Effect of tillage intensity on N mineralization of different crop residues in a temperate climate

Abstract

To evaluate the effect of tillage intensity on the N mineralization pattern of winter wheat residues, sugar beet residues, Italian ryegrass and maize residues undisturbed soil samples were taken from six sites under different tillage management. Site NT K had been managed for 10 years under reduced tillage (RT), whereby the last 4 years the crops were sown using direct seeding (NT). Site RT CSE had been managed for 20 years under reduced tillage (RT) and site RT H for 3 years. For each site under RT a nearby site under conventional tillage (CT) was selected (CT K, CT CSE and CT H). On site NT K and site RT CSE a significantly higher amount of SOC in the 0–10 cm was accumulated compared to the respective CT sites. Between site RT H and site CT H no such significant difference was found. However, the content of microbial biomass C (MB-C) and the β-glucosidase and urease activities were higher on all RT sites compared to the respective CT sites. This indicates that these microbiological and biochemical parameters seem to be very sensitive for alterations in management intensity. After 98 days, more N was immobilized under NT K than under CT K by adding winter wheat residues (expressed as kg ha −1 and as % of total added N). This higher immobilization potential can be explained by a higher microbial activity and a change in microbial population. Under RT CSE and RT H net N immobilization of the winter wheat residues was found, but the pattern was less pronounced than for NT K. However, when expressed as % of total N added, N immobilization of winter wheat residues was higher under CT than under RT, which indicates that high C:N residues when incorporated, decompose more slowly under RT than under CT. Similar results were found comparing the N mineralization pattern of maize residues under RT H and CT H. The residues of sugar beet and Italian ryegrass at site CT H released N more rapidly and to a higher extent, 74.1% and 66.2%, respectively (expressed as % of total N added) than under RT H at the end of the incubation. The slower mineralization of N rich crop residues under RT compared to CT means that there is less potential risk for nitrate leaching to occur, which may result in a higher N efficiency in RT compared to CT.