Leaching Methods Can Underestimate Mineralization Potential of Soils

• Published in: Communications in Soil Science and Plant Analysis Vol. 47; no. 13-14; pp. 1701 - 1708
• Main Authors: Mulvaney, Richard L., Otto, Rafael, Griesheim, Kelsey L., Su, Kai, Trivelin, Paulo Cesar Ocheuze
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 05.08.2016; Taylor & Francis Ltd
• Subjects: air drying; Alfisols; Ammonium; ammonium compounds; ammonium nitrogen; Biological N availability index; Brazil; Calcium chloride; Histosols; Illinois; Leaching; mineral N production; Mineralization; Mollisols; N fertilizer requirement; net mineralization; nitrates; nitrites; nitrogen; Nitrogen dioxide; Oxisols; potassium chloride; soil incubation; temperate soils; USA, Illinois; ASW, Brazil; Brazil; Illinois
• ISSN: 0010-3624; 1532-2416; 1532-2416; 1532-4133
• DOI: 10.1080/00103624.2016.1206561

Aerobic incubations to estimate net nitrogen (N) mineralization typically involve periodic leaching of soil with 0.01 M calcium chloride (CaCl 2 ), so as to remove mineral N that would otherwise be subject to immobilization. A study was conducted to evaluate the accuracy of leaching for analysis of exchangeable ammonium (NH 4 + )-N and nitrate + nitrite (NO 3 − + NO 2 - )-N, relative to conventional extractions using 2 M potassium chloride (KCl). Ten air-dried soils were used, five each from Illinois and Brazil, that had been amended with NH 4 + -N (1 g kg −1 ) and NO 3 - -N (0.6 g kg −1 ). Both methods were in good agreement for inorganic N analysis of the Brazilian Oxisols, whereas leaching was significantly lower by 12-48% in recovering exchangeable NH 4 + -N from Illinois Alfisols, Mollisols, and Histosols. The potential for underestimating net N mineralization was confirmed by a 12-wk incubation experiment showing 9-86% of mineral N recoveries from three temperate soils as exchangeable NH 4 + .