Humusica 2, Article 15: Agro humus systems and forms

Humusica Humus Agriculture Agro humus system Agricultural soil structure Soil structure Agricultural soils classification Soil biology Soil biological structure Anthropic mull Soil and agriculture 1. Introduction Agro humus systems arise from natural humipedons which have been influenced (e.g., strongly or slightly modified, simplified, ferti- lized) by man with the purpose of temporary or permanent food pro- duction or growing vegetation for various economic purposes. Agro humus systems correspond to agricultural or urban soils, tilled, shallow or deep ploughed, amended with organic and/or mineral fertilizers. Monocultures, rotation crops, arboriculture, grazing, fertilization, pes- ticides and herbicides are in current use in most of these soils, de- pending on the type of agriculture, and the main properties of the original humus systems are more generally no longer recognizable be- cause they have been strongly modified by man. However, in Agro humus systems we can find structures and soil trophic networks dis- playing the natural expression of life. The purpose of our classification is first to “circumscribe and describe” the present-day humipedons. For that, we defined some specific terms used in the description. Second, we indicated the nearest natural reference for eventual actions of physical- chemical restructuration and biological reactivation of the modified Abbreviations: ST, USDA Soil Taxonomy; WRB, World Reference Base for Soil Resources ABSTRACT Agro humus systems correspond to agricultural humipedons. Specific terms and diagnostic horizons are defined and topsoil profiles are described. With this new vocabulary, which focuses on the biological structure of the A horizon, we can compare these humipedons with their original natural expression. Under human pressure for agricultural purposes, natural humipedons evolve toward anthropic Mull (See Humusica 1, articles 5 and 6 for natural humus horizons) or Amphi (Mull with layers of still not incorporated OH organic horizons) humus systems. In each humus system, we define a few humus forms in order to estimate the biological health of the soil, with a rapid observation realisable in the field by the naked eye. Histic anthropic Anmoor is also possible, as well as Hydro or Epihistic intergrades to Terrestrial systems. WRB qualifiers and Soil Taxonomy subgroup ad- jectives are reported at the end of the article and can be used for a more detailed classification.