Managing Fertilizer Inputs

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Managing Fertilizer Inputs Prepared for 2006
Extension Agent Update, Conrad
by Clain Jones, Extension Soil Fertility
Specialistclainj_at_montana.edu 406
994-6076http//landresources.montana.edu/soilfert
ility
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Questions

• How many of you know what N fertilizer sources
  are available in your county?
• Of those, how many have ammonium nitrate
  available?
• Why am I asking?

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Objectives

• Determine if its worth fertilizing
• Discuss prevalence and causes of yellow winter
  wheat
• Introduce concept of Nitrogen Use Efficiency
• Cover common myths and facts about fertilizers
• Tissue testing, Montys, Liquids, Volatilization

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Should I fertilize?

• What does answer depend on?
• - Nutrient levels in soil
• - Fertilizer price, crop price
• - Yield response curve
• - Yield potential (and optimism!)

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Yield Response Curve, Golden Triangle
Data from G. Jackson Graph from D. Griffith
If had 50 lb N/ac in soil, and yield potential
was 53 bu, would you fertilize? How much? (Duane
G. will show you later) Why does shape of
curve matter?
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Spring wheat yield as affected by water and N,
Havre
MEY Maximum economic yield or return from N
assuming a 201 wheat price (/bu) to N cost
(/lb) ratio.
Engel et al. (Fertilizer Fact 25).
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Who has received calls asking about yellow
winter wheat this year, or knows they have yellow
winter wheat in their county?
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LOW N
HIGH N
Post Farm May 11, 2006
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Winter Wheat, Moccasin, Crop Rotation Study
(2005 spring pea, winter pea, fallow, spring
wheat) May 10 2006
Previous crop pea spring wheat pea
Why?
Photo Chen, C.
Crop effect Any guesses on previous crop of
yellow winter wheat?
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Should I topdress?

• If wheat is still yellow after this warm spell,
  and/or yield potential has increased
  substantially from when fertilizer decision made,
  then yes. (again will come down to economics)
• Caution if using color to determine if wheat is
  deficient, verify that it is not disease
  (generally more spotty in appearance), cold
  stress (more brown and not uniform) or a sulfur
  deficiency (yellowing in new leaves first).

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• What should I topdress with?
• If temperatures are warm, use ammonium nitrate
  (AN) if available.
• If temperatures are cool and irrigation water is
  turned on, or ½ inch of rain is in the forecast,
  use urea (UR) or urea ammonium nitrate (UAN).
• If want an immediate green-up response, and AN is
  not available, use ammonium sulfate (AS). Blend
  AS and UR for the best compromise between
  green-up and cost. Ex ASUR1/32/3 as N.

One caution Ammonium sulfate can volatilize on
calcareous soils.
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Questions/Discussion?
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Nitrogen Use Efficiency (NUE)

• Calculated by dividing grain yield (lbs) by N
  input (lbs)
• Ex NUE yield/(Soil N Fertilizer N)
• NUE sometimes is also expressed as of N applied
  (or available) that is removed. (check units)

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What factors increase NUE?

• Fertilizing less.

Spring Wheat, Joplin
(G. Jackson, unpub. data)
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What other factors increase NUE?

• Preventing losses
• -Minimizing volatilization (will cover
  later)-Minimizing leaching (ex Avoiding over
  watering)
• Using reasonable yield goals, and topdressing if
  needed
• Banding near seed?

Malhi and Nyborg, 1992.
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Other strategies to increase NUE?

• Optimize fertility of other nutrients

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Winter wheat response to P fertilization (N rate
110 lb/ac)
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Questions on Nitrogen Use Efficiency?
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Fertilizer Myths and Facts

• Myth Tissue testing and soil testing give you
  similar information.
• Fact Yield response curves have been developed
  mostly for soil tests, yet not tissue tests
  therefore, fertilizer rates should be based on
  soil tests.
• Fact Tissue tests are better at determining
  nutrient deficiencies.
• Fact Need to make certain that correct plant
  part (ex upper four leaves, stem, whole plant)
  is sampled.

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Tissue Testing What does it show?

