Toxin-producing microscopic fungi in plant manure have a negative effect on soil life, researchers note


The results of research into the effects of microscopic fungal toxins on soil life have been recently published. The study revealed that under the influence of corn kernels contaminated with certain mycotoxins, the proliferation of springtails, which play an important role in plant growth and humus formation, has been significantly reduced, with potentially negative consequences for crop production. The research was carried out by the staff of the Environmental Chemistry and Ecotoxicology Research Group of the ELKH Centre for Ecological Research, the Department of Animal Feed and the Department of Zoology and Animal Ecology at Szent István University.

Everyone has heard of poisonous mushrooms, but they automatically remind us of deadly amanita and other cap mushrooms. However, there are microscopic fungi that infect our crops, most commonly grain, invisibly or barely visibly. These fungi can also produce toxins (mycotoxins) depending on environmental stress (excessively cold or hot weather, drought, excessive rainfall, etc.). Exactly what conditions trigger toxin production can vary from species to species. The fact is, however, that these toxins are dangerous to humans and animals if their quantity reaches the critical limit in a product, the consignment of grain in question is declared unfit for human consumption. In this case, one of the methods of utilization is to dilute it with  fodder that is not contaminated with mycotoxins and then use the crop as animal feed or, in its original state, as plant manure.

The researchers investigated the effects of using contaminated maize plant as fertilizer on soil life, more precisely on springtails. Springtails (Folsomia candida) are tiny, insect-like creatures of a few millimeters that are older than insects. They play an important role in the propagation and regulation of plant fungi (mycorrhiza) without which most plants would have difficulty growing or would not grow at all. They also play a role in humus formation and the decomposition of dead plant matter.

In their research, experts mixed experimentally high-dose aflatoxin-contaminated corn in various volumes into artificial soil. The effect of different concentrations on the proliferation, survival and avoidance behavior of the Folsomia candida springtail has been tested in the laboratory, and whether it consumes contaminated food was also observed. In the end, no significant effect on survival was found, but it emerged that the number of offspring decreased significantly – by less than half – even at the lowest concentration applied which, even in this case, exceeded the value occurring in practice, compared to clean soil and the control group. At the highest concentration, which was multiple times the amount occurring in practice, it was hardly possible to find young organisms. Although the animals chose yeast, i.e. their usual diet, primarily over aflatoxin-contaminated corn, they nevertheless consumed it. What was surprising was that the springtails did not avoid the contaminated soil and tried to stay in the aflatoxin-containing soil even though they began to die from the toxin. It is likely that the fungus (Aspergillus flavus) used in the experiment was basically good-quality food for them as long as it did not produce mycotoxins, which is why the organisms were attracted to it even though it was explicitly a trap for them due to its high toxin content in the case studied.

For all these reasons, researchers recommend that aflatoxin-contaminated grain should not be used as a fertilizer in agriculture, as this will damage soil life, which could lead to yield losses in the long run. Instead, the use of contaminated corn for biogas production is recommended as an alternative.