Soil degradation is a major environmental problem worldwide, and there is strong evidence that the soil degradation processes are an immediate threat to both biomass and economic returns, as well as a long-term threat to future crop yields. The vulnerability of the European soils to the degradation processes is certainly high and it strongly increases in the Italian soils due to the higher variability of the environment.
• 21.3% of the national soil cover is at risk of desertification (41.1% of centre and south Italy).
• Main soil degradation processes are erosion, flooding and landslides, losses of organic matter, sealing, aridity, contamination and salinization following the impact of human activities.
• Soil degradation during the last 40 years caused a decrease of about 30% in their water holding capacity and a proportional shortening of the return time of catastrophic events.
• Soil degradation has also caused an impairment of several other eco-services, e.g., quality of foods and landscape.
At the European level the estimated costs of some aspects of the soil degradation can be the following:
• erosion: 0.7 – 14.0 billion €,
• organic matter decline: 3.4 – 5.6 billion €,
• salinisation: 158 – 321 million €,
• landslides: up to 1.2 billion € per event,
• contamination: 2.4 – 17.3 billion €,
Since agricultural conventional production systems have resulted in excessive erosion and soil degradation, there is need to control and fight such degradation.
Scientific results have clearly showed that the agricultural management systems can play an important role in preventing soil degradation provide that appropriate management practices are adopted. Long-term field experiments in different types of soils have shown that alternative tillage systems, like minimum tillage, ripper subsoiling, etc., improve the soil structural quality. The continuous conventional tillage causes a decrease of soil organic matter content that is associated to a decrease of aggregate stability, leading, as a consequence, to the formation of surface crusts, with an increase of runoff and erosion risks.
To protect soil from erosion, an adequate supply of organic matter is crucial, because it is able to improve the structural characteristics; the role of vegetation cover is also crucial, as it reduces the rain drops impact and then the surface crusting, and delays the onset of surface runoff phenomena. According to the principles of Conservation Agriculture, for tree crops the surface grass cover is a viable strategy, particularly in areas where a significant increase in climate aggressiveness is expected. The greatest hindrance to its diffusion is the competition for water between herbaceous cover and main crop. Where it is possible to overcome this constraint, such a management system has proved more effective than reduced tillage.
Other aspects of very dangerous soil degradation (erosion) in the hilly environments are represented by land levelling and scraping. After levelling, slopes being prepared for plantation (in particularly vineyard) are almost always characterised by the presence of large amounts of incoherent earth materials accumulated with scraper, very vulnerable to water erosion.
Subsoil compaction is strongly under evaluated, even though the presence of a ploughpan at the lower limit of cultivation is largely widespread in the alluvial soils of the plains cultivated by monoculture and it is responsible of the frequent flooding of such plains in occasion of heavy rains concentrated in a short time (rainstorm), because the presence of this ploughpan strongly reduced drainage. Alternative tillage practices, like ripper subsoiling, are able to avoiding the formation of this compact layer.
Marcello Pagliai - firstname.lastname@example.org