• Nutrient status of plants at the time of
  sampling, indicating deficient or adequate soil
  nutrient supplies.
• Unseen deficiencies and may confirm visual
  symptoms of deficiencies.
• Toxic levels of metals or excessive nutrients
  critical for determining forage nitrate toxicity.
  MontGuide fact sheet 200205 or
  http//www.montana.edu/wwwpb/pubs/mt200205.html

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Types and Methods of Tissue Testing

• Lab Plant Analysis vs. Cell Sap, In-Field
  Analysis
• Lab Tissue testing is an accurate, quantitative
  analysis of specific nutrients.
• Results take more time to obtain and samples need
  to be collected carefully.
• Cell Sap analyses with in-field instruments are
  qualitative analyses, often indicating very low,
  low, medium or high nutrient levels in the plant.
• Immediate results allow for possible fertilizer
  adjustments when used with historical soil
  analyses and fertilizer records.

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How to Sample for Lab Analysis

• 1) Sample when symptoms first appear
• 2) In the same field or area, collect similar
  samples of plant materials from plants that
  appear abnormal and also collect samples of
  healthy plants for comparative analysis.
• 3) Make sure that symptoms are not due to factors
  such as drought stress, insect or disease damage
  or mechanical injury.
• 4) Collect the correct parts, clean by brushing
  or with distilled water, pat dry and mail to the
  lab in a paper bag or envelope.

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Sample collection
Flynn et al. 2004. Sampling for Plant Tissue
Analysis. New Mexico State University Extension.
Guide A-123
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Whats happening with this spring wheat crop?
What would you recommend?
Previous fall soil sampling measured 76 lb
N/ac Tissue tests report N at 1.7 P at 0.3 K
at 2.8 Ca at 0.41 Mg at 0.25 S at 0.14 All
micronutrients at sufficient levels.
Photo courtesy of The Mosaic Co. Website accessed
05/17/2006
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Sufficiency Values for Plant Growth
Adapted from Soil Fertility Handbook, Oklahoma
State University.
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Tissue Testing in Conjunction with Soil Testing

• Soil testing analyzes current and future
  availability.
• When both are used, fertilization practices can
  be adjusted to specific plant needs for optimal
  yield.

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QUESTIONS?
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More myths about fertilizers

• Myth You can get something from nothing
• Fact It takes about 2-3 lb N to get a bu of
  wheat.
• Myth Low nutrient solutions can take N out of
  the air, or mobilize soil nutrients.
• Fact Low nutrient solutions can not take N out
  of the air, and appear to have little to no
  effect (at rates prescribed) on mobilizing soil
  nutrients.

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Plant Food vs. Fertilizer Affects on Winter
Wheat Yield
a
b
b
b
b
b
Jackson. 2005. unpub. data
Fertilizer 16-30-0 with seed, 64-0-25 applied
broadcast while planting. M1 38 oz/ac of
Montys Seed Starter 4-15-12 applied to the
seed. M2 48 oz/ac of Montys Seed Starter
4-15-12 applied to the seed, plus 16 oz/ac of
Montys All Purpose Growth 8-16-8 M3 58 oz/ac of
Montys Seed Starter 4-15-12 applied to the seed,
plus 16 oz/ac of Montys All Purpose Growth
8-16-8, plus 16 oz/ac of Montys Root Bloom
2-15-15 Humic Acid (dry product) 64 oz/ac.
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Plant Food vs. Fertilizer Affects on Winter
Wheat Protein Content
a
b
b
b
b
b
Jackson. 2005. unpub. data
Fertilizer 16-30-0 with seed, 64-0-25 applied
broadcast while planting. M1 38 oz/ac of
Montys Seed Starter 4-15-12 applied to the
seed. M2 48 oz/ac of Montys Seed Starter
4-15-12 applied to the seed, plus 16 oz/ac of
Montys All Purpose Growth 8-16-8 M3 58 oz/ac of
Montys Seed Starter 4-15-12 applied to the seed,
plus 16 oz/ac of Montys All Purpose Growth
8-16-8, plus 16 oz/ac of Montys Root Bloom
2-15-15 Humic Acid (dry product) 64 oz/ac.
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• Myth Liquid fertilizers work much better than
  granular fertilizers
• Fact While in some cases liquid fertilizers work
  better than granular, once granular fertilizers
  dissolve, the two are essentially identical.
• Fact Foliar applying liquid metal micronutrients
  CAN be more effective than soil applied granular.
  WHY?
• Fact Liquid fertilizers, due to expense of
  hauling water, are almost always more expensive
  per unit of nutrient.

