Sensitivity of Nitrogen Mineralization Indicators to Crop and Soil Management

Abstract

Soil nitrogen (N) mineralization indicators are useful only if they are sensitive to management practices. The precision of measurement and the sensitivity of the following indicators to crop sequence, tillage, and liming effects were compared: (i) mineral N production during a 24‐day incubation under aerobic conditions, (ii) ammonium (NH₄)‐N production under waterlogged conditions, (iii and iv) hot potassium chloride (KCl)–extractable and hydrolyzable NH₄‐N (the latter obtained by subtracting initial NH₄‐N from extracted NH₄‐N), and (v) protease activity. The coefficients of variation decreased in this order: protease activity>KCl‐hydrolyzable NH₄‐N>aerobic incubation>KCl‐extractable NH₄‐N=anaerobic incubation. Most of the test results obtained using the indicators were correlated with each other. Mineralizable N measured by aerobic and anaerobic incubation was sensitive to tillage, liming, and crop sequences, especially when using soil 5‐cm deep. Hot KCl‐extractable NH₄‐N was influenced by tillage but not liming, and less sensitive than the incubation procedures to crop sequence. The protease assay produced no significant test. It was concluded that anaerobic incubation can provide a relatively sensitive assessment of management effects on soil mineralizable N.