Illinois Soybean Association Summary Report: Can applying nitrogen increase yields and improve compositional quality? Background: As Illinois growers continue working toward higher soybean yields, many are questioning the role fertility may play in breaking current yield barriers. To help growers make informed fertility decisions, ISA recently hosted a summit focused on the use of nitrogen in soybean production. Participants in the day-long discussion included key soybean researchers from universities and industry and industry partners, as well as ISA directors and local agronomists. The heart of the question, “Can Illinois farmers expect to see a yield response to supplemental nitrogen?” still remains unanswered. Complicating the answer is an apparent disconnect between the nitrogen (N) needed to support higher soybean yields and the inconsistent response to additional nitrogen in field trials. Researchers cited several examples showing that the amount of nitrogen removed by a 60 bu/a yield clearly exceeds the amount that can be fixed by the nodules on the soybean plant and that soybeans do not leave residual nitrogen for the next corn crop. Yet, field trials results are often inconclusive regarding whether to apply N on soybeans. As a result of this roundtable discussion, attendees offered perspectives on best management practices for growers, as well as suggestions for areas where additional research is needed. Key Takeaways for Growers: Always start by looking at the overall system for managing soybeans and be sure that no factors other than N are limiting. Supplemental nitrogen typically is not needed for yields in the 60- to 70-bushel range. High-yielding beans (greater than 70 bushels) may need supplemental nitrogen because the nitrogen needed by the plant will exceed the amount available from fixation. Early N applications may inhibit nodulation, so current research is looking at 60 to 70 pounds of urea or UAN (urea ammonium nitrate) per acre with a urease inhibitor at the R3 stage when N demand begins to increase while N fixation begins to wane. More research and local, on-farm trials are needed before best management practices or recommendations on applying N are finalized. Due to environmental concerns regarding the use of nitrogen on corn, care should be used before making added nitrogen a standard practice on soybeans. Key highlights by presentation: Howard Brown, Growmark: Status of soybean fertility Fertilizing soybeans is not common Deficiencies are rare and farmers should use a soil test for fertilizer application rates Soybeans fix up to 50% of their own N with the rest coming from the soil Iron and manganese deficiencies occur in areas with high pH
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Illinois Soybean Association Summary Report: Can applying nitrogen increase yields and improve compositional quality?
Background: As Illinois growers continue working toward higher soybean yields, many are questioning the role fertility may play in breaking current yield barriers. To help growers make informed fertility decisions, ISA recently hosted a summit focused on the use of nitrogen in soybean production. Participants in the day-long discussion included key soybean researchers from universities and industry and industry partners, as well as ISA directors and local agronomists. The heart of the question, “Can Illinois farmers expect to see a yield response to supplemental nitrogen?” still remains unanswered. Complicating the answer is an apparent disconnect between the nitrogen (N) needed to support higher soybean yields and the inconsistent response to additional nitrogen in field trials. Researchers cited several examples showing that the amount of nitrogen removed by a 60 bu/a yield clearly exceeds the amount that can be fixed by the nodules on the soybean plant and that soybeans do not leave residual nitrogen for the next corn crop. Yet, field trials results are often inconclusive regarding whether to apply N on soybeans. As a result of this roundtable discussion, attendees offered perspectives on best management practices for growers, as well as suggestions for areas where additional research is needed.
Key Takeaways for Growers:
Always start by looking at the overall system for managing soybeans and be sure that no factors other than N are limiting.
Supplemental nitrogen typically is not needed for yields in the 60- to 70-bushel range.
High-yielding beans (greater than 70 bushels) may need supplemental nitrogen because the nitrogen needed by the plant will exceed the amount available from fixation.
Early N applications may inhibit nodulation, so current research is looking at 60 to 70 pounds of urea or UAN (urea ammonium nitrate) per acre with a urease inhibitor at the R3 stage when N demand begins to increase while N fixation begins to wane.
More research and local, on-farm trials are needed before best management practices or recommendations on applying N are finalized.
Due to environmental concerns regarding the use of nitrogen on corn, care should be used before making added nitrogen a standard practice on soybeans.
