Consequences of the loss of organic carbon
The maintenance and recovery of soil fertility is one of the issues that most concern the agricultural sector.
The numerous scientific studies and data relating to the organic substance content and overall fertility of the soil indicate that over 50 years of intensive agriculture have caused, in many cases, a drastic decrease in values and a worrying drift towards drying up.
What is of particular concern in soil fertility is, among others, the presence and percentage of organic carbon which, globally, in cultivated soils is progressively decreasing.
According to recent data processed by ISPRA, the trend referring to the most recent years is negative; in fact, compared to the stock referring to 2012, there is a decrease of 2.6 million tonnes in 2019 and 2.9 million tonnes in 2020 respectively.
The FAO spoke along the same lines at the recent World Food and Agriculture Forum in Berlin in 2022.
According to this report, it is essential to reverse the process of soil degradation to feed a growing world population, protect biodiversity and contribute to solving the planet’s climate crisis.
Furthermore, after the oceans, soils are the main carbon sinks and play a crucial role in mitigating climate change and adapting to it. Due to the degradation of the planet’s soils, up to 78 giga tons of carbon have already been released into the atmosphere (one giga ton is equivalent to the mass of 10,000 fully loaded US aircraft carriers). According to the map of organic carbon sequestration in soil at a global level, soils, if well managed, could sequester up to 2.05 petagrams of CO2 equivalent per year (remember that one petagram is equivalent to one million billion grams), thus offsetting up to 34 percent of greenhouse gas emissions from agricultural land.
The latest FAO report has raised a worrying alarm as agricultural systems in much of the world, the result of the complex interweaving of interactions between soil, land and water, are at a “breaking point”.
The main threat is represented by soil erosion. It is estimated that, by 2050, soil erosion could result in the removal of 75 billion tons of soil, which in turn would result in up to 10 percent loss of agricultural crops.
Another problem is represented by soil pollution which, unfortunately, is constantly increasing and compromises the quality of the food we ingest, the water we drink and the air we breathe. Excessive or inappropriate use of agricultural chemicals is one of the causes of the problem. Since the beginning of the 21st century, annual global chemical production has doubled to approximately 2.3 billion tons and is projected to grow by 85 percent by the end of the decade.
As if this were not enough, another critical issue linked to salinisation is added to this panorama, which affects 160 million hectares of cultivated land in the world and every year compromises the productivity of 1.5 million hectares of land.
This scenario involves a decrease in global soil fertility and a worrying decrease in organic substance which raises more than one alarm bell as it is responsible for a series of biogeochemical benefits and balances of fundamental importance in the soil.
Healthy soils with stable levels of soil organic matter are also better equipped to prevent and combat various pathologies and, in general, soil organic matter performs its function through three essential levels:
– Chemist; the organic substance of the soil significantly improves its ability to store and replenish essential nutrients (such as nitrogen, phosphorus, potassium, calcium and magnesium) and retain toxic elements. It allows the soil to cope with changes in chemical reaction and its pH and helps soil minerals to be more available;
– Physicist; Soil organic matter improves soil structure. A fundamental function that contributes to controlling soil erosion and improving water circulation and infiltration and water retention capacity, providing roots, plants and soil organisms with better living conditions;
– Biological; Soil organic matter is the primary source of carbon (C), an essential element for providing energy and nutrients to soil organisms. This element contributes fundamentally to improving the functionality and activity of microorganisms in the soil and increasing biodiversity. Furthermore, carbon capture in the soil reduces CO2 emissions into the atmosphere, contributing to the mitigation of climate change.
Furthermore, there is a direct relationship between soil biodiversity (also linked to topsoil biodiversity) and the organic carbon content of the soil.
For this reason, the European Union’s Green Deal has paid particular attention to this issue, also with a view to achieving climate neutrality by 2050. Among the most relevant measures in order to achieve this objective, in addition to strategies for biodiversity (Biodiversity Strategy 2030), agriculture and agri-food (Farm to Fork) and the climate (European Climate Law), the Union has also placed the strategy for soil protection among its primary objectives. In this regard, we recall objective 15.3 of the UN Agenda 2030 which has as its focus: combating desertification, restoring degraded land and soil, including land affected by desertification, drought and floods, and achieving neutrality of land degradation by 2030.
