EXCALIBUR FIELD TRIALS – A TOOL TO ASSESS THE EFFECT OF MICROBIAL INOCULA TO SOIL BIODIVERSITY AND PLANT PERFORMANCE
Article by Eligio Malusá, Lidia Sas-Paszt, Małgorzata Tartanus
Instytut Ogrodnictwa (Research Institute of Horticulture – INHORT), Skierniewice, Poland.
The field trials planned in the project are playing a key role to achieve the project objective, which is to improve the knowledge on soil biodiversity dynamics in relation to the different agro-ecological factors to enhance the efficacy of biocontrol and biofertilization practices in horticultural farming. For this reason, they have been defined in relation to the climatic and soil characteristics present in the different countries of the project’s partners institutions for the three crops concerned: apple, strawberry and tomato (Fig. 1-3). In particular, the different following factors, which are known to affect the efficacy of applied biofertilizers and biopesticides, have been considered in setting the trials:
- Soil management (organic or integrated) – including the following different practices: fertilization (organic/inorganic), tillage (reduced/intensive), cover crops/mulching (yes/no), pre-planting inoculation (yes/no), soil-borne pathogens management (yes/no);
- Canopy management – including the following treatments: foliar/soil application of biofertilizers/biopesticides, frost protection (yes/no);
- Microbial-based products – including the following treatments: formulations (consortia or single strain), complex formulations (microbial inoculum +plant biostimulant or single product).
The number of microbial inocula or formulations planned to be tested in the different trials vary depending on the aspect to be addressed (i.e. plant protection in case of biopesticides or plant growth in case of biofertilizers) and the strains available. Furthermore, they depend on the different characteristics/needs of the three crops as well as of their production system (open field or protected crop).
A comprehensive analytical assessment of initial soil physico-chemical
- biological properties for all experimental sites is planned to be performed to obtain the largest and deepest possible assessment of the native biodiversity in the field hosting the trials. This will be followed by the monitoring of changes in these properties as well as by evaluating how these properties are affecting the inoculated strains during the trials.
To this aim, the soil mineralogical, textural and chemical composition is planned to be determined in association with direct pedological observations (profiles) using also innovative methods like proximal soil sensing (electromagnetic induction, gamma-ray spectroscopy). This work is expected to determine their main pedogenetic processes, soil characteristics and limitations (among them waterlogging susceptibility, nutrient status, compaction) which could strongly affect the success and the dynamics of inoculated microorganism. A particular focus in this respect is posed on nutrients content (macro and micro-elements) and the soil organic matter and its fractions.
The soil microbial diversity (bacteria, archaea, fungi, oomycetes and microbiome structure) will be assessed using both culturable-dependent procedures and DNA-based methods on both bulk and rhizospheric soils and the plant tissues. The latter will be analysed particularly to check the presence of mycorrhizal fungi in roots and their level of colonization.
Considering that macro, meso and microfauna populations (earthworms, arthropods, nematodes, protists) in and above the soil are affecting the persistence and dynamics of inoculated microorganisms (but are also affected by bio-inocula), we have planned to evaluate these biological elements in the trials. The data from soil samples will be used to calculate diversity indices, based on the concept that the number of groups morphologically well adapted to the soil is proportional to the soil quality.
Data obtained from the different analyses and trials (including classical diversity indices – e.g. Shannon’s index and other indexes – e.g. the QBS-ar index which better define the biological status of the agro-ecosystem) will be organized and elaborated to draw an overall framework of the initial biodiversity of soils and cropping systems under contrasting pedo-climatic conditions. Indeed, soil micro and macro organisms form complex interactions within specific ecological niches. By exploring these interactions, also with the use of multivariate network analyses, we believe that we will be able to understand the complexity of functional processes before any crop species is introduced in the field and during the growth of the crops treated with the selected inocula. With this knowledge, we plan to develop a decision supporting system that could help farmers and advisors in obtaining the best result from the biofertilizers and biopesticides applied in their fields.