Organic fertilizers in fruit orchards (Biofruitnet Practice Abstract)

Summary

Alternating and integrating different fertilizers, depending on the nutrient budget and the soil status of plant available nutrients, can lead to a more balanced nutrient input.
Practical recommendations. When planning to use organic fertilizers consider alternative recommended fertilizers:
1) Clover-grass pellets or silage, from on-farm sources (preferred) or external sources; 2) Waste materials (e.g., biogas digestate, residues from yeast production, household wastes); 3) External fertilizers locally available (e.g., composts or extracts)
New fertilization strategies must be developed: 1) The mineralization rate of the products: liquid fertilizers, stillage, biogas digestate - mineralize rapidly and thus when applied in spring N supply matches well with fruit tree N demand, while compost materials have a very low N availability (< 10%) in the year of application; 2) Site specific features (e.g., cropping system, management practices, soil type, climate).
When searching for alternative fertilizers: 1) Compatibility with existing farm machinery; 2) Production costs, including labor and machinery costs (e.g., for clover-grass silage produced by the farmer) 3) Acceptance by certification bodies or additional quality schemes (e.g., from retailers) and potential contaminations (in case of waste derived fertilizers)