Carbon Accumulation in Arable Soils: Mechanisms and the Effect of Cultivation Practices and Organic Fertilizers

Jörg Gerke

doi:10.3390/agronomy11061079

Abstract

The organic carbon content of soils is a key parameter of soil fertility. Moreover, carbon accumulation in soils may mitigate the increase in atmospheric CO2 concentration. The principles of carbon accumulation in arable soils are well known. The inclusion of clover/alfalfa/grass within the rotation is a central instrument to increase soil organic carbon. In addition, the regular application of rotted or composted farmyard manure within the rotation can increase soil organic carbon contents much more than the separate application of straw and cattle slurry. Humic substances, as a main stable part of soil organic carbon, play a central role in the accumulation of soil carbon. A major effect of compost application on soil carbon may be the introduction of stable humic substances which may bind and stabilize labile organic carbon compounds such as amino acids, peptides, or sugars. From this point of view, a definite soil carbon saturation index may be misleading. Besides stable composts, commercially available humic substances such as Leonardite may increase soil organic carbon contents by stabilization of labile C sources in soil.

Highlights

The organic carbon content of soils is a key parameter of soil fertility
Soil organic matter has a strong impact on soil fertility [1,2]
This is in direct contrast to the concept of C saturation of soils according to Schmidt et al [7], which excludes humification as a relevant process for soil organic matter formation

Summary

Introduction

Soil organic carbon (SOC) strongly affects the global C cycle because it represents the greatest C pool accounting for 2–5 (kg C × 1015) [1,3]. Soils contain more carbon than atmosphere and vegetation combined [4]. Elevated CO2 levels may be reduced by increased storage of C in soils as SOC. An overview of the principles and mechanisms of soil organic carbon storage and ways to increase this carbon pool in agricultural soils will be given. The standpoint view of the FAO, the food and agriculture organization of the United Nations, from 2017, is critically discussed. The application of commercially available organic fertilizers will be discussed in their effect to increase soil organic carbon

Organic Carbon—Some Agronomic Considerations

Mechanisms of Soil Organic Carbon Accumulation in Arable Soils

Compost and Farmyard Manure Application

Findings

Commercial Organic Fertilizers and Soil Organic Carbon