不同施肥管理對土壤之磷及氮劃份之影響

Abstract

摘要 磷與氮為土壤之重要資源，而不同的施肥管理及耕作制度會影響磷與氮在土壤中的變動及有效性。本研究的目的在探討經不同施肥管理之後，對土壤磷及氮的型態及轉變的影響。本試驗取行政院農業委員會農業試驗所、高雄區農業改良場旗南分場及桃園區農業改良場三處不同試驗土壤進行分析。本試驗利用Sui 和 Thompson (1999) 序列萃取法，以不同強弱的萃取劑來劃分土壤中的磷，將土壤磷劃分為水萃取磷、碳酸氫鈉萃取有機磷及無機磷、氫氧化鈉萃取有機磷及無機磷、鹽酸萃取磷及殘餘磷；利用 Bremner (1965) 的土壤有機態氮劃分法將土壤有機態氮劃分為水解性全氮、水解性銨態氮、胺基醣態氮、胺基酸態氮及不可辨認的水解性氮。農業試驗所土壤為經九年十八作之後的土壤，試驗共有七種處理；旗南分場土壤為經十六年處理者，設二個輪作系統，各具慣行、折衷及有機等三種農耕法，共設六種處理；桃園區農業改良場土壤為設施栽培，施用不同有機資材及化學肥料共七種處理。 試驗結果顯示，就農業試驗所土壤而言，施用堆肥及搭配化學肥料的處理，可以使土壤有效性磷增加。而施用有機肥料對土壤的總氮及可水解全氮有顯著影響。與對照組比，施用肥料處理之碳酸氫鈉萃取無機磷、氫氧化鈉萃取無機磷劃份佔全磷的比例提高，顯示磷肥添加會直接增加易變動部份的無機磷源。旗南分場土壤結果顯示，施用有機資材使有機區與折衷區處理者的有效性磷較慣行區高。土壤中的總氮和可水解全氮濃度，皆為有機區 > 折衷區 > 慣行區。比較有機區與慣行區，顯示施有機肥料會使可水解全氮所佔比例下降，而不可水解氮的比例上升，水解性銨態氮的比例下降，不可辨認的水解性氮所佔比例增加。顯示所施入之有機肥主要補充至不可水解氮、不可辨認的水解性氮劃份。桃園區農業改良場之土壤，除大豆粕及雞糞堆肥處理外，施用其他有機肥料處理的總氮及可水解全氮濃度均顯著高於化學肥料處理者。而各有機肥料處理則因其礦化特性不同而對於土壤中氮濃度有不同的影響。綜上所述，經由不同時間的不同的施肥管理下，會使土壤磷及氮的化學特性產生顯著的變化。 關鍵詞：施肥管理、磷劃分、氮劃分

Abstract Nitrogen (N) and phosphorus (P) are important resources of soil for plant growth. Different fertilization managements and cropping systems affect the transformation and availability of N and P in soil. The purpose of this study was to investigate the effects of different fertilization management after different periods on the form and transformation of N and P in soils. A sequential extraction technique to fractionate P and the method proposed by Bremner to separate N in different fractions were used. Soil samples were taken from a nine-year field experiment (TARI) with seven treatments, a sixteen-year experiment (KDARES-CBS) with two rotation systems combined with three fertilization managements, and a four-year greenhouse experiment (TDARES) with seven treatments, respectively. The results indicated that application of compost and chemical fertilizer increased the concentrations of available P in soil at TARI. Soil total N and total hydrolyzable N were significantly influenced by the application of organic fertilizer. Compared with CK treatment, application of fertilizer increased the proportion of H2O-P fraction, NaHCO3-IP fraction, and NaOH-IP fraction, respectively. This result indicated that application of P fertilizer increased labile inorganic P. In KDARES-CBS experimental soil, the concentrations of available P in soils of organic farming and intermediate farming were higher than that of conventional farming. Application of organic fertilizer decreased the proportion of total hydrolyzable N fraction and hydrolyzable NH4-N fraction, and increased the proportion of nonhydrolyzable N fraction and unidentified hydrolyzable N fraction, respectively. In TDARES experimental soils, except SBM and PC treatments, the concentrations of total N and total hydrolyzable N of other organic fertilizer treatments are higher than those of Chem treatment. In conclusion, the characteristics of N and P of soil change significantly after different fertilization managements. Key words: Fertilization management, Phosphorus fractions, Nitrogen fractions.