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Compiled by Bao Hien

Enhanced-efficiency nitrogen fertilizers can improve crop yields and nitrogen uptake, but their effectiveness depends significantly on soil properties. Research conducted by the International Fertilizer Development Center (IFDC) found that urea deep placement and certain nitrification inhibitors delivered relatively consistent results across two soil types tested, while many other products did not maintain their advantages under all conditions.

Published by IFDC on September 24, 2026, the findings highlight the need to evaluate advanced fertilizers under specific growing conditions rather than assuming that these products consistently outperform conventional nitrogen fertilizers.

Testing Different Fertilizers on Two Soil Types

Enhanced-efficiency nitrogen fertilizers (EENFs) are designed to improve nitrogen availability to crops or reduce nitrogen losses to the environment. This category includes slow-release fertilizers, controlled-release coated fertilizers, and products containing inhibitors that regulate nitrogen transformation processes in soil.

To evaluate the agronomic effectiveness of these products, researchers at IFDC, with funding from the US Environmental Protection Agency (EPA), conducted greenhouse experiments using sorghum. The study compared 11 enhanced-efficiency nitrogen fertilizers with conventional urea, urea-ammonium nitrate (UAN) solution, urea deep placement (UDP), and an unfertilized control.

Soil samples were collected from Iowa and Minnesota, two US states with different soil physicochemical properties. The researchers measured three main indicators: grain yield, aboveground biomass yield, and plant nitrogen uptake. Considering these indicators together provides a more comprehensive assessment of fertilizer performance than grain yield alone.

Urea Deep Placement and Two Nitrification Inhibitors Show Promising Results

The results showed that the effectiveness of enhanced-efficiency nitrogen fertilizers varied considerably between the two soil types. A product that performed well in one soil did not necessarily maintain the same advantage in the other.

Among the treatments evaluated, urea deep placement and two nitrification inhibitors—DMPSA (dimethylpyrazole succinic acid) and Pronitridine—delivered relatively consistent results. These treatments showed advantages in sorghum yield and plant nitrogen uptake compared with conventional urea and many other enhanced-efficiency products.

Urea deep placement involves placing fertilizer below the soil surface, typically near the active root zone, to reduce nitrogen losses and improve crop access to nutrients. Nitrification inhibitors, meanwhile, slow the conversion of ammonium into nitrate in soil. Depending on soil conditions and fertilizer management practices, this can help reduce certain forms of nitrogen loss, including nitrate leaching and nitrous oxide emissions.

However, the study does not establish that every product within these two categories performs equally well under all growing conditions. The observed advantages should be interpreted within the scope of the experiments conducted, rather than as evidence of universal superiority across all soils and crops.

Effectiveness Depends on Soil and Growing Conditions

Nitrogen occurs in several forms in soil and undergoes continuous biological, chemical, and physical transformations. Transformation rates, water-holding capacity, organic matter content, and microbial activity can all influence fertilizer effectiveness.

For example, nitrification inhibitors may be particularly beneficial when soil conditions favor nitrification and the risk of nitrogen loss in nitrate form is substantial. Their benefits may be more limited when nitrification is not a major pathway of nitrogen loss. Similarly, the effectiveness of slow-release and coated fertilizers depends on nutrient-release characteristics, temperature, moisture, and crop nutrient demand.
Therefore, a fertilizer's technology or product category alone cannot establish whether it will outperform conventional urea. Soil characteristics, weather conditions, crop type, application timing, and fertilizer placement must also be considered.

This is a key implication of the IFDC study: enhanced-efficiency nitrogen fertilizers do not automatically deliver the same benefits under all conditions. Their actual performance must be established through testing relevant to each cropping system.

Fertilizer Selection Should Be Based on Field Evidence

For farmers and agricultural advisers, the findings suggest that nitrogen fertilizer selection should be guided by soil characteristics and crop nutrient requirements rather than by manufacturers' general performance claims.

Where local trial data are unavailable, urea deep placement and nitrification inhibitors such as DMPSA and Pronitridine may be worth considering for further evaluation. However, their effectiveness should be verified under local soil, climate, and farming conditions before they are recommended for widespread adoption.

The study should also be interpreted in light of its experimental limitations. Results from greenhouse experiments involving sorghum and two soil types are insufficient to establish the economic benefits, emission-reduction potential, or suitability of individual products for other crops and agroecological regions.

The central message is that enhanced-efficiency nitrogen fertilizers are not a universal solution for every farm. Identifying the most suitable product requires an understanding of the interactions among fertilizer, soil, and crop, supported by field trials and assessments of nitrogen-use efficiency under actual production conditions.