The effects of topdressing organic nitrogen on wheat protein

Final Report for ONE10-114

Project Type: Partnership
Funds awarded in 2010: $11,540.00
Projected End Date: 12/31/2010
Region: Northeast
State: Vermont
Project Leader:
Dr. Heather Darby
University of Vermont Extension
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Project Information

Summary:

The demand for local organic food is steadily increasing throughout Vermont and New England. Consumers are asking for bread baked with locally grown wheat; however bakers have been slow to incorporate local wheat flour because of low protein content. Much of the wheat currently produced in Vermont has protein levels below what most commercial mills would consider suitable for flour production. Topdressing N to increase protein quantity and quality is recommended for conventionally grown wheat, but the effectiveness of topdressing organic N sources needs evaluation.

In 2010, we explored the relationship between topdressing organic nitrogen amendments (composted poultry manure, Chilean nitrate, and an available bagged fertilizer-Pro-Booster), the application times (tillering and flag leaf), and how these two factors influence the quality and quantity of grain protein, on farm. First year results demonstrated that topdressing can have a positive impact on both yield and quality. Organic N sources applied at flag leaf and as split applications at tillering and flag leaf stages had significantly higher protein levels than N just applied at tillering or on the control plots. Pro-Booster applied at the flag leaf stage resulted in protein levels of 13.4% which was 3 percentage points higher than the other fertility treatments applied at this stage. Grain moisture, falling number and DON levels were not significantly different between the timing applications of the organic amendments.

In addition, a simple cost benefit analysis was conducted to determine cost effectiveness of this practice. The most expensive amendment was Chilean Nitrate but actually cost less per unit of plant available nitrogen (PAN) than the other amendments. There was a minimum yield increase of 15% when additional N was applied to wheat as compared to the control. There was also as much as 4% CP concentration increase in wheat when topdressed with organic N sources. This could translate into a $30 premium per ton on protein. If a farm has an average yield of 2 ton per acre for winter wheat this would be a $60 premium if the farm met the 12% minimum CP level for the mill. In the experiment only the Pro-booster treatment met and exceeded the 12% minimum CP level.

However, one year of data is not adequate to confidently recommend that farmers begin changing fertility practices. Our group is repeating the study in 2011 to further solidify the results.

Introduction:

The demand for local organic food is steadily increasing throughout Vermont and New England. Consumers are asking for bread baked with locally grown wheat, but bakers have been slow to incorporate local wheat flour because of the challenges associated with obtaining grains that consistently meet bread-baking standards. A survey of eight bakeries and seven food co-ops was conducted by the Vermont Localvores in 2006 to assess the demand for Vermont grown grains. All those surveyed indicated a strong consumer interest and a willingness to pay between 10% and 25% more for Vermont grown grains. At the time of the survey, only one bakery was using Vermont grown whole wheat; others expressed interest, but listed availability, quality and ease of distribution as the primary barriers to local sourcing (Localvore, 2007). Supplying this expanding market for bread wheat represents a significant opportunity for the region’s farmers but it will not be sustainable unless quality issues can be rectified. While Vermont farmers have long grown small grains for animal feed on dairy and crop farms, they lack local knowledge and research information on how to produce high quality grains for bread end-use markets using organic methods.

One of the major quality issues facing northern grain producers is the protein content of their wheat. Much of the winter wheat (bread wheat) currently produced in Vermont has protein levels consistently under 12%, below what many commercial mills would consider suitable for flour production. The majority of commercial mills have target protein levels of 14-15%. In general, higher grain proteins result in improved baking characteristics of flour. Research suggests the amount of soil nitrogen (N) available to the plant during plant growth directly influences the quantity and quality of grain protein. Assuring adequate nitrogen (N) availability during plant growth is one of the primary challenges of organic winter wheat production in the Northeast. The most economical and practical approach for organic producers is to incorporate N amendments prior to seeding their wheat. However, sources with low carbon to nitrogen (C:N) ratios (e.g., green manure and liquid dairy manure) may release substantial N in the fall and promote early tillering and vegetative growth; which can impact winter survival rates.

