Soil Fertility and Nutrient Management Update

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Soil Fertility and Nutrient Management Update

• Patricia Steinhilber
• Agricultural Nutrient Management Program
• University of Maryland College Park
• psteinhi_at_umd.edu
• www.anmp.umd.edu

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Major Topics

• soil sampling and testing
• organic matter testing and managing
• manure management
• sampling and testing
• calibrating application equipment
• PSNT when applied to corn
• adopting current adaptive assessments
• be aware of expanded adaptive management in our
  future

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Soil sampling is a critical step!

• the soil test is the basis of the nutrient
  recommendation
• the recommendation can only be as good as the
  sample the lab received
• see sampling card for advice on sample collection
  and preparation

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Soil Sampling

• be careful about delineating management units
• if any of these factors differ, sample separately
• soil complex
• previous fertility regime
• cover crop and its management
• previous crops
• sample correctly depth and number
• 8 inches 15-20 per field or management unit
• sample prep break up clumps and mix, mix, mix

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Value of Soil Tests

• best pre-plant indicator we have of potential
  nutritional products
• mine them for information!
• excellent investment

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Soil Test Value and Response to Nutrients
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Soil Tests

• best if maintained in the high end of the
  optimum range or the low end of the excessive
  range

0
25
50
100
medium
optimum
low
excessive
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Testing and Managing Organic Matter (OM)

• organic matter is multifaceted
• often is not part of a standard analysis at a
  soil test lab
• Pay extra its worth the
• if you change labs, you may see a change in OM
  because of differences in techniques
• burn off OM with very high heat or very strong
  acids

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Adequate organic matter is important for

• nutrient holding capacity
• water holding capacity
• water stable aggregates
• resistance to erosion
• high water infiltration rates
• greater water storage in root zone
• greater oxygen supply in root zone oxygen
• better tilth

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Biomass Composition

• the living component of the soil
• consists of a range of creatures
• as small as microscopic bacteria
• as large as worms and other creatures that are
  visible to the unaided eye
• and everything between

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Biomass Functions

• nutrient cycling
• digest plant and animal materials (residues),
  using what they need and leaving behind what they
  do not
• mineralization

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Biomass Functions (contd)

• creation of biopores
• larger organisms move through soil creating
  channels
• channels promote water infiltration and create a
  healthy balance between large and small pores
• large pores (allow rapid infiltration of rainfall
  and replenishment of oxygen in the root zone)
• small pores (store water for plant use)

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Residues and By-productsComposition

• dead stuff - crop residues, dead roots and bodies
  of dead soil creatures
• by-products - materials that plant roots and soil
  creatures release or exude into the soil

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Residues and By-productsFunctions

• fuel and nutrients for soil creatures
• energy and nutrient source for most of the soil
  creatures
• formation and maintenance of soil aggregates
  (structure)
• sticky and gummy by-products of residue
  decomposition hold soil particles together into
  clumps or aggregates

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Humus Composition

• stable end product of residue decomposition
• composes the majority of organic matter
• resists further decomposition (1 per year)
• it is not a good nutrient or energy source for
  soil creatures

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Humus Functions

• high surface area
• charges at many locations on the surface
• effective at holding water and nutrients

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Manure Management (MM) 1 Sample Manure

• sampling manure is as critical and challenging as
  sampling soil
• application rate will be based on analysis
• a reliable analysis requires a representative
  sample
• collect a sample as close to time of utilization
  as is practical

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Sampling Principles

• Collect 10-15 samples.
• before application
• from various depths locations in a pile
• from agitated liquid storage facility
• during loading
• during spreading

NOTE Include bedding in the sample to the same
extent as it exists in the pile.
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Sampling Principles (contd)

• 2. Mix composite sample very well.
• 3. Sub-sample composite.
• 4. Package and ship to lab.
• Plastic resealable bags (double bagging
  recommended)
• Plastic bottles or jars (never glass)

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See NM-6 for more information on sampling manure.
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Manure A Variable Nutrient Source
solid dairy manure, on an as is basis, 891
samples, from 1995 to 2002
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MM 2 Calibrate Manure Spreader

• 2 common methods
• load-area method
• weight-area method
• Keep calculation worksheets in your records.

