Soil bacteria : Healthy soils thanks to soil bacteria

Pest insects and plant-pathogenic fungi that live in the soil and attack plant roots are extremely difficult to ward off with pesticides. They therefore pose a great problem in agriculture and cause substantial damage. Some naturally occurring soil bacteria offer a means of combating them: they can colonise plant roots very efficiently, trigger the self-defense mechanisms of the plants and keep harmful fungi and insects off the plants.

The project aimed to investigate whether the number and activity of plant-beneficial bacteria of the genus Pseudomonas in Swiss soils used for wheat cultivation is connected with the soil’s natural resistance to diseases. In addition, the team wanted to find out with which cultivation method these beneficial bacteria can be stimulated. Using Pseudomonas bacteria and other beneficial microorganisms, notably insecticidal roundworms (nematodes), new biocontrol methods to prevent diseases and pests in wheat and other agricultural crops ought to be developed.

Plant-beneficial Pseudomonas bacteria are abundant and exhibit varied antifungal activities in Swiss agricultural soils. High numbers of certain groups of these bacteria seem to correlate with low numbers of certain fungal pathogens and with resistance to certain diseases. However, in addition to the investigated pseudomonads there are probably many more microorganisms contributing to soil health. The results show that it is possible to manipulate the number of beneficial microbes with cultivation methods. The number of bacteria of a specific group with high antifungal activity, for example, was higher in integrated production systems without tillage. The conducted field trials with wheat indicate that the application of these beneficial bacteria can help the plants to cope with stress caused by diseases and pests.

The results of the project show that beneficial microorganisms are present in Swiss agricultural soils and actively contribute to soil health. Therefore, more (applied) research is needed to suitably adapt agricultural practices so that these naturally occurring “policemen” can multiply.

The development of new biocontrol methods against diseases and pests in agricultural crops will contribute to safer and more environmentally friendly food production.

Sustaining and improving soil health with plant-beneficial bacteria