In addition, excess soil mineral N is susceptible to leaching over the winter. Sources with higher C:N ratios may have better synchrony with crop uptake, but not supply enough total N to obtain high grain protein levels. Research suggests that nitrogen accumulated during wheat’s vegetative period primarily increases yield, whereas N applied after flowering increases grain protein concentration (Jenner et al., 1991). For these reasons, topdressing N to increase protein quantity and quality is recommended for conventionally grown wheat, but the effectiveness of topdressing organic N sources has not been sufficiently evaluated. Synchronizing N release with plant demand is the key challenge in systems that rely on biological mineralization of organic N amendments (Watson et al., 2002).

Therefore, topdressing small amounts of more readily available N sources (e.g., fish meal) may be a way to affect protein content and quality. In collaboration with our co-operating farmer, we will assess three different organic N sources; fish meal, Chilean nitrate, and oilseed meal, applied at three different times during the growing season; spring application, application at flowering, and a combination of the two. It was our intention, through this on-farm research project, to explore the relationship between topdressing organic nitrogen amendments, the application times, and how these two factors influence the quality and quantity of grain protein. In doing so, it will contribute to the long-term profitability and sustainability of organic agriculture and farms in Vermont and throughout the Northeast.

Project Objectives:

We established a trial at Gleason Grains in Bridport, VT. The purpose of this project was to determine whether topdressing organic nitrogen (N) amendments, during key times of wheat development, would increase grain protein and yields. The amount of protein in wheat depends largely on soil nitrogen availability during plant growth. Higher protein levels generally result in improved baking characteristics. Assuring adequate available nitrogen (N) for grain yield and protein are the primary challenges of organic winter wheat production.

[See article on page 2 in Northern Grain Growers Association newsletter, attached.]

Cooperators

Click linked name(s) to expand
  • Erica Cummings
  • Ben Gleason
  • Roger Rainville

Research

Materials and methods:

The seedbed at the Bridport location was prepared by conventional tillage methods. All plots were managed with practices similar to those used by producers in the surrounding areas (Table 2). The plots were seeded with winter wheat (var ‘Redeemer’) on September 13, 2009. Prior crop in 2009 was soybeans and in 2008 a sweet clover cover crop.

In early April of 2010 the experiment was imposed within the winter wheat field on the Gleason Farm. The experimental design was a randomized complete block in a split plot design. Treatments were replicated four times. The main plots were amended with one of 3 organic N amendments. The amendments used were; ‘Cheep Cheep’ (4% N), Pro-Booster (10% N), and Natural Nitrate of Soda (16% N). The product ‘Cheep Cheep’ is an OMRI approved and widely available dehydrated poultry litter product. It has a guaranteed analysis of 4-3-3. The OMRI approved ‘Pro-Booster’ is a fertilizer manufactured for North Country Organics in Bradford, VT. The blended fertilizer is composed of vegetable and animal meals and natural nitrate of soda. It has a guaranteed analysis of 10-0-0. The OMRI approved Natural Nitrate of Soda is more commonly known as ‘Chilean Nitrate’. It is mined from Northern Chile. It has a guaranteed analysis of 16-0-0. The use of Natural Nitrate of Soda is allowed, however, it is limited to supplying no more than 20% of the crops total N requirements.

In the case of wheat it was assumed that an average yield of 4000 lbs would uptake approximately 100 lbs of N per acre. Therefore the allowed application rate of N from ‘Chilean Nitrate’ would be 20 lbs per acre. The goal was to supply the wheat with 20 lbs of N from each fertilizer source. The organic fertility sources (‘Cheep Cheep’ and ‘Pro-Booster’) contain mostly organic-N and therefore the amount of N available to the plants would be only a percentage of the total applied. Based on past data collection and information from the companies it was assumed that 50% of the total N from the ‘Cheep Cheep’ would be available and 30% from the ‘Pro-Booster’. The topdress amendments were broadcast applied by hand at the required time. Hence the ‘Chilean Nitrate’ was applied at a rate of 125 lbs per acre, the ‘Cheep Cheep’ at 1000 lbs per acre, and the ‘Pro-Booster’ at 600 lbs per acre. An unfertilized treatment served as a control.

