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Agronomics

Common Questions About ESN

The following is not intended to be complete or detailed use recommendations for all geographies, crops, or applications. User assumes all responsibility for proper use and handling of specific geographies, crops, and applications. Please consult your Nutrien ESN representative for complete recommendations for use. 

Still have questions? Ask an Agronomist.

What guidelines can you provide for ESN application in winter wheat in Western Canada?

We have seen excellent results with ESN application in the drill rows with winter wheat. In Western Canada, this is probably the most common use of ESN in one-pass direct-seed systems. Where the soil freezes and stays frozen through the winter, ESN release will shut down until the spring thaw. For fall application in the seed row, we recommend a high percentage of your N as ESN, typically 75 to 100% to provide for maximum seed safety.

We use a factor of 2 to 3X for ESN, meaning ESN is safe up to about 2 to 3 times the normal safe rate of urea. If using 100% ESN, you should be safe up to 3X; for a blend using ESN for 75% of the total N, we suggest dropping back to 2X the safe rate of urea to account for the effects of the soluble fertilizer used with the ESN. For many dryland systems, the safe rate of ESN will accommodate the entire N application to be applied in the seed.

What is the recommended rate and timing of application for ESN in soybeans?

Previous research has shown that soybean plants may cease forming nodules if there is a large amount of available nitrate in the soil. For this reason, soluble forms of nitrogen are not recommended for application until after flowering. Using ESN should allow for more flexibility in this type of application because of the controlled release mechanism.

Our current recommendation is to apply ESN somewhere between the V5 and V7 growth stages. This allows enough time for the ESN capsules to hydrate, start releasing urea into the soil, and for that released nitrogen to convert and move down the soil profile to the soybean root. Typical rates have been in the range of 40 lbs N/ac, to 80 lbs N/ac as ESN.

Is it better to apply ESN pre-plant or top dress in corn?

For corn, we have had great results with one pre-plant application as well as top-dress applications. We generally recommend a high percentage of the N from ESN, 70 to 90%, depending on residual soil fertility, previous crop, and carryover N from the last crop. ESN may also be applied as an early top-dress with some limitations. If top dressing ESN is your preference, apply early – before about V6 to V8 – and include more urea or ammonium sulfate, as much as 50% of the total remaining N needs. For sandy soils or conditions of severe early season N loss, top-dress ESN applications may actually be preferred to pre-plant applications.

Does fall applied ESN continue to work the following spring?

Where the soil freezes and stays frozen through the winter, ESN release will shut down until the spring thaw. A small amount of N generally becomes available within the first week – typically about 15 to 25% – due to normal imperfections in the coating of some granules. The remainder of the N releases according to soil temperature. In the winter, due to colder temperatures, the ESN will remain inside the coating. When spring temperatures begin to rise, the N release will resume. The N releases over about 50 to 80 days at a soil temperature of about 20°C.

Can ESN be banded in the fall?

Fall band application worked very well in research we conducted at the University of Minnesota. You can blend your P, K and ESN and apply your entire fertility program in a strip till operation in the fall.

Another option is to apply most of the N as ESN in the fall, but hold back some portion for an in-season side- or top-dress. This option obviously requires an additional application, but gives you more flexibility to adjust for changing conditions and yield potential. For this option, we suggest about 70 to 80% of your N as ESN in the strip till with the balance applied in-season according to need.

We do not recommend fall application in sandy soils, because they are prone to winter or early spring leaching, or where soils do not stay frozen through the winter.

Can ESN be applied in the fall?

Fall nitrogen application may increase the risk of N loss in some environments and is therefore not recommended in those areas. Spring N application is usually a preferred practice in many regions. Where fall N application is an acceptable practice according to soil type, environmental conditions, and cropping system, ESN is a great alternative to other N sources. In dryland cropping systems in arid and semi-arid areas, such as Western Canada and the Great Plains, fall may be the preferred application time for ESN. For these geographies, cool, dry conditions in late spring and early summer, may inhibit release from ESN unless it is incorporated. Because the N in ESN remains protected through cold winter periods, it reduces the risk of N loss and can improve N-use efficiency over conventional N sources that pose a greater risk. Areas that remain warm and wet through winter and early spring may not be suitable for fall ESN application. In these areas, ESN or ESN blends may be appropriate for some fall-seeded or winter crops. Consult your ESN dealer or Nutrien representative to discuss fall ESN applications.

What is the maximum rate at which I can apply ESN in corn without injuring the seed?

