Soil erosion is a serious problem. Soil is not only lost, but lost soil accumulates elsewhere, causing problems. Soil and nutrients may end up in rivers and other water bodies, seriously affecting aquatic life.
It takes time to replace lost soil. Under favourable climatic conditions it might take up to 2,000 years to generate a mere 10cm of topsoil, and this might take longer in dry, arid regions.
Use of saline water for irrigation is another soil deteriorating factor. This, together with over-fertilisation, leads to salt accumulation, and with the exception of plants that can tolerate such saline conditions, most are damaged by excessive salts. High salinity, especially when dominated by sodium containing salts, may cause serious structure deterioration, leading to erosion and possible desertification.
Over-fertilisation, especially with manure and compost of inferior quality, and the excessive use of pesticides, will contaminate the soil with harmful metals and organic substances. The build-up of excessive levels of nitrate and other nutrients in soil from over-fertilisation, also poses a threat to underground and surface water.
Industrial and mining activities can also lead to soil contamination. When it rains, acidic gases liberated from industry and the burning of fossil fuel, also end up in soil, and in some sensitive areas this can acidify the soil, with disastrous consequences.
Compaction is another threat to soils. The use of heavy agricultural machinery compresses and compacts the soil in such a way that water percolation is impaired, leading to an increase in run-off and consequently erosion.
Soil degradation is expensive. In 2011, around 24 billion tons of soil were lost worldwide, and it is estimated that globally, soil loss costs around €400 billion a year.
Soils in Malta are relatively young, and by soil standards they are relatively immature. The dry and warm climate of the Mediterranean region slows down soil forming processes.
The soils are calcareous in nature, a result of a limestone-based parent rock and a dry climate. They are slightly alkaline, and with regard to texture, range from the sandy type to the very clayey type; however the majority are clay loams.
Soil colour ranges from white, light brown, reddish and in some clay-rich areas, even olive green. Local farmers tend to classify local soils according to colour and texture, and references to soil as bajjad, qastni, ħamri, ramli and grass are quite common.
Very little has been done to measure the extent of erosion, nutrient dynamics, and microbial function in local soil
Scientifically the soils have been classified initially in 1960 by Lang, and recently through the Malsis study, a soil information system for the Maltese islands. The project studied the soils from a physical and chemical aspect, and categorised them into various classes according to their characteristics.
However, very little information is available with regard to how these soils function and interact with their surrounding environment.
Through the years, perhaps due to lack of resources, very little has been done to measure, for example, the extent of erosion, nutrient dynamics, and microbial function in local soil. To manage this limited resource in a sustainable way, this information is required.
On many occasions while walking along parts of the local coast after an October storm, one notices that for the odd half a kilometre or so, the sea may appear brown, red or murky with soil material that has been carried away by storm water. Overusing and misusing land will eventually lead to soil degradation.
In 1960, there was around half a hectare of farming land for every person on Earth. It is estimated that by the year 2020, there will be only a third of that left.
Removal of forests, overgrazing, monoculture, irrigation with saline water, dumping of toxic waste, erosion, and climate change will increase the pressure on soil. The United Nations declared 2015 as the International Year of Soil in order to make people aware of the importance of this vital resource. It is up to each and every one of us to protect it.
(Concluded)
Anthony Sacco is a senior lecturer in soil sciences and environmental microbiology at the Department of Rural Sciences and Food Systems of the University’s Institute of Earth Systems.