Key highlights by presentation: Howard Brown, Growmark: Status of soybean fertility
Fertilizing soybeans is not common
Deficiencies are rare and farmers should use a soil test for fertilizer application rates
Soybeans fix up to 50% of their own N with the rest coming from the soil
Iron and manganese deficiencies occur in areas with high pH
Potassium deficiencies occur in some areas
Fertilizer is usually not considered a limiting factor in soybean production
A limiting factor(s) can have the greatest impact on yield, even with the best conditions for all other growing factors
On-farm trials are important as we move forward with addressing the N questions Harold Reetz, Reetz Agronomics: Soybean’s Nitrogen Requirements
100-bushel soybean crop requires 548 lbs. of N (5 to 5.5 lbs. per bushel)
58% of the N requirements on average come from N fixation
Soybeans can fix enough N for a 60-bushel soybean crop
Any additional N comes from the soil
N uptake takes off by mid July as N fixation begins to slow
Too much soil N (nitrate or NO3) will depress N fixation Larry Purcell, University of Arkansas: Understanding soybean growth and nitrogen fixation
and what it tells us about N uptake and partitioning
Soybeans generally take up 3.6 to 5.4 lbs. N per acre per day
If a foliar fertilizer is 20% N and the application rate is 2 quarts per acre, this provides only ~0.8 lbs. N
Due to the low amount of N delivered, foliar N fertilization cannot contribute meaningful amounts of N to the crop
N fixation is more sensitive to drought than photosynthesis, so you will see a greater response to N fertilizer during a drought due to greater crop growth rates
N fixation (at least in Arkansas conditions) continues through R6 and R7 if the plants are not stressed and well-watered
Individual nodules last 4 to 5 weeks, total nodulation lasts 8 to 12 weeks
N fixation begins about 3 weeks after emergence
Large amounts of N are required for soybean seed production, but under low soil N conditions, about 90% of the N in seed was derived from N2 fixation
N2 fixation is capable of providing essentially all the N required for today’s high seed yields, and fixation continued at high rates almost until maturity
Seed N accumulation rates are considerably greater than rates of N2 fixation
N is remobilized from leaves and stems to meet seed demand
N does not appear to be a limitation to yield under most conditions today
However, under drought conditions, high rates of N fertilization can increase yield Fred Below, University of Illinois: Soybean Response to Fertilizer N
62-bushel crop requires 272 lbs. of N and 80% of it goes with the seed
N fixation peaks at R5 and then declines (in Illinois observations)
70 bushels is the upper yield limit that N fixation can support
Soybeans fix N into uriedes, and soybeans can take up uriedes from the soil; uriedes do not depress nodule formation or N fixation
Deep placement of N below the nodule zone has some promise as a fertility approach
Only 50 to 60% of soybean N is obtained from N2 fixation, and the proportion decreases with increasing yield levels
Low N supply requires remobilization from leaf N, which decreases photosynthesis and yield potential
N is obtained from soluble N (nitrate) in the soil, soil organic matter mineralization, N2 fixation and supplemental fertilizer N sources
An antagonism exists between NO3- and N2 fixation in nodules with fertilizer application
Observations show that urea-N is perceived differently by the plant than other forms of N and ammonia
Seth Naeve, University of Minnesota: Nitrogen on Soybean: Protein and Oil
Compositional quality response to N is more unpredictable than yield
There is a greater opportunity for N response during grain fill (R5)
Seed protein response to N was more common in in vitro (60% increase) and hydroponic experiments (20% increase) and less common in field experiments (1% or less increase)
Natural variation in oil and protein concentrations in the seed can mask the impact of N
Newer varieties appear to respond better to N than older varieties Lila Vodkins, University of Minnesota: Soybean Genetics
Apply N and look at gene response to see what the plant is doing in the roots, leaves and seed
Gene expression profiles show when protein is deposited in the seed
Expression analysis can look at every gene in the amino acid and protein pathways
Downward trends in seed protein are gene regulatory activities
Identified soybean line with increased protein levels of about 50%
Areas needing additional research Overall:
Do we need to optimize N fixation before considering N supplementation?
Who is researching N fixation today? What are the best options for field measurement?
Can farmers inoculate with more efficient rhizobia than what we’re using today?
Do we need more site-specific rhizobia?
What is the level of nitrate in the soil that can depress N fixation?
Is N fixation being suppressed in the soil environment in other ways?
Should we approach the N concerns as a “system” solution on how to increase yield and N is one component?