The split plots were the timing of the N fertilizer application. The plots were fertilized by hand at the tillering stage (Feekes Growth Stage 5, F5), the flag leaf stage (Feekes Growth Stage 8, F8), or a split application with half the rate at both growth stages. On April 5 2010, the tillering (F5) amendments were applied and the flag leaf (F8) application was on May 20, 2010.

Plots were sampled for soil nitrates prior to organic N application and at key developmental stages until the wheat reached physiological maturity. From each plot a composite of 10 soil cores (1 inch dia., 12 inch depth) was taken, placed on ice, and transported to the testing laboratory on the day of sampling. Soil nitrates were measured using flow injection analysis. In addition, plant samples were taken to determine total nitrogen concentration by combustion analysis at the same time as soil sampling. The tissue samples consisted of 2 rows of wheat top growth, 12 inches in length, and replicated twice per plot. Samples were put into clean paper bags, placed on ice, and transported directly to the laboratory for analysis. All soil was analyzed at University of Vermont’s Agricultural and Environmental testing laboratory. Plant samples were sent to Cumberland Valley Analytical Services in Hagerstown, MD for analysis.

Due to an inundation of sweet clover, the plots had to be mowed on July 30, 2010 and dried down before harvesting with an Almaco SP50 plot combine on August 2, 2010. Following harvest, seed was cleaned with a small Clipper cleaner. Once cleaned the sample was weighed to determine yield. An approximate one pound subsample was collected to determine quality. Quality measurements included standard testing parameters used by commercial mills. Test weight was measured by the weighing of a known volume of grain. Generally the heavier the wheat is per bushel, the higher baking quality. The acceptable test weight for bread wheat is 56-60 lbs per bushel.

Once test weight was determined, the samples were then ground into flour using the Perten LM3100 Laboratory Mill. At this time flour was evaluated for its protein content, falling number, and mycotoxin levels. Grains were analyzed for protein content using the Perten Inframatic 8600 Flour Analyzer. Grain protein affects gluten strength and loaf volume. Most commercial mills target 14-15% protein. The determination of falling number (AACC Method 56-81B, AACC Intl., 2000) was measured on the Perten FN 1500 Falling Number Machine. The falling number is related to the level of sprout damage that has occurred in the grain. It is measured by the time it takes, in seconds, for a stirrer to fall through a slurry of flour and water to the bottom of the tube. Falling numbers greater than 350 indicate low enzymatic activity and sound quality wheat. A falling number lower than 200 indicates high enzymatic activity and poor quality wheat. Deoxynivalenol (DON) analysis was analyzed using Veratox DON 5/5 Quantitative test from the NEOGEN Corp. This test has a detection range of 0.5 to 5 ppm. Samples with DON values greater than 1 ppm are considered unsuitable for human consumption.

Mixed-model analysis was calculated using PROC MIXED procedure of SAS. Mean separation among treatments involving fertilizer source and timing of application were obtained using the LSMEANS procedure when the F-test was significant (P< and equal to 0.10).

Research results and discussion:

RESULTS

Soil and Plant Nitrogen

There were no significant differences in soil nitrate-N levels at tillering, flowering, or physiological maturity. However, significant variation found between replicates may have reduced the ability to identify differences amongst the treatments. The Pro-booster amendment raised plant nitrate-N levels higher than other organic soil amendments (See attached document with Table 3). With the exception of Pro-booster, applying organic fertility sources at the tillering stage did not increase plant nitrate-N compared to the control. Application of Pro-booster at tillering and flagleaf stages increased plant nitrate-N compared to the control and other amendments.

