Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 1995
Publication Date: N/A
Interpretive Summary: An improved understanding of how crop and soil management practices affect N cycling is needed to develop sustainable agricultural production practices. We measured the amount of labeled N fertilizer that was removed by the harvested portions of corn, wheat, and cotton crops to obtain this information for a major Coastal Plain Soil. Disked and non-disked tillage comparisons were included in the study but had only a slight effect on the recovery of labeled fertilizer, and this was attributed to differences in crop yield. Tillage did not appear to have an effect on how N was cycled in the soil and taken up by these crops. Total recovery by the crops ranged from 22 to 35% of the applied fertilizer, with most being taken up by the crop that received the labeled material. However, labeled fertilizer continued to be cycled from crop to crop and from year to year. When sampling was ended, 27 to 31% of the labeled fertilizer was still present in the top 90 cm of the soil profile. This information will help improve management practices and the overall sustainability of agriculture.
Technical Abstract: This research was conducted to determine the fate of 15N fertilizer that was applied to corn, wheat, or cotton in a 2-year rotation on Norfolk loamy sand. A urea and ammonium nitrate solution that had a 5 atom percent (ATM%) label was applied to each of 48 microplots. Surface tillage effects were statistically significant (P </= 0.05) for 5 of 12 yield comparisons. The ATM% 15N in the crop was not affected by tillage treatment. Total removal of labeled fertilizer by all crops in the 2-year rotation ranged from 22 to 35% when averaged for both tillage treatments. Most recovery (45 to 60%) occurred with the crop to which the 15N fertilizer was applied. The ATM% 15N in the soil was increased to a depth of 90 cm by 15N fertilizer applications. Calculated amounts of fertilizer remaining in this portion of the soil profile ranged from 27 to 31% of the applied amount when measured 23 to 40 months after application. This study demonstrates the amount of N cycling that can occur through various organic and inorganic N pools from crop to crop and year to year.