Refining physical aspects of soil quality and soil health when exploring the effects of soil degradation and climate change on biomass production: an Italian case study

Abstract

Abstract. This study is restriced to soil physical aspects of soil quality and – health with the objective to define procedures with worldwide rather than only regional applicability, reflecting modern developments in soil physical research and focusing on important questions regarding possible effects of soil degradation and climate change. In contrast to water and air, soils cannot, even after much research, be characterized by a universally accepted quality definition and this hampers the internal and external communication process. Soil quality expresses the capacity of the soil to function. Biomass production is a primary function, next to filtering and organic matter accumulation, and can be modeled with soil-water-plant-atmosphere simulation models, as used in the agronomic yield-gap program that defines potential yields (Yp) for any location on earth determined by radiation, temperature and standardized crop characteristics, assuming adequate water and nutrient supply and lack of pests and diseases. The water-limited yield (Yw) reflects, in addition, the often limited water availability at a particular location. Real yields (Ya) can be considered in relation to Yw to indicate yield gaps, to be expressed in terms of the indicator: (Ya/Yw) × 100. Soil data to calculate Yw for a given soil type (the genoform) should consist of a range of soil properties as a function of past management (various phenoforms) rather than as a single representative dataset. This way a Yw-based soil-characteristic soil quality range is defined, based on semi-permanent soil properties. In this study effects of subsoil compaction, overland flow following surface compaction and erosion were simulated for six soil series in the Destre Sele area in Italy, including effects of climate change. Recent proposals consider soil health, which appeals more to people than soil quality and is now defined by seperate soil physical, -chemical and – biological indicators. Focusing on the soil function biomass production, physical soil health at a given time of a given type of soil can be expressed as a point (defined by a measured Ya) on the defined soil quality range for that particular type of soil, thereby defining the seriousness of the problem and the scope for improvement. The six soils showed different behavior following the three types of land degradation and projected climate change up to the year 2100. Effects are expected to be major as reductions of biomass production of up to 50 % appear likely. Rather than consider soil physical, chemical and biological indicators seperately, as proposed now for soil health, a sequential procedure is suggested logically linking the seperate procedures.

Targeting the soil quality and soil health concepts when aiming for the United Nations Sustainable Development Goals and the EU Green Deal

“…In conclusion, parameters for soil health for a given soil type at a given time and place, are (i) soil structure, expressed by descriptions in soil survey reports and supported by bulk density values and measured infiltration rates and, possibly, by penetrometer values; (ii) water and air regimes, as estimated by drainage class in soil survey reports, that can be expressed indirectly by the widely used, but static, parameter, namely "available water", for defining the water content between two pressure heads, which, however, poorly represent natural dynamic soil water and air regimes (dynamic modelling presents more realistic data as will be discussed later; e.g. Bouma, 2018;Bonfante et al, 2019); and (iii) organic matter contents.…”

Soil Security in Sustainable Development

“…Figure 4 shows values for each soil that are generally decreasing in the coming century. For a detailed analysis the reader is referred to [21]. Here we emphasize that the analysis can also be made for different forms of soil degradation of which the effects of compaction ( Figure 5) and erosion ( Figure 6) on Yw will be shown.…”

“…Yw values for six soil series in the Destre Sele area, indicating effects of the reference climate and three climate scenarios of the Inter-governmental Panel on Climate Change (IPCC) (from[21]). …”

“…Effects of soil erosion on Yw in each of the six soil series. Eroded soil series represent Phenoforms of the particular Genoform, assuming that erosion has not resulted in a change of classification (from[21]). 6.…”

“…Facing 'Codification' as a Major Challenge to Connect Science with the Policy ArenaEffects of a plowpan on Yw in each of the six soil series, again expressed for four climate scenarios. Compacted soil series represent Phenoforms of the particular Genoforms (from[21]).…”