Lack of Response to N:
What other yield-limiting factors exist?
How does this work in areas that are not high-yield environments?
Are N fixation and/or soil reserves currently meeting the crop’s N needs?
How does N mineralization from organic matter affect outcomes? Role of environment on response to N:
How does drought affect response to N?
Are yield responses different in marginal soils?
How do high-yield environments respond to N?
What considerations are needed for certain lower-yield environments? Poor nodule establishment Extremely low soil N at planting Plant water stress Soil pH problems Low soil temperature Absence of native Bradyrhizobium
Nitrogen fertilizer: Source, form and timing:
Do organic forms of N provide a more steady supply of N that soybeans respond to during pod fill than inorganic sources applied supplementally?
What is it about organic forms of N that make it more effective?
How much N is being mineralized in soybean fields in season?
When are preplant or at-plant N applications on soybeans effective and under what conditions?
Is applying N at planting on double crop soybeans beneficial?
What are the other yield-limiting factors?
What are the high-yield scenarios where N is limiting?
What is the right high-yield system where N is required?
What is the relationship between C and N in the soil and nutrient release?
How can yield responses to N applications be more consistent?
Keep in mind that N on corn and water quality is a major concern. Research activities that ISA could consider: Research first needs to focus on understanding more about applying N on beans, then on developing recommendations on when to apply and how much. All N recommendations for soybeans need to be based on science.
Develop a field test for measuring N fixation in the field.
Determine why N responses are inconsistent in the field.
Look at soil health relationship to nodulation and N fixation. A good soil health environment is conducive to better nodulation and N fixation.
Assess nitrogen budgets including soluble N forms in the soil and mineralization N under the soybean crop during the season to see if soil N is plentiful in different environments.
Looking at different rates, forms and timing (preplant or at plant) of N and how it affects stand establishment, vigor, N fixation and yield.
Investigate whether supplement N is more beneficial to double-cropped soybeans.
What’s the “scoop” on manure and impact on nodulation and fixation?
Harold ReetzReetz AgronomicsMonticello, Illinois
February 14, 2014
Nitrogen Distribution in Soybeans (Above Ground)
Iowa State University Extension
Generalized N Budget for Soybeans
Summary of Soybean N ResearchReviewed by University of Nebraska Staff
• 637 data sets (site‐year‐treatment)‐‐‐1986‐2006• 0.013 Mg soybean seed yield per kg increase in N accumulation• 50‐60% of N demand met by biological N2 fixation• N fixed in most cases not sufficient to replace N exported in harvested seed• Partial N balance (fixed N in above‐ground biomass‐N in seeds) was negative in 80% of the data sets; mean N mining of ‐40kg ha‐1 (about 36 lb/A)
• Below ground N contribution of 24% brought N balance to ‐4kg ha‐1 (3.6 lb/A)• N fixation tended to be reduced when N fertilizer was applied• Deep‐placed (below nodulation zone) and late season (during grain fill) application may increase yield response to N fertilization in high‐yield environments.
High Yield Soybean Nutrient Uptake (101 bu/A)
Source: Spectrum Analytic Lab
Table 20 shows nutrient uptake requirements for soybeans under maximum economic yield conditions at various stages of growth, based on research by - Dr. Ray Flannery, who raised 101 bu/A soybeans in 1986. The research was performed on a Freehold sandy loam soil, testing very high in P and K, with a pH of 6.0 to 6.5. Total nutrient applications were 150 lbs/A N, 200 lbs/A P2O5, and 300 lbs/A K2O applied preplant, and two fertigations. Figure 13 shows nutrient storage in plant parts at the green stage of development.
