Hydroponic Common-Bean Performance under Reduced N-Supply Level and Rhizobia Application.

Area of Science:

• Agricultural Science
• Plant Physiology
• Microbiology

Background:

• Inorganic nitrogen (N) fertilizers are crucial for crop production but can lead to environmental issues.
• Common beans (Phaseolus vulgaris L.) possess the ability to form symbiotic relationships with rhizobia for biological nitrogen fixation (BNF).
• Hydroponic systems offer controlled environments for studying plant nutrient uptake and symbiotic interactions.

Purpose of the Study:

• To investigate the impact of reduced inorganic nitrogen (N) fertilizer application on hydroponic common bean yield, quality, and biological nitrogen fixation (BNF).
• To assess the effectiveness of different rhizobia strains in enhancing BNF under varying N supply levels.
• To determine optimal N-use efficiency strategies for common bean cultivation in hydroponics.

Main Methods:

• A two-factorial experiment was conducted using hydroponically grown common beans.
• Three inorganic N supply levels (100%, 75%, 50% of standard) were applied during the vegetative stage, with subsequent reductions for the 75% and 50% treatments during the reproductive stage.
• Two rhizobia strains (Rhizobium sophoriradicis PVTN21 and Rhizobium tropici CIAT 899) and a no-inoculation control were used.

Main Results:

• The 50%-25% mineral-N application regime significantly increased nodulation, BNF, and fresh-pod yield compared to other treatments.
• The 75%-25% regime reduced nodulation and BNF, leading to significant yield losses.
• Both rhizobia strains enhanced nodulation and BNF, but this capacity decreased with higher inorganic N input. Strain PVTN21 showed superior performance.

Conclusions:

• Optimizing nitrogen-use efficiency in hydroponic common beans can enhance biological nitrogen fixation (BNF) and yield.
• Reduced inorganic N application, particularly the 50%-25% regime, is a viable strategy for sustainable common bean production.
• Utilizing effective rhizobia strains, like PVTN21, can further improve BNF and yield while reducing mineral N dependency and environmental impact.