Nitrogen and carbon dynamics in prairie vegetation strips across topographical gradients in mixed Central Iowa agroecosystems

Authors

Marlin Perez-Suarez, Iowa State UniversityFollow
Michael J. Castellano, Iowa State University
Randall Kolka, USDA Forest Service
Heidi Asbjornsen, University of New HampshireFollow
Matthew J. Helmers, Iowa State UniversityFollow

Date of this Version

2014

Citation

Agriculture, Ecosystems and Environment 188 (2014) 1–11.

Comments

This article is a U.S. government work, and is not subject to copyright in the United States.

Abstract

Reductions of nitrogen (N) export from agricultural lands because of changes in specific N stocks andfluxes by incorporation of small amounts of prairie vegetation strips (PVS) are poorly understood. Theprimary objective of this study was to evaluate the effect of the presence and topographical position of PVSon soil and plant carbon (C) and N stocks relative to annual crop and native prairie vegetation. The studywas implemented within three small adjacent watersheds, treated with one of the following cover types:(1) 100% row-crop agriculture (CROP); (2) 20% prairie vegetation (PVS) distributed along the contouracross three topographical positions: upslope, sideslope and footslope position; and (3) 100% 17-year oldreconstructed native prairie (RNP) as the control condition. Total soil organic C (SOC), total soil N (TN),inorganic N availability as indexed by ion exchange resins, N stocks in plant biomass and litter, and theratio of C3:C4plant species were measured during the 2010 growing season. Results showed that over fiveyears of treatment, PVS footslope improved soil quality by increasing TN by almost 100% and SOC by 37%;while CROP footslope TN decreased by 31% and SOC decreased by 28%. Overall, N stocks in plant biomassand litter were higher in PVS compared with RNP, except in the footslope where the lower N plant stockswas associated with higher C₃ abundance in RNP. Nitrogen availability was higher in CROP (25.4 ± 1.4),followed by PVS (10.2 ± 1.3), and RNP (2.2 ± 1.4); with the highest values recorded in the upslope positionfor PVS and RNP, and the footslope for CROP. These findings are important for designing watersheds withPVS to reduce N accumulation in the footslope position and promote additional N retention in soil organicmatter and plant biomass, thereby minimizing N losses to streams.