Common Questions About ESN

ESN release is generally continuous at a rate dependent on soil temperature, although there is minimal release in the first few days as ESN starts to take in soil moisture (see chart below). Soil moisture is necessary for the release process (diffusion), but soil temperature controls the rate of the process as long as sufficient water is present.  Moisture only becomes limiting when the soil surrounding the ESN granule is very dry – near the permanent wilting point.  Above that minimum moisture content, soil water does not affect the rate of release. The nitrogen release rate from ESN is temperature dependent, but there is not a specific “on-off” temperature. ESN can start releasing nitrogen at temperatures above freezing, but the release is very slow at lower temperatures and increases gradually as temperature increases.

Product quality is continuously monitored by our in-house lab to ensure ESN meets our quality and release standards. There may be small variations in coating from one granule to another, but the overall release rate is monitored continuously to meet the desired release specification.

ESN’s polymer coating is built to withstand normal application stress, but it can become damaged by excessive handling. Because of this, Nutrien recommends that ESN is handled and blended as little as possible and added to the blender last to minimize physical wear. The following blending recommendations should be followed to maintain the quality of ESN granules:

Belt conveyors are preferred and the use of screw augers and drag chains should be minimized.

Belt angles should never exceed 18 degrees, and any belts exceeding 13 degrees should be cleated to prevent roll-back.

If augers are used, large diameters are preferred, as small diameter equipment can increase contact with moving parts.

All transfer equipment should be in good repair with minimal rust and scale.

To prevent wear on the ESN coating, excessive blending should be avoided, and blending times kept to the minimum needed for uniform mixing.

Inclined axis cement-mixer type blenders cause the lowest abrasion to ESN, followed by vertical auger blenders and horizontal auger blenders.

For horizontal auger blenders, ESN should be loaded into the last bin before blender exit to minimize auger contact.

Avoid using blenders to transfer ESN if blending is not needed.

If adding liquid chemicals to the blend, always use a drying agent to absorb excess liquid before using ESN.

If using ESN in a blend with other fertilizer products, blend all other products first, add the ESN, and blend for as little time as required. It is essential to avoid excess blending, and blenders should be run as full as possible. Inclined-axis blenders (cement-mixer type) cause the least product abrasion followed by vertical-auger blenders (Doyle type).

ESN’s coating encapsulates a soluble nitrogen fertilizer. The coating forms a protective barrier that acts as a semi-permeable membrane surrounding the fertilizer granule. Tiny, molecular-size pores in the polymer coating allow water to enter the granule slowly. The water dissolves the soluble fertilizer which then diffuses, or oozes, out through the coating into the soil. The rate of the process is controlled by soil temperature. ESN’s coating remains intact through the release process maintaining the protective barrier and controlling N supply to the crop. ESN does not release N by swelling, rupture, or “breakdown” of the coating.

ESN release is controlled by soil temperature. Some moisture is needed to initiate the diffusion process and continue dissolving the urea inside the coating, but temperature controls the rate of the process.

Water is part of the release mechanism needed to dissolve the urea inside the ESN coating. But it does not regulate the rate of release except when the soil becomes dry enough to limit the process. This occurs near the wilting point of soil moisture. Above that, as long as the fertilizer is in good contact with the soil, there is little or no difference in the release rate with differences in soil moisture. Soil temperature is the primary regulating factor.

In other words, the release rate will be similar in saturated soil to that in unsaturated conditions. This is one of the benefits of ESN. While conventional fertilizers and even inhibitors may be affected by excess moisture, ESN continues to protect N in very wet conditions as well as in dry conditions.

No, the ESN polymer is still there, working to keep your nitrogen protected. The ESN coating is designed to release over 50 to 80 days, and protect your nitrogen for that period of time. One large rainfall does not compromise the ESN coating or cause all of your nitrogen to release very quickly. However, any nitrogen that was released from the coating and not used by the crop before the rain came is subject to losses.

We would typically describe the release of ESN to be about 50 to 80 days, but temperature and moisture can alter the timing of its release.

Moisture has little effect on the rate of release as long as there is adequate moisture to maintain the process. If ESN is incorporated into the soil and there is sufficient moisture to grow a crop, there would be little effect of moisture. Moisture only becomes a concern when it is surface applied and not incorporated in areas with limited or infrequent rainfall.

As an example, let’s compare a couple of different environments. In the Midwest U.S., we have many no-till corn growers who use ESN as a top dress with no incorporation with great success. Rainfall in these areas is typically sufficient to provide intermittent moisture to continue the release. By comparison, in the Great Plains, we would not recommend top dress applications for dryland cropping because rainfall is too infrequent.

The release of N from ESN is temperature dependent, but there is not a specific “on-off” temperature. Practically, ESN can start releasing N at temperatures above the freezing temperature of water, since liquid water is necessary for the diffusion process, but ESN releases very slowly at cold temperatures to protect the N when crops are growing slowly. ESN release does not start at 50 degrees F, but the release is very slow at lower temperatures and increases gradually as temperature increases to better match crop N demand.

Typically, most users are using ESN in a blend with other soluble fertilizers such as urea, MAP or DAP, ammonium sulfate, etc. This accomplishes several other objectives such as supplying other needed nutrients and making sure the crop has some immediately available nitrogen for early growth. Typically, we expect some immediately available N from ESN, as the effects of normal handling and blending processes will produce some immediate release. The normal range of immediately available N when ESN is first applied would be about 15 to 25% if proper care is taken during handling.

A small percentage of ESN granules are buoyant and may float in water. Some surface movement is possible if surface water flow is strong enough to erode soil in conventional-till, or erode residue in no-till. Significant movement of ESN offsite is rare and results from the combination of recently applied ESN, sloping topography, bare soil, and sufficient rainfall for erosion, a combination that should be avoided. ESN may be less prone to floating and movement if the fields previously received a moderate rain that firmed soil or residue contact with the granules. Light incorporation is preferred where possible to prevent the possibility of granule movement.

