Dairy leftovers as crop biostimulants and the future of agricultural sustainability


Since industrialisation, agriculture has been heavily dependent on synthetic fertilisers to boost crop growth and yield, resulting in environmental and economic challenges.


Dr Francesco Vuolo of Sacco Srl, Italy, is making use of dairy fermentation leftover from manufacturing industries to build a circular, green economy for a more sustainable future.


Read more in Research Features


Read the original research : https://doi.org/10.3390/land11091544


Image Source: Shutterstock / LariBait





Hello and welcome to Research Pod! Thank you for listening and joining us today.


In this episode, we look at Dr Francesco Vuolo of Sacco Srl, Italy and collaborators, who, using lactic acid bacteria fermentation’s byproducts, have created a new organic agricultural biostimulant to promote greener, more sustainable crop growth and yield.


Now, more than ever, there is an urgent push towards sustainability in agriculture. Governments across the world are advocating for a reduction in synthetic fertiliser usage, while also promoting biological solutions to enhance crop performance and yield. The EU Green Deal has committed to ensuring a climate-neutral continent by 2050, a clean and circular economy, and to protect biodiversity.


During human evolution, the traditional hunter-gatherer lifestyle has developed into a more settled existence that depends on reliable sources of food. This has resulted in significant changes in farming practices. To enhance the yield of cultivated plants, humans slowly adopted the use of natural fertilisers – substances, such as animal waste, that are added to soil to increase its fertility. The development of synthetic fertilisers in the early twentieth century pioneered an agricultural revolution that transformed global food production. Synthetic fertilisers form a predominant source of essential nutrients that might be lacking in the soil. However, the excessive use of synthetic fertilisers has weakened the soil and polluted water bodies, thereby affecting aquatic life.


Nitrogen, phosphorus, and potassium are elements present in soil that are essential for plant growth and development. Nitrogen is necessary for plants since it is a component of chlorophyll, the green pigment used in photosynthesis, while also being the building block of amino acids that make up proteins. Phosphorus is a major constituent of DNA and RNA, the nucleic acids that control cell functions. Potassium is essential for the plant vigor and the functioning of a multitude of enzymes in plants. Together, these elements enhance cell growth and function, aiding the increase in biomass and yield of fruits/seeds. In addition, these nutrients support a healthy composition of soil microbes, without which plants cannot survive.


Healthy soils normally have enough of these elements available to support plant growth. However, a number of factors which include the intensification of farming methods, mean that Nitrogen, phosphorus, and potassium, or, NPK, are not always available for plant nutrition. In fact, farmers need to add extra synthetic NPK to sustain crop development, which further impairs natural soil ecosystems by altering the ideal natural balance of the soil nutrients through dangerous accumulations.


To reduce the harmful effects of synthetic fertilisers on the ecosystem, governments worldwide are promoting the development of new organic fertilisers that can enhance agricultural productivity. Several biostimulants have already been developed to replace or to integrate synthetic nitrogen and increase the organic carbon content of the soil to stimulate plant growth. This new generation of biofertilisers can help achieve a greener economy by avoiding the costly effects of synthetic fertiliser-derived pollution. Biofertilisers also help sustain microbial communities in the soil, increasing soil biodiversity and enhancing plant performance. To supplement this, a circular, green economy would use byproducts from one industry to fuel another. This symbiosis between different industries can drive the global food production and subsequently reduce wastage.


The food industry creates 1.3 billion tonnes of waste each year. With global population increase and the demand for more food, food wastage has already become a big problem. A change of perspective is necessary: food industries need to exploit the ‘waste’ as a useful ingredient (when possible) for other industries. Circular economy as such can boost agriculture, if applied appropriately.


The dairy and pharmaceutical industries produce lactic acid bacteria (otherwise known as LAB) through fermenation, to yield probiotics and starter cultures for products, such as yoghurt, cheese, etc. This fermentation results in a broth which is generally discarded. In a previous study, Vuolo and collaborators demonstrated that distillation of this broth not only recovers huge amounts of water, but also concentrated nutrients which can later be used as soil fertiliser. Vuolo and his team showed that soil beneficial microbes and nutrient composition were stimulated by this fermentation byproduct – called eluate – which is rich in nitrogen and organic acids. This result motivated the team to investigate the effects of the eluate on plant growth and yield.


In recent research funded by Sacco Srl, Italy, Vuolo and his colleagues demonstrated the effects of this novel biostimulant, LAB eluate, on crop growth and yield by observing lettuce and tomato plants grown in soil in a greenhouse. To test the biostimulant, the plants were fed with a commercial fertiliser containing NPK, at the recommended amounts, or fed with a combination of fertiliser and LAB eluate. In this way, the composition of Nitrogen was either entirely from fertiliser, 100%, or 70% from fertiliser and 30% from LAB eluate. The scientists monitored plant biomass, canopy – the spread of plant leaves, and fruits, in addition to characterising the soil microbial community.


The researchers demonstrated that the eluate replaced 30% of total nitrogen available to the plants and increased the growth of lettuce and tomato plants compared to 100% synthetic NPK fertilizer. While an increase in canopy and biomass of leaves was observed for lettuce, there was an increase in tomato biomass and fruit numbers in plants fed with eluate, but with delayed fruit ripening. The researchers suggest that is because the high nitrogen content in soil causes delayed fruit ripening. They also found a shift in the microbial composition of soils surrounding the tomato plants that were fed with eluate.

The researchers have already tested the effect of the LAB eluates on cereals, corn, and other extensive crop cultures. The results are really encouraging, as the eluate showed perfect integration to their common practices, and their application is compatible with the crop systems.


Dr Vuolo commented on how their results be scaled up, given that LAB eluate shifts the composition of microbes in soil of pot-grown plants.  He explained that “the microbial composition after the eluate application is enriched in what’s known as ‘Plant Growth Promoting Microorganisms’ which are stimulated by the nutrients of the eluate – and is technically a fermentation broth for microbes. Thanks to its unique blend, the Plant Growth Promoting Microorganisms grow and proliferate and dominate the root microflora. On a large scale, this represents a good counterbalance to the effect of synthetic fertilisers, which are intended to nourish the plants only, and by doing so, they disrupt the natural plant-microbe interactions, which are instead restored thanks to the eluate.”


Vuolo also shared his thoughts on how cross-industry collaborations could be accelerated to enable a greener, circular economy.  He explained that “An ideal solution would be the creation of networks of companies, which may find synergies in their models, that are ultimately orientated towards the needs of the final customer. This may be achievable through associations, but a change in mindset should be applied by all the market leaders. We need to act together and not as many individuals.”


The researchers put forward the idea that LAB eluate can be a sustainable choice to reduce the amount of synthetic nitrogen applied to crops and yet, boost crop growth. The study shows that by considering the waste from the dairy industry as a new biostimulant, soil biodiversity can be protected, and a circular green economy can be achieved.


As Vuolo concludes, ‘This innovation complies with the new EU Green Deal frame, aiming to reduce chemical fertilisers, and change agricultural methods toward a cleaner future.’


That’s all for this episode – thanks for listening, and stay subscribed to Research Pod for more of the latest science.


See you again soon.

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