Nitrogen Mineralization from Soil Organic Matter and Crop Residues: Field Validation of Laboratory Predictions

Abstract

AbstractAccurate prediction of N mineralization under field conditions would promote optimal N‐use efficiency from both organic and inorganic sources. This study was conducted to assess the utility of microplot cylinders with mixed‐bed exchange resins for monitoring field N mineralization, to compare laboratory predictions with field measurements of N mineralization, and to determine the impact of using ground (≤1 mm) crop residues in the laboratory to predict N mineralization of unground (≤25 mm) residues in the field. Nitrogen mineralization from soil organic matter and hairy vetch (Vicia villosa Roth) residues was followed in the laboratory at 15, 20, and 25 °C with 0, 2150, 4300, and 6450 kg vetch ha‐1 equivalent loading rates of ≤1 mm particle‐size residue. Ground and unground residues were added to microplot cylinders at loading rates equivalent to 0, 4028, and 5010 kg vetch ha‐1 and installed in potato (Solanum tuberosum L. Norwis) crop rows in two growing seasons. Nitrogen mineralization from soil organic matter under field conditions was overestimated by laboratory predictions; however, field measurements of N mineralization from both ground and unground vetch residues were closely predicted by a complementary laboratory study. These data indicate vetch residue N mineralization under these modified field conditions (i.e., microplot cylinders) can be predicted from laboratory studies that use ground residues, constant temperatures, and variable residue quantities. This finding may advance our ability to model and account for residue N mineralization when developing N management recommendations.