B1-2F、B1-5F、B2-2F及B2-5F)，共12個處理。每個月採收植體一次，採取之植物體分析養分和抗氧化物質，土壤則分析基本性質。結果顯示，在本研究之生物炭添加下，對土壤pH之影響小，但增加植物有相之磷與鉀。在產量和氮、磷與鉀吸收量中，添加生物炭皆有些微上升，其中為B1-5為最高，而添加石灰則與生物炭效果相似。稻殼製成之生物炭本身含有較多鉀，施加於土壤後，植體鉀吸收量則有明顯上升，植體收穫後土壤中鉀的含量明顯也高出許多，以B2較高。添加石灰後使磷的吸收量上升，顯示添加石灰可幫助磷的吸收。有機質肥料處理在產量和氮、磷與鉀吸收量為最差，可能添加量不足植體生長所需。本研究得之紫色葉用甘藷之花青素、總酚類含量與清除DPPH能力與前人研究測得之值較低。添加生物炭可使總酚類與花青素含量上升，但上升情況則不一致。四個採收時期花青素與總酚類最高含量皆出現在添加B1處理 (僅第三次採收之B2-5F除外)。隨著種植時間花青素含量下降，而總酚類含量則上升。添加生物炭可使產量、作物養分吸收量上升，且以350℃下製成之生物炭以50 g kg-1添加效果為最佳，有無再添加化學肥料，皆可達到相同結果。The application of biochar to soil obtained under high temperature pyrolysis of biomass can be taken as a kind of carbon sequestration, which can reduce greenhouse gas dissipation into the air. Biochar can be used as a soil conditioner. Application of biochar into soil resulted in increasing soil aeration, reducing greenhouse gas dissipation, and increasing the soil pH. The physicochemical characteristics of biochar depend on the pyrolytic temperature, raw materials, and other conditions of pyrolysis. In vivo, free radicals come from oxygen molecules and excessive free radicals cause DNA fragmentation and cell death. The purple leaf sweet potato is a common vegetable in Taiwan, it can adapt to a wide range of growth conditions and has a rapid growth rate. Studies have shown that fertilizer, lime, soil conditioner, or environmental condition affect the anthocyanin content of various vegetable. The purpose of this study was to investigate the effects of rice hull biochar generated at two different temperature (350℃ and 800℃) on the growth, nutrient uptake, and antioxidant activity of purple leaf sweet potato. There were twelve treatments, with four replicates for each treatment. There were control (Cont), applying chemical fertilizer (Chem-F), applying lime and chemical fertilizer (LEF), applying organic fertilizer (Org-F), applying 20 g kg-1 and 50 g kg-1 of biochar (B1-2, B1-5, B2-2, B2-5), and applying 20 g kg-1 and 50 g kg-1 of biochar and chemical fertilizer (B1-2F, B1-5F, B2-2F, B2-5F). The plants were sampled every month. The concentrations of nitrogen, phosphorus, potassium, anthocyanin, phenolic of the plant samples were analyzed. DPPH scavenging ability of the plant samples were also determined. Results showed that there was no difference on plant yield and nutrient uptake among different treatments. Biochar application resulted in a greater yield, nitrogen, phosphorus and potassium uptake. The dry matter yield of organic fertilizer treatment was the lowest among all treatments, which would be could be due to the insufficient supply of nitrogen. Application of biochar resulted in an increase in the total phenolic and anthocyanin contents. However, there was no consistent effect on the total phenolic and anthocyanin concentrations among biochar treatments. The plant of B1 treatment had the highest anthocyanin and phenolic concentrations. Anthocyanin content of leaves of purple leaf sweet potato decreased with the periods of growth, while an increase in the total phenolic content was noted