應用土壤水分及氮平衡耦合模式評估坡地水稻田氮汙染潛勢

Applying a coupled soil water and nitrogen balance model to evaluate nitrogen contamination potential of paddy field on slope land

陳昆宏(Kun-Hung Chen)

指導教授 ： 陳世楷

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00356

摘要

農業活動為重要之非點源汙染來源，大量使用化學肥料對環境的負面影響近年來逐漸顯現。而集約式施肥易導致氮素汙染地下水和地表水，不僅造成環境和生態破壞，對人類健康亦造成潛在性之危害。
水稻為台灣主要作物，其每年期作面積高達25萬公頃以上，在農業作物的化學肥料消耗量中占極大的比例。水稻在種植期間多保持湛水狀態，施用化學肥料時經過氮素轉化過程，其中產生之硝酸鹽氮可藉由滲漏到達地下水或藉由降雨逕流及排水進入其他地表水體。本研究根據現地監測資料發展驗證水田及氮平衡耦合模式，模式考量水田根系土壤及湛水層之氮素轉化過程，如化肥水解、硝化、脫硝、揮發、礦化、固定、植物吸收及滲透淋洗等。以新竹縣新埔水稻田實驗田區2010年兩次期作田區排放之逕流水質硝酸鹽氮濃度進行模式檢定與驗證，其判定係數R2分別為0.95及0.012，驗證結果不佳導因於兩期作在基肥施用期間，排水之硝酸鹽氮濃度存在極明顯之差異，可能係一期作初期低溫造成硝化作用速率下降所致。建議模式之模擬應將溫度效應納入考量，同時利用更長期之觀測資料修正驗證此一模式。利用二期作經過檢定之模式模擬水稻田不同施肥量對周邊水體之氮污染潛勢，當施用氮肥量達200kg/ha時，對地表逕流及地下水之汙染負荷均仍在2kg/ha以下，遠低於揮發及脫硝作用逸失之氮量，顯示水田施肥之硝酸鹽氮汙染潛勢並不高，研究成果可提供作為農業非點源控制及評估農業迴歸水再利用之參考依據。

關鍵字

非點源汙染 ； 氮平衡模式 ； 水收支 ； 化肥

並列摘要

Agriculture activities are probably the most significant anthropogenic non-point pollution source. In recent years, the intensive application of chemical fertilizers in a large amount is responsible for the negative impact on the environment gradually. Nitrogen contamination in both groundwater and surface waters, resulting in the environmental and ecological destruction, and may pose potential hazards to human health.
Paddy rice is the main crop with the cultivation area about 0.25 million ha per year in Taiwan, accounts for a significant share of fertilizer consumption among agriculture crops. Losses of nitrate from applied chemical fertilizer may be high from paddy fields as they are in flooded condition for most of the cropping period. Nitrate is soluble and moves with the water percolating to groundwater or leave out by drainage or runoff. In order to evaluate the contamination potential of nitrate-N, a nitrate and water budget model includes all the important N-transformation process such as fertilizer hydrolysis, nitrification, denitrification, volatilization, mineralization, immobilization, plant uptake, and percolation that occur in both soil and pounding water for paddy field is established in this study. The model was calibrated and validated by in-situ data of fertilizer application rate, water budget measurement and water quality analyses continued for two crop periods in Hsin-pu experimental paddy field located at Hsin-chu County, north Taiwan. Model simulation results indicate that coefficient of determination (R2) for two crop periods are 0.95 and 0.012, respectively, which is not well enough to pass the verification standard due to the significance difference between the first crop and the second crop on the nitrate concentration of drainage water during the early stage of basal fertilizer application. Low temperature during the early stage of the first crop may reduce the the rate of nitrification which result in the low nitrate concentration of drainage water. It is suggested that the factor of temperature should be taken into account for mode simulation, and long-term monitor on water quality is necessary to improve the effectiveness of this model. Applying the model to simulate the nitrate load from drainage water during the second crop period and assume the fertilizer application rate increase from 120kgN/ha to 200kgN/ha, the results show that both of nitrate loss from drainage and from percolation are smaller than 2kgN/ha, far below the N loss from denitrification and volatilization. It can be confirmed that fertilizer application of paddy field not the main non-point pollution source and the potential pollution load could be reduced by well drainage water control and rational fertilizer management. This research can apply a basis for non –point pollution control and assessing the re-use of agricultural return flow in paddy field.

並列關鍵字

Nonpoint source pollution ； N-balance ； water balance ； chemical fertilizers

參考文獻

[7] 翁菁羚，土壤有機氮形態對臺灣中部三種針葉林土壤氮礦化作用之影響，碩士論文，國立臺灣大學森林環境暨資源學系，臺北，2006。

[13] 陳榮五、李健捀、郭孚燿、廖萬正，作物合理化施肥技術，臺中區農業專訊第六十一期，2008， 第24-25頁。

[4] 吳添益、蔡政賢、張素真，「水稻合理化施肥技術」，苗栗區農業專訊，第四十二期，2008，第2-4頁。

[14] 潘昶儒、余宣穎、黃井約，「水稻優質栽培施肥管理模式」，花蓮區農業專訊第六十五期，2008，第12-15頁。

[8] 張格綸，應用蒸發皿係數推估地區蒸發散量之研究，碩士論文，國立成功大學資源工程學系，臺南，2007。