Macro- and microscale gaseous diffusion in a Stagnic Luvisol as affected by compaction and reduced tillage

A Simojoki,O Fazekas-Becker,R Horn

doi:10.2137/145960608786118820

Abstract

Intensification of mechanical agriculture has increased the risk for soil compaction and deformation. Simultaneously, reduced tillage practices have become popular due to energy saving and environmental concerns, as they may strengthen and improve the functioning of structured soil pore system. Soil aeration is affected by both compaction and reduced tillage through changes in soil structure and in the distribution of easily decomposable organic matter. We investigated whether a single wheeling by a 35 000 kg sugar-beet harvester in a Stagnic Luvisol derived from loess near Göttingen, Germany, influenced the gas transport properties (air permeability, gaseous macro- and microdiffusivities, oxygen diffusion rate) in the topsoil and subsoil samples, and whether the effects were different between long-term reduced tillage and mouldboard ploughing. Poor structure in the topsoil resulted in slow macro- and microscale gas transport at moisture contents near field capacity. The macrodiffusivities in the topsoil under conventional tillage were slower compared with those under conservation treatment, and soil compaction reduced the diffusivities by about half at the soil depths studied. This shows that even one pass with heavy machinery near field capacity impairs soil structure deep into the profile, and supports the view that reduced tillage improves soil structure and aeration compared with ploughing, especially in the topsoil.;

Highlights

Two opposing major trends dominate soil management in present mechanized agriculture
We investigated whether a single wheeling by a 35 000 kg sugar-beet harvester in a Stagnic Luvisol derived from loess near Göttingen, Germany, influenced the gas transport properties in the topsoil and subsoil samples, and whether the effects were different between long-term reduced tillage and mouldboard ploughing
We showed that the topsoil of Stagnic Luvisol is generally characterized by a poor soil structure with limited air space and slow gas transport in both macro- and microscale at moisture contents near the field capacity

Summary

Introduction

Two opposing major trends dominate soil management in present mechanized agriculture. Economic pressures lead to more intense production with bigger and heavier machines on ever fewer and larger farms. This will increase the risk of a more intense subsoil compaction in the future, even if reduced ground contact pressure at an identical mass are less harmful for soil structure (Peth et al 2006). Wheeling that produces mechanical stresses exceeding the internal soil strength causes compaction and shear processes that deteriorate aggregates, resulting in a more complete homogenization of soil structure even at high bulk densities. Compaction may temporarily increase soil respiration rates, as the organic matter protected within the aggregates is exposed for microbial decomposition. The extent to which the results on uniaxial soil compaction in the laboratory or those on the homogeneous compaction of experimental fields apply to normal farming is occasionally questioned (Schäfer-Landefeld et al.2004, Koch et al 2005), many researchers validated them in situ (Peth et al 2006, Richards et al 2000)

Objectives

Methods

Results

Discussion

Conclusion