Testing plant growth promoting microorganisms in the field - a proposal for standards

Area of Science:

• Agricultural Microbiology
• Sustainable Agriculture
• Plant Science

Background:

• Growing markets exist for plant growth promoting microorganisms (PGPM) and biological agents in agriculture, offering sustainable alternatives to agrochemicals.
• Unlike registered plant protection products, PGPM marketed as soil improvers or biostimulants in the EU lack mandatory efficacy testing under field conditions.
• Existing regulations focus on safety rather than proven field performance, with no uniform guidelines for efficacy trials.

Purpose of the Study:

• To address the absence of uniform guidelines for PGPM field trials.
• To propose standardized guidelines for the design, implementation, data collection, and evaluation of PGPM field trials.
• To enhance the reliability and comparability of efficacy data for PGPM products.

Main Methods:

• Review and evaluation of selected research papers on PGPM field trials.
• Analysis of existing literature to identify common deficiencies in trial design and data collection.
• Development of proposed guidelines based on identified gaps and best practices.

Main Results:

• The majority of reviewed studies exhibited clear experimental designs and proper data evaluation.
• Frequent deficiencies identified include a limited number of tested environments and crop species.
• Insufficient description of site and agronomic management, along with missing soil humidity and temperature data, were common issues.

Conclusions:

• The proposed guidelines aim to standardize PGPM field trial methodologies.
• Adherence to these standards is expected to improve the expressive power and reliability of tested microbial products.
• Implementing these guidelines will contribute to more robust evidence supporting the efficacy of PGPM in sustainable agriculture.