Long‐term rotation diversity and nitrogen effects on soil organic carbon and nitrogen stocks

Marty R Schmer,Brian J Wienhold,Sophia M Becker,Gary E Varvel,Virginia L Jin

doi:10.1002/agg2.20055

Abstract

AbstractUnderstanding the impacts of long‐term fertilizer management and rotation diversity on soil C and N is needed under a changing climate. The objective of this study was to evaluate the effects of N fertilizer level and crop rotation diversity on soil organic carbon (SOC) and soil N stocks from a 34‐yr study located in eastern Nebraska. Seven crop rotations (three continuous cropping systems; two 2‐yr crop rotations; and two 4‐yr crop rotations) and three N levels were compared. Soil samples were taken to a depth of 150 cm. Differences in SOC stocks were largely confined to the 0‐ to 7.5‐cm depth, with greater SOC (P = .0002) in rotations than continuous cropping systems and greater SOC (P = .0004) in 4‐yr vs. 2‐yr rotations. Total soil N was greater with increased crop rotation diversity for the 0‐ to 30‐cm soil profile. Greater SOC levels occurred with N fertilization for the 0‐ to 7.5‐cm depth. At the 0‐ to 150‐cm soil depth, SOC stocks were similar between N levels and greater for the 4‐yr vs. 2‐yr crop rotations (P = .0492). Trends in total N stocks were similar to those of SOC stocks. Overall, crop rotation had a larger effect on SOC and N stocks than N fertilizer.

Highlights

Sustainable crop production requires management strategies aimed at enhancing the potential to sequester or increase soil organic carbon (SOC)
Crop rotation had a larger effect on SOC and N stocks than N fertilizer when evaluated for the cumulative soil profile (0– 150 cm)
Previous results from this study showed similar SOC stocks between crop rotation in the 0- to 150-cm soil profile after 14 yr, indicating the duration required for crop rotation practices to significantly change SOC (Varvel, Liebig, & Doran, 2002)

Summary

Introduction

Sustainable crop production requires management strategies aimed at enhancing the potential to sequester or increase soil organic carbon (SOC). Maintaining or increasing SOC provides greater resiliency to agricultural systems under extreme weather events. Agricultural management strategies to increase SOC within annual cropping systems include cover crops, residue retention, diverse crop rotations, crops with greater root mass, and N fertilizer (Jarecki & Lal, 2003; McDaniel, Tiemann, & Grandy, 2014; Paustian et al, 2016; Poffenbarger et al, 2017; Tiemann, Grandy, Atkinson, MarinSpiotta, & McDaniel, 2015). Significant SOC responses to management changes (i.e., crop rotation, N fertilizer management) may take years to detect, so the ability to quantify management effects improves with experiment duration

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Discussion

Conclusion