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Liquid and Solid Fertilizers
Havlin et al. 2005 and Nutrient Management Module
10 (MSU Extension pub. 4449-10)
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Liquid fertilizers could be the right choice IF

• A high value crop needs immediate corrective
  fertilizer.
• Equipment and water are available.
• Weeds are being sprayed anyways.
• Confirmed micronutrient deficiencies are
  occurring applying liquid provides soluble
  micronutrients which are absorbed by the plant
  instead of sorbing or precipitating when applied
  to the soil.

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QUESTIONS?
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• Myth 50-70 of applied urea will volatilize
• Fact Volatilization amounts will depend highly
  on temperature, pH, moisture, application method,
  residue, etc., and appear to be fairly low in
  Montana based on N source comparisons.
• Fact Urea will volatilize if applied on moist,
  warm soil, and not incorporated within a few
  days, so well thought out application is
  necessary.

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Factors Affecting Volatilization

• Soil pH and Temperature
• Wind
• Cation Exchange Capacity (CEC). WHY?
• Buffering capacity (resistance to pH change)
• Soil moisture/humidity
• Rainfall/Irrigation following fertilization
  (depth in soil)
• Ground cover/vegetation/residue. WHY?
• Soluble and Exchangeable Calcium

Bottom line Large number of factors make
volatilization amounts VARIABLE and difficult to
predict.
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1. Soil pH and Temperature Effects on Relative
Amount of Ammonia in Soil Solution
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2. Wind
Ammonia Loss
Fillery et al., 1984
Wind Speed

• SO, avoid applying if have high winds in forecast.

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3. Cation Exchange Capacity

• As CEC increases, volatilization rates generally
  decrease (Fenn and Kissel, 1976). Why?
• 1. Less NH4 in solution to volatilize
• 2. Increased pH buffering capacity (next slide)

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4. Buffering Capacity
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5. Effect of Soil Water Content
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6. Rainfall/Irrigation

• 1/10 inch of rain/irrigation dissolves
  fertilizer, allowing volatilization.
• 1/2 inch of rain/irrigation pushes dissolved
  fertilizer about 2 in. into soil, essentially
  stopping volatilization if within about 2 days of
  fertilization (Meyer et al., 1961 Lloyd, 1992)

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Effect of Incorporation Depth
Urea Rate100 lb N/ac Texture silt loamSoil
pH 6.5Temp. 75o F
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7. Effect of Grass Residue
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Effect of Residue, Contd

• Volatilization was found to be approximately 2
  times higher in the upper 1.5 inches under
  no-till than under conventional tilled systems
  (Dick, 1984).

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8. Exchangeable Ca2 Decreases Volatilization
(Fenn and Kissel, 1976)
Why? Calcium can tie up a carbonate ion,
preventing pH rise AND open up 2 exchange sites
for ammonium.
Implication Less concern with volatilization on
soils with high exchangeable Ca levels (generally
indicated by high CEC). Good news for MT. Doesnt
matter though if urea doesnt reach soil.
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Note

• Grant Jackson and I, and three other faculty from
  ID and WA, have finished a final draft of a urea
  management guide. It is now out for review, with
  an anticipated publication time of this Fall.

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Conclusions

• The question, Should I fertilize?, will largely
  be answered by economics (Duane Griffith will
  cover this afternoon)
• Nitrogen use efficiency can be improved with good
  placement and timing, reasonable yield goals, and
  a balanced fertility program.
• Tissue testing can be useful in verifying
  nutrient deficiencies, but is not useful in
  determining fertilizer amounts.
• Low nutrient liquid fertilizers (less than 2 lb
  nutrient/ac) do not increase yield or protein
  over control treatments.
• Liquid fertilizers and granular fertilizers are
  generally equally effective, yet each has its
  advantages and disadvantages.
• Urea volatilization can be minimized with well
  thought-out placement and timing.