Effect of amendment of manure and corn residues on soil N mineralization and enzyme activity

Abstract

Understanding the effect of manure and crop residue application on N mineralization in soil is crucial in order to minimize nitrate contamination of surface and groundwater. Besides, developing an alternative management practice for corn residue burning is of great importance and needs more knowledge about inorganic N dynamics. Here we conducted a laboratory experiment to study the effect of corn residue application on inorganic N dynamics and soil enzyme activities in soils with different manure fertilization histories. The laboratory experiment was a combination of 3 fertilization histories of: 0, 50 and 100 Mg cow manure ha−1 year−1 for five consecutive years; and 3 residue treatments including: no residue, corn shoot and corn root application. We monitored inorganic N periodically during 20 weeks of incubation. We also monitored the activities of urease, L-asparaginase, L-glutaminase and β-glucosidase before and after incubation. Our findings show that for residue-amended soils, inorganic N decreased in the first 2 weeks of incubation by 50 to 86%, followed by a gradual increase. In contrast, for control soils without residue amendment, the inorganic N concentration increased from 64 to 86% during the first week of incubation. Our results thus show that the application of corn residues can control the flush of inorganic nitrogen and reduce the potential of nitrate leaching in manure-applied soils. Furthermore, manure application at the highest rate increased the activity of urease by 47%, L-asparaginase by 70%, L-glutaminase by 60% and β-glucosidase by 78%. β-glucosidase increased due to corn shoot application by about 8% and was the most responsive enzyme to the treatments. Overall, the enzyme activities were more influenced by manure application history than corn residue application.