Nitrogen is one of the most powerful levers in modern agriculture. When supplies are inadequate, crops often produce less biomass, fewer seeds and smaller grains. Yet applying more nitrogen is not a simple solution. Crops commonly absorb only a fraction of the fertilizer supplied to fields; the remainder can leach into waterways, escape as nitrous oxide or undergo chemical transformations that contribute to air and climate pollution. Farmers therefore face a biological paradox: plants need enough nitrogen to build a productive canopy, but excessive applications are expensive and can damage ecosystems. Nitrogen-use efficiency, or NUE, describes how effectively a plant converts available nitrogen into harvestable yield. According to the review by Dmitry Veselov, Jiangzhe Zhao, Alla Korobova and colleagues, improving NUE will require understanding not just how nitrate enters roots, but how plants interpret its presence and coordinate their entire body in response.

The first step is nitrate perception. Plant roots use transporter proteins to acquire nitrate from soil, but some of these transporters also act as “transceptors”—molecules that combine transport activity with sensory functions. One of the best studied is NRT1.1, also known as CHL1 or NPF6.3 in Arabidopsis. Its activity changes with nitrate concentration, allowing roots to respond across a broad range of nutrient availability. At low nitrate levels, high-affinity NRT2 transporters help capture scarce ions; at higher concentrations, other transport systems become more important. NRT1.1 can also influence the distribution of auxin, another plant hormone, thereby altering the formation and elongation of lateral roots. This allows a plant to proliferate roots in nutrient-rich patches rather than spending the same amount of energy everywhere. Once nitrate is detected, calcium signals, protein phosphorylation and transcription factors such as NLP6 and NLP7 help activate a rapid nitrogen-response program.

Cytokinins add a second layer of control to this nutrient-sensing network. These hormones are produced in roots and shoots, and their concentration depends on a balance between biosynthesis, transport and breakdown. Nitrate availability can stimulate the expression of isopentenyl transferase, or IPT, enzymes involved in cytokinin production. In particular, nitrate-responsive changes in root IPT activity can increase the synthesis of cytokinin precursors, including forms that are converted into trans-zeatin, a biologically active cytokinin. Other enzymes, including cytokinin oxidases and dehydrogenases known as CKXs, remove or deactivate the hormones. The result is a dynamic system rather than a simple on–off switch: a change in nitrate supply can alter cytokinin production, chemical form and movement through the plant. Recent evidence highlighted in the review suggests that fluctuations in nitrate may even influence IPT3 through changes in chromatin and histone modification, allowing roots to adjust hormone production as nutrient conditions shift.

The direction of cytokinin movement is crucial. Root-derived cytokinins can travel upward through the xylem, carrying information about soil conditions to leaves and growing shoots. Transporters such as ABCG14 and related proteins help load and move cytokinin compounds over long distances, while purine permeases and other transport systems contribute to local distribution and hormone homeostasis. The shoot is not simply a passive recipient of this chemical message. It also sends information back to the roots through sugars, nitrogen-containing metabolites and mobile peptides. CEP peptides produced in roots under nitrogen limitation can be processed into signals that travel upward and stimulate shoot-to-root messages, including CEPD-like proteins that regulate nitrate uptake. Cytokinins therefore participate in a two-way conversation: roots report the availability of nitrate, while shoots communicate their demand for additional nitrogen. This feedback prevents the plant from absorbing nutrients indiscriminately when its leaves cannot use them efficiently.

The most visible consequence of this communication appears below ground, where nitrate and cytokinin signals help reshape root architecture. When nitrate is scarce, plants may favor deeper or more extensive roots capable of exploring a larger volume of soil. In a localized nitrate-rich patch, they can stimulate lateral root growth near the nutrient source. Cytokinins interact with auxin in this process, often exerting opposing effects on root and shoot development. High cytokinin activity in some root zones can limit primary root elongation, while reduced cytokinin levels may permit a larger root system. This explains why genetically or chemically reducing cytokinin degradation in roots can produce plants with enhanced root growth, improved mineral accumulation in shoots and greater drought tolerance. The effect is context-dependent, however. A root that grows farther is not automatically more efficient; constructing and maintaining extra tissue requires carbon. The plant must balance the energetic cost of exploration against the expected benefit of finding and absorbing more nitrate.

Above ground, cytokinins help determine whether newly acquired nitrogen becomes productive leaf area or is diverted elsewhere. Adequate cytokinin signaling promotes cell division, leaf expansion and chloroplast development, the process by which cells build the photosynthetic machinery that captures light. In rice, wheat and other cereals, higher cytokinin status has been associated with increased photosynthetic capacity under favorable nitrogen conditions. This connection is chemically logical: nitrogen is required to build chlorophyll and many photosynthetic proteins, including Rubisco, the enzyme that fixes carbon dioxide. Cytokinins can also influence stomatal behavior, chlorophyll maintenance and the expression of genes involved in carbon assimilation. By coordinating nitrogen uptake with photosynthetic activity, the plant can convert absorbed nitrate into sugars more efficiently. Those sugars, in turn, provide energy and carbon skeletons for nitrate assimilation, creating a feedback loop between carbon and nitrogen metabolism.

