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Utilizing 4R Nutrient Stewardship to Manage Nitrogen as a System in 2022

04/08/2022

We are experiencing unprecedented volatility in global supply issues and commodity price inflation on many products, particularly fertilizer. The questions on nitrogen supply are occupying a lot of time at present in the distribution channel.

Questions remain on how many acres of wheat will make it through to spring and how many farmers will increase soybean acres, which influences the final corn acres and nitrogen requirements.

<>Currently, the "Return to Land, Labour and Equipment" favours corn by nearly $200 an acre; better returns than soybeans and wheat, depending on yields. We recognize that every farm is different and encourage you to work with us to run budgets for your crop rotation.

Managing nitrogen applications during uncertain times requires revisiting the fundamentals of nitrogen use. A 4R stewardship approach of nitrogen management is appropriate.

The 4Rs of Nutrient Stewardship for Nitrogen

Source

In row crops, the dominant forms of N are urea, ESN and urea ammonium nitrate solutions (UAN often with a guarantee of 28% or 32% N) and a limited amount of anhydrous ammonia. Understanding the features and benefits of each product is essential.

Rate

Rate is a function of specific field response, potential yield and price of corn relative to the cost of nitrogen.

Time

Applying nitrogen fertilizer can profoundly change the yield response at any given rate. Some customers pre-plant nitrogen, others side-dress nitrogen, and few do Y Drop applications in mid-season. There are ways to enhance nitrogen utilization regardless of timing. Using nitrogen stabilizers will reduce potential environmental losses and keep nitrogen around longer to improve yields.

Place

Where we place the nitrogen influences potential losses that reduce nitrogen use efficiency and impacts final yields. Incorporating pre-plant and side-dressing N below ground and using N stabilizers helps to increase nitrogen use efficiency even further.

On-farm Nitrogen Rate Trials

In 2021 we conducted Nitrogen Rate Trials on corn with customer and owner co-operators to determine the value of a biological nitrogen-fixing bacteria called Envita. The purpose of those trails was to run different nitrogen rates with and without Envita to see where the advantages might be on Envita by nitrogen rate.

The trials will be published shortly; however, Envita provided inconsistent results in our trials. The real value in the plots is the response to nitrogen in the check treatment.

On-farm trials are invaluable in understanding the N response in specific field conditions.

Summary chart of optimum nitrogen rates in 2021

(previous crop was soybeans)

CSTW-Dale-N-Trials_Corn_Envita_chart.JPG

The maximum economic yield was based on $1.30 per pound of N and $7.00 per bushel of corn.

There were nine locations with various N rates. The first column is the site number. The second column is the lowest N rate used. The next column is the yield produced at that rate. The third column is the percent of maximum economic yield that rate produced. The next column is the optimum N rate, and the next is the yield produced at the rate. The next is the farmers' normal rate, and the final column is how much over or under the farmers' normal rate was compared to the economic rate.

The average lowest actual N rate on all plots was 95.56 lbs. which produced an average yield of 202.33 bushels per acre. That represents 84.9% of the maximum economic yield with the first 95 lbs. of applied N.

The optimum N rates produced the maximum return to nitrogen. Going beyond this point resulted in losing money on the nitrogen investment. In other words, adding more N produced progressively smaller yield increases and did not generate enough additional revenue to cover the incremental N cost—the Law of Diminishing Returns.

The optimum N rate was 181.1 lbs. of actual N, which produced an average of 237.78 bushels per acre.

The final column indicates that the farmers' normal rates were, on average, 24.11 lbs. of actual N higher than the optimum rates in 2021. It is worth pointing out that some fields could have used 40 lbs. more N and some 70 lbs. less N. The longer-term goal for "Managing Nitrogen as a System" is to know which fields are responsive and which fields are less responsive.

Certainly, a range in values speaks to the site-specific nature of nitrogen and field management. Applying nitrogen within +/- 20 lbs. of the optimum N rate is likely the best we can do in any given year.

The optimum rate of nitrogen is dependent upon yield potential. Rainfall drives yield potential, and yield potential drives nitrogen demand. It is the balancing act of figuring out at the beginning of the season with our initial assessment of application rate whether or not the growing crop will experience a nitrogen demand or nitrogen supply issue during the later growth stages. With this in mind, let's review some considerations for nitrogen rate adjustments in 2022.

