As of: 04/19/2023 4:09 p.m
Nutrients found in cabbage, carrots or wheat come from the soil on which they grow. However, giving back these nutrients as fertilizer is not always easy. The TU Munich has solutions.
When it comes to fertilization, conventional farmers have it easier than organic farmers: they can replace the nutrients that are removed from the field with the harvest with mineral fertilizers – nitrogen, phosphorus, potash or sulfur, for example. Synthetically produced mineral or artificial fertilizers are energy-intensive to produce and not very sustainable – the largest phosphorus deposits are in Morocco and Western Sahara, while potash usually comes from Russia, China or Canada. But they cover the nutritional needs for the next harvest.
Without livestock, there is no natural fertilizer
Conventional farmers usually also keep more animals per hectare than organic farmers, so they also have sufficient manure such as manure and liquid manure. In organic farming, there are fewer animals, making it more difficult to balance nutrients. “The trend in agriculture is that we have more and more arable farms that have fewer animals. And if we don’t have animals, we don’t have any manure to spread,” says Dr. Lucie Chmelikova, who heads the ProBio project at the Technical University of Munich. Without manure and liquid manure there would be no fertilizer for the fields.
Is compost from organic waste the solution?
Another problem for organic farmers: mineral fertilizers are not permitted in organic farming. So how do we keep the soil fertile and productive? The research project of the Technical University of Munich aims to simply bring the nutrients back from the city to the field – through organic waste compost.
That sounds simple and obvious, but it is extremely complex: everyone involved must come together, farmers, waste recyclers, organic associations, science – including consumers. Most farmers, however, shrug off the word “organic waste”: it just brings rubbish, pests and weeds onto the field, according to the common opinion. Many people still remember the pictures from the 1990s, when organic waste was left untreated on the fields.
Quality compost: The production is complex
Anyone who watches the organic waste transporters unloading at the AVA in Augsburg understands the concerns of the farmers. “It’s really embarrassing what some people mean by organic waste,” says Markus Jakob, shaking his head. He takes care of the sale of organic waste compost at AVA in Augsburg, one of ProBio’s project partners. “You can see all the plastic pollution here, all the foreign substances, metals – that’s what we’re confronted with.” What seems hard to imagine when looking at this littered biowaste turns out to be actually possible.
With the most modern screening and cleaning processes, through fermentation in the biogas plant and then intensive composting processes, the organic waste is processed and cleaned until the organic waste finally becomes valuable quality compost. Hygienized, RAL-certified and – for the batches where it is possible – with the particularly strict approval for organic farming.
Compost has important micronutrients
When an organic farmer uses such compost as fertilizer, he kills several birds with one stone. It not only brings the important primary nutrients such as nitrogen, phosphorus, potash or sulfur into the soil, because they are found in abundance in the organic waste compost. The micronutrients important for the plants, such as boron, selenium or molybdenum, also reach the field via the organic residues. And: the carbon in the compost helps to build up humus. This improves the water storage capacity of the soil – an important property in times of climate change.
Good crop yields with compost fertilizer
Organic farmer Johannes Kreppold from Aichach in Swabia is also a ProBio project partner. He swears by fertilizing with compost. “With mineral fertilization one says: the plant needs nutrients – nitrogen, phosphate, potash. And then you fertilize the plant in its mouth. With compost fertilization you try to make the soil so fit that it can do everything for the plant provides what she needs to eat healthily.”
For many years he has been working successfully with his own compost made from cattle manure, tree clippings and rock dust. His harvest results are impressive: ten tons of grain maize per hectare or six tons of baking wheat. For the research project, he is now comparing the effect of organic waste and green waste compost on his fields with that of his own compost. His conclusion: “I have had very good experiences with my own compost and would not say that the other composts are much worse.”
Nutrients in abundance
The research results of ProBio show so far: Biowaste composts have different effects depending on the location and crop rotation, but they are consistently positive: on soil life, the humus content, plant health and also on the yield. Theoretically, around 2.7 million tons of certified organic waste compost are available every year in Germany for organic farming – a huge nutrient cocktail, sufficient for over one million hectares of land. So far, only a fraction has been used.
The annual phosphorus requirement of organic grain alone can be covered with about five tons of compost per hectare. And there would be far more nutrients available. But that’s where consumers are challenged: Anyone who wants to support this kind of circular economy only throws what really belongs in the organic waste bin.