Wheat Yield and Quality:

Differences among fertilizer types were observed for yield and crude protein (CP) in this experiment (See attached document with Table 4 and Figure 1). The ‘Chilean Nitrate’ product resulted in significantly higher yields than the control. The ‘Cheep Cheep’ and ‘Pro-Booster’ had the did not differ significantly in yield as compared to the control plots. The ‘Pro-Booster’ amendment resulted in a CP concentration of 13.4% which was significantly greater than any of the other treatments. Grain moisture, falling number and DON levels were not significantly different between organic fertility treatments. (Table 4, attached below).

The timing of the organic N fertilizer application had a significant impact on yield and crude protein concentrations of winter wheat (See attached document with Table 4 and Figure 2). A split application of organic N fertilizer at the tillering and flag leaf stage resulted in the highest yields of 1545 lbs ac-1. The highest crude protein concentration was observed when organic N sources were applied at the flag leaf stage. Application of organic N sources at the tillering stage resulted in the lowest crude protein concentration. Grain moisture, falling number and DON levels were not significantly different between the timing applications of the organic amendments (Table 5, attached below).

There were significant fertility source x application time interactions observed in the experiment. A fertility source x application time interaction was observed for yield (Figure 3). This suggests that the organic N fertility sources will vary across the range of application times. For example, ‘Cheep Cheep’ and ProBooster applied at tillering had a significant increase in yields over the ‘Chilean Nitrate’ or the Control. This presumably has to do with the slow release nature of this amendment potentially supplying N to the plant over a longer period of time. This would be compared to the ‘Chilean Nitrate’ being more rapidly available. Interestingly when ‘Chilean Nitrate’ was applied at the flag leaf stage it resulted in significantly higher yields than the other fertility treatments. Interestingly, the ‘Cheep Cheep’ and ‘ProBooster’ performed similarly to the Control. Again the slow release nature of the N from these products may have limited the amount of plant available N during this period of rapid uptake. When the applications were split there were no significant differences between treatments.

A fertility source x application time interaction was observed for crude protein concentration (Figure 4). This suggests that the organic N fertility sources will vary across the range of application times. Application of N sources at tillering did not result in protein increases as compared to the control. However, applications of N fertility sources at the flag leaf stages did result in a significant increase in crude protein as compared to the control. The ‘ProBooster’ application resulted in the highest crude protein concentrations. Increases in crude protein concentrations were only significantly higher than the control in the ‘ProBooster’ treatments. Overall, the application of organic N sources at the flag leaf stage resulted in the best chance to improve wheat protein levels.

DISCUSSION

The first year of data suggests that organic N sources applied at flag leaf and as split applications at tillering and flag leaf stages had significantly higher protein levels than N just applied at tillering or the control plots. Interestingly, Pro-Booster applied at the flag leaf stage resulted in protein levels that were three percentage points higher than the other fertility treatments applied at this stage. Wheat that received topdress amendments always resulted in higher protein levels than the unamended controls. Across all treatments Pro-Booster had the highest protein level of 13.4%. These preliminary results indicate that Pro-Booster may be a viable organic fertilizer source for increasing winter wheat protein. However, one year of data is not adequate to confidently recommend that farmers begin changing fertility practices. We have received funding to collect a second year of data to verify our results.

Research conclusions:

These first year results demonstrated that topdressing can have a significant impact on both yield and quality. However, one year of data is not adequate to confidently recommend that farmers begin changing fertility practices. Additional SARE funding has allowed us to repeat the study in 2011 to verify the results. Farmers are excited to implement some new practices to improve wheat quality on their farms. This was obvious based on the turnout at the on-farm field day held in June as well as other events. There have been numerous farms that were anxious to experiment with topdress applications of nitrogen in organic wheat.

