While conventional pesticides can be beneficial for ensuring crop yields, they are also ecologically damaging. In a bid to provide a greener alternative, a team of scientists has developed a natural pesticide — that’s also a fertilizer — made out of a combination of agricultural and beer brewing waste.

As part of the study, scientists at Spain’s Neiker Basque Institute for Agricultural and Development mixed rapeseed cake (a byproduct that results from extracting oil from the rapeseed plant) and bagasse (a byproduct that remains when sugar is extracted during beer brewing).

Building on previous studies, the scientists also added cow manure to the mix which they then applied to the soil in a commercial greenhouse where the lettuce was growing. Previously, the greenhouse had experienced yield losses of up to 45 percent due to nematodes in the soil which prevented the plants from properly drawing nutrients from the earth.

Following the addition of the mixture to the greenhouse lettuce crops at the beginning of a growing season, the scientists found significantly fewer parasites in the roots of the plants compared to control crops that remained untreated. What’s more, the researchers found that the treated soil also experienced a 15 percent increase in crop yield.

The success of the technique is largely due to the high nitrogen content of the rapeseed cake and bagasse, which boosted the activity of beneficial microbes in the soil while killing the nematodes. The hydrogen may also help breaks down organic matter, such as the manure present in the mixture, enabling it to act as a more effective fertilizer.

Original study: Frontiers in Sustainable Food Systems — Biodisinfestation With Agricultural By-Products