Soil fertility characteristics in North Carolina pastures as affected by spatial separation and renovation with annual forages

Authors: Franzluebbers, Alan; POORE, MATT - North Carolina State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2022
Publication Date: 12/4/2022
Citation: Franzluebbers, A.J., Poore, M.H. 2022. Soil fertility characteristics in North Carolina pastures as affected by spatial separation and renovation with annual forages. Agronomy Journal. 115:384-394. https://doi.org/10.1002/agj2.21218.
DOI: https://doi.org/10.1002/agj2.21218

Interpretive Summary: Renovation of perennial pastures may be periodically needed to reestablish more desirable forage species or to improve nutrient and/or physical conditions of soil. A specific reason for renovation in the southeastern United States is to eliminate the wild toxic tall fescue variety and replace it with a friendly novel-endophyte tall fescue variety. This often requires some time to reduce the natural seed bank of wild tall fescue. A proposed method during seedbank elimination time is to use high-quality annual forages to overcome the expected decline in forage availability when killing an otherwise reliable forage source. An ARS scientist in Raleigh North Carolina partnered with the Amazing Grazing program at North Carolina State University and private farmers in different regions of the state to evaluate the soil health implications of a renovation strategy with simple and complex mixtures of annual forages. Neither annual forage treatment planted with no-till technologies caused significant improvement in soil health, but importantly also did not cause a decline in soil health condition. An additional finding from the study was the recognition of strong spatial variations at the local level that were sometimes more important than often recognized variations among physiographic regions, i.e. among coastal, piedmont, and mountain regions. The results of this research can be used by farmers, agricultural advisors, extension specialists, and scientists to make better decisions for pasture management to support productivity and environmental quality goals.

Technical Abstract: Spatial variation in soil properties is often considered significant across broad geographical regions due to soil formation factors. However, fine-scale variations might also be significant. This study was conducted with the original intent of assessing how simple and complex mixtures of annual forages might be used to renovate perennial pastures. Private farmers in the Flatwoods, Piedmont, and Blue Ridge Major Land Resource Areas of North Carolina tested annual forages to renovate tall fescue pastures. Soil was sampled in multiple random locations in each field at depths of 0–6, 6–12, and 12–20 cm at the beginning and ending of a 3-yr annual forage evaluation. Relative variation among five components (year of sampling [n = 2], physiographic region [n = 3], annual forage treatment [n = 2], soil depth [n = 3], and random variation from pseudoreplicates [n = 3 in 2015 and n = 5 in 2018]) was assessed for four soil physical, 10 soil biological, and 16 soil chemical properties. Soil chemical properties were mostly affected by physiographic region (47 ± 26% of total variation) and soil depth (33 ± 18%), soil biological properties were mostly affected by soil depth (63 ± 25%) and random pseudoreplication (14 ± 6%), and soil physical properties were equally affected by pseudoreplication (35 ± 21%), physiographic region (32 ± 18%), and soil depth (29 ± 22%). The type of annual forage had no discernible effect on soil properties, even the most biologically active. A diversity of spatial variations was important, suggesting that regional-level ecological investigations require careful attention to an appropriate sampling design considering multiple factors.