水田耕作方式對土壤養分含量之影響

Effects of Cultivation Methods on Nutrient Contents in Paddy Fields

李怡賢(Lee Yi-Hsien)

指導教授 ： 葉一隆

國立屏東科技大學/工學院/土木工程系所/碩士(2010年)

https://doi.org/10.6346/NPUST.2010.00254

摘要

摘要內容：
水田不僅是糧食生產場所，在水稻種植過程，田區操作亦具有生態與生活機能。政府為提倡水田三生效益，並活化水稻生產過剩之田區使用；因此，利用休耕水田進行蓄水，並種植綠肥作物以補充土壤養分。本研究探討三種操作方式對於水田土壤營養元素：有機碳、土壤pH值、有效性磷、K、Ca、Mg、Fe、Cu、Mn、Zn的影響，三種不同操作包括A田區第一期作種植水稻、第二期休耕種植綠肥後蓄水，B田區第一、二期皆種植水稻及C田區全年皆休耕且未種植作物。
本文根據水稻田操作方式規劃4個取樣時程，S1為一期稻作種植前，S2為一期稻作收割後，S3為綠肥翻耕蓄水前及S4為蓄水結束後曬田期間，分別取樣六次觀察土壤營養元素在土壤層內的移動與存蓄，其中第一次取樣為田區蓄水狀態。由分析結果可知，在全土樣分析及在深度變化上，除pH以外其他養分元素隨土壤深度越深濃度分佈越低，以稻作根系深度60 cm為上下層之分界點，三田區之不同操作其下層濃度分佈變化不大，並檢定上層營養元素濃度差異。在S2階段，A田區平均pH、Mg、K及Zn濃度比B、C田區濃度高，深度上層具極顯著差異，Ca在全土樣分析上顯示C > B > A之濃度分佈。S4階段有機碳、pH、Mg、K、Fe及Zn平均濃度亦有顯著差異，Ca濃度在上層土樣分析顯示A >C > B，且A田區與B田區有極顯著差異。在循環操作上沒有施用化學肥料的A田區有效性-磷、Mg、K在六次取樣上都有最高平均濃度分佈，C田區Mn於六次取樣上皆呈最高平均濃度。
另外，在蓄水階段全土樣K、Fe、Mg、Cu、Zn與有效性-磷等在六次取樣中平均濃度呈現最高分佈，其中在最高A田區K濃度比最低C田區濃度高41 ppm，Mg以最高濃度A田區比最低B田區最大濃度差異為90 ppm，分析結果也顯示土地操作方式不同對於土壤肥力元素的濃度變化具有明顯影響。

關鍵字

水田休耕 ； 土壤養分 ； 蓄水 ； 變異數

並列摘要

Due to a surplus in rice production, and to promote the beneficences of paddy field production, living, and ecological functions, the government in Taiwan encourages farms to store water in fallowed paddy fields or to plant green manure to supply soil nutrition.
This study investigated the change in soil nutritional elements (pH, organic carbon [OC], available phosphorus (AP), potassium [K], calcium [Ca], magnesium [Mg], iron [Fe], copper [Cu], manganese [Mn], and zinc [Zn]) in paddy fields. Three operational fields were compared. One field was first planted in rice. Green manure was then planted and turned over in the second cropping period. The field then stored water (Field A). In Field B, rice was planted in both cropping periods. Field C was fallow all year.
The sample timing followed four rice-planting schedules, which included: before the 1st rice crop (S1), after the 1st rice crop (S2), before green manure turn over and water storage (S3), and field exposure to sun after water storage (S4). In addition, one sample was taken while water was stored. Six soil-sampling intervals were taken to examine the mobility and retention of nutritional elements. In each sampling field, six sampling sites were selected and seven samples were taken from each site at 15 cm intervals, for a total soil depth of 105 cm. The examination was divided into upper and bottom layers. The nutritional elements did not show a significant change in the bottom layer; therefore, only elements in the upper layer were tested. Typically, the element concentrations decreased with the increase in soil depth. pH values did not decrease.
During the S2 sampling schedule, the pH and the concentrations of Mg, K, and Zn in Field A were higher than concentrations in Fields B and C in both total samples and samples in the upper layer. The Ca concentrations in the field total samples followed the trend Field C > Field B > Field A. During the S4 sampling schedule, the pH and the concentrations of OC, Mg, K, Fe, and Zn were significantly different in the three different fields. Ca concentrations in the fields followed the trend Field A > Field C > Field B in the upper layer. Although, chemical fertilizer was not applied to Field A, the concentrations of Mg, Mn, K, and AP were higher than the concentrations in Fields B and C.
In addition, when water was stored in the field, the concentrations of K, Fe, Mg, Cu, Zn, and AP were highest in Field A. The highest mean K concentration in Field A was 41 ppm higher than the lowest mean concentration in Field C. The highest mean Mg concentration in Field A was 90 ppm higher than the lowest mean concentration in Field B. This study demonstrated that the green manure stored water operation in Field A affected the mobility and retention of nutrients in the field.

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