Tools for Managing Nitrogen

1
Tools for Managing Nitrogen

• Cecil County Mid-Winter Meeting
• February 20, 2007
• Patricia Steinhilber
• UMCP
• Ag Nutrient Management Program

2
Why the Interest in N?

• nitrogen fertilizer prices have dramatically
  increased
• cost of N fertilizer is closely linked to cost of
  natural gas
• increase in price is indicative of a long term
  trend
• global increase in demand for energy

3
Why the Increase in Price?

• N fertilizer production is an energy-intensive
  process
• Haber-Bosch process
• hydrogen (H2) nitrogen (N2) ammonia (NH3)
• hydrogen gas (H2) from natural gas
• nitrogen gas (N2) from the atmosphere
• natural gas is steam reformed to make hydrogen
  gas
• nitrogen gas must be separated from air
• nitrogen and hydrogen are combined at very high
  temperature and pressure

4
The Nitrogen Management Mantras (since early
1990s in MD)

• apply N based on realistic yield goal
• 1 lb N/bu expected yield
• split-apply N fertilizer on corn
• apply 30 40 lbs/A at planting
• remaining N as sidedress
• when utilizing manure, use PSNT, the
• Pre-Sidedress Nitrate Test

5
Yield Goal Issues

• few producers have field-specific yield records
• long-term data suggest that yield goals are not
  as good a predictor of N requirements as once
  thought
• some states have moved on to a new pre-plant soil
  test for N recommendations
• Illinois Soil Nitrogen Test (ISNT) aka sugar
  amino soil nitrogen test

6
The Rationale for Split Application of N

• if the N is not yet applied, it can not be lost
• heres why it works
• Penn State Agronomy 12

7
DE Yield Data on Split Application of N on Corn
(bu/A)
8
Why is PSNT Recommended for Manured Corn?

• Assumptions are made and estimates are used in
  calculating a manure rate and any additional N
  fertilizer needed
• manure analysis reflects the manure applied
• mineralization (breakdown rate) of organic
  nitrogen was average
• ammonia losses were typical
• recommended rate was actually applied

9
Rationale for PSNT

• On fields with a history of manure use or forage
  legume, early season nitrate is proportional to N
  availability later in season
• Warning! PSNT was never intended and should
  not be used on fields where fertilizer N has
  historically been the only source of N

10
PSNT The Specifics

• soil is sampled to a depth of 12 inches
• corn is 6 to 12 tall
• portable, easy-to-use meters allow local analysis
  of soil and rapid delivery of results
• sidedress rate is determined (0 to 80 lbs. N/A)
• widely used across NE and Midwest, though
  interpretations differ by state
• used in MD since 1992

11
Here is an example of a Nitracheck meter that is
used during the PSNT process.
Photo by UMCP, ANMP staff
12
Additional Nitrogen Mantras

• monitor crop with new in-season techniques when
  appropriate and modified for our state
• chlorophyll meter
• learn about fertilizer technology innovations
• increase return from fertilizer investment
• monitor success of N management activities
• corn stalk nitrate test (CSNT)

13
Rationale for Chlorophyll Meter

• nitrogen chlorophyll greenness
• portable meter measures greenness of leaves
• widely used in Great Plains to monitor status of
  irrigated corn, as a fertigation guide
• supplemental N can be applied via
  irrigation
• a reference strip is required as
  greenness varies across hybrids

Rothamstead photo
14
Use of the Chlorophyll Meter in Dryland Corn

• a new application a pre-sidedress chlorophyll
  test (PSCT)
• work at Penn State indicates it is useful
• evaluation in Maryland will continue
• could replace the PSNT if it is reliable
• less strenuous sampling, more expensive equipment
  (meters cost 1,400)

15
Keep Up With Fertilizer Technology
InnovationsMaximize utilization of fertilizer
youve applied.

• reduce transformations to mobile forms
• reduce the transformation to gaseous forms
• reduce rate of nutrient release
• reduce reactions of nutrients with soil (a P
  issue)

16
Reduce Transformations to Mobile Forms

• nitrification inhibitors NH4 NO2-
• N-Serve is a bactericide that kills targeted
  organisms, Nitrosomonas
• investigated in late 1980s, not effective in MD
• yield response was not observed in many locations
  most years
• chemical degraded too rapidly under MDs mild
  weather conditions

17
Reduce the Transformation to Gaseous Forms

• aka minimizing ammonia volatilization
• affects broadcast, surface-applied urea, UAN,
  ammonium nitrate and manure
• ammonium in the presence of hydroxyl (OH-) can
  produce ammonia gas
• NH4 OH- H2O NH3

18
So How Does Urea Relate to Ammonia Loss?

• urea is converted to ammonia by the enzyme,
  urease
• if urease activity is blocked, the rate of
  conversion is reduced
• urease is ubiquitous in soil on crop residue
• enter urease inhibitors, like Agrotain

19
Urease Inhibitors
urease

• urea ammonia carbon dioxide
• urease inhibitors (UIs) temporarily block the
  action of urease
• may block urea conversion until rain moves urea
  into the soil
• not effective all years - depends upon weather
• never effective in conventional till or when urea
  is banded

20
Reduce the Rate of Nutrient Release

• protect nutrients with a physical barrier
• ESN, Environmentally Smart Nitrogen
• a polymer-coated urea
• diffusion of urea is temperature controlled

http//www.agrium.com/uploads/How_Technology_Works
.pdf
21
Corn Yield Data from DE(150 lbs/A N)
22
Reduce Reactions of Nutrients with Soil

• Protect nutrients with a chemical shield
• AVAIL for enhanced P availability
• coated with a chemically-reactive material
• protects P from chemical fixation
• 2 major questions in MD
• In what soil test ranges is it useful?
• How should P recommendation be adjusted?

23
End-of-Season N Assessment

• corn stalk nitrate test (CSNT)
• developed in Iowa, used in many states as a
  retrospective analysis
• evaluation in MD will continue
• rationale corn plant with an oversupply of N
  accumulate nitrate in their stalks

24
Interpretation of CSNT(ppm nitrate, several
states)

• lt250 low N was limiting yield
• 250 700 marginal too close for comfort
• 700 2000 optimal N was not limiting
• gt2000 excess N rate can be reduced with no
  loss of yield
• more recent research suggest use only as an
  excess/not excess tool

25
Suggestions for Responding to Excess CSNT

• use fertilizer N only?
• see if yield goal is actually based on long-term
  yields in fields
• after several years of excess CSNT, cut back on
  N rate
• use manure?
• collect a representative sample at least yearly
• re-calibrate spreader
• still excess for several years? discuss with
  nutrient management planner

26
In Closing

• use existing and proven tools
• keep up with new tools and technologies
• As energy and fertilizer prices climb, the value
  of lost nitrogen increases, justifying additional
  investment in loss prevention.
• - (Paul Fixen, PPI)