Total Nutrient Accumulation for 101 bu/A Soybeans
Nutrient Distribution in 101 bu/A Soybeans
Nitrogen Distribution in Soybeans (Above Ground)
N Requirement Relative to Yield Level
Yield Above Ground N Uptake@ 4.73 lb N/bu
Seed N Removed@ 3.3 lb N/bu
40 bu/A 189 lb/A 132 lb/A
88 bu/A 415 lb/A 290 lb/A
N in seed was 6.34%
• 3 primary sources of N in Soybeans• N2 fixation Bradyrhizobium• Nitrate and ammonium in the soil• Fertilizer N
• 50‐60% of N comes from N2 fixation; remainder from the soil • Maximum N2 fixation is about 300 lb N/A.• When fertilizer N is applied, N2 fixation can be reduced
• @ 45 lb N/A, maximum fixation is about 190 lb N/A• @ 90 lb N/A, maximum fixation is about 125 lb N/A
Summary of Soybean N ResearchReviewed by University of Nebraska (Salvagiotti, et al)
• About half of 67 studies reported positive response to N fertilizer.• Average yield response was 8 bu/A• 10 bu/A response when < 45 lb N/A was applied at growth stage R3 (beginning pod)• 9 of 12 studies (75%) with yields >67 bu/A had positive response to N
• In high yield environments, fixed N and soil N may not meet the N demands of soybean plants.
• High yield environments have a higher probability of response to N fertilizer.
Summary of Soybean N ResearchReviewed by University of Nebraska (Salvagiotti, et al)
• High yielding environments• Certain Lower yield environments
• Poor nodule establishment• Extremely low soil N at planting• Plant water stress• Soil pH problems• Low soil temperature• Absence of native Bradyrhizobium
Conditions favoring soybean response to N fertilizer
Summary of Soybean N ResearchReviewed by University of Nebraska (Salvagiotti, et al)
Do high yielding soybeans need N fertilizer?• Maybe• Yield response may only be marginally profitable• Depends on risk from N price vs soybean price• Local trials are an important guide
Dr. T. Scott Murrell. 2012. Do High Yielding Soybeans Need to Be Fertilized with Nitrogen? Plant Nutrition Today, 2012 #4 IPNI PNT Spring2012.pdf. International Plant Nutrition Institute.www.ipni.net .
Dr. Harold F. Reetz, Jr.Reetz Agronomics107 S. State Street
2003: What cost $1 billion dollars over the prior 2 decades of work to complete in 2003?
2013: What cost $4000 and took less than 2 weeks to do the same thing in 2013?
ANSWER: The First Human Genome Sequence
2003: It cost $1 billion dollars over the prior 2 decades of work to complete the first human genome sequence 2 billion assembled base pairs of DNA
2014: It is projected to cost only $1000 in 2014 and take only days to complete a human genome sequence .
Now thousands of people are having their DNA sequenced for diagnosing genetic and non genetic diseases including cancer at major medical centers although not yet in routine clinical use. The new term in use is “personalized medicine”.
QUIZ Time
2010: What cost >$10 million and several years prior to complete?
2013: What costs $4000 and take less than 2 weeks to do the same thing in 2014?
ANSWER:
The First Soybean Genome Sequence
2010: What cost >$10 million and several years to complete?
2013: What costs $4000 and take less than 2 weeks to do the same thing in 2014?
The Public/Private Effort Drove a Revolution in Sequencing Technology
Now Referred to as “Next Generation” SequencingThe $1000 human genome sequence is predicted for 2014
Illumina GAII or HiSeq Instruments at Keck Center, UI
DNA mRNA Proteins Traits
Whole genome sequencing of DNA
Transcriptomics: Sequencing of all the mRNA (messenger RNAs) of different tissues
The proteins can be predicted from the DNA or RNA sequences
The goals is to understand traits with these new sequencing approaches that were not feasible to do just 5 years ago
Current project goals in our lab: -Find all the mRNAs and small RNAs expressed in a seed - Dissect how they control important traits as protein and oil composition in the developing seed
Approaches:
•There are potentially 78,000 genes (gene models) that code for proteins in soybean as shown by the recent sequencing of the soybean genome
•We determine the expression of all 78,000 genes in different developmental times of seed development by sequencing the messenger RNA populations yielding up to 100 million raw sequence reads from each sample.
•The sequence reads are aligned to the 78,000 gene models to find which ones match and determine their relative expression in the different tissues or conditions.
