Using a morphological approach to evaluate the effect of traffic and weather conditions on the structure of a loamy soil in reduced tillage
Résumé
A morphological approach and soil porosity have been used to evaluate the effect of compaction and climate on the soil structure of a loamy soil in a reduced tillage system. The study was carried out between 2000 and 2006 as part of the long-term "cropping systems and soil structure" experiment conducted in Estrées-Mons in northern France. Soil hydraulic, mechanical and pore morphological properties were also measured to characterise the effects on soil structure dynamics. A complementary characterisation of the soil structure was conducted on a microscale.The method for morphological description of the soil macrostructure was well suited to studying soil structure dynamics in reduced tillage systems. Results showed that the soil structure in the layer without tillage depended in the first instance on compaction intensity. Structural porosity was partly preserved in the cropping system with little compaction. In contrast just one operation, such as the harvest of sugar beet (Beta vulgaris L.), was sufficient to reduce structural porosity for 5 years even though no further compaction occurred during this period. Morphological analysis revealed the evolution of highly compacted zones under the effects of weather conditions. Platy soil structures were systematically observed in the upper part of the highly compacted zones under the tilled layers, with cracking slowly penetrating deeper into the soil with time. The structure types observed corresponded to specific soil properties resulting from the transformation of the soil structure over time. A micro-morphological assessment was performed to get detailed information about the network of cracks. The morphological characterisation showed that a visual morphological approach was insufficient for revealing the entire network of cracks.