Another on-farm trial was planned to record plant loss from topdress of N at flowering. However due to the weather the application could not be performed. Further verification of results will definitely lead to adoption of this practice by several farmers in New England.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

In addition to the research experiment farmers and other interested stakeholders were invited to the Gleason Farm to learn about the trial and other aspects of wheat production. Producing High Quality Organic Bread Wheat, an on-farm workshop was held June 8, 2010 at Gleason Grains in Bridport, VT. The workshop highlighted the NE SARE funded organic fertility experiment. In addition, Ben Gleason discussed crop rotation and weed control in wheat grown for human consumption. We viewed Ben’s wheat processing facility including his seed cleaning and meadows mill operation. This event had 53 attendees consisting of farmers, Extension, and other agricultural professionals. Many of the farmers were anxious to view project results. The results from the project were also presented at the Northern Grain Growers Association Winter Conference on March 7, 2011. There were 150 attendees (farmers, agricultural service providers, educators, and students) at the conference. Participants came from Quebec, Ontario, NY, CT, MA, NH, ME, and VT. The presentation on topdressing wheat was attended by 20 conference participants. Research results of the project were provided as a handout to all conference attendees. An article was also published in the group’s newsletter and posted on both the ngga.org and uvm.edu/extension/cropsoil/ websites in the winter of 2011. In addition, the research report is posted on the UVM Extension crops and soils website (www.uvm.edu/extension/cropsoil).

Project Outcomes

Project outcomes:

A simple economic analysis of the amendment costs was performed to get a sense of benefit to applying additional N to wheat. The goal would be to see increased yield and quality so that the farmer would be able to justify the cost of the amendment as well receive a higher return on the crop.

The most expensive amendment was Chilean Nitrate. However, since it is readily available it actually cost less per unit of plant available nitrogen (PAN) than the other amendments. To apply 20 lbs of PAN the lowest cost was $90.6 per acre. Would a farmer make back the initial investment of the fertilizer plus additional income on increased yields and quality? Commercial mills often pay a $5 per ton premium for every half percent protein over the base of 12% CP. A current price for organic wheat is $450 per ton.

From this first year of research there was a minimum yield increase of 15% when additional N was applied to wheat as compared to the control. There was also as much as 4% CP concentration increase in wheat when topdressed with organic N sources. This could translate into a $30 premium per ton on protein. If a farm has an average yield of 2 ton per acre for winter wheat this would be a $60 premium.

However, given this scenario it is assumed that the farm met the 12% minimum CP level for the mill. In the experiment only the probooster treatment met and exceeded the 12% minimum CP level. Therefore topdressing may also help the farmer from receiving dockages at the mill. In terms of yields an extra 15 to 20% yield will supply additional income as well. Another season of data will help confirm economic benefits and pitfalls to applying additional N to wheat.

Farmer Adoption

Farmers are excited to implement some new practices to improve wheat quality on their farms. This was obvious based on the turnout at the on-farm field day held in June as well as other events. There have been numerous farms that were anxious to experiment with topdress applications of nitrogen in organic wheat. At least 5 farmers followed up with additional questions after reading or listening to a presentation on the research. Another on-farm trial was planned to record plant loss from topdress of N at flowering. However due to the weather the application could not be performed. Further verification of results will definitely lead to adoption of this practice by several farmers in New England.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

This research project will be continued into the 2011 growing season. Several years of research will be required to verify results. At this time it appears as though further research will be needed to evaluate mineralization rates of various organic amendments. It was obvious from the data that organic amendments released nitrogen (N) at a slower rate compared to the Chilean Nitrate. It is well documented that N based fertilizer sources should be added at the critical stages such as tillering and flowering. However, given the lag time for N release of the organic materials new standard recommendations will need to be developed. Lastly, farmers have asked how much of the wheat in their fields would be damaged from applications at tillering or flowering? Will the wheat be killed or will there be reduced yields? This question will be answered through further on-farm studies.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.