The Application of Mycorrhizal Fungi and Organic Fertilisers in Horticultural Potting Soils to Improve Water Use Efficiency of Crops

In recent years, the addition of microorganisms such as Plant Growth-Promoting Bacteria (PGPB) and mycorrhiza are becoming more popular, both in research as well as in practical use. While inoculants are usually not necessary for plants cultivated outdoors on biologically active soil, they can be useful on sterile substrates, newly created artificial landscapes, and also in soils that have been managed using non-selective sterilization methods, such as fumigation. In a multi-year lysimeter experiment, we investigated the influence of a commercial mycorrhizal inoculum on water use efficiency and biomass production of maize, sunflower, sweet clover, sweet sorghum, cup-plant and tall wheatgrass when exposed to high or low ground-water levels. Results showed that all plants benefited from the mycorrhizal association. Mycorrhizal-inoculated plants were more successful in terms of dry matter production and water use than the non-mycorrhizal plants. The source of the mycorrhiza—autochthonous or introduced—made no significant difference. The results indicate that inoculation with mycorrhiza and promotion of the naturally abundant mycorrhiza in agricultural production systems can significantly contribute to a sustainable production of crops. Effects depended on plant species, cultivar, soil type, ground-water level and the mycotrophy of the individual crop species.

Conclusions

In our experiments all plant species benefited from mycorrhizal association. Colonised plants of all species had greater dry matter production and less water use than non-mycorrhizal plants, independent of the fungal origin-applied or autochthonous. The different species varied in the degree of their reaction to the mycorrhiza. The effect was more pronounced the lower the ground water level. Results showed that mycorrhiza can not only improve the growth of high performance crops, but also promote their adaptation to different environmental conditions such as deep groundwater levels. The results also indicated that inoculation with mycorrhiza in biologically active soils is not necessary. However, they may be useful in sterile substrates, newly-created artificial landscapes, and also in soil that has been managed using non-selective sterilization methods, such as fumigation.

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