添加植體對除草劑施得圃在土壤中的消散及土壤菌相的影響

Abstract

近年來農業耕作型態改變，綠肥作物被大量使用以取代部分化學肥料。因此本實驗目的即為探討添加常見的綠肥植物大波斯菊 (Cosmos bipinnatus) 及羽扇豆 (Lupinus luteus) 於不同土壤中對疑似環境荷爾蒙除草劑施得圃(Pendimethalin) 消散的影響，並觀察綠肥孵育過程中土壤菌相結構的變化。本實驗將羽扇豆與大波斯菊分別施用於pH 5.2的三坑子土系 (Sankengtzu, Sk) 及pH 7.7的二林土系 (Erhlin, Eh) 兩種試驗土中，並於孵育110天期間分別取樣並分析土壤中施得圃殘留量，以觀察綠肥對施得圃消散的影響。中性Eh土壤中添加羽扇豆、大波斯菊及未添加植體，施得圃半生期分別為 46.3, 52.6 及 34.8天；但在酸性Sk土壤中則分別為 49.0, 54.9 及 62.2天。此結果顯示酸性土壤環境下施得圃的消散情形較中性土壤環境中緩慢，但添加綠肥後則有助於酸性土中施得圃的消散。 土壤菌相結構變化則以Biolog EcoplateTM 及變性梯度電泳 (Denaturing gradient gel electrophoresis, DGGE) 檢視菌相的改變，並分別以主成分分析及UPGMA比較改變情形。結果發現，施得圃與綠肥的添加皆會使孵育初期的微生物族群改變且單純化；但經110天孵育後微生物族群會隨時間而互有消長，而使110天後的微生物族群與孵育初始產生明顯變化。添加綠肥處理下經孵育110天後微生物族群結構會與對照組相似，而有施得圃的施用則與對照組相似度較低；但羽扇豆添加於中性土中處理下，經孵育後有助於減輕施得圃對微生物族群的衝擊。因此，土壤pH及所添加綠肥性質的差異，皆為造成土壤菌相結構改變的原因。

Green manure is primarily used in environmentally friendly agricultural practices to reduce the application of chemical fertilizer and herbicide. A widely used dinitroaniline herbicide, pendimethalin, was found to be the endocrine disrupting potential herbicide in recent studies. In this study, the cosmos (Cosmos bipinnatus) and lupin (Lupinus luteus) were amended in Sankengtzu (pH 5.2) and Erhlin (pH 7.7) series soil, respectively. The dissipation of pendimethalin in the soil was investigated and the effect of pendimethalin on soil bacterial community structure during the degradation periods was also studied. In the dissipation experiments, half-life of pendimethalin in Erhlin soil was 34.8 days. After amended the cosmos and lupin, the half-life of pendimethalin were 46.3 and 52.6 days. In Sankengtzu soil, the half-life of pendimehtalin increased to 62.2 days. After amended the cosmos and lupin, the half-life decreased to 49.0 and 54.9 days. The results revealed that the pendimethalin degradation process is more critical in Sankengtzu soil. The cosmos and lupin amended would be beneficial to degrade of pendimethalin in Sankengtzu soil. The soil microbial community diversity has been discussed in terms of the genetic by using PCR-DGGE data and functional diversity by using the Biolog EcoplateTM. From the Ecoplate method, PCA analysis indicated that microbial communities were relatively close under the pendimethalin treatments for 24 hours, and the green manure treatments revealed the same effects. After incubated for 110 days, the microbial communities clearly differed from the initial communities (24 hours). This is also in agreement with the results of the DGGE methods. The microbial communities of the blank treatment were relatively close with the green manure treatment, but seperated after applied pendimethalin in 110 days. Morever, only the lupin treatment was not so influenced by pendimethalin in Erhlin soil. Therefore, the soil pH and green manure properties resulted in different effects to soil microbial community diversity.