Scaling from the growth chamber to the greenhouse to the field: Demonstration of diminishing effects of mitigation of salinity in peppers inoculated with plant growth-promoting bacterium and humic acids

- Scaling from the laboratory to the field showed diminishing effects of mitigation of salinity in pepper.
- Growth promotion of plants did not affect yield of fruits under saline conditions.
- The potential that laboratory results may not scale is a factor to be considered in this research field.
- There is scientific value in negative results regarding improvement of plant yield by inoculation.

The capacity of pepper plants to alleviate salt stress when inoculated with the plant growth-promoting bacteria (PGPB) Pseudomonas stuzeri and/or supplementation with humic acids was compared under in vitro conditions in a growth chamber (three independent experiments), greenhouse (four experiments) and field conditions (two experiments). Although inoculation with PGPB or humic acids significantly mitigated negative effects of salinity on germinating pepper seedlings under in vitro conditions, the effect was far less marked under greenhouse conditions and almost non-existent under field conditions, having no impact on yield of peppers under saline conditions. This study demonstrates that the improvement in growth with PGPB and humic acids in vitro may not be scalable from the laboratory to greenhouse and to field conditions. Not all PGPB improvements scale from the laboratory, greenhouse to field conditions and that the potential that laboratory results may not scale is a factor to be considered in this research field.