Management of Useful Microorganisms in Tropical Soils
One of the nicest parts of the IPPC 2015 were the organization of workshops on diverse topics in plant protection where one could discuss about specific topics and their future prospects.
The workshop “Management of Useful Microorganisms in Tropical Soils” was chaired by Mr. Jose Pereira da Silva Jr (Brazilian Agricultural researcher) and by Mr. Falko Feldmann (JKI). At the start of the workshop Mr. Jose Pereira highlighted his experiences made in tropical soils followed by an open discussion about the use of rhizobium, its application to the soil along with the fungicidal side effect on the population of rhizobium.
Interestingly, in Brazil 85 million tons of soybeans are cultivated on 24 million hectare without applying nitrogen fertilizer. They are only using rhizobium as plant treatment. The problem that occurred in previous years was that the application of fungicides / insecticides seems to decrease the population of rhizobium / microorganism in the soil, thus reducing the nitrogen fixing capacity of soybean. Unfortunatley, application of fungicides is important to control soil born diseases which otherwise will cause major yield losses. Jose Pereira was able to show that there is no direct effect of the fungicides on the symbiosis process but on the population of the microorganisms. The question was raised from the audience if a lower concentration of fungicide would be okay? Mr. Jose Pereira replied that with less concentration of the fungicide there will be less effect on the population of microorganisms but in return will not control the disease efficiently. Falko Feldmann asked if it might be possible to separate the fungicide treatment from the rhizobia treatment by putting the rhizobia below the seed so roots can grow to it. Jose Pereira replied that the problem is that rhizobium does not survive for a long time. He tested various fungicides from different companies and developed an application strategy were the fungicide is applied 2 months before rhizobia so it will not affect the population of rhizobia. However, they have to look for new strains of rhizobia every year to get maximum nitrogen fixation. Overall, rhizobia treatment is not so expensive in Brazil as costs for 1 hectar are less than 2 euro and the marginal return for soybeans is higher than for other crops. In summary, the right application technology for fungicides and/or rhizobia will have a positive effect on yield and helps to sustain the population of rhizobia.
In his impulse presentation Mr. Falko Feldmann referred to mycorrhizae, endophytes and management practices to improve the soil health which in the long term will increase crop productivity and profitability.
Additional factors affecting soil health are abiotic and biotic environmental factors as well as fertilization regime. Furthermore, plant roots grown in tropical soil can look absolutely different from roots of the same plant grown under sterile conditions. For example, rubber trees grown in vitro show an intensive and very fine root system, whereas you will never find such rubber tree roots in nature. Especially if in tight contact with mycorrhizae fungi plant roots recycle products immediately after taken up by these fungi and don’t develop in an expansive root system. However, within this context the mycorrhizae genotype plays a major role that needs to be studied more intensively in the future.
Then Falko Feldmann enlightened us about the biodiversity as ultimate key to the success of any agricultural system. If we come to know what’s going on in the soil that we are managing, we can use this knowledge for better plant growth. One of the research areas of the future will be the microbiome which will lead us to a complete new way of thinking about plant growth and plant health.
In the following discussion the floor was open for questions. One of the aspects coming up was about the general regulation of the bio-fertilizer products in the EU and around the world. Falko Feldmann explained the recent developments within EU regulation regarding the indirect effect of bio-fertilizers on plants. After the workshop we had the opportunity to interview Jose Pereira da Silva Jr and Falko Feldmann.

Young Scientist:
How do you think the future of bio-fertilizers and the application technology of microbial inoculum?

Mr. Jose Pereira da Silva Jr:
Best is to consider all the options that we have for biocontrol. Biocontrol is easy to register and easy to integrate with other measures. Due to a lot of disease surveillance in Brazil one must have to do seed treatment with fungicides which will decrease the population of rhizobium. We have to think more seriously about the application of the fungicides two months before rhizobium application or we will have to rely more on integrated management approaches.

Young Scientist:
Do you think that management of useful microorganisms can help the farmers in developing countries?

Mr. Falko Feldmann:
Especially for the developing countries it is the solution for a lot of problems concerning photorespiration in plants e.g. as we saw in the presentation of Mr. Jose Pereira regarding cultivation of soybean on 24 million hectare of land without using nitrogen fertilizer. This already saved a lot of fertilizer and reduced the cost for the production of soybean dramatically. If this would be transferred to the other tropical regions of the world it could lead to much higher yields at less costs. It’s not only restricted to rhizobia as there are lots of different microorganism, e.g. N-fixing bacteria and mycorrhizae fungi, that can also play an important role for plant health as well. One option for the future could be to manage the soil in such a way that beneficial microorganisms naturally occurring in the field are promoted by management strategies to increase in number leading to the healthy plant.

Young Scientist: How do you see the future of these useful microorganisms in Germany?

Falko Feldmann:
In Germany microorganism play an important role as component of integrated plant management. We are recently classifying them for their MOA e.g. following the potential they conserved and so on. You may discriminate between direct acting plant protection products used against biotic and abiotic stress and bio-fertilizers which are used as substitute for nutrients. How much this can bring for Germany has been showen by an experiment in East Germany in the 1980s where a lot of fertilizer was saved by using such organisms. This shows that it is also possible in our region, although most likely not for all production systems/situations. However, indirect acting microorganism are recently not finally classified and we are still discussing regulations to discriminate them from bio-stimulants.

Young Scientist: What do you think how we can use these microorganisms all over the world with different cultivation systems.

Falko Feldmann:
These microorganisms are not restricted to any country. You can use them anywhere but what we need it to really acknowledge the importance of these microorganism and to recognize their potential for plant health. Very often traditional farming methods already make use of those microorganisms without knowing about it. For example, the high diversity of cultivated plants in China improves cycling of nutrients. Traditional farming systems have developed over several centuries based on learning by doing. Nowadays, there is the risk of losing the knowledge about traditional cultivation systems and especially the knowledge about microorganism maintaining such systems. We need to better understand how microbial communities can be managed for a better plant health.

Regards
Muhammad Awais Zahid
University of Hohenhiem

On left Muhammad Awais Zahid Student at Hohenheim, In middle Dr Kari A. Peter Assistant professor from Penn state University (USA) , on right Dr Julia Meitz-Hopkins from Stellenbosch University (South Africa)