Using a Nitrogen Stabilizer When Top-Dressing Corn Improves Nitrogen Use Efficiency and Benefits Crop Yield

Side-dressing refers to the practice of applying nitrogen fertilizer after the crop has been planted, usually during early vegetative growth, a common practice in a corn fertilizer program. Laying nitrogen along the rows ensures it is available when corn has the highest demand, typically between V4 and V8. Side-dressing corn has several benefits including improving yield potential and reducing nitrogen lost to the environment, which increases nitrogen use efficiency. Nitrogen can be broadcast or dribbled on top of the soil or injected below the surface and can use dry or liquid fertilizer. While side-dressed nitrogen is well-placed for good uptake by fast growing corn, environmental conditions present when these applications are made can reduce the amount of the fertilizer available to the crop.

Effective nitrogen management is important for maximizing corn yield and reducing nitrogen escaping into the environment. Nitrogen losses through volatilization, denitrification, and leaching can reduce the efficiency of side-dress applications. Urea or urea ammonium nitrate (UAN) solution applied to the soil surface is susceptible to volatilization loss when the urea is converted to ammonia by the enzyme urease found in naturally occurring soil bacteria (Fig. 1). Loss from volatilization can be slowed using a stabilizer, such as TIMAC AGRO USA’s products EXCELIS MAXX, that contains the urease inhibitor NBPT. Combining EXCELIS MAXX with the nitrogen fertilizer used in the side-dress application slows the chemical reaction that converts urea to ammonia, increasing the amount time for the corn to use the nitrogen.

Fig. 1. Chemical equation for the urease enzyme, leading to loss of surface applied nitrogen due to volatilization

Environment plays a large role in the conversion of urea to ammonia. Conditions such as alkaline soil surface pH, soil temperatures above 50°F (10°C), air temperatures higher than 75°F (24°C), low soil moisture, and stubble in no-till fields all can promote nitrogen loss. Urea can lose up to 30-50% of its nitrogen through volatilization when conditions are conducive. Using EXCELIS MAXX significantly slows this loss, which can dramatically impact crop productivity.

Nitrogen loss from the soil surface is not the only issue facing side-dress applications. Injecting UAN below the soil surface places the fertilizer close to plant roots and reduces surface losses such as volatilization and run-off, but it faces risks. When placed under the soil surface, ammonium (NH4⁺) can be converted into nitrate by soil bacteria, which is a form of nitrogen that is susceptible to leaching from the soil. EXCELIS MAXX contains a 2^nd active ingredient, dicyandiamide (DCD), that temporarily blocks the enzyme activity that starts the conversion process. In this use, EXCELIS MAXX keeps the nitrogen in the NH4⁺ form longer, making the side-dress application more resistant to loss from leaching. This also slow denification, which converts the soil nitrogen supply into ammonia and other nitrogen-containing gases, which leave the soil and end up as air pollution. 

Side-dress also offers a good opportunity to correct other nutrient issues corn might be facing, including deficiencies in micronutrients. This means that a side-dress application is a good opportunity to add micronutrients to the fertility program. TIMAC AGRO USA’s BLUE Micro-Balancer Complete offers an all-in-one package to add micronutrients such as zinc (Zn), boron (B), manganese (Mn), and sulfur (S), which all play essential roles in vegetative and reproductive growth. Integrating micronutrients into the top-dress nitrogen application can enhance efficiency and crop performance. 

EXCELIS MAXX and BLUE Micro-Balancer Complete also brings industry-leading biostimulants that are active on soil bacteria and plant roots. These biostimulants support strong root growth which enables the crop to better take up water and nutrients. They also increase microbial populations that play roles in the mineralization process that helps liberate nutrients from organic matter in the soil. EXCELIS MAXX contains TIMAC’s patented Rhizovit complex, which contains natural plant abstracts that promote plant root exudates. These exudates attract microbes, which further support plant growth by supplying soil supplies of nutrients. BLUE Micro-Balancer Complete contains a suite of biostimulant technologies that are active on both plant growth and soil microbe populations. Combining these biostimulants with necessary micronutrients positions the crop in the best situation for the most efficient use the side-dress fertilizer. This helps grow more crop while reducing environmental population. 

Fig 2. The nitrogen cycle.