The review also draws attention to cytokinin’s role in delaying leaf senescence, the orderly deterioration of leaves as plants age or face nutrient stress. During grain filling, cereal crops depend heavily on flag leaves to continue producing carbohydrates that are transported into developing seeds. Nitrogen availability and cytokinin signaling can help maintain these leaves for longer, preserving photosynthetic activity at a stage when grain weight is being determined. At the same time, cytokinin metabolism must be carefully controlled. Excessive or poorly timed signaling can disrupt the balance between vegetative growth and reproduction. Enzymes such as CKXs act as important regulators of this balance. Research in rice has shown that altering CKX activity can affect grain number, grain filling and the relationship between carbohydrate-producing leaves and developing grains. Some transport proteins may even carry both sugar and cytokinin, linking the movement of energy and growth signals directly within developing cereal grains.

Nitrogen and cytokinin signaling may also help crops cope with drought, salinity, heat and flooding—stresses that are becoming more consequential as climates change. Nitrate can influence stress-related gene expression, antioxidant defenses and the production of reactive oxygen species, molecules that serve as signals at controlled levels but can damage cells when they accumulate excessively. Cytokinins interact with abscisic acid, the hormone strongly associated with drought responses, as well as with ethylene and other signaling pathways. Under water deficit, changes in cytokinin production and transport can alter the balance between shoot growth and root investment, helping plants conserve resources while continuing to search for water. In some systems, stress-induced cytokinin synthesis has been linked to coordinated regulation of carbon and nitrogen assimilation. Nitrate nutrition has also been associated with improved tolerance to salinity and heat, although the benefits depend on dose, timing, species and environmental conditions. Too much nitrogen can intensify stress by stimulating growth that the plant cannot support with available water.

The authors emphasize that these findings do not justify simply adding hormones or more fertilizer to fields. Cytokinins are powerful regulators, and their effects vary with tissue, developmental stage, nitrate concentration and interactions with other hormones. Instead, the review points toward precision strategies that might match fertilizer placement and timing to the plant’s signaling capacity. Localized fertilizer application could encourage roots to forage in nutrient-rich zones without saturating the entire soil profile. Breeding or gene editing might target nitrate sensors, cytokinin transporters, IPT biosynthetic enzymes or CKX catabolic enzymes to create crops that maintain productivity with less nitrogen. Beneficial soil microbes that produce or modify cytokinins could provide another route, particularly under drought or nutrient stress, although field performance remains difficult to predict. The central message is that future high-efficiency crops may be designed not only to absorb more nitrate, but to make better decisions about when, where and why to use it. By treating nitrate as both food and information, agriculture could move closer to producing more grain with less fertilizer—and make the plant’s own communication network part of the solution.

Subject of Research: Interaction between nitrate signaling and cytokinin hormones in plant nitrogen-use efficiency, growth, stress resistance and crop productivity

Article Title: Interaction between nitrates and cytokinins in the regulation of nitrogen use efficiency, plant growth, abiotic stress resistance and productivity

Article References: Veselov, D., Zhao, J., Korobova, A. et al. “Interaction between nitrates and cytokinins in the regulation of nitrogen use efficiency, plant growth, abiotic stress resistance and productivity.” Plant and Soil (2026). Original research page

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09011-7

Keywords: nitrate uptake, nitrogen-use efficiency, cytokinin signaling, cytokinin transporters, root architecture, crop productivity, drought resistance, cereal grain filling

The researchers found that the combined treatment reduced cumulative ammonia volatilization by 27.1 percent compared with conventional urea fertilization during a complete rice-wheat rotation. The result is particularly notable because the amended organic fertilizer was applied with a 30 percent reduction in mineral nitrogen input, yet crop productivity was largely maintained. The findings point toward a potential strategy for making fertilizer use more efficient without simply asking farmers to apply less and accept lower yields. Instead, the approach aims to control what happens to nitrogen after it enters the soil.

“Reducing fertilizer input is only useful if farmers can maintain crop production at the same time,” said corresponding author Haijun Sun. “Our results suggest that combining biochar with dicyandiamide in organic fertilizer can help balance these goals by retaining nitrogen, limiting ammonia losses, and supporting crop growth.” That balance is central to the global fertilizer challenge. Nitrogen is indispensable for plant proteins, chlorophyll, and growth, but when it is converted into gaseous ammonia and lost from farmland, farmers may need to spend more on replacement fertilizer while nearby communities and ecosystems absorb the pollution.

The experiment covered two complete rice and wheat rotations from 2022 to 2024 in greenhouse soil columns. The researchers compared conventional urea fertilization with three treatments that used lower amounts of mineral nitrogen: conventional organic fertilizer, organic fertilizer amended with biochar, and organic fertilizer containing both biochar and dicyandiamide. The soil-column design allowed the team to monitor nitrogen movement and ammonia emissions under controlled conditions over successive crop seasons. Unlike a short laboratory test, the two-year rotation captured repeated changes in soil chemistry, crop uptake, and fertilizer behavior across both flooded rice and relatively dry wheat production.