ESN’s primary release mechanism is by diffusion thru tiny, molecular-size pores in the polymer coating. A few granules may contain tiny flaws from the coating process, or may be damaged by normal handling processes. These granules release N quickly on contact with water. While a small portion of the N in ESN may be released quickly through these imperfections, the primary release mechanism is by diffusion thru intact coatings. Sulfur-coated urea, an older technology, does release N through fractures or degradation of the sulfur coating.

ESN was designed to be applied at or before planting on many crops. One purpose of controlled-release fertilizers is to allow all the needed N to be applied in one pre-plant application. ESN’s release is temperature sensitive; it releases slower in cool temperatures. ESN applied in cool soils before spring planting will release more slowly while the crop is small and growing slowly. As the soil warms crop growth increases and ESN release increases to match crop N demand. This temperature-controlled mechanism naturally synchronizes N release to crop demand. Hundreds of university studies on various crops have demonstrated excellent ESN performance as a single N application at or before planting.

ESN stays soft if there is moisture to diffuse into the coating and maintain the urea solution inside. Under conditions of severe, extended drought where ESN is left on the soil surface, it may slowly dry out and may become hard. It will rehydrate and become soft once moisture is present again.

No. ESN’s coating remains intact during the process of N release. ESN does not release nitrogen by “breakdown” of the coating but rather by diffusion of nitrogen through the coating. Nitrogen inside the coating dissolves and diffuses through the coating. The coating does not dissolve in contact with water or “break down” or come off over the course of the growing season.

No. ESN protects against volatilization even more effectively than urease inhibitors and for a longer time. Urea released from ESN is less susceptible to volatilization because only a small amount is released at a time, which maintains a lower urea concentration and prevents the temporary rise in pH around the fertilizer granule that is responsible for causing ammonia volatilization.

Freezing temperatures virtually stop release from ESN. Diffusion of water into the ESN granule is stopped and, if some urea has already begun to dissolve, the release of urea solution through the coating also ceases. If ESN has not yet hydrated – the urea has not yet begun to dissolve – the urea inside the coating will remain in the solid state until temperatures warm sufficiently for diffusion to begin again. ESN granules do not rupture, burst, or disintegrate upon freezing and will persist for long periods intact in frozen conditions. These properties make ESN a great alternative for fall applications in areas where soils are frozen during winter.

ESN will continue to release in very dry soil. Laboratory studies have demonstrated that soil moisture does not slow the ESN diffusion process and N release until soil moisture dries to about 20-30% of field capacity (near the permanent wilting point). At this point, the release can slow or, at even lower soil moisture content, even cease. Very dry conditions for an extended time may inhibit the release of N from ESN if it is left on the dry soil surface, but the process will recommence when moisture is present again. But even in very dry soils, ESN can continue to release N if it is in good contact with the soil. Some studies have shown there may be benefits to using ESN to control vegetative growth in very dry conditions and thereby reduce moisture stress.

Nutrien has two ESN production facilities, one in New Madrid, MO and one in Carsland, AB.

Usually, ESN will pass through the gut before any significant N is released from the coating. Cattle do not graze particularly close to the ground and will therefore pick up very little ESN. But even in the event they do ingest, modest amounts of urea are not a hazard to ruminants. Urea is often fed to cattle as a non-protein nitrogen supplement for a portion of their protein needs.

Usually, ESN will pass through the gut before any significant N is released from the coating. We have not done any assessments on the impact on birds if they should eat ESN, but we don’t believe there should be any toxicity. There is actually a patent on a similar coated material for use as a non-protein nitrogen source for ruminants.

United States – Incentive Programs

In the U.S. there are two main incentive programs available to growers – EQIP and CSP. Every state sets their own priorities and resource concerns, and structures their available funding based on resource priorities and national initiatives.

The Environmental Quality Incentive Program (EQIP) is a voluntary incentive program that awards financial contracts to farmers for trying a new conservation practice. Managed by the individual states, dollars should be available to you for improving environmental practices. ESN qualifies under the 590 nutrient management rules, which vary by state.

The Conservation Stewardship Program (CSP) is a voluntary national program that provides financial and technical assistance to promote the conservation and improvement of soil, water, air, energy, plant and animal life, and other conservation purposes on Tribal and private working lands. The conservation practices for CSP are determined in partnership with local NRCS offices.

The best way to find out which program is best for you is to contact your local NRCS office and ask them about available funds when using ESN under EQIP or CSP.

Canada – Incentive Programs

The Canola Council of Canada developed the Canola 4R Advantage program with funding through the On-Farm Climate Action Fund (OFCAF). The program offers incentives to help growers initiate or advance 4R Nutrient Stewardship on canola acres. The funding is allocated to each province to help pay for best management practices (BMPs) in four areas: soil testing, field zone mapping consulting services, enhanced efficiency fertilizer (EEF) and preferred application methods.

Applications are expected to open in June 2023 for the second year of this program. Please read the information from the Canola Council of Canada for details on qualifying and how to apply for the program.

ESN would not qualify as certified organic because the urea inside the coating does not qualify and the coating itself is a manufactured polymer.

Since ESN does not absorb moisture from the air, it remains free-flowing, even after extended storage. It can be stored indefinitely if kept dry. ESN has been observed to improve the condition of stored blends. Some retailers and growers have found adding ESN to blends to be stored can improve the condition and flowability of many blended fertilizers.

Care should be taken to minimize granule abrasion that results from excessive handling. Belt conveyors are preferred. Moving ESN with screw augers, especially when operated at high speeds and low volumes, should be minimized.