Scientific Considerations for the IPNI Global Maize Project
Center Establishment (A-Sites)
Note: Throughout this description, the term ecological intensification (EI) is used. This term was developed by Cassman (1999)
and defines a production system that satisfies the anticipated increase in food demand while meeting acceptable standards for
environmental quality. Unlike past high yield efforts, EI focuses not only on production, but also profitability, sustainability, and
creating a favorable biophysical and social environment.
Ref: Cassman, K.G. 1999. Ecological intensification of cereal production systems: Yield potential, soil quality, and precision
agriculture. Proc. Natl. Acad. Sci. 96:5952-5959.
Objectives:
 To use ecological intensification (EI) practices to improve yields over time at a faster rate
than farmer practice, while minimizing adverse environmental impacts
 To test the ability of the Hybrid Maize simulation model to predict yield potential at
individual maize locations
 To provide data needed to calibrate a nitrogen nutrition module being developed for the
Hybrid Maize module
Expected duration: 5 – 10 years
Expected location: university or government research centers.
Minimum treatments:
1. EI cropping system
2. Average farmer management practices
These treatments are to be whole plots (not present as split plots on other existing whole plots).
During the duration of this experiment, management approaches associated with each treatment
are expected to change. The same experimental units will be used year after year to produce
long-term effects. Maize should be grown in a rotation representative of the area where the
research center is located. The experimental units should be a size appropriate for conducting
environmental measurements.
Proposed minimum set of measurements (we would like the feedback of your scientists and will
consider other suggestions you and they make).
1. Latitude, longitude, and elevation of the sites(s)
2. Description of the predominant soil types, using an appropriate soil classification system
3. Maize grain dry matter yield. This requires the following measurements:
a. harvest area (ha)
b. wet weight of grain (kg)
and either
1
c. grain moisture content (%)
or
d. wet weight of grain sample (g)
e. oven dry weight of grain sample (g)
4. Whole plant dry matter accumulation and nutrient (N, P, and K) uptake at physiological
maturity. This requires measuring the following:
a. dry matter of at least the following plant parts:
i. grain
ii. cob
iii. stover (leaves, stem, husks, tassel)
b. nutrient (N, P, K) concentration (% on a dry matter basis) of the following plant
parts:
i. grain
ii. cob
iii. stover (leaves, stem, husks, tassel)
c. soil organic C (combustion), soil inorganic C, particulate organic matter C, soil
bulk density, total N, extractable ammonium-N, extractable nitrate-N, extractable
P, extractable K, soil pH (water), electrical conductivity, and particle size
distribution on the 3 following depth increments:
i. 0-5 cm
ii. 5-10 cm
iii. 10-20 cm
and optionally
iv. 20-30 cm
v. 30-60 cm
vi. 60-100 cm
Note: for more information on these tests with references to step-by-step
procedures, see pages 29-31 in the file “0802 ARS GRACEnet Follett.pdf”
5. Daily weather data, described in Appendix A.
6. Crop and soil management information, described in Appendix A and B.
Data sharing
It is our intention for cooperating researchers to share their raw data and associated metadata
with IPNI for storage in a data repository for access to all cooperating researchers in the Global
Maize project. This sharing can be after an initial period (yet to be determined) that allows
researchers to use the data for local purposes first. Please make the co-chairs of the working
group know of any issues that arise from this request. Our intention is to consider the individual
publication needs of cooperating researchers as well as the need for cross-institutional
collaboration that relies on access to more than just local data.
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Data request
An important aspect of this project is the collection of the research and analytical methods used
by researchers involved in this project. Please gather from cooperating researchers any
procedures and protocols that they use and share them with the co-chairs of the IPNI working
group.
Yield-Gap-Partitioning Studies (C-Sites).
Objective s:
 to conduct a global, coordinated assessment of the gap between the maize yield obtained
by current average farming practices and the yield that can truly be achieved through
improved crop nutrition, alone or in concert with other management improvements
 To test the ability of the Hybrid Maize simulation model to predict yield potential at
individual maize locations
 To provide data needed to calibrate a nitrogen nutrition module being developed for the
Hybrid Maize module
Expected duration: 1 year
Expected location: one at the government or research center where the A-Site exists, and others
on farmer fields if possible
To attain the objectives, a series of “yield gap partitioning studies” will incorporate some or all
of the treatments listed below.
