合鴨有機田與慣行田的氮收支模式比較

隨著環保意識的抬頭，於民國34到60年間常見的傳統水耕法－合鴨有機農法，又再度風行於台灣農村。合鴨有機農法屏棄了農藥以及化學肥料，利用合鴨取食害蟲、踩踏水田抑制雜草生長，並增加水中溶氧量。同時，合鴨糞便也能減少有機肥料使用量，降低溢流入環境的營養。本實驗的目的在建構，奉行有機耕作精神的合鴨農法之氮收支模式，了解稻作期間的氮流失量、田區內固氮能力以及對福壽螺等害蟲的抑制結果，較之慣行田是否能減少對環境的衝擊，維護地力。實驗結果顯示，在排水曬田時流失的氮素量，慣行田流失的氮素較合鴨田多。合鴨田及慣行田在收割後之單位氮素淨收支均為正值，慣行田較合鴨田高，表示休耕後的慣行田會徑流出更多的氮素到環境中。影響田區土壤氮素變化量的因素中，以固氮量為最大宗，合鴨田區的土壤間固氮力比慣行田區好。綜合實驗結果顯示，不施灑農藥、使用有機肥料的合鴨農法，不僅更能控制福壽螺等害蟲數量，較之慣行田，更降低了農耕活動流失氮素對環境的衝擊，達成地力永續經營的目的。

關鍵字

合鴨農法；慣行農法；氮收支；固氮

並列摘要

Owning to the rise of environmental consciousness and concerns about harmful effects of chemical compounds on the human body during agricultural processes around the whole world, the traditional rice-duck organic farming, the common agricultural methods in rural area between 1945 and 1971, becomes popular again in Taiwan. Different from conventional farming, the method of rice-duck organic farming uses ducks instead of pesticides and chemical fertilizers to feed pests and stamp paddy fields for suppressing weed and increasing the amount of dissolved oxygen in the water. Meanwhile, as a result of the reducing the amount of organic fertilizer, the duck organic farming can diminish the amount of nutrient overflowing into the environment. By building up the nitrogen budget model of rice-duck organic farming, the purpose of this study is to understand whether rice-duck organic farming can reduce the impact of fertilizer on the environment and maintain fertility by comparing nitrogen loss during the processes of cultivation and the capability of fixed nitrogen and the inhibition of apple snails and other pests between rice-duck organic and conventional farming. The results showed that the amount of nitrogen loss during the drainage is 57.79 g-m^(-2) in duck paddy field and 62.79 g-m^(-2) in conventional paddy field respectively. The amount of soil nitrogen was 8.7 g-m^(-2) in duck paddy field and 21.4 g-m^(-2) in conventional paddy field, which indicated the latter would release more nitrogen into the environment during the fallow. Nitrogen fixation was the dominating factor affecting the change in the amount of soil nitrogen. There were 64.06 g-m^(-2) in duck paddy field nitrogen and 54.07 g-m^(-2) in conventional paddy field of nitrogen fixed in the soil, which suggested rice-duck paddy field had better capability of nitrogen fixation in the soil. Without spilling tea-seed meal, the number of apple snails would be out of control; on the contrary, the number of apple snails in the duck paddy field had been maintained in 0-20 per 9 m^2 by duck feeding. In the conclusion, compared to conventional paddy farming, duck farming, without pesticide and chemical fertility, not only showed more control over the number of apple snails and other pests, but also reduced the environmental impact by the loss of nitrogen produced from agricultural activities, to likely achieve sustainability agricultural use.

並列關鍵字

duck organic farming ； conventional farming ； nitrogen budget ； nitrogen fixation

國際替代計量

合鴨有機田與慣行田的氮收支模式比較

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