Boosting Soil Nitrogen and Lemon Balm Harvest with Special Bacteria

Jenn Hoskins
28th March, 2024

Boosting Soil Nitrogen and Lemon Balm Harvest with Special Bacteria

Image Source: Natural Science News, 2024

Key Findings

  • In Vietnam, PNSB bacteria boosted lemon balm growth and soil nutrients
  • Lemon balm treated with PNSB had 23% more essential oil, even with less fertilizer
  • PNSB could help reduce chemical fertilizer use, benefiting the environment
In recent years, the quest for sustainable agricultural practices has led scientists to explore the potential of beneficial bacteria in enhancing crop growth and soil health. A notable example of such bacteria is the nitrogen-fixing purple nonsulfur bacteria (PNSB), which have shown promise in supporting plant development. A recent study[1] conducted by researchers at Can Tho University has shed light on the impact of these bacteria on the cultivation of lemon balm, an herb valued for its essential oils. Lemon balm requires fertile soil rich in nitrogen (N) to thrive. However, the excessive use of chemical fertilizers poses environmental risks, including water pollution and the disruption of soil ecosystems. To address this, the researchers investigated the effects of PNSB strains Rhodopseudomonas palustris TLS06, VNW02, VNW64, and VNS89 on soil fertility, nitrogen uptake, and lemon balm growth, aiming to reduce the reliance on synthetic N fertilizers. The study involved nine different treatments, varying the amount of nitrogen fertilizer used and the presence of PNSB. Remarkably, the application of PNSB led to increased plant height and branching. Even without any nitrogen fertilizer, lemon balm plants treated with PNSB exhibited a significant increase in stem and leaf biomass compared to those without PNSB, highlighting the bacteria's role in promoting plant growth. Moreover, the study found that soil properties improved with the addition of PNSB. In plots where no nitrogen fertilizer was used, the presence of PNSB increased concentrations of ammonium (NH4+), soluble phosphorus (P), and exchangeable potassium (K+)—key nutrients for plant growth. This suggests that PNSB can enhance soil nutrient availability, potentially reducing the need for chemical fertilizers. The most striking result was observed when 85% of the recommended fertilizer rate was combined with PNSB. This treatment not only yielded more lemon balm but also increased the essential oil content by 23% compared to plants receiving 85% N without PNSB. This finding is significant for farmers looking to maximize both yield and quality of their crops while minimizing environmental impact. The findings of this study resonate with previous research demonstrating the benefits of PNSB in agriculture. A prior study[2] showed that the purple non-sulfur bacterium Rhodopseudomonas sp. significantly boosted tomato plant growth and fruit quality, suggesting that PNSB could be a valuable biofertilizer for a variety of crops. Additionally, the study aligns with earlier research[3] on the use of plant extracts to stimulate growth and immune responses in fish. Just as lemon balm extract was found to enhance the growth and health of rainbow trout, the application of PNSB appears to provide similar benefits to plants, improving their growth and the quality of their produce. The research at Can Tho University contributes to a growing body of evidence supporting the use of PNSB as an environmentally friendly alternative to chemical fertilizers. By harnessing the natural abilities of these bacteria, farmers can improve soil health, crop yield, and product quality, all while reducing the environmental footprint of agriculture. This study not only offers practical solutions for lemon balm cultivation but also opens the door to broader applications in sustainable farming practices.

BiochemPlant ScienceAgriculture


Main Study

1) Improving nitrogen content in soil and lemon balm (Melissa officinalis L.) yield by purple nonsulfur bacteria Rhodopseudomonas palustris in two consecutive seasons.

Published 27th March, 2024

Related Studies

2) Enhancement of growth and yield of tomato by Rhodopseudomonas sp. under greenhouse conditions.

3) Effect of lemon balm (Melissa officinalis) extract on growth performance, digestive and antioxidant enzyme activities, and immune responses in rainbow trout (Oncorhynchus mykiss).

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