Proposed as required:
1.
2.
3.
4.
5.
6.
current farmer fertilization practice (FFP)
ample NPK (or 3 other nutrients known to be limiting)
ample PK (-N)
ample NP (-K)
ample NK (-P)
no NPK (nutrient check)
Proposed as optional:
7. FFP + improved crop management practices (ICM), where ICM are improvements in
practices other than FFP
8. ICM practices + ample NPK (or other 3 nutrients)
Attainable yield is measured in this study by treatment 2 and/or treatment 8 if the latter is
implemented. Yield potential is estimated from the Hybrid Maize model, using an appropriate set
of local weather data, crop management practices, and soils information.
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These studies are intended to last one year at a given site (one site-year) and should be located in
fields representative of normal crop rotations and management practices used by farmers near the
research center (A-site).
Proposed minimum set of measurements (we would like the feedback of your scientists and will
consider other suggestions you and they make).
1. Latitude, longitude, and elevation of the sites(s)
2. Description of the predominant soil types, using an appropriate soil classification system
3. Maize grain dry matter yield. This requires the following measurements:
a. harvest area (ha)
b. wet weight of grain (kg)
and either
c. grain moisture content (%)
or
d. wet weight of grain sample (g)
e. oven dry weight of grain sample (g)
4. Daily weather data, described in Appendix A.
5. Crop and soil management information, described in Appendix A and B.
Data request
We know that much of these data have probably already been collected in your region. As you
meet with scientists, please discuss with them the possibility of them sharing existing data of this
sort with the Global Maize project team. We would like to create a central database for storing
the raw data from these types of studies so that we can eventually conduct global assessments of
yield gaps that exist from lack of proper crop nutrition.
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Appendix A:
Required Data for Running Hybrid Maize,
Based upon documentation accompanying the model
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Description of the Hybrid Maize Simulation Model
Hybrid-Maize is a computer program that simulates the growth of a corn crop (Zea mays L.) under nonlimiting or water-limited (rainfed or irrigated) conditions based on daily weather data. Specifically, it
allows the user to:
 Assess the overall site yield potential and its variability based on historical weather data;
 Evaluate changes in attainable yield using different combinations of planting date, hybrid
maturity, and plant density;
 Explore options for optimal irrigation management;
 Conduct in-season simulations to evaluate actual growth up to the current date based on realtime weather data, and to forecast final yield scenarios based on historical weather data for the
remainder of the growing season.
Hybrid-Maize does NOT allow assessment of different options for nutrient management nor does it
account for yield losses due to weeds, insects, diseases, lodging, and other stresses. The model is
available at: http://www.hybridmaize.unl.edu/
Weather Data Needed by the Hybrid Maize Simulation Model
The Hybrid Maize model has two primary simulation modes: 1) long-term (multi-year, with a suggested
10 year minimum period) and 2) single year. In the long term mode, average yield potential is estimated
over a number of years while in the single year mode, yield potential for only one year is estimated. An
additional option is provided for estimating yield potential either under optimum conditions, where
water is not limiting, or under rainfed/irrigated conditions where water is limiting. The minimum set of
weather data are different for the optimal or rainfed options, as shown below in Table A-1.
Table A-1. Daily weather data required to run the Hybrid-Maize model
Data description
The following daily weather data must be reported in metric units.
