Ask The Expert: gChem’s Darryl Ramoutar on Nitrogen Management

Darryl Ramoutar, Ph.D., Global Technical Director, Agriculture, for gChem

AgriBusiness Global: Can you describe how nitrogen stabilization can be achieved using chemistry and beneficial microbes? What are the benefits of using this type of technology? In what applications is this technology most useful?

Darryl Ramoutar: Nitrogen is a foundational nutrient in crop production, enabling plants to build structural tissue and sustain the metabolic processes that drive growth and yield. In natural systems, soil microorganisms convert atmospheric nitrogen and decomposing organic matter into plant‑available forms through nitrogen fixation, mineralization (ammonification), and nitrification. While these processes supply some nitrogen, they are insufficient to meet the demands of contemporary, high‑yield agriculture.

As a result, supplemental nitrogen fertilization is a standard practice and a critical component of global food security. Modern cereal crops, including corn, wheat, and rice are bred for productivity and biomass accumulation, requiring nitrogen levels that exceed what soils can naturally supply.

In commercial farming systems, synthetic nitrogen is applied in several chemical forms, each with distinct handling, application, and uptake characteristics. Common sources include urea, valued for its high nitrogen concentration and cost efficiency; anhydrous ammonia, a high‑analysis nitrogen source injected into the soil under pressure; ammonium nitrate, which provides immediately available nitrogen but requires careful handling; and urea ammonium nitrate, a liquid fertilizer well suited for fertigation and precision application.

ABG: What are the long-term effects on soil health and microbial diversity?

DR: Soils can be amended with beneficial microorganisms to stabilize nitrogen primarily through biological immobilization and competitive nutrient uptake. When microbial inoculants are introduced, soil microorganisms assimilate inorganic nitrogen (such as ammonium and nitrate) to construct cellular biomass, temporarily converting it into organic forms that are less susceptible to leaching or volatilization losses. As microbial populations turn over and decompose, this immobilized nitrogen is gradually mineralized and released back into the root zone, thereby functioning as a slow‑release nutrient source for plants. It should be noted that while microbial denitrification may lead to nitrogen loss, high soil quality is grounded in a balanced amalgamation of biological, chemical, and physical soil properties.

According to Chen et al. (2002, 2003), several key microbial processes are involved in soil nitrogen transformations. These include nitrogen‑fixing bacteria, such as Rhizobia, which convert atmospheric nitrogen (N₂) into biologically available nitrogenous compounds that plants can utilize for growth. Additionally, nitrifying bacteria play a critical role in nitrogen cycling; ammonia‑oxidizing microorganisms (often referred to as nitritifiers) oxidize ammonium to nitrite, while nitrite‑oxidizing microorganisms (nitratifiers) further oxidize nitrite to nitrate. In natural and managed ecosystems, these soil microbial communities collectively promote efficient nitrogen cycling, improve nutrient retention, and enhance the synchrony between nitrogen availability and plant demand.

ABG: Are there any challenges with using this type of technology? How can those be overcome?

DR: Regardless of formulation, all nitrogen sources are susceptible to loss through volatilization, leaching, and denitrification. To improve nitrogen use efficiency and protect yield potential, farmers increasingly rely on stabilizing technologies. Urease inhibitors such as N‑(N‑butyl) thiophosphoric triamide (NBPT) slow the conversion of urea into ammonia gas, reducing volatilization losses, while nitrification inhibitors including nitrapyrin and dicyandiamide temporarily limit microbial conversion of ammonium to nitrate, decreasing leaching and denitrification. In addition, polymer‑coated fertilizers provide controlled nutrient release, aligning nitrogen availability more closely with crop uptake patterns.

Despite its agronomic value, NBPT presents formulation challenges due to limited solubility and chemical instability, requiring robust solvent systems to achieve stable, concentrated commercial products. For decades, N‑methyl‑2‑pyrrolidone (NMP) served as the solvent of choice for NBPT formulations; its strong polar aprotic character enables excellent solubilization of NBPT and similar active ingredients, supporting high‑load concentrates with good storage stability. However, NMP has come under increasing scrutiny following its classification as a reproductive toxicant, particularly in the European Union, leading to regulatory pressure and market‑driven efforts to eliminate its use.

ABG: What can we expect moving forward with this technology? Are there any related trends we should keep an eye on?

DR: Formulators have turned to alternative solvent systems with improved safety and sustainability profiles. Ethyl lactate, a biodegradable solvent derived from renewable feedstocks, has gained attention due to its low toxicity and favorable environmental characteristics. Another emerging option is dihydrolevoglucosenone, a dipolar aprotic solvent produced from cellulose via wood‑pulp processing. While these materials differ from NMP in solvency strength and physical properties, appropriate blending and formulation strategies can achieve acceptable NBPT solubility and stability. Glycols, particularly propylene glycol, are also commonly incorporated as co‑solvents or formulation aids. When used in combination with primary solvents and stabilizers, glycols can enhance miscibility, manage viscosity, and improve low‑temperature performance while contributing to extended shelf life. Their broad regulatory acceptance makes them attractive components of modern stabilizer formulations.

Dimethyl sulfoxide (DMSO) represents another potential polar aprotic alternative, offering strong solvency and lower regulatory concern relative to NMP. DMSO’s well‑known penetrative properties may influence the distribution of stabilized nitrogen in soil-plant systems, though such effects require careful evaluation to ensure agronomic benefit and compliance with safety guidelines. Overall, the shift away from NMP has accelerated the adoption of multicomponent solvent systems. Rather than single‑solvent replacements, successful NBPT formulations increasingly rely on tailored blends that balance performance, safety, regulatory compliance, and sustainability, reflecting broader trends shaping innovation in nitrogen management technologies.