The fertility conditions of European soils, unfortunately, as highlighted in the following figure, are of considerable concern to the objectives of policies in this sense.
In general, the organic carbon content should be greater than 1 percent in agricultural soils to promote the absorption of nutrients by plants.
The data tells us that on average 45 percent of mineral soils in Europe have a low or very low organic carbon content (0-2 percent) and 45 percent have a medium content (2-6 percent). To increase the sequestration of organic carbon and to enhance the processes of removal of CO2 from the atmosphere by plants, the European Green Deal aims to adopt shallow and less invasive tillage practices on cultivation lands and sustainable agricultural management such as converting arable land to grass, incorporating straw, green manures and cover crops. In this regard, the distribution of organic soil improvers also contributes such as compost obtained from ligneo-cellulosic organic matrices and biochar, which is a vegetal carbon obtained from the thermochemical transformation of organic materials, with a thermochemical process not exceeding 300 °C, in the absence or in any case with little oxygen (pyrolysis).
The increase in organic carbon stocks in cultivated soils and the reversal of carbon losses (estimated at 0.5 percent per year) is, therefore, one of the objectives of the European Green Deal on the agriculture front. Furthermore, in support of the “climate neutrality by 2050” objective, the European Commission has urged Member States to balance the emissions caused by poor use of agricultural land with reforestation actions, carbon absorption “sinks”, reduction of chemical pesticides by 50 percent and fertilizers by 20 percent by 2030, the use of precision agriculture and 25 percent of organic agriculture, and the planting of approximately three billion new trees in the next twenty years. years.
Added to this is the recent European Union nature restoration law which will introduce recovery measures on 20% of land and sea by 2030, covering all degraded ecosystems by 2050.
Agroecology with its practices of biodiversification of crops and protection of the soil and its biodiversity therefore represents the fundamental prerequisite for responding to the FAO statements and the EU sustainability policies.
The data that indicate agroecology and, in any case, organic (or organic) agriculture as fundamental production models, to reverse the trend of decreasing soil fertility, are now countless. Among other things, a Global Scientific Symposium on organic carbon (GSOC17) which took place in Rome from 21 to 23 March 2017, organized by FAO, underlined this aspect.
The data presented on that occasion provided an equivocal scenario; in fact, in recent times SOC (Soil Organic Carbon) has been lost especially in soils intended for ‘traditional’ cultivation at a range equal to 50-70% of the total. A process that would be further exacerbated by desertification and soil degradation. However, systems that are based on the reuse of organic matter and crop rotation tell us that they can increase SOC levels.
The report is also based on numerous scientific studies. An investigation published in 2013, for example, compared the results of 24 tests in the Mediterranean basin, between biological and non-biological systems. The former managed to sequester 3559.9 kilograms of CO2 per hectare in the soil every year. If the system were implemented worldwide, the study finds, seized SOC would reach 17.4 Gt each year.
The conclusion is that the large-scale introduction of regenerative and organic cultivation and breeding systems can significantly contribute to the stabilization of CO2 in the atmosphere. In fact, there is no need to invest in expensive, potentially dangerous and insufficiently tested technologies, such as carbon capture and storage or geo-engineering techniques. All we need is to apply existing agricultural solutions and work on research to increase carbon sequestration levels; and this objective can only be achieved through the implementation on a European scale of the Farm to Fork strategy and therefore the diffusion of biodiversified systems that make low use of synthetic substances and deep processing as we will also see in the following chapters.
Agroecological practices contribute significantly to SOC which is the parameter that measures the quantity of organic carbon present in the soil and which derives mainly from the decomposition of organic materials of plant and animal origin.
Soil organic carbon is critical to the health and fertility of agricultural land. It helps improve the structure of the soil, its ability to retain water and nutrients, as well as its resistance to erosion. Furthermore, soil organic carbon is also an important carbon sink, contributing to the regulation of the carbon cycle and influencing the greenhouse gas balance in the atmosphere.
For this reason, maintaining and increasing SOC are important objectives for the sustainable management of agricultural land. Agricultural practices such as growing cover crops, rotating crops, using compost or manure, and reducing intensive plowing help promote the accumulation of organic carbon in the soil. These practices also promote soil biodiversity and the overall health of agricultural ecosystems.