Every year on 5 December the UN brings attention to the health and importance of increasing the productivity of soil on World Soil Day. Increasingly, soil health and sustainable crop development has risen in its importance as the world’s population expands amidst rising global temperatures.
Soil health and productivity integral to feed the world
Rising global temperatures have brought unpredictable levels of rainfall – as in too little, or sometimes too much, that affect crop yields in different parts of the world. There is mounting pressure on how we can feed the world in the most efficient and effective way with the least impact on earth. Maintaining the health of soil is integral to this, as is sustainable crop development.
Intensive and industrial farming methods and crop production can influence soil health through soil degradation. How fertiliser is used, and in what quantities, is an additional influencing factor on soil health, and on greenhouse gas (GHG) emissions.
In this blog we will focus mainly on how healthy micro-organism communities can increase soil productivity by making nutrients available for crop growth, amongst other issues surrounding fertiliser application and its effect on soils. But, before we do that, let’s briefly look at some of the benefits and challenges of current fertilisers.
Controlled-Release Fertilisers use less phosphate resources, but pose micro-plastic problems
The use of conventional Controlled-Release Fertilisers (CRFs) have provided an efficient uptake of fertilisers for increased crop yields and reduced environmental impacts through the use of less product. However, the high costs associated with CRFs can be a limiting factor in that they are not implemented widely across agriculture.
Additionally, the use of petrochemical based CRFs involve the use of plastic polymers, which are not biodegradable and lead to an accumulation of plastic impurities in soil.
This highlights the urgent need of developing efficient fertilisers that produce less GHG emissions along the supply chain by using biobased, bioactive coatings with natural plasticisers for soil improvers that is elaborated in a SUSFERT scientific publication.
On UN World Soil Day, SUSFERT would like to draw attention to the subject of probiotics, or the role that micro-organisms play in maintaining healthy soils and crops.
The role of micro-organisms and probiotics in soil
Increasingly, scientists understand the vital, symbiotic role that micro-organisms play in both human and animal gut health, contributing to better, overall well-being. Micro-organisms have a similar role to play in soil health.
SUSFERT Scientific Co-ordinator from the Austrian Institute of Technology (AIT), Centre for Health and Bioresources, Günter Brader, tells us why micro-organisms are a novel approach in sustainable fertiliser development.
Micro-organisms essential to the breakdown of fertilisers
Micro-organisms are the general term used for all fungi, bacteria, oomycote (fungi-like organisms that can be parasites), and unicellular organisms like algae, for example. When people talk about probiotics they usually refer to (in food and medicine) a micro-organism, or a mix thereof, which have a function, or a certain purpose for human health or digestion.
In agricultural terms, some micro-organisms have probiotic activities that help fertilisers solubilize. In simple terms, probiotics help the bound and unavailable nutrients to be set free for plant growth. In addition, the probiotics can also act as plant growth promoters, which is not dissimilar to how probiotics work in human health.
Essentially, micro-organisms in the soil help mobilize nutrients such as phosphate, iron or zinc, so that the plant can better absorb these minerals. When this happens, the availability of those nutrients for crops becomes active, and early plant development is fostered, or promoted by an improved root growth.
In this way, probiotics can either indirectly influence nutrient availability, or they can suppress other pathogenic, or saprophytic micro-organisms in a way that can prohibit the spread of certain plant diseases.
Fertilisers enhance microbial activity in soil
For micro-organisms to be effective, they must be present in large concentrations. The presence of microbial communities is dependent on plant colonization and the rhizosphere (the space surrounding the root, or soil interface), which in turn reduces or alters the presence of microbial communities. By adding specific probiotics, the microbial community can be shifted in the desired way.
The distribution of micro-organisms in soils may not be equal. This is the purpose of adding fertiliser products to enhance the microbial, or probiotic activity in different soils by having a positive effect on nutrient and water availability that improves root growth.
Micro-organisms integral to SUSFERT fertiliser development
SUSFERT aims to develop novel granules, micro-granules and liquid fertilisers that contain micro-organisms, also in combination with coated calcium for turf improvement. This can lead to a reduction in the need to apply phosphate because the micro-organisms make phosphate more available for plant use.
Additionally, microbial siderophores are intrinsic to sustainable iron entry for crop uptake. Usually, there is plenty of iron supply in soils, but the limestone soils of the Mediterranean region have less iron availability for plants. The SUSFERT siderophores can substitute less biodegradable synthetic ones currently being used.
Maintaining the integrity of soil in European agriculture
We need to reduce the number of fertiliser applications per season and prevent the leaching of nutrients into the environment for multiple reasons. This means developing more efficient fertilisers that require one application per season.
By developing bio-based coatings compliant with biodegradability parameters, the controlled release of nutrients can be improved, carbon can be added to the soil, and the entry of less degradable synthetic coatings into the environment can be reduced.
SUSFERT aims for a reduction in mined phosphate
Essentially, the SUSFERT project aims to reduce the usage of mined phosphate and manufactured superphosphate to develop novel bio-based fertilisers, as well as to improve the availability of iron supply.
Because micro-organisms can reduce the unnecessary entry of phosphate into the environment by enabling the availability of the mineral for the plant to absorb, less phosphate is needed which has a positive impact on the CO2 footprint within the agri-food chain system, including within the farm gate.
Mined phosphate that is manufactured as superphosphate fertiliser (which basically is rock phosphate dissolved in sulfuric acid) is an extremely energy intensive process. So, if fertilisers were more efficient and derived from other sustainable sources, we would need less mined, imported phosphate that is transported over long distances, and less processed superphosphate for fertilisers. This would in turn reduce CO2 emissions associated with fertiliser transport and production.
An additional advantage of micro-organism presence in fertilisers and soil is that less processed phosphorus sources (that come from struvite and rock phosphate) can be used. This reduces the energy demand due to a reduced processing need.
SUSFERT contribution to sustainable fertiliser development
The fertilisers currently under development use waste products such as struvite for fertiliser production; probiotics and a fungal siderophore to increase nutrient availability; and lignosulfonate coatings from renewable materials for longer term nutrient release and soil improvement. The project’s solutions are ongoing and are being demonstrated in field trials across Europe.
Co-authored by Philippa Webb-Muegge and Dr. Günter Brader.
This project has received funding from the Bio Based Industries Joint Undertaking (BBI-JU) under the European Union’s Horizon 2020 research and innovation program under grant agreement No. 792021.
Dr. Günter Brader studied biology at the University of Vienna and obtained his PhD in plant biology in 1997. After gaining post doc experience in the field of molecular biology and plant-microbe interactions at the Institute of Biotechnology and the Department of Genetics at the University of Helsinki, Finland, he was appointed to be Docent in Plant Molecular Biology by the Helsinki University. He is now a senior scientist at the Austrian Institute of Technology. Brader is author of more than 60 peer reviewed publications. The research interests of Brader are in the field of plant-microbe interactions, and in understanding and characterizing plant diseases. His work also focusses on the exploitation of beneficial bacteria for biocontrol and nutrient solubilization and the description of the underlying mechanisms.