强酸性黏土施用堆肥对土壤磷素化学与植物吸收磷素的影响

强酸性黏土施用堆肥对土壤磷素化学与植物吸收磷素的影响 強酸性黏土施用堆肥對土壤磷素化學與植物吸收磷素的影響 Compost Induced Changes in the Chemistry and Plant Uptake of Phosphorus in a Strongly Acidic Clay Soil 研究生,喬鮑伯 Babou Ousman Jobe 指導教授,蔡秀隆 Tsai, Shiow-Long 許正一 Hseu, Zeng-Yei 【摘要】 磷是植物的必需營養元素,缺乏時,限制農業生產。在熱帶與亞熱帶低投入的農業體系裡,磷的問題是相當明顯的。磷肥在提高和維持作物的產量是非常重要的,但是在大部分的地區卻是不足夠,即便施用磷肥對作物的有效性仍然是有限。同樣地,石灰通常會與土壤的組成分產生不利的化學反應,以致磷的無效性更為惡化。施用堆肥對許多貧瘠酸土(包括缺鄰)的改善有很好的潛力。雖然如此,施用堆肥作為經營管理熱帶地區酸性極育土壤(Ultisol)的策略時,必須考慮到如何減少堆肥誘導的磷吸附行為,改善堆肥施用效率。 本研究採用未經耕作的極育土(Typic Hapludult)為試驗土壤,在實驗室以玉米與芥藍菜作為生物檢測的材料,探討施用堆肥及石灰對極育土中磷的吸附行為以及植物可利用性的影響。研究結果顯示,堆肥可以顯著的減少磷的吸附,施用石灰反而使磷的溶解性惡化。總之,減少磷的吸附是受到堆肥的生化特性密切的影響,諸如pH緩衝能力與總磷含量。低pH緩衝能力或高總磷含量的堆肥比高pH緩衝能力或低總磷含量的堆肥在減少磷的吸附上更有效。堆肥磷的肥料當量在土壤磷的變化上是與礦物磷肥相等的,甚至在作物磷的營養、生長與乾物質生產亦是相等。 在堆肥系統內磷變化的速率比較慢,因為是由於Bray1磷的酸性磷與殘餘磷的緩衝效果。同樣地,整合堆肥與礦物肥料的施用在磷的可利用性與作物生長上也觀察到有協同作用。綜合以上結果,在極育土壤施用堆肥能夠增進與支撐作物的生產,可以提高在以極育土壤為重要農業資源的熱帶與亞熱帶的地區的社會福利。 關鍵字,極育土、堆肥、磷吸附、石灰潛勢、總磷、磷可溶性、磷素養分 【Abstract】 Phosphorus (P) is an essential plant nutrient, the short supply of which, extensively limits agricultural production. This P problem is no where more evident than in the low–input agricultural systems of the subtropics and the tropic. Mineral P fertilizers are vital to increase and maintain crop yields, but are ill,afforded in most of the regions, and where applied transform into inorganic and organic forms of limited availability to plants. Similarly, lime in some cases can produce unfavorable chemical reactions with soil constituents, thereby exacerbating the problem of P unavailability. Composts are available locally and can potentially address a multitude of acid soil infertility conditions, including P. However, the use of compost as a strategic tool to manage the P fertility of tropical acid soils, such as Ultisol, is dependent on the knowledge of the compost,induced mechanisms and their relative importance in the reduction of P sorption. Experiments were conducted on uncultivated clay Ultisol (Typic Hapludult) to evaluate the influence of compost on P solubility in laboratory incubations and plant availability in plastic house, using kale and maize as assay crops. By comparison, compost has mitigating effect on P sorption, where as lime applied as CaCO exacerbates the problem of P solubility. However, reduction in 3 +P sorption was differentially influenced by compost biochemical properties, such as H consumption capacity or lime potential and total P content. Low lime potential or high total P content composts are +more effective than the high H consumption capacity or low total P composts. Fertilizer equivalency of compost P was equivalent to the inorganic P added as mineral fertilizer on soil P lability and even exceeded mineral fertilizer on the P nutrition, growth, and dry matter production of crops. The lower rate of decline in P lability in the compost,system compared with the fertilizer,system was, because of the buffering effect of the acid,P and residual P fractions on Bray 1 extractable P. Similarly, synergism in the integrated use of compost and fertilizer was observed on P availability and crop growth. Collectively, these results indicate that compost use has the potential to expand and sustain crop production on Ultisols, thereby enhancing the welfare of societies in the tropics and subtropics where Ultisols are important agricultural resource. Keywords,Ultisol, Compost, P sorption, Lime potential, Total P, P solubility, P nutrition