As part of the EXCALIBUR project, the Natural History Museum in London is seeking to understand why certain micro-organisms have the ability to increase the bioavailability of some essential mineral nutrients in soil.
In their latest research, they selected bioinoculants that were individual species rather than commercial mixtures, and were chosen on the basis of several criteria:
- That their components were used in EXCALIBUR.
- That they show biological diversity.
- They were known to be able to dissolve minerals in soils.
The species selected were two bacteria (Bacillus subtilis and Paenibacillus polymyxa), and the fungus Clonostachys rosea. These three inoculants were provided by INTERMAG, INHORT and KIS, institutions that are also involved in agricultural research or the production of crop stimulants.
The agricultural soils used for incubation were provided by some EXCALIBUR partners: RINOVA, KOB, TU-Graz and INHORT, and were slightly amended by adding 3% of the soil of three minerals containing nutrients of interest: iron phosphate (Fe and P), talc (Mg) and potassium feldspar (K). In this way, the presence of the nutrients was guaranteed.
The experiments lasted 6 months at a temperature of 25°C, in a humidified atmosphere that maintained ~10% by weight of water content in the soils.
This study provides an evaluation of the most promising individual inoculants from the perspective of increasing the availability of mineral nutrients in the soil.
The results have revealed that the fungus C. rosea is more efficient than bacteria in generating bioavailable essential nutrients across a wide range of soil characteristics. The fungus does so in 40% of cases, while bacteria do so in 31-33% of experiments.
In the future, an in-depth analysis of the results will be carried out to investigate the causes of the variable effectiveness of the bioinoculants in promoting nutrient availability and to establish procedures to increase it.