The 4Rs of Nutrient Stewardship for Nitrogen

To ensure that we have enough nitrogen supply for the spring, we need to optimize nitrogen use.

  • The Ontario Nitrogen Calculator is an underutilized tool to help determine a base N rate recommendation. Entering the current price of nitrogen in the calculator suggests N rates should be reduced by 20 lbs. per acre from last year.
  • We must consider realistic yield goals and adopt an "Effective Nitrogen Rate" approach, which considers the most economical rate and practices that protect the applied nitrogen from environmental losses.
  • Utilizing a 4R Nutrient Stewardship approach focusing on source, rate, timing, placement and use of nitrogen stabilizers will protect the application from excessive N loss and gain more yield potential.
  • Split applications often bring advantages in increasing nitrogen use efficiency, some pre-plant, side-dress and possibly Y drop later in-season.
  • As much as possible, avoid surface applications of urea and urea containing fertilizer without immediate incorporation. If incorporation is not possible, treat the product with a urease inhibitor such as Anvol to limit volatilization losses. As much as 30% or more of applied N can be lost over a week to 10 days under the right environmental conditions.
  • Ideal conditions for loss are warm, dry, windy, high pH, low CEC soils and lots of surface residue. 
  • It would take a half-inch of rain within 12 hours after application to limit losses.
  • Once urea-type fertilizer or any nitrogen source is incorporated into the soil, it will be converted by the nitrogen cycle into nitrate nitrogen. Nitrate nitrogen is the only form of N that can be lost from the soil. Either by denitrification in waterlogged soil conditions and released as nitrous oxide, most likely on heavier or higher clay content soils. Or through leaching losses in sandy soil with excess rainfall that moves nitrate out of the root zone. 
  • To delay the inevitable transformation to nitrate nitrogen, use a nitrification inhibitor with UAN such as Tribune. A dual-action inhibitor that contains both a urease inhibitor, NBPT and a nitrification inhibitor like DCD and Pronitridine. This product effectively reduces volatilization losses with shallow banded UAN and delays the conversion of ammonium nitrogen to nitrate nitrogen by 14 to 21 days. Often a long enough delay to coincide with optimum N uptake timing of corn.
  • Corn is equally capable of using ammonium nitrogen very effectively, so the delay in conversion to nitrate has no impact on yield.
  • The corn plant actually expends less energy taking up ammonium N and converting it into amines in the plant cells to build proteins.
  • In the past, we have generally accepted that slightly over-fertilizing was less risky than underapplying. The trials indicate that perhaps we can trim N rates by 20+ lbs. per acre based on the economics of the corn and nitrogen price relationship.
  • Consider trying Envita, a biological nitrogen-fixing bacteria in strips to measure potential responses.
  • There is no need to apply more N in pounds per acre than we produce in bushels per acre, i.e., 200 bushels of corn does not need more than 200 lbs. of N; often much less.
  • If you are applying those higher rates, we need to figure out where the N is going because it is not going into the crop.
  • Corn following soybeans should need 27 to 35 lbs. less N per acre than corn after corn.
  • Consider growing corn in your highest-yielding fields, and soybeans in lower-yielding fields in 2022.
  • High-yielding fields are most likely the most efficient fields in providing mineralized N from organic matter and offer the greatest amounts of plant-available water to support higher yields. Higher-yielding fields take up more nitrogen but do not necessarily need more applied nitrogen per bushel of corn to achieve higher yields.
  • Before deciding on your final pre-plant or side-dress rates, take appropriate N credits from corn starters, manure, and other organic amendments, including cover crops such as red clover and legumes.
  • Consider doing N-rate strip trials on your farms this year. It does not have to be extensive. A low rate of less than 50 lbs. and high rate of 250 lbs. of actual N can be used to determine optimum N rates using a Delta Yield Calculator. This approach will help you gain insight into nitrogen response on your various fields that can be used for future rate adjustments. We are happy to discuss this concept further. Contact your local AGRIS Crop Sales Specialist.

Have a Plan

We are experiencing unusual circumstances with the supply chain. We are all in it together, and it requires all of us to make adjustments. Engaging in crop planning on your farms by field, by crop, by product with your trusted advisor alleviates considerable uncertainty and optimizes the use of all inputs.

Our goal is to help you “obey MOM” - Minimize the size of your environmental footprint, Optimize harvested yields and Maximize nutrient utilization.

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