Next Generation Illumina Deep Sequencing Technology Used to Sequence mRNAs or Small RNA Populations
Yields 200 Million Sequence Reads Per Sample
Illumina GAII or HiSeq Instruments at Keck Center, UI
Williams cultivar is used as the standard cultivar source for seed and seedling tissues
Seed Coat Cotyledon
Shoot tips
Unifoliates
StemGerminated Cotyledons Roots
Immature SeedYoung Seedling
5-6mgReference
Day 0Fertilization/Flowering
4 DAFGlobular Stage
8-10 DAFHeart Stage
12-14 DAF 17-19 DAF 22-24 DAF 5-6mgReference
Day 0Fertilization/Flowering
4 DAFGlobular Stage
8-10 DAFHeart Stage
12-14 DAF 17-19 DAF 22-24 DAF
Global Expression Analyses of Soybean Seed Development Including Very Early Stages Post-Fertilization Using
Illumina Next Generation Sequencing
• Total RNA from the younger whole seeds was extracted and subjected to high throughput sequencing (RNA seq)
•12 to 77 million sequence reads of the mRNAs from each of 7 stages using Illumina “Next Generation” Sequencing, Keck Center, University of Illinois
- 4 DAF (days after flowering)-12-14 DAF-22-24 DAF-5-6 mg fresh weight per seed -100-200 mg fresh weight per seed -400-500 mg fresh weight per seed-mature dry seed
• Seed coats and cotyledons are dissected from immature soybean seed at various stages of fresh weight during seed development including the mid-maturation stages when soybean accumulates proteins and oils.
• The mRNAs and small RNA populations were sequenced.
Selection of Genes with Highest Expression During Different Stages (Each line represents expression of a different gene)
12-14 Days After Flowering
Young Cotyledons, 5-6 mg
Mid to Late Maturation Cotyledons
Mature Seed Cotyledons
Beta‐conglycinin gene models (black) peak in RPKM at 100‐200mg cotyledonGlycinin gene models (pink) peak in RPKM at 400‐500mg cotyledon
Glycinin and Beta‐Conglycinin Storage Protein Gene Models Have High Expression in Mid‐to Late Maturation Seeds
Omega‐6‐fatty acid desaturases (black) tend to have higher RPKMs throughout development than omega‐3‐fatty acid desaturases (pink)
Expression of Omega Fatty Acid Desaturase Gene Models Throughout Seed Development
RNA Seq Data for Genes Encoding Enzymes in the Pathway to Lysine
Aspartate kinase
Aspartate semi-aldehyde dehydrogenase
Bio Rep 1
Homoserine dehydrogenase
Homoserine kinase
Enzymes in the Pathway to Threonine
Bio Rep 2
Threonine synthase
Graphs depict our RNA Seq data from developing seed for genes encoding enzymes
in the pathway to threonine
Using transcriptome sequencing of developing seed to examine expression of enzymes in the pathway to nitrogen accumulation
Could be done with different applications of nitrogen or growth conditions to genes that are changed in gene expression
Could use genetic lines that differ in nitrogen response
Glutamate-ammonia ligase
Glutamate synthase (ferredoxin)
Glutamate synthase (NADH)
Ammonia Assimilation Pathway
Source: Soybase
Soak in water 24hrs
Glutamate-Ammonia Ligase
23.9 22.3 21.8 11.5 0.7 0.1 0.0
0.5 10.1 25.6 89.6 249.0587.4 400.0
14.0
320.0
Glutamate-Ammonia Ligase
Seed Development Seedling Cotyledons
Soak in water 24hrs
Glutamate Synthase
5.6 5.1 7.1 4.6 4.7 7.5 2.5
2.0 14.2 22.0 27.4 70.892.3 119.3
27.0
19.0
Glutamate Synthase
Seed Development Seedling Cotyledons
Urea Cycle
Argininosuccinatesynthase
Argininosuccinate lyase
ArginaseCarbamoyl-phosphate synthase
Ornithine carbamoyltransferase
Asparagine Biosynthesis
Source: Soybase, superpathway of asparagine biosynthesisBoth enzymes give an identical list of gene models.
Asparagine synthase (glutamine-hydrolysing)
Aspartate-Ammonia Ligase
Aspartate-Ammonia Ligase/ Asparagine Synthase
Seed Development Seedling Cotyledons
Combined data
ii ki iI
Recently, we have shown it to be a tissue-specific example of gene silencing or naturally occurring RNA interference by CHS siRNAs that are produced in a tissue specific manner, Tuteja et al, Plant Cell 21, 3063-3077, 2009.
Therefore all commercially-grown yellow soybeans grown on millions of acres are the result of a naturally generated, non-transgenic siRNAmediated gene silencing locus.
