PROJECT RESULTS

Optimizing Wheat Yield and Protein on the Canadian Prairies

Dr. Cynthia Grant

Brandon Research Centre
Agriculture and Agri-Food Canada
Brandon, Manitoba  R7A 5Y3  Canada

Table of Contents:

• Background and Objectives
• Procedure and Project Activities
• Results and Discussion
• Conclusions

ARDI Project:

Total Approved:

Date Approved:

Project Status:

#98-147

$60,000

November 16, 1998

Completed November, 2001

Background and Objectives:

A major factor enhancing the competitive position of Canadian wheat in international markets is its high protein quantity and quality. Milling and baking quality of wheat generally improves with increased protein content. Therefore, customers are willing to pay premiums for high protein wheat. These premiums are passed on to the producer, creating interest in managing for high protein content. Since N is a primary building block of protein, N management will have a major effect on protein content of a crop. Proper N management can help to optimize protein content, while avoiding adverse effects on crop production and the environment.

Protein content of wheat is influenced by N supply and the grain yield through which the N is distributed. Therefore, any factors which influence N supply or grain yield will influence the protein concentration. Soil and environmental conditions, cultivar and agronomic practices will all influence protein concentration of the crop (Figure 1). Nitrogen fertilizer applied before or at seeding tends to have an influence on both yield and protein concentration. Delaying N application through the season tended to decrease the influence on grain yield and increase the influence on grain protein. However, little information is available to determine the interaction of N fertilizer management, environment and cultivar on grain yield and protein content, and on final baking quality of the bread produced from the wheat grown under these management regimes. For example, late applications of foliar applied N on late-seeded wheat could increase the measured protein content of the crop, but have a negative effect on baking quality, if the N absorbed by the crop was not metabolized into the high quality protein required for enhancing loaf volume. It is important that we ensure that the management practices we use in crop production not only optimize wheat yield and protein content, but also maintain or improve the quality of our wheat for its final intended use. This will help to maintain or improve our competitive position on international markets.

1. To determine the influence of both pre-seeding and in-crop N management on wheat yield, protein content and baking quality.
2. To determine the interaction between environmental conditions and N management in effects on wheat yield, protein content and baking quality.
3. To determine if increasing grain protein concentration with late-season applications of N impacts on the quality of the bread produced.
4. To determine factors that can predict the likelihood of attaining an economic increase in grain yield or protein content with late-season applications of N.

Funding for this study and related projects was provided by ARDI, Western Grains Research Foundation, Western Co-operative Fertilizers, Ltd. Envirotest Laboratories, Simplot Ltd and the matching Investment Initiative program of Agriculture and Agri-Food Canada.

Procedure and Project Activities:

Field studies were conducted at several locations in the Parkland region of Manitoba and Saskatchewan over four years to evaluate the effects of rate, placement, source and timing of N application on hard red spring wheat yield and protein content. The study was composed of a series of related field experiments, each evaluating specific aspects of N management for protein enhancement. Each experiment was a randomized complete block design with four replications. Each study was repeated at between two and four locations in Manitoba and Saskatchewan. The experiments evaluated:

1. Response of grain yield, grain protein content and milling and baking quality of wheat to a 15 kg N ha^-1 addition of soil-applied urea or foliar-applied urea ammonium nitrate at 3 in-crop stages as compared to applying all the N at seeding.
2. Response of grain yield, grain protein content and milling and baking quality of wheat to a 15 kg N ha^-1 addition of soil-applied ammonium nitrate or foliar-applied urea ammonium nitrate at 3 in-crop stages as compared to applying all the N at seeding when the crop was seeded in April or early May as compared to late May or early June.
3. Response of grain yield, grain protein content and milling and baking quality of wheat to a 15 kg N ha^-1 addition of soil-applied urea or foliar-applied urea ammonium nitrate at three in-crop stages as compared to applying all the N at seeding with low or high initial applications of N fertilizer at seeding.
4. Effectiveness of chlorophyll readings using a SPAD metre and leaf N analysis at various stages of growth to evaluate N status to predict final protein content and likelihood of a response to in-crop N applications.

