Long-term Management Effects and Temperature Sensitivity of Soil Organic Carbon in Grassland and Agricultural Soils

Rajan Ghimire,Prakriti Bista,Stephen Machado

doi:10.1038/s41598-019-48237-7

Rajan Ghimire, Prakriti Bista + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-48237-7

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Abstract

Soil organic carbon (SOC) is integral to soil health and agroecosystem resilience. Despite much research, understanding of temperature sensitivity of SOC under long-term agricultural management is very limited. The main objective of this study was to evaluate SOC and nitrogen (N) dynamics under grasslands and winter wheat (Triticum aestivum L)-based crop rotations in the inland Pacific Northwest (IPNW), USA, and measure SOC mineralization under ambient and elevated incubation temperatures. Soil samples were collected from 0–10 and 10–20 cm depths from an undisturbed grassland (GP), winter wheat-pea (Pisum sativum L) rotations under conventional tillage (WP-CT) and no-tillage (WP-NT), and winter wheat-fallow rotation under conventional tillage (WF-CT) and analyzed for SOC and N pools. Soil samples were incubated at 20 °C and 30 °C for 10 weeks, and SOC mineralization rates were estimated using the first order kinetic model. The GP had the greatest amounts of SOC, total N (TN), and microbial biomass carbon (MBC) and WP rotations had higher inorganic N content than other treatments. The SOC mineralization at elevated incubation temperature was 72–177% more than at the ambient temperature, and the greatest effect was observed in GP. The SOC storage under a given management did not have consistent effects on soil carbon (C) and N mineralization under elevated temperature. However, soil disturbance under WP-CT and WF-CT accelerated SOC mineralization leading to soil C loss. Reducing tillage, integrating legumes into crop rotations, and growing perennial grasses could minimize SOC loss and have the potential to improve soil health and agroecosystem resilience under projected climate warming.

Highlights

Long-term experiments provide valuable information required for understanding management effects on Soil organic carbon (SOC) dynamics and such information is a prerequisite for designing sustainable agroecosystems[12,13]
The first-order kinetic model has been used for estimating the decomposition characteristics of organic materials, C0, the labile fraction of SOC that is sensitive to changes in management or the environment, and k, the decomposition rate constant[14]
Soil pH averaged for two depths was significantly greater under grass pasture (GP) (6.4) than under all wheat-based rotations (WP-NT, WP-CT, and wheat-fallow rotation under conventional tillage (WF-CT)) in which soil pH ranged from 4.8 to 5.2

Summary

Introduction

Long-term experiments provide valuable information required for understanding management effects on SOC dynamics and such information is a prerequisite for designing sustainable agroecosystems[12,13]. Designing controlled experiments to evaluate the role of individual factors (e.g., temperature) on SOC dynamics may provide information on the relative response of diverse management systems to changes in climatic variables[19]. The first-order kinetic model has been used for estimating the decomposition characteristics of organic materials, C0, the labile fraction of SOC that is sensitive to changes in management or the environment, and k, the decomposition rate constant[14]. This information is necessary to facilitate the management changes needed to improve agricultural sustainability under changing climate. The main objectives of this study were to i) evaluate chemical and biological soil properties at 0–10 cm and 10–20 cm depths under selected long-term plots of the PLTEs representing diverse crop rotations and tillage systems, ii) evaluate SOC mineralization at 20 °C and 30 °C temperatures under these treatments, and iii) model the temperature sensitivity of SOC mineralization using a first-order kinetic model

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