These data must cover the entire growing season from either the
date of planting or emergence to the date to physiological maturity
minimum air temperature (°C)
maximum air temperature (°C)
total solar radiation (MJ m-2) -can be estimated from minimum
and maximum air temperature if solar radiation measurements
are not available)
precipitation (mm)
wind speed (km h-1)
relative humidity (%)
potential evapotranspiration (mm) – can be estimated from
windspeed, relative humidity, min temp., max temp, and solar
radiation
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Water is not
yield-limiting
Water is yieldlimiting
X
X
X
X
X
X
X
X
X
X
Obtaining Weather Data for the Hybrid Maize Simulation Model
Satellite-derived solar and meteorological data for the entire earth have been put together by the
United States National Aeronautics and Space Administration (NASA). The data exist in the
Agroclimatology Archive and are available at http://earth-www.larc.nasa.gov/cgibin/cgiwrap/solar/agro.cgi?email=agroclim@larc.nasa.gov. Daily data are available on a 1° latitude by 1°
longitude global grid and are listed in Table A-2. To retrieve the data, the user must know the latitude
and longitude of the desired location and, optionally, the altitude. If these coordinates are not known,
they may be found by using the freely available Google Earth application (http://earth.google.com). The
parameters used by Hybrid Maize are in bold font. The labels in the data set differ, depending on
whether Option 1 (pre-selected data) or Option 2 (user-selected data) is chosen on the website when
retrieving data. Additionally, if altitude is provided as an optional input, maximum, minimum, and
average temperatures will be adjusted mathematically for that altitude.
Table A-2. Parameters available for download from NASA (bold indicates a parameter that can be used
by the Hybrid Maize model).
Data set labels for the
following data retrieval
options
Earliest year for
Parameter
Units
Option 1
Option 2
which data exist
Year
-WEYR
YEAR
-Day of year
--
WEDAY
DOY
--
Average top-of-atmosphere
insolation
MJ m-2 d-1
--
toa_dwn
1983
Average solar radiation or average
insolation incident on a horizontal
surface
MJ m-2 d-1
SRAD
swv_dwn
1983
Average downward longwave
radiative flux
MJ m-2 d-1
--
lwv_dwn
1983
Maximum air temperature at 2m
above the earth’s surface
°C
TMAX
T2MX
1983
Minimum air temperature at 2m
above the earth’s surface
°C
TMIN
T2MN
1983
Precipitation
mm
RAIN
RAIN
1997
Wind speed
km h-1
WIND
--
missing
°C
TDEW
DF2M
1983
Dew point
7
Average air temperature at 2m
above the earth’s surface
T2M
T2M
1983
Maximum air temperature at 2m,
adjusted for the specified altitude
--
T2MXC
1983
Minimum air temperature at 2m,
adjusted for the specified altitude
--
T2MNC
1983
Average air temperature at 2m,
adjusted for the specified altitude
--
T2MC
1983
RH2M
RH2M
1983
Relative humidity
°C
%
Important considerations for preparing weather for the Hybrid Maize simulation model are found in the
Hybrid Maize software user’s manual.
Management Data Needed by Hybrid Maize Simulation Model
The following management data are needed for running the Hybrid Maize model. Requirements differ
for optimum and water limited conditions.
Table A-3. Site and crop management data required to run the Hybrid-Maize model.
Data description
Water is not
yield-limiting
Water is yieldlimiting
X or
X
X or
X
X
X
X or
X
X or
X
X
X
Year
Date of planting or emergence (one of the following)
Date of emergence (month, day)
Date of planting (month, day)
Seed depth (cm)
Maturity (one of the following)
Total GDD (10°C basis)
Relative maturity and seed brand
Planted population
Maximum rooting depth (cm)
X
8
Topsoil (upper 30cm) characteristics
textural class
initial moisture status (% field capacity)
bulk density (g cm-3)
X
X
X
Subsoil characteristics
textural class
initial moisture status (% field capacity)
X
X
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Appendix B:
Hybrid Maize N Module Data,
from Dan Walters
Professor, Soil Science
Dept. of Agronomy and Horticulture
University of Nebraska
279 Plant Science Hall
Lincoln, NE 68583
dwalters1@unl.edu
+1 402 472 1506
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Table B-1. Database Template for Global Maize N Model Development: Required Variables
Variables Name
Unit
Category
Description
Year
Required
Year of experiment
SiteName
Required
Name of experiment site or nearest weather station
Soil
Required
Soil series
Longitude
Required
Site longitude
Latitude
Required
Site latitude
Texture
Required
Soil texture class
Required*
Depth of water table. *Required for the rainfed fields
CV_Type
Required
Cultivar type: open-pollinated or hybrid
CV_Name
Required
Name of the cultivar used
General Site Information
WTDepth
m
Management Information
PlantingDate
dd-mm
Required
Date of planting
MaturityDate
dd-mm
Required
Date of physiological maturity
PrevCrop
Required
Previous crop: ie: maize, soybean, drybean, rice
ResidueMgt
Required
Tillage
Required
Previous crop residue management: all retained, partially
retained, all removed, or burned.
