Optimising Crop Production by Combining Organic-Based and Mineral Fertiliser Sources: Agronomic Performance, Soil and Environmental Considerations

Organic materials, such as manure, compost, digestates, and biosolids, have a long history of use in European agriculture, providing essential nutrients and organic matter to soils. While these materials contribute positively to soil health and crop productivity, their use in specific regions, coupled with inadequate management, poses environmental and financial risks, including nutrient imbalance, enhanced leaching, and greenhouse gas emissions, in addition to the negative cost-benefit outcomes.

In response to growing environmental concerns and regulatory initiatives like the European Green Deal and Farm to Fork Strategy, there is a rising emphasis on promoting the closure of nutrient cycles. This has encouraged the development of ‘organic-based’ fertilisers (OBFs), which are products that combine organic matter and nutrients from organic origin with/without mineral nutrients. The expansion of this market is rapid in Europe, whilst it is also gaining traction in other regions.

Understanding the agronomic and environmental performance of OBFs and how their use fits into current mineral fertiliser practices is crucial for the development of OBF-based crop production optimisation within the principles of regenerative agriculture. This paper reports studies conducted in the laboratory and greenhouse, as well as in field trials at the Research Centre, Hanninghof, in North-Western Germany which sought to systematically evaluate the effects of commercially available OBFs and prototypes, alone or in combination with mineral fertilisers (integrated nutrition) on key crops such as maize, oilseed rape, and winter wheat. The evaluations included product types (i.e. with different organic raw materials and nitrogen (N)-forms) and application strategies. Application strategies evaluated fertilisation solely with OBFs or with supplementation using mineral N top-dressing. The performance evaluation was focused on crop growth, nitrogen fertiliser replacement value (NFRV), risk of nitrate leaching, ammonia volatilisation, nitrous oxide emissions, and remaining stable organic carbon fraction. Our studies conclude that OBFs can be integrated within current fertiliser practices to maintain or improve crop yields and to support the maintenance of soil health. Efficacy indicators such as NFRV can improve understanding of the most optimal way to integrate OBFs into crop programmes as a supplementation to mineral fertilisers, whilst improving resource use efficiency via circularity and without compromising on yield.