Among the treatments, the combination of biochar and dicyandiamide produced the most consistent result. Across the full rotation, it was the only organic fertilizer treatment that significantly reduced cumulative ammonia emissions compared with conventional urea. Biochar alone reduced cumulative ammonia volatilization by 5.9 percent compared with conventional organic fertilizer, while adding both biochar and dicyandiamide achieved a much larger 33.6 percent reduction relative to that treatment. These results suggest that the two amendments may work through complementary mechanisms rather than simply adding the same effect twice.

Biochar is a carbon-rich material produced by heating biomass under oxygen-limited conditions. Its porous structure can alter soil water retention, nutrient adsorption, and the chemical environment surrounding fertilizer particles. In this study, the researchers linked biochar application to better regulation of ammonium concentrations and pH in the soil and the floodwater covering rice. This matters because ammonia volatilization is strongly influenced by the balance between ammonium ions and dissolved ammonia. Higher pH shifts more ammonium toward gaseous ammonia, making it easier for nitrogen to escape. By moderating this chemical environment, biochar may help keep nitrogen in a less volatile form for longer.

Dicyandiamide, commonly known as DCD, is a nitrification inhibitor that slows the microbial conversion of ammonium into nitrite and nitrate. That process can be beneficial under some conditions because plants can absorb nitrate, but rapid nitrification can also increase the risk of nitrogen leaching and nitrous oxide production. By delaying the transformation, DCD may extend the period during which ammonium remains available for plant uptake or retention in the soil. The researchers observed altered nitrogen transformation patterns in the amended treatment, indicating that the inhibitor helped reshape the timing and pathways of nitrogen cycling rather than merely reducing one isolated emission.

The study also examined soil bacteria and found that biochar-containing fertilizers reduced the abundance of Nitrospirota, a bacterial group associated with nitrite oxidation, one of the key steps in nitrification. The shift suggests that the amendments may change the microbial niches involved in nitrogen conversion by modifying factors such as pH, moisture, carbon availability, and nutrient distribution. However, the researchers emphasize that their microbial analysis was based on taxonomic profiling. Detecting changes in the abundance of a bacterial group does not directly prove that a particular organism performed a specific biochemical function, so future work using functional genes, enzyme measurements, and isotope tracing will be needed to confirm the mechanisms.

The environmental gains did not appear to come at the expense of another major greenhouse gas. Cumulative nitrous oxide emissions showed no significant differences among the fertilizer treatments, an important finding because strategies that suppress ammonia can sometimes redirect nitrogen losses into other pathways. The combined treatment also maintained rice yields at levels comparable with conventional fertilization, while conventional organic fertilizer and biochar-only organic fertilizer reduced rice grain yields. The researchers estimated through Monte Carlo simulations that the combined treatment could generate potential benefits of approximately 36,600 Chinese yuan per hectare per year under the experimental conditions, reflecting fertilizer savings and reduced nitrogen-related environmental and health costs.

The result is promising, but it is not yet a universal prescription for farmers. The experiment was conducted in controlled soil columns rather than commercial fields, where rainfall, temperature swings, soil types, irrigation practices, fertilizer placement, and management decisions can vary dramatically. The economic estimate also depends on local fertilizer prices, crop yields, pollution costs, and the availability and quality of biochar and dicyandiamide. Field-scale trials will be essential to determine whether the ammonia reductions persist under real farming conditions and whether the treatment remains affordable and practical across different rice-wheat systems. Even with those limitations, the study offers a striking example of how combining carbon-based soil amendments with targeted nitrogen management could help turn fertilizer from a major source of pollution into a more efficient tool for feeding a growing population.

Subject of Research: Nitrogen fertilizer efficiency, ammonia volatilization, biochar, dicyandiamide, soil nitrogen cycling, and rice-wheat crop production

Article Title: Ammonia mitigation and economic gains from dicyandiamide and biochar-amended organic fertilizer: a 2-year rice-wheat rotation study

News Publication Date: 22-Jun-2026

Web References: https://doi.org/10.48130/aee-0026-0016; Agricultural Ecology and Environment

References: Huang W, Wang L, Gong X, Bian R, Lu X, et al. 2026. “Ammonia mitigation and economic gains from dicyandiamide and biochar-amended organic fertilizer: a 2-year rice-wheat rotation study.” Agricultural Ecology and Environment 2: e019. DOI: 10.48130/aee-0026-0016

Image Credits: Wang Huang, Lisha Wang, Xueliu Gong, Rongjun Bian, Xinyue Lu, Yuanqing Bu, Yunyi Liang, Haijun Sun, Yanfang Feng, Changlei Xia, Jiang Jiang, and Lihong Xue

Keywords: ammonia volatilization, biochar, dicyandiamide, organic fertilizer, nitrogen fertilizer, nitrogen cycling, rice-wheat rotation, soil microbiome, nitrification inhibition, sustainable agriculture, crop productivity, agricultural pollution