For fertilizer placed with the seed, we use a factor of 2 to 3X for ESN, meaning ESN is safe up to about 2 to 3 times the normal safe rate of urea for your soil conditions and planter configuration. If using 100% ESN, you should be safe up to 3X; for a blend using ESN for 75% of the total N, we suggest dropping back to 2X the safe rate of urea to account for the effects of the soluble fertilizer used with the ESN. Large amounts of N are not applied with the seed in corn because of the wide row spacing and the sensitivity of corn to seed-placed fertilizer. For broadcast applications or fertilizer banded with a minimum separation of at least 2-3 inches from the seed, there is no practical limit to how much ESN you can apply.

How much ESN can I top dress on corn?

You can do an early top dress application, at about the V6 or six-leaf growth stage. How much you should apply depends on how much nitrogen was in the soil at planting and how much you may have already applied in other fertilizer applications. Typical top dress applications at this time would consist of a blend comprised of about 50 to 75% of the remaining N needs as ESN with the balance as a soluble N source such as ammonium sulfate or urea.

Can ESN be blended with other fertilizers? Does blending destroy the ESN coating?

Yes, ESN can be blended with other fertilizers. In fact, it blends well with other fertilizers. ESN is designed to withstand normal handling processes. Proper handling and blending will not destroy the coating. Excessive blending may damage the coating and reduce ESN’s effectiveness. To help avoid abrasion of the coating, add ESN to the blend last and mix for the minimum time required to achieve uniformity. The blend will remain dry and flowable. ESN is the perfect product to improve any nitrogen program. Ask your retailer how it can help you.

Can I be more profitable by saving money and using a lower percentage of ESN in my blends?

Some ESN users attempt to cut costs by reducing the portion of ESN in the blend and therefore do not realize ESN’s optimum performance and full benefits. ESN recommendations are based on hundreds of studies in many environments and designed to produce the best possible performance. These studies show that best results and greater profitability are achieved using the amount of ESN recommended for each crop and time of application. In most cases this is at least 50% to as much as 100% of the total crop N needs as ESN. Remember that the portion of N applied as conventional, immediately available N sources is fertilizer N that is unprotected. ESN is designed to release in synchronization with crop demand, so only a small amount of immediately available N is typically needed. Using ESN as recommended produces greater yields and profitability than lower-cost alternatives that may appear to be a bargain but fail to provide the performance and profitability of ESN.

Do fertilizer spreaders damage the ESN coating?

ESN is designed to be applied using the same application equipment that is used for other dry fertilizers, including both spinner and air-flow type applicators. While some effect of handling and spreading is unavoidable, granules can be damaged by improper handling, proper procedures and adjustment of spreaders will assure damage is minimized, and ESN retains its protective coating and performs as it should. Where possible, air-flow spreaders should be adjusted to use slower air speeds, to minimize impact on ESN.

Does ESN need to be soil incorporated to work effectively?

No. Research and grower experience show that ESN works very well when surface applied in many geographies where intermittent moisture or even heavy dew is present. Many users have had great results top-dressing winter wheat and no-till corn. To maintain a more predictable N release rate, it is advisable to incorporate ESN where possible. Surface application without incorporation is generally not recommended in semi-arid and arid areas without irrigation. When surface applied to very dry soil, ESN granules have difficulty absorbing water and may be slow to release nitrogen. Some moisture is required to initiate and maintain that process. In arid and semi-arid areas without irrigation, incorporation is recommended.

How deeply do I need to incorporate ESN?

In many areas where intermittent precipitation or dew is present at somewhat regular intervals, no incorporation may be necessary. In areas of limited rainfall, such as dryland cropping systems in arid and semi-arid areas, some light incorporation is highly recommended. ESN need not be deeply incorporated as with a moldboard plow, but typically a harrow or sometimes even broadcast ahead of the seeder provides sufficient incorporation into the soil surface to provide good contact with the soil.

How should ESN be spread?

ESN can be applied using either spinner or air flow machines. ESN should be double spread for uniformity when using a spinner because fertilizer tapers off at the edges of the spread pattern. Always ensure the spreader is properly calibrated to deliver the desired N rate.

If ESN is more efficient, can I reduce the amount of nitrogen I apply?

ESN has been proven to increase N-use efficiency in many crops and environments. Growers often ask if this means they can reduce overall N rates when using ESN. University studies indicate when ESN is applied as recommended, a lower rate of ESN can indeed maintain crop yields similar to the normal recommended rate of conventional N sources. However, profitability is usually greatest and risk lowest if ESN is used at the same rates as the grower’s conventional program. The typical yield increase observed with recommended ESN applications is usually worth more than the savings achieved by reducing the N rate. Each user should perform comparison profit calculations using their own costs and estimated ESN performance in their environment. Contact your ESN representative for assistance in estimating these profit comparisons. In some crops that may be sensitive to excess N supply, it may be beneficial to reduce the N rates somewhat with ESN to prevent loss of crop quality or yield from excess N.

