短期施用雞糞生物炭對小白菜產量與銅鋅吸收之影響

Abstract

農畜廢棄物隨著人類對農畜產品的需求量增加而增加，雖然一般會製成堆肥再利用，但難以大量消耗。若將雞糞製備成生物炭可以利於儲藏、運輸和施用過程中的環境衛生考量。生物炭可用以改善土壤的物化特性，提升土壤的生產力，並能吸附土壤重金屬離子與有機污染物，且生物炭的穩定結構能長期將有機物儲存在土壤中，達到增加土壤固碳的效果。然而目前尚不了解雞糞生物炭短期施用對於作物生長的影響和對土壤性質改良的效果。 本研究選用臺灣常見的畜牧廢材蛋雞糞為材料，分別以350℃(B3)與550℃(B5)碳化製備成生物炭，再以桃園坡堵系的表土進行盆栽試驗。研究分成兩個部份，試驗一之目的為探討不同溫度製備之雞糞生物炭，不同比例施用下，對土壤性質改善和對作物生長的影響。另一方面，試驗二為將不同雞糞生物炭施用到不同濃度人工添加銅污染土壤中，目的為探討不同溫度製備之雞糞生物炭，對降低土壤中重金屬毒害的效果和對作物生長的影響。 研究結果顯示350℃與550℃製備成生物炭施加2.5%以上會促使供試土壤的pH、EC、有機碳含量、有效性氮含量和有效性磷含量上升。施加350℃雞糞生物炭2.5%(B3+2.5)和5%(B3+5)與全化肥添加處理(F)的產量無顯著差異，推斷350℃雞糞生物炭施加至2.5%可達到小白菜所需要的肥料需要量。以小白菜磷肥需要量為基準添加350℃(B3P+N)或550℃(B5P+N)雞糞生物炭，額外補足氮肥至推薦施用量之處理，與全化肥添加處理(F)的產量則無顯著差異，推斷以磷肥推薦使用量施用雞糞生物炭，額外補足氮肥至推薦施用量之方式，可以減少化學肥料磷肥和鉀肥的使用，避免田間過度施用化肥。550℃製備之雞糞生物炭以氮或磷肥需要量為基準施加之處理(B5N和B5P)的小白菜產量與對照組(CK)比較則無顯著差異。550℃製備之雞糞生物炭的K和Na含量高，在較高施加量下導致土壤EC值過高(EC >4 dS/m)，小白菜受到鹽害無法生長，因此550℃製備之雞糞生物炭不能大量施加，無法達到消耗雞糞之目的。反之350℃製備之雞糞生物炭，相較於550℃製備之雞糞生物炭，以2.5%以上施加可促進小白菜生長，達到消耗雞糞之目的。最多可添加之上限未經評估，而施加大於5%可能會因為EC大於4 dS/m影響小白菜之生長。在人工添加銅的土壤中施加生物炭，無法降低重金屬銅之有效性，小白菜因銅濃度高而影響生長。土壤中有效性鋅濃度低，因此小白菜對鋅吸收量低。

Poultry farming produces a large amount of litter, which has caused waste management challenges in Taiwan. A potential strategy to effectively deal with poultry litter is to produce poultry-litter biochar, which may provide environmental and economic benefits including the improvement of soil fertility and quality, the increase of crop productivity, sorbent for organic and inorganic contaminants, and the increase of soil carbon sequestration effect. However, the effects of short-term applying chicken manure-derived biochar on the yields, the amount of crops uptake copper and zinc, and soil properties remains unclear. In this study, we choose Taiwan's common livestock chicken manure as waste material, which was pyrolyzed respectively at temperature 350℃(B3) and 550℃(B5) to produce biochar. Bok choy(Brassica rapa L.) was grown in pots containing Taoyuan Po-Tu series topsoil amended with biochar in greenhouse. The objectives of this study were to examine the effects of pyrolysis temperature of biochar (350℃, 550℃) and the application rate (2.5%, 5%) on growth of bok choy as well as its uptake of copper and zinc. In addition, the biochar were added to different concentrations of copper-spiked soil(150 and 300 mg/kg), to examine the effects of biochar to reduce the toxicity of heavy metals, and the impact on crop growth conditions. Both chicken manure-derived biochars were able to increase the soil pH, EC, organic carbon, and available phosphorus at the addition rate of 2.5%. The yields of adding biochar pyrolyzed at 350℃ at the rate 2.5% (B3+2.5) and 5% (B3+5) have no significant differences to compare with fertilizer treatment (F), show that 2.5% of biochar pyrolyzed at 350℃ added is able to reach the fertilizer requirements of bok choy. Adding biochar pyrolyzed at 350℃and 550℃at the rate of phosphorus required, and then extra add urea to reach the nitrogen required (B3P+N and B5P+N), which have no significant differences when compared to fertilizer treatment (F), show that this might be the way to replace fertilizer usage. While 550℃ pyrolyzed biochar added at the rate of phosphorus or nitrogen required (B5P and B5N) have no significant differences with control. Biochar pyrolyzed at 550℃ content a higher rate of potassium and sodium. Bok choy which was treated with biochar pyrolyzed at 550℃ grew poorly or even died at the 5% addition rate, as too high of EC value (above 4 dS/m ) is harmful to plant. Therefore, a large amount of biochar pyrolyzed at 550℃cannot be applied. Conversely, biochar pyrolyzed at 350℃ promote the growth of bok choy, can achieve the purpose of consumption of chicken manure. We suggested to apply more than 2.5% of 350℃ pyrolyzed biochar to improve plant growth, but the highest rate was not evaluated in this study. However, over 5% of biochar pyrolyzed at 350℃ added may increase the EC value higher than 4 dS/m. Application of biochar in the artificial spiked-copper soil did not reduce copper toxicity to bok choy. The low concentration of available zinc content in soil result in a low absorption of zinc in bok choy.