Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/21/2001
Publication Date: N/A
Technical Abstract: The objective of the study was to find out the changes in N and 15N as well as C and natural abundance 13C in soil samples taken from micro-plots of enriched N superimposed on a tillage, residue and N fertilizer study. The experiment at Rosemount, MN was started in 1980 with 2 tillage treatments [till (T) or no-till (NT)]; 2 residue options [residue returned (r) or residue harvested (h)]; and 2 N rates [2 or 20 g N m-2 as (NH4)2S04]. The 2 and 20 g N m-2 rate corresponded to 40 and 4 atom-% 15N, respectively. Corn was grown for 15 years and subsequently cropped to soybean for 5 yr. Fertilizer N was not added for the soybean crop. Soil 15N increased with yearly additions of enriched N. Treatments with residue returned had higher 15N than residue harvested; NT had higher 15N than T. Among treatments, Th had the lowest 15N. Treatment effects on soil C and natural abundance 13C were most evident on the surface. Soil C was clearly affected by tillage, residue and N fertilization, while 13C was affected only by tillage and residue treatments. Decrease in 13C due to soybean was evident only at the surface. Treatments with residue returned corresponded to the crop change.