Tillage management: ie. conventional, ridge tillage, notill
WaterMgt
Required
Water management: specify whether irrigated or rainfed
IrrAmt
mm
Required*
FN
kg N ha-1
Required*
Total amount of irrigation for the growing season. *Required if
irrigated
N rate. *Required when including fertilizer N treatments
PPD
plants ha-1
Required
Plant population density
Required*
NSource
Required*
Type of N fertilizer. *Required when including fertilizer N
treatments
Amount of N applied early (ie: fall application in northern
hemisphere). *Required if applicable
Amount of N applied pre-plant (ie: spring application in
northern hemisphere). *Required if applicable
Amount of N applied as split application (first split). *Required
if applicable
Amount of N applied as split application (second split).
*Required if applicable
Amount of N applied as split application (third plus the rest of
the splits). *Required if applicable
Amount of manure applied. *Required if applicable
ManureType
Required*
Type of manure applied. *Required if applicable
ManureYear
Required*
Year of manure applied (current, second year since applied, or
>= 2 year since applied). *Required if applicable
Required
Grain yield, 15.5% moisture. The minimum input requirement
for a database must include the yield without applied N (Y0).
NAmtEarly
kg ha-1
Required*
NAmtPrePlant
kg ha-1
Required*
NAmtSplit1
kg ha-1
Required*
NAmtSplit2
kg ha-1
Required*
NAmtSplit3p
kg ha-1
Required*
ManureAmt
kg ha-1
Plant information
Y
12/6/2008
Mg ha-1
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Table B-2. Database Template for Global Maize N Model Development (Optional Variables)
Variables Name
Unit
Category Description
General Site Information
Altitude
m
Optional Site altitude
Weather
Optional Weather information may be provided (at least
containing average daily temperature and rainfall) or
simply provide weather data containing
temperature and rainfall data during the growing. If
available historical weather will also be useful.
Management Information
CV_Maturity
days
CV_GDD
deg days
HarvestDate
dd-mm
FP
kg P ha-1
FK
kg K ha-1
Optional
Optional
Optional
Optional
Optional
Maturity days of the cultivar used
GDD (planting to maturity) of the cultivar used
Date of harvest
P rate (elemental P)
K rate (elemental K)
Plant information
GDM
TDM
HI
UN
UP
UK
Optional
Optional
Optional
Optional
Optional
Optional
Grain dry matter
Total above ground dry matter
Harvest index
Total N uptake
Total P uptake
Total K uptake
Mg ha-1
Mg ha-1
kg ha-1
kg ha-1
kg ha-1
Soil Information
Clay
%
Silt
%
Sand
%
SOM
%
pH
Bray_P
Olsen_P
K_Exc
NO3-N
mg P kg soil 1
mg P kg soil-1
mg K kg soil-1
mg N kg soil-1
BD
g cm-3
12/6/2008
Optional* Clay content, 0-20 cm. *Alternatively provide soil
texture classification of the profile
Optional* Silt content, 0-20 cm. *Alternatively provide soil
texture classification of the profile
Optional* Sand content, 0-20 cm. *Alternatively provide soil
texture classification of the profile
Optional Soil organic matter, 0-8" depth (0-20 cm), or soil
organic C, specify the method
Optional Soil pH, 0-8" depth (0-20 cm), water-based
Optional Bray-1 P, 0-8" depth (0-20 cm)
Optional
Optional
Optional
Optional
Olsen P, 0-8" depth (0-20 cm)
Available K, 0-8" depth (0-20 cm)
Residual soil nitrate N before planting, specify
sampling depth
Soil bulk density, 0-8" (0-20 cm)
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12/6/2008
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