The microbiota in agricultural soil can help to suppress fungal soilborne plant diseases that are otherwise difficult to control. Microbes also have an impact on yield and the ability of soil to sequester carbon. Microbial activity can be affected by agricultural management practices and crop sequences.
In her doctoral dissertation, Ansa Palojärvi, research scientist at the Natural Resources Institute Finland (Luke), studied the impact of agricultural management practices on microbial communities in soil and the ecosystem services they produce. The dissertation also identified useful indicators for monitoring beneficial microbial activities in soil and the quality of agricultural soil.
The ability of soil microbes to suppress fungi (fungistasis) and soilborne plant diseases strengthened when tillage intensity was reduced. “Based on long-term studies, agricultural management practices have the potential to promote beneficial microbial activity in soil. The results could not be generalised down to the level of a single measure, but the ability to suppress disease could be linked to a microbial and fungal biomass in soil and a high concentration of carbon easily available for micro-organisms”, Palojärvi says.
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Soil health is important for the sustainable intensification of crop production
The study indicated that cultivation methods that accumulate organic matter in soil have an impact on plant growth. “When conditions are made favourable for diverse microbes, their activities beneficial for crop production can also be strengthened in soil.” In addition to soil tillage methods, soil microbial communities and crop productivity can be affected by means of a diverse range of crop species and a combination of crop rotation and soil tillage methods. Perennial crops maintain abundant rhizosphere microbes throughout the growing season. Plants able to form a mycorrhiza, maintain arbuscular mycorrhizal fungi in soil that may affect the phosphorus availability of crops.
Soil microbes are also linked to carbon sequestration, forming persistent organic carbon in soil. Reduced tillage intensity affected the placement of organic matter in the soil profile and accumulated it on the surface.
Soil tests available also for farmers?
The dissertation identified indicators that help to assess the level of soil disease suppression, i.e. the ability to reduce the incidence of soilborne diseases. Simple laboratory tests serve to determine the microbial activity of soil. In the future, the indicators will benefit research, and they can be used to develop tools for farmers to assess the state of soil. “These tests help to monitor soil microbes and the impact of agricultural management practices on them. Microbiological soil ecosystem services require simple indicators of the soil quality to develop and monitor sustainable agriculture.”
Research offers means to sustainably improve the efficiency and resilience of crop production. “In the light of the research results, it is vital to consider the functioning of the whole soil microbiome in planning sustainable agricultural methods, allocating subsidies and sustainably improving the efficiency of production.”
Ansa Palojärvi will defend her doctoral dissertation on Beneficial microbial activity supporting sustainable agriculture in the Faculty of Biological and Environmental Sciences at the University of Helsinki on 14 May 2021 at 12 noon. Professor Wietse de Boer (Netherlands Institute of Ecology (NIOO-KNAW), Department of Microbial Ecology & Wageningen University, the Netherlands) will be the examiner.