Is ESN recommended for use on all acres?

ESN is designed for soil and environments that are at risk for N-loss and where nitrogen is a limiting factor for growth. The added value of ESN may not be realized in soils that have other limiting factors such as compaction, drought, flooding, imbalance of other nutrients and excessively high or low pH. ESN does not correct existing problems in the soil other than the loss of N from traditional sources. ESN may have some benefits not related to N loss that results from continuous feeding and controlled-release nitrogen supply.

Does ESN need to be blended with other nitrogen fertilizers to work effectively?

In many situations, ESN need not be blended with other N sources. ESN was designed to release N in approximate synchronization with the N demand of many crops. It was designed to serve as a “stand-alone” N source in many situations. Hundreds of studies on corn, potatoes, cotton and other summer crops or fall applications on winter cereals have proven excellent results using ESN to supply all the N needed in one application. There are situations where ESN may be or should be blended with an immediately available N source, such as urea or ammonium sulfate, to meet immediate needs of a growing crop. For example, if ESN is used for spring top-dress of winter wheat after wheat has broken dormancy, some immediately available N is recommended. Or if top-dressing corn with ESN after about V6 growth stage, ESN should be blended with an immediately available N source to meet immediate N needs of the crop. The greatest benefit of ESN usually occurs when using ESN for a majority of the N fertilizer needs.

Is ESN effective as a nitrogen application on pasture, hay and silage orchard grass and alfalfa? If so, how many pounds per acre and what blend of ESN with traditional N do you recommend?

Where urea is normally applied multiple times on these crops, ESN can substitute for those applications. For pasture, we would normally recommend sufficient soluble nitrogen, such as urea or ammonium sulfate, to cover about the first month of growth after application, with the balance as ESN. In the spring, the first flush of growth (first cutting) is almost always the largest with declines in successive cuttings. So if harvesting for hay or silage, it is especially important to maximize this cutting. Grass is very responsive to N, especially in the first spring growth.

It’s important to include enough soluble nitrogen to take advantage of this fast, early growth. We recommend a blend with 40 to 60% of the N coming from an immediately available source and the remainder coming from ESN. The soluble N supports immediate growth, and ESN feeds the subsequent growth. Depending on the length of growing season, total N rate and the amount of ESN, ESN should provide sufficient N supply for the second and possibly third cuttings without an additional application. If grazing and the early flush is more than can be utilized, more ESN might be used to control the early growth and better equalize growth across the summer.

Alfalfa generally does not need fertilizer N except at establishment or in conditions were N fixation may be limited by poorly aerated soils or low pH. ESN could be used in situations where some supplemental N is beneficial. In this case, we recommend a blend with minimal soluble N so as not to stimulate weeds and grasses.

How does ESN’s coating control nitrogen release?

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.

Is ESN release controlled by soil moisture?

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.

How do drought and flood conditions affect the release of nitrogen from ESN?

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.

Will a heavy rainfall within 24 hours of ESN application compromise the longevity of the product or change the results?

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.

How do temperature and moisture level impact the speed of release of ESN?

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.

At what temperature does ESN begin to release? Does ESN release N below 50 degrees F?

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.

How much N is available when ESN is first applied?

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.

Do fertilizer spreaders damage the ESN coating?

ESN is designed to be applied using the same application equipment that is used for other dry fertilizers, including both spinner and air-flow type applicators. While some effect of handling and spreading is unavoidable, granules can be damaged by improper handling, proper procedures and adjustment of spreaders will assure damage is minimized, and ESN retains its protective coating and performs as it should. Where possible, air-flow spreaders should be adjusted to use slower air speeds, to minimize impact on ESN.

Does ESN float? Will ESN granules wash away in heavy rain?

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.

Does ESN release N through coating failures or fractures?

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.

Does ESN release too quickly to be applied pre-plant?

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.

Does ESN stay soft for the entire growing season?

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.

Does the ESN coating “breakdown” or come off in water or soil?

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.

If nitrogen in ESN releases as urea, does it volatilize in the same way as urea when left on the surface?

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.

What happens if ESN freezes?

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.

Will ESN work if the soil is very dry?

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.

Is there a risk of loss if livestock consume ESN?

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.

Is ESN harmful to birds or animals if they eat it?

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.

Are there government incentives that apply for the use of ESN?

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.

Can I be certified organic and use ESN?

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

How long can ESN be stored?

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.

How should ESN be handled?

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.

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