Humic acids from waste flows and manure: a valuable biostimulant?

Humic acids are widely used in horticulture because of their supposed positive effect on crop quality and yield. Wageningen Research is investigating whether the humic acids from waste water contribute to the more efficient use of fertilizers in agriculture.

Humic acids are used as biostimulants in agriculture and horticulture. Humic acids contribute naturally to increasing crop productivity and crop health. For commercial applications, humic acids are extracted from leonardite, a type of lignite. Organic waste streams such as animal manure, organic waste and sewage sludge also contain humic acids. This project investigates whether recovered humic acids from residual flows could form an alternative to commercial humic acids produced from lignite.

Improved crop growth by humid acids

Humic acids can improve crop growth by means of a number of mechanisms. Commercial suppliers of humic acids supply these products due to the increased nitrogen uptake, improved root growth and higher product yield. The positive effects of humic acids are partly related to processes that take place in the soil, making nutrients and micronutrients more readily available. In addition, various physiological effects are seen in plant roots, which improves the absorption of nutrients and increases the plant's resistance to stress. On the other hand, there is also scepticism about the supposed effects of humic acids. In the scientific literature, such effects are often demonstrated under conditions that are not relevant to agricultural practice. In addition, soils already contain humic acids naturally, which makes it doubtful whether a little extra humic acid could contribute to improved crop quality.

Membrane technology

Humic acids are found in high concentrations in residual flows from installations in which organic waste such as manure, fruit/vegetable waste or plant-based waste is processed. High concentrations of humic acids are also found in the effluent from sewage treatment plants. Membrane technology makes it possible to extract these humic acids in concentrated products. The humic acids obtained in this way are considerably cheaper than current commercial products made from leonardite (lignite). The extraction of humic acids from waste water therefore makes these products available for use in sectors in which the use of traditional humic acids is not cost-effective.

The research being performed by Wageningen Research focuses on demonstrating the possible positive effects of humic acid concentrates from residual flows on crop yield. Various trials are being carried out to assess the effect on germination, rooting and nutrient uptake. 

This project is being financed by TKI Deltatechnologie, Attero, Opure, Van Iperen, Tauw en Stowa.