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Weight-area Method

• Collect nutrient-supplying material on a small
  portion of a field and project the rate of
  application on this area to a per-acre basis
• This is the preferred method for dry fertilizer
  application equipment
• Concepts can be readily applied to the
  volume-area method
• It is also useful for some manure application
  equipment

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Load-area Method

• Determine the weight of a load of material and
  apply the entire load to a portion of a field.
• Measure the area covered and project the rate of
  application on this area to a per-acre basis.
• This is the preferred method for liquid manure
  and some dry manure applications.

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Manure A Complex Nutrient Source

• a mixture of metabolic waste solid waste from
  the digestive system
• metabolic waste is soluble
• urea (mammals), uric acid (birds)
• feces is a mixed bag
• undigested feed
• microbe bodies
• cell wall debris from animal gut

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Manure A Complex Nutrient Source (contd)

• manure is a complex mixture
• soluble nutrient forms
• urea, ammonium, nitrate
• labile organic nutrient forms
• break down quickly when added to soil
• stable organic nutrient forms
• break down slowly month to years
• mineral forms of nutrients of varying stability

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Mineralization Rates (fraction of original
organic N)
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MM 3 Recognize Uncertainty in Manure Utilization

• mineralization rates are averages
• actual mineralization may vary due to composition
  of manure, soil, or weather conditions
• confirming adequate N is very important for crops
  fertilized with manure!
• pre-sidedress nitrate test (PSNT)

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Within an Animal Type

• Delaware study of 20 litters for commercial
  broiler houses incubated with same soil
• average mineralization was 66
• range was 21 to 100
• USDA study of 107 dairy manures in Northeast
• mineralization ranged from 0 to 55

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Soil Differences?

• In a Georgia study with one broiler litter and 9
  soils under controlled conditions
• average mineralization rate was 62
• ranged from 41 to 80
• loamy sands gt sandy loams gt clays

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The Weather?

• mineralization is a microbial-driven process
• cooler than usual?
• wetter than usual?
• drier than usual?
• Slower breakdown of labile organic materials!

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MM 4 Use In-season Adaptive Management
Techniques

• Pre-sidedress Nitrate Test (PSNT) for corn
• determines nitrogen adequacy or inadequacy on
  corn
• when corn is 6 12 tall
• Extension nutrient management advisors are
  trained and ready to analyze PSNT samples for you
• grossly underused in Harford County

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Adaptive N Management is Exploding!

• increase nitrogen use efficiency (NUE)
• NUE worldwide for grains is 33
• In US NUE is 42
• maximize recovery of applied N
• convert as much fertilizer N as we can into grain
  and then conserve the balance as SOM
• minimizes reactive N released to the environment
• account for season-to-season and field-to-field
  variability

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Adaptive Management is a
Process
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Adaptive Management Tools

• Focuses on in-season N management
• PSNT
• Active Crop sensors
• LCM
• End of season assessment
• CSNT
• Yield monitoring

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Active Optical Sensors

• Emit light in the red and near infrared
  wavelength
• Measures spectral reflectance in a 3/8 x 24
  area
• Samples at a frequency of 60 times/sec
• Average reflectance measurements calculated every
  second

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How Active Sensors Work

• Measure crop vigor using simple ratio or NDVI
• NDVI (NIR Red)/(NIR Red)
• Correlate sensor reading to crop vigor and N need
• Not affected by
• light conditions
• atmospheric conditions
• variety

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Sensor Based N Management

• Constant Rate Hand Held

Variable Rate Application
Greenseeker
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Virginias Methods

• 60 sites across Virginia since 2000
• Irrigated and non-irrigated
• Conventional and no till
• Various rotations, hybrids, varieties, and soil
  types
• Wide range of pre-plant, starter, and in-season N
  rates (including VR)

• Collected spectral measurements and an assortment
  of plant physical and chemical characteristics at
  various growth stages
• Determine grain yield

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Virginias Approach

• Generated calibration models
• High-N reference (prefer Low-N as well)
• Developed N fertilization algorithms

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Variable Rate with GreenseekerTM UMD, VT, and
OSU Collaboration

• MD will build on VT algorithms
• Previous GreenseekerTM recommendations were made
  on corn at leaf stages V 6-7
• Attempting to move recommendations to V 4

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Results from Virginia

• GreenSeekerTM compared to farmer practice
• Virginia wheat studies
• 8 increase in grain yield (7 bu/ac)
• 10 reduction in N (10 lb N/ac)
• Virginia corn studies
• 5 increase in grain yield (11 bu/ac)
• 21 reduction in N (21 lb N/ac)

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Results from Maryland
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Questions?