Beer Waste Helps Kill Crop Parasites

Although the use of conventional pesticides is harmful to the environment, farmers still need a way of keeping crop-damaging organisms at bay. According to a new study, an eco-friendly combination of agricultural and beer brewing waste products may be able to help.

When the oil is extracted from harvested rapeseed plants (aka canola), a solid byproduct known as rapeseed cake is left over. Likewise, after the sugars have been extracted from grains in the commercial beer brewing process, a byproduct called bagasse is created.

Building on earlier studies, scientists at Spain’s Neiker Basque Institute for Agricultural Research and Development recently mixed rapeseed cake with beer bagasse, along with fresh cow manure. The mixture was then applied to the soil in a commercial greenhouse where lettuce was being grown.

Previously, that greenhouse had experienced yield losses of up to 45 percent due to the presence of Meloidogyne incognita nematodes in the soil. These parasitic roundworms lay their eggs in the roots of plants, forming galls that reduce the roots’ ability to draw nutrients from the earth. Even after conventional chemical fumigation had been carried out, the parasites were still present.

Led by PhD student Maite Gandariasbeitia, the researchers added their special mixture to the soil of some of greenhouse’s lettuce crops, at the beginning of a growing season. It was subsequently observed that the plants in those crops had significantly fewer galls on their roots than plants in untreated control crops, plus the crops in the treated soil ultimately had a 15-percent-higher yield.

Gandariasbeitia states that this effect was due mainly to the high nitrogen content of the rapeseed cake and bagasse. That nitrogen boosts the activity of beneficial microbes in the soil, while killing nematodes. It additionally breaks down organic matter – such as the manure included in the mixture – allowing it to more effectively serve as fertilizer.