This example shows how small RNAs can control traits. Does a similar process regulate other gene networks to influence protein composition and quantity?
Small RNAs lead to yellow seed coats produced by the naturally occurring alleles of the I (Inhibitor) locus in soybean
Yellow Hilum Saddle Self color
RNA Seq Reveals Quantitative Differences in Expression Levels of the CHS7 and CHS8 Genes of Yellow and Pigmented Genotypes
CHS7 and CHS8 are 6-8 fold more highly expressed in the pigmented genotypes
Comparison of some soybean genes with higher normalized expression (sequence reads per million) in high protein transgenic line versus control line
using “Next Generation” sequencing.
Gene models shaded in green show enhanced expression in the high protein sublines
5608 Transcription Factors Displayed by Their Expression Levels at Different Stages of Soybean Development
Transcription factors (TFs) are “master regulators” controlling the expression of many other genes to either increase or decrease their levels of gene expression.
The networks of genes whose expression is regulated by TFs control plant traits including protein and oil amounts and likely can influence the amino acid composition of the seed.
Expression of a TF generally would precede the change in expression of the genes in the networks they control, ie storage proteins, oils, amino acid biosynthetic enzymes.
Therefore, the TFs expressed early in seed development are likely to have the greatest influence on the ultimate composition of the seed.
The key is finding the TFs critical in this process especially as their expression levels are often low compared to other genes as those coding for enzymes and certainly compared to the major seed storage proteins.
We have completed high throughput sequencing the entire complement of TFs in normal development of soybean seeds.
Examination of lines that vary in protein and oil content and amino acid composition with high throughput RNA sequencing is one approach to the goal of improving seed composition. Particular emphasis should be placed on transcription factors in these lines.
Why Transcription Factors Are Important in Seed Composition
Nitrogen on Soybean: Protein and Oil
Nitrogen on Soybean: Protein and Oil
Seth NaeveUniversity of MinnesotaSeth NaeveUniversity of Minnesota
Assumption and background• N fertilizer will be most effective for
soybean yield (and presumably seed [N]) when applied during seed filling– Deibert et al. (1979)– Afza et al. (1987)– Shibles (1998)
• A review of the literature shows the range of expected responses– Yield + / Protein +– Yield + / Protein 0– Yield 0 / Protein +– Yield 0 / Protein 0
Rotundo and Westgate (2009)
Relative response of soybean seed protein content (mg per seed) and concentration (%) to nitrogen supply. Symbols and bars represent mean response and 95% confidence interval, respectively. The number of studies included in the meta-analysis are indicated in the figure.
Rotundo and Westgate (2009)
• In vitro studies increased [protein] by ~ 60%• Hydroponic studies resulted in a ~20%
increase in [protein]• The average [protein] increase in field
studies was only ~1%• However, the response appeared to be rate
dependent. – Applications of <100kg ha-1 resulted no response– >100kg ha-1 (planting-V6) = ~2%– >100kg ha-1 (R1-R4) = ~3%
Rotundo and Westgate (2009)
• Rotundo and Westgate also examined environmental variability in seed quality through the Uniform Variety Trials.– They found a 18% variation in seed protein and
23% variation in seed oil– This ‘natural’ variation dwarfed any treatment
effects noted in their meta-analysis
Rotundo and Westgate (2009)• Oil
Genetic Gain X Management• Eric Wilson, et al. (2014)• 59 MG II’s and 57 MG III’s released from
1928-2007)• Minnesota, Wisconsin, Illinois, and Indiana• Lines were either planted with or without
added urea (total of 560 kg N ha-1)– Split application (pre-plant and V5)– Split forms (ESN and Urea + Agrotain)
Wilson et al – observations• Oil concentration increased with release
dates, but no N affect• N fixation at MG II locations was smaller
(23% of total N compared with ~60% in MG III locations).
• Longer leaf retention in fertilized plots
Casteel et al. (2013)• Paper presented at the ASA meetings• Casteel partitioned plants from the
genetic gain study at V4, R2, R4, and R6
• Found increased leaf biomass and N concentration across year of release at all stages sampled
• Found increased allocation of whole-plant N to leaves at R6 over release date– MG II – from 25 to 36% (from 1928 to 2011)– MG III – from 21 to 32% (from 1923 to 2011)