Prospects for humic acid products from digestate in the Netherlands : quickscan

The goal of this research was to examine the prospects for humic acid products and in particular a humic acid product produced from animal manure/digestate. Based on a literature review it is concluded that humic acids are used worldwide as biostimulants and overall positive effects on crop growth are reported, but variation in results is high. Stakeholders explained during interviews that in the Netherlands the use of Humic acid products are mostly related to niche markets. For conventional agriculture in the Netherland the value of humic acids has not been proven yet, this can be explained by the high fertility of the Dutch soils, and high yields that are already obtained without adding humic acids. Also field experiments were done. In several field experiments with potatoes and onions the specific humic acid product was tested. Adding the humic acids (on soil and as foliar spraying) did not benefit crop growth, but also did not harm the crops. No effect was found on the development of diseases.