Results and Discussion:

Protein content increased with increasing N fertilization when N was supplied at the time of seeding. Nitrogen applied in-crop varied in its effectiveness in increasing protein content. In-crop N applications may not be needed on soils that can supply enough N to the crop late in the season from mineralization of organic residues or reserves of nitrate-N. In-crop N applications may be useful to enhance protein content when N supply during the growing season is less than the N required by the crop for optimum yield and protein content.

Late in-crop applications of 15 kg of N per hectare in addition to the pre-plant N applications generally increased grain protein content, however, increases recorded were relatively small. When the in-crop N was applied as ammonium nitrate at the boot stage, which tended to be one of the most effective source-timing combinations, protein content ranged from approximately 1% higher to 0.6% lower than when all the N was applied at the time of seeding. The effectiveness of the surface-applied in-crop N may have been lower than N applied at seeding, which was in-soil banded, due to immobilization in the surface residues.

On average, application of a portion of the N as urea or UAN tended to be less efficient than application of all N at the time of seeding. With urea and urea ammonium nitrate (UAN), N losses can occur both by immobiliation on surface residues and volatilization. Use of Agrotain with urea or UAN to reduce volatilization losses increased protein content. Protein content was higher when the N was applied at anthesis than at either tillering or boot. Protein content was also higher with soil-applied urea than with foliar-applied UAN. The advantage of urea over UAN tended to be greater at the earlier growth stages.

Soil-applied ammonium nitrate also tended to perform better than foliar applications of UAN, when the wheat was seeded early in the growing season. However, when seeding was delayed until late May or early June, ammonium nitrate produced higher protein content than UAN when applied at tillering, but produced lower protein content than UAN when applied at boot or anthesis. When application is delayed later in the season, the soil is frequently dry and there is less time for N uptake and translocation. Under these conditions, soil-applied N may not be taken up effectively by the plant and foliar-applied UAN may have a greater impact on grain protein content than soil-applied sources.

The generally poor performance of foliar applications of UAN is likely because little of the N is actually absorbed through the leaf. The majority of the "foliar-applied" N is accessed by roots once the fertilizer washes off and reaches the soil. Soil-applied dribble-banded or broadcast in-crop N tends to be more effective than foliar application, if there is sufficient moisture for the N to be dissolved and moved into the root zone. Soil application of in-crop N will also reduce the risk of crop damage due to leaf burn.

Milling, mixing and baking quality generally closely followed the protein content of the grain. When protein content of the grain increased, whether through application of N at the time of seeding or through in-crop applications of N, most of the bread-making parameters measured increased as well. Therefore, it appeared that the protein produced by both high N application rates or applications of N late in the season was still effective in increasing most measurements of milling and baking quality. Further milling and baking quality analysis will be completed in the following year.

Conclusions:

Milling and baking quality of wheat generally improves with increased protein content. Therefore, customers are willing to pay premiums for high protein wheat. These premiums are passed on to the producer, creating interest in managing for high protein content. For optimum protein content, N must be available to the crop through grain filling. Application of sufficient N at seeding can increase protein content. In may cases, protein was increased as much or more when all the N was applied at the time of seeding than when a 15 kg N ha^-1 portion was reserved and applied in-crop. Considering the extra cost of in-crop applications, it may frequently be more economic to apply all the N at seeding, unless there is potential for large denitrification or leaching losses or if lodging is a serious concern. Where N supply later in the season is restricted, for example due to insufficient N applications at seeding, in-crop N applications may enhance protein content. In-crop N may also be beneficial on soils with a history of fallow, where late season N mineralization may be low. Ammonium nitrate would be preferable to urea as an N source, due to the lower risk of volatilization losses from ammonium nitrate. On-soil applications of urea or ammonium nitrate tend to increase N to a greater extent than foliar applications. With late N applications, particularly when seeding is delayed, there may be insufficient time and moisture for uptake from the soil and foliar applications may be more beneficial than on-soil applications.

Milling and baking quality of the grain appears to closely follow protein content of the grain, even where the protein was increased by late-season application of N. Therefore, use of in-crop N applications are unlikely to have a negative effect on grain quality and can be used as a tool to enhance protein content to target protein premiums.

Acknowledgments:

This project was made possible through funding from the Governments of Manitoba and Canada through the Canada-Manitoba Agri-Food Research and Development Initiative (ARDI).

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