Agronomy Agronomic Articles

Balancing Yield, Protein & Lodging

The 2018 Bourgault Nitrogen & Wheat Trials - Cutting Edge, Winter 2020

Yield Relative to N Availability

Increased yield and protein is typically tied to an increase in nitrogen (N) fertilizer when all other nutrients are adequate. The issue with simply applying more N to a wheat crop is the risk of the crop lodging. There are also economic and logistical considerations that go along with heavier rates.

Required Fertilizer:

Many agronomists use a factor of around 2.5 lbs of available N per bushel of wheat at 13.5% protein. Others use a factor of 3.3 lbs of N to achieve their goal. To calculate how much fertilizer is required for a target yield, it should first be calculated how much nitrogen will be provided by the soil. Soil tests provide the residual nitrogen levels along with the percent organic matter (%OM). The %OM gives a rough indication of how much N will be released by microbial activity during the growing season, a process called mineralization. Typically, a range of 5 lbs N/%OM to 15 lbs N/%OM is used. A good reference can be found online from A&L Laboratories (www.alcanada.com). Once this has been determined, the total nitrogen to be applied to reach the desired yield can be estimated.

The wild card in this calculation is the amount of N that will actually be released throughout the season, which is not only dependent on the %OM, but also the soil type, soil temperature, and the overall climatic region. This is typically why some producers are shocked in some years where they achieve higher yields than they were expecting. In these years, there may have been more N released from the soil than usual which, despite our best efforts is difficult to predict.

An Example:

A producer’s soil test results say there is 20 lbs of residual N. The organic matter is 4%, so if we estimate approximately 10 lbs of N will be released per % of organic matter, this will provide an additional 40 lbs of N.

If a grower has a yield goal of 70 bu/acre of wheat, they require approximately 175 lbs of total N. Take what is in the soil and minus from what you need, the fertilizer requirement equals 115 lbs of nitrogen (175 lbs-20 lbs-40 lbs=115 lbs N).

Case Study:

2018 Wheat Yield & Protein Chart

This chart shows a yield and protein comparison between a standard nitrogen package to an increased nitrogen package. The standard fertilizer package consisted of 110-40-15-0, with the increase containing a total fertility package of 130-40-15-0. All the phosphorus and potassium was placed in the seed row.

This year, one of the goals of the Bourgault Agronomy team was to explore nitrogen responses to yield and protein in Brandon wheat. A comparison was made between the standard nitrogen package to an increased nitrogen package. The standard fertilizer package consisted of 110-40-15-0, with the increase containing a total fertility package of 130-40-15-0. All the phosphorus and potassium was placed in the seed row.

There was a slight bump in yield with the increased nitrogen, although not significant, but with no increase in protein. This indicates we are still lower than the amount of nitrogen required to maximize yield, and have not yet began to increase the protein. There was no lodging in any of the treatments.

The surrounding field ended up with an average yield of 75 bu/acre at 12% protein. This protein level was less than desired, but a good yield was achieved.

What Happened?

Using the calculation outlined above, let’s see if we can determine why we missed the protein mark. Our soil contained 15 lbs of residual N, and the organic matter was 4.6% with approximately 10 lbs N/%OM, equating to 46 lbs N. This equated to 61 lbs of N available to the crop from the soil. The applied fertilizer rate provided 110 lbs of N, equaling a total of 171 lbs of N. If we use the requirement of 2.5 lbs of N per bushel of wheat, we get a calculated yield of 68 bu/acre.

With the inverse relationship of yield to protein at insufficient nitrogen levels, this points to why we did not achieve high protein and that our yield potential may not have been reached. The target yield was 70 bushels, which was achieved, but the nitrogen was still going to yield, and did not shift to increasing protein.

Looking to next year, we will be looking to increase our nitrogen rates, along with adding sulfur to the fertility package. Although we are using a semi-dwarf variety with good stand ability rating, an increase in N fertility increases the risk of lodging considerably.

Plant Growth Regulators

Manipulator in Wheat

There was an observed 10cm (4") reduction in height on the treated area versus the untreated check. Left side: Untreated check - 80 cm. Right side: Treated with Manipulator - 70 cm

A new tool available to Canadian producers this year, are plant growth regulators (PGRs). Just now available in the Canadian market, these have been used in Europe for over 25 years. This year the agronomy team tried Manipulator, a registered PGR with the active chlormequat applied at the 5 leaf stage. Manipulator was applied on a quarter-section, except for a one acre area used as a check. This was not a replicated trial, but a three bushel increase in yield was observed from using the PGR. This increase in yield did not provide enough economic benefit, as this product costs roughly $15/acre, plus application. Even though there was not distinct yield advantage, there was an observed 10cm (4") reduction in height on the treated area versus the untreated check.

Looking ahead, this may play a vital role to decrease with the risk of lodging when there is an increase of soil applied fertilizer. Although this was a simple trial, it mimicked studies conducted at the Indian Head Agriculture Research Foundation (IHARF) that show the shortening of the crop and reduced lodging, especially in varieties that are typically taller and more prone to lodging. In the IHARF trials conducted over the past 6 years, there were some significant yield increases. These results can be found at IHARF.ca.

Review Records for Tomorrows Plans

It is important that producers look back on their fertility program and compare it to what they ended up with for yield and protein in wheat. By doing some simple calculations, the results of the year can be analyzed, which can be valuable when making future fertility plans. Although these calculations are straight forward in these examples, determining exactly how much to expect from the soil is not a simple task as it is not an exact science. There is a high level of variability, dependent mostly on the weather and moisture.

A Bourgault seeding system allows for high rates of fertilizer to be safely placed at the time of seeding when equipped with the Mid Row Bander® fertilizer application system. When paired with large, highly configurable 7000 Series air seeders, producers can maximize their returns on any farming operation. As producers look to increase their yields and quality, there are new products coming onto the market that can be incorporated into their farming operation that will give more flexibility and options to increase efficiency and productivity. The Bourgault Agronomy team will continue to gain knowledge and experience to share with all producers.