N vô cơ trong đất chủ yếu là trong các hình thức của nitrat (NO3) và amoni (NH4). Nitrit là hiếm khi xuất hiện với số lượng phát hiện, và xác định của nó là bình thường không có cơ sở, ngoại trừ trung lập cho đất kiềm nhận NH4 NH4-sản xuất phân bón (Keeney và Nelson 1982). Đất các phòng thí nghiệm kiểm tra thường xác định NO3 để ước tính N có sẵn trong đất nông nghiệp, trong khi các phòng thí nghiệm phân tích vườn ươm cây và đất rừng thường xác định cả hai NO3 và. | II. DIAGNOSTIC METHODS FOR SOIL AND ENVIRONMENTAL MANAGEMENT Section Editors . Schoenau and . O Halloran 2006 by Taylor Francis Group LLC. 2006 by Taylor Francis Group LLC. Chapter 6 Nitrate and Exchangeable Ammonium Nitrogen . Maynard Natural Resources Canada Victoria British Columbia Canada . Kalra and . Crumbaugh Natural Resources Canada Edmonton Alberta Canada INTRODUCTION Inorganic N in soils is predominantly in the form of nitrate NO3 and ammonium NH4 . Nitrite is seldom present in detectable amounts and its determination is normally unwarranted except in neutral to alkaline soils receiving NH4 and NH4-producing fertilizers Keeney and Nelson 1982 . Soil testing laboratories usually determine NO3 to estimate available N in agricultural soils while laboratories analyzing tree nursery and forest soils often determine both NO3 and NH4. There is considerable diversity among laboratories in the extraction and determination of NO3 and NH4. In addition incubation methods both aerobic and anaerobic have been used to determine the potentially mineralizable N see Chapter 46 and nitrogen supply rates using ion exchange resins see Chapter 13 . Nitrate is water-soluble and a number of solutions including water have been used as extractants. Exchangeable NH4 is defined as NH4 that can be extracted at room temperature with a neutral K salt solution. Various molarities have been used such as M K2SO4 M KCl M KCl and M KCl Keeney and Nelson 1982 . The most common extractant for NO3 and NH4 however is M KCl . Magill and Aber 2000 Shahandeh et al. 2005 . The methods of determination for NO3 and NH4 are even more diverse than the methods of extraction Keeney and Nelson 1982 . These range from specific ion electrode to manual colorimetric techniques microdiffusion steam distillation and continuous flow analysis. Steam distillation is still sometimes employed for 15N however for routine 2006 by Taylor Francis Group .
