Carbon Dots Enhance Bioavailability of Nitrogen in Soybean Crops

In an article recently published in the journal ACS Nano, researchers discussed the utility of carbon dots to increase nitrogen bioavailability to support soybean growth and nutritional quality under drought stress.

Carbon Dots Enhance Bioavailability of Nitrogen in Soybean Crops

Study: Carbon Dots Improve Nitrogen Bioavailability to Promote the Growth and Nutritional Quality of Soybeans under Drought Stress. Image Credit: nnattalli/

Nitrogen Fertilizer

The development of nitrogen fertilizer has significantly raised crop yields, resulting in a significant increase in agricultural output and the first agricultural “green revolution”. The bioavailability of nitrogen fertilizers is less than 50%; hence increasing fertilizer investment does not result in a permanent boost in crop output. Meanwhile, the overuse of nitrogen fertilizer has given rise to other environmental problems. To achieve sustainable agriculture, it is crucial to increase nitrogen’s bioavailability and lessen its detrimental effects on the ecosystem worldwide.

Soybean: A Crucial Commodity

About 366 million tons of soybean (Glycine max) are produced annually on a global scale. To increase soybeans' ability to withstand drought and retain their nutritional value, nitrogen usage needs to be increased. Despite being relatively new, nano-enabled agriculture is a field with both prospects and difficulties.

The future of nano-enabled agriculture seems bright if the underlying interactions between plants and engineered nanomaterials (ENMs) can be fully understood. By fostering global food security, agricultural nanotechnology can enormously benefit the general public.

Significance of Carbon Dots

Due to their small size, low toxicity, good optical qualities, and inexpensive supplies, carbon dots, a rising star of the carbon ENMs, have demonstrated promising results in nano-enabled agriculture. There are still questions about whether carbon dots can increase soybeans' ability to withstand drought by enhancing nitrogen bioavailability, though.

Due to the decent distribution of carbon ENMs in soil, previous investigations suggested that lower concentrations of the carbon ENMs could influence nitrogen fixation in legumes.

In this study, the authors increasednitrogenbioavailability through soil application of carbon dots (5 milligram kilogram-1), which helped soybean grow and become more nutritious, and reduced the economic losses brought on by drought stress. Application of carbon dots to the soil improved nodules' capacity to fix nitrogen, controlled rhizosphere activities, and eventually enhanced nitrogen and water intake by drought-stressed soybean. The application of carbon dots under drought stress boosted soybean nitrogenase activity by 8.6% compared to control and increased nitrogen content in soybean shoots and roots by 18.5% and 14.8%, respectively.

The team demonstrated the release of nitrogen from the soil, by encouraging the production of roots through carbon dots in the soil and by controlling the activity of the beneficial microbial communities. Additionally, the expression of the genes GmNRT,  GmLB, GmAMT, and GmAQP in roots was elevated by 1.2-, 2.7-, 1.8-, and 2.3-folds, respectively, in comparison to control, which suggested improved nitrogen transport and water uptake. Furthermore, due to increased nitrogen bioavailability, the fatty acids, proteins, and amino acids in soybean grains were improved by 6.9%, 3.4%, and 17.3%, respectively.

The researchers postulated that carbon dots in soil could increase the ability of soybean to withstand drought and absorb nitrogen by controlling the rhizosphere exudates and microorganisms and boosting the nodules' capacity to fix nitrogen. Thus, this study examined soybean growth under drought stress following soil application of carbon dots, looked into the processes by which carbon dots increase nitrogen bioavailability, and evaluated soybean yield and nutritional quality following carbon dots application.

Performance Characteristics of Carbon Dots on the Soybean Growth and Nutrition

The particles of carbon dots were uniformly spherical and had an average size of 2.8 ± 0.5 nanometers. The characterization findings supported carbon dots' numerous functional groups and chemical makeup, which were also consistent with their superior water dispersibility. Additionally, the fresh weights of soybean roots and shoots increased by 59.8% and 49.6%, respectively, while their dry weights increased by 41.4% and 54.6%.nitrogencontent in soybean shoots and roots increased significantly after carbon dots were applied to the soil, by 18.5% and 14.8%, respectively. The number of nodules increased by 19.5% after carbon dots were applied to the soil.

GmLb3 was upregulated by 66.1% in response to carbon dots, while the expression levels of GmLb1, GmLb2, and GmLb4 were noticeably upregulated by 4.2, 3.8, and 2.1 times, respectively. Following carbon dots exposure, the expression of GmNRT2;1, GmNRT2;2, and GmNRT2;5 was considerably increased by 1.6-, 2.1-, and 1.8- folds, while GmNRT2;4 and GmNRT2;6 was also enhanced by 49.0% and 39.6%, respectively. The net photosynthetic rate increased by 2.0 times due to the leaf's 18.5% higher nitrogen content.

Despite a 50% decrease in soil moisture, the soil application of carbon dots increased soybean production by 25.2% and quality due to improved nitrogen bioavailability via regulation of the rhizosphere process and enhancement of nodule nitrogen fixation. The increase in nitrogen bioavailability in soybean offered a workable way to increase crop nitrogen use efficiency, which helped to reduce the overuse of nitrogen fertilizer and lessen environmental harm. The benefit was that carbon dots-enabled agriculture might save significant soybean losses.

Conclusions and Future Perspectives

In conclusion, this study showed that soil application of CDs could improve crop tolerance to environmental stress and foster sustainable agriculture growth.

The authors mentioned that the biocompatibility and chemical inertness of CDs in the food chain, on the other hand, were better suited to encouraging their use in real-world agricultural production. However, they highlighted that these numbers came from pot tests and that longer-term field studies will be necessary in the future for more precise information.

The team emphasized that carbon dots-enabled agriculture holds promise for enhancing soybean quality and drought resistance, which is important for ensuring food security in the face global climate change.


Wang, C., Ji, Y., Cao, X., et al. (2022) Carbon Dots Improve Nitrogen Bioavailability to Promote the Growth and Nutritional Quality of Soybeans under Drought Stress. ACS Nano.

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Surbhi Jain

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Surbhi Jain

Surbhi Jain is a freelance Technical writer based in Delhi, India. She holds a Ph.D. in Physics from the University of Delhi and has participated in several scientific, cultural, and sports events. Her academic background is in Material Science research with a specialization in the development of optical devices and sensors. She has extensive experience in content writing, editing, experimental data analysis, and project management and has published 7 research papers in Scopus-indexed journals and filed 2 Indian patents based on her research work. She is passionate about reading, writing, research, and technology, and enjoys cooking, acting, gardening, and sports.


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