4R Nutrient Management Study Guide

Performance Objective 3
Discuss the use of NMAN software to calculate the total amount of manure
produced in a year by an operation.

NMAN is a software tool, developed by OMAFRA, you can use to determine the best way to store,
treat and use materials, such as manure, on your farm. NMAN is organized in a series of linked
sections called worksheets. The MSTOR worksheet in the program will help you to estimate the volume
of manure generated on a farm and the resulting amount of storage needed. This worksheet allows
you to include other materials, such as milking centre wash water, silo seepage and treatments such as
anaerobic digesters.

NMAN uses basic information about manure production from the Nutrient Management Tables but also
adjusts the values based on inputs including livestock weight, bedding amount and dry matter content
of the manure, if the user enters other than the default values. NMAN can also override the manure
type produced, if desired.

For instance, based on the Table 1 excerpts under P.O. 1, 120 beef backgrounders in a confinement
system at an average weight of 308kg and 90% utilization will produce approximately 733 m3 per year:

120 cattle * 0.90 utilization * 308kg /1000kg * 0.0604 m3 1000kg/day * 365 days/year = 733 m3

Additional details regarding NMAN can be found on the OMAFRA website:
http://www.omafra.gov.on.ca/english/nm/nman/agrisuite.htm

Performance Objective 4
Discuss why it is necessary to build up a set of manure nutrient tests in order to
develop reliable average values for a particular operation that can eventually be
substituted for published values.

Fertilizer adjustments based on a manure analysis will be more accurate than those based on average
values. Manure analysis is necessary because the quantities of nutrients contained in manure will vary
from farm to farm, especially the phosphorus and potash components. The type of livestock, feeding
ration, bedding, added liquids and storage system all affect the final nutrient analysis. Phosphorus
tends to be concentrated in the solids, while potassium levels tend to be higher in the liquid portion,
therefore the level of agitation will affect nutrient levels being applied to a field.

Even within the same farm, manure is inherently variable depending on the growth stage of the
animals, changes in rations, amount of dilution, etc. Grab samples represent a snapshot of the
manure within the storage. Depending on how variable the manure is and how carefully the sample is
homogenized before sub-sampling, they will vary from one sampling period to the next.

As more samples are collected, an average value will emerge that reflects the most likely value for the
manure in storage. For even greater accuracy, you can segregate the samples from different sampling
periods. For example, you could group all of the spring samples together and all the fall samples in a
different group. The averages would reflect the differences in feeding regimes and dilution of the manure.

PROFICIENCY AREA V - Manure Management 151

Performance Objective 5
Calculate the total nitrogen, phosphorus and potassium in the manure produced by
an operation in a year using published or test values of manure nutrients.

Total yearly nutrient production for an operation can be calculated by assessing the nutrient content in
a given volume of manure and then multiplying that amount by the total estimated manure production
on the operation. Nutrient content of manure can be estimated from the manure databank in NMAN
or from the summary chart shown in Table 5.2 (below). The nutrient content of manure can also be
determined by laboratory analysis of a representative sample, which is the preferred method to ensure
the most accurate nutrient values are used.

In the example shown for Performance Objective 3, NMAN calculates that the 733m3 of manure produced
yearly by 120 beef backgrounders has a fresh mass of 631 tonnes. Table 5.2 gives an average total N
concentration of 0.73% for solid beef manure. Therefore the beef backgrounders on the operation produce
about 4.6 tonnes of total nitrogen in their manure. Note that using NMAN in this scenario would be
preferable to Table 5.2 as it would adjust values for dry matter percentage and other factors.

Table 5.2. Average Nutrient Analysis of Livestock Manures

Manure (# of Dry Total NH4-N P2 K Ca Mg S Zn Cu Mn
Type Samples) Matter N1 % ppm ppm
Fresh Weight Basis ppm
% %% %%%% 22
-
Liquid 3.8 0.40 0.265 0.13 0.17 0.12 0.06 0.06 85 30 64
(924) 204
Swine 40
Solid 107
(54) 29.8 0.90 0.258 0.47 0.56 - - 0.14 172 103 61
112
Liquid 10.6 0.83 0.558 0.3 0.3 1.6 0.08 0.08 70 11 140
(137) 33 113
Poultry
Solid
(623) 52.6 2.37 0.550 1.11 1.17 4.6 0.28 0.16 238

Liquid 8.5 0.36 0.153 0.09 0.24 0.49 0.14 0.04 48 17
(860) 29
Dairy
Solid
(150) 24.2 0.61 0.128 0.17 0.50 1.54 0.36 0.08 95

Beef Liquid 7.95 0.52 0.179 0.13 0.43 0.7 0.3 0.04 57 14
(81) 28.6 0.73 0.101 0.23 0.57 1.5 0.41 0.09 129 36

Solid
(176)

Sheep Solid 31.3 0.76 0.186 0.27 0.7 1.5 0.38 n/a3 170 20
(54)

Horses Solid 33.41 0.42 0.068 0.13 0.36 1.7 0.56 n/a3 73 23
(32)

Data from manure analysis provided from Ontario Labs collected between 1992 and 2004. Micro nutrient data is obtained from a smaller subset of data. Micronutrient
concentration is highly dependent on animal diet, so will vary widely between farms.
1 Total N = Ammonium-N + Organic N
2 %P = total phosphorus
3 n/a = data not available

Chart source: Soil Fertility Handbook, Publication 611, 2006, p.101.

152 PROFICIENCY AREA V - Manure Management

Performance Objective 6
Use record keeping to measure
the total manure produced by
an operation in a year.

In addition to the standard financial and
production records, it is important to keep
track of the manure production on the farm. It
will allow validation of estimated application
rates, provide better accounting for nutrient
credits from applied manure (when combined
with manure analysis), and provide early
warning of leaks from storage.

There are several Tables provided in this Manure Sample Ready to Submit to Lab. Courtesy Christine Brown

chapter that illustrate the standard nutrient

analyses of manure, how to calculate the available nutrients, and what constitutes a nutrient unit. Other

information that should be documented includes:

• manure test analysis if available;

• the type and age/stage of production of livestock/poultry;

• field identification for application (where, when and how much manure applied);

• method of application;

• commercial fertilizer applied;

• soil and weather conditions at time of application;

• crop grown;

• crop yield;

• soil test data; and,

• volume of any manure that was sold.

Taking a Manure Sample. Courtesy Christine Brown

PROFICIENCY AREA V - Manure Management 153

Competency Area 2
Adequacy of the Land Base for Applying Manure

Performance Objective 7
Use the Phosphorus Index to assess the risk of loss of phosphorus from a field and
how it may exclude some fields from receiving manure and/or require setbacks.

The Phosphorus Index is an indicator of the risk of surface water enrichment with P from runoff. It takes
into account proximity to water, land management and erosion potential as well as P soil test and
fertilization to assess risk.
The P Index considers many factors, such as the conditions of a field (phosphorus levels in the soil,
soil erosion and soil runoff risk), the quantity of nutrients to be applied along with their methods of
application, and the distance to the nearest surface water.
The P Index assigns a number - 0, 1, 2, 4, 8 or 16 - to each of the conditions which can affect
phosphorus losses, where 0 is the lowest P loss potential and 16 is the highest P loss potential. This is
completed according to the probability of P loss from the site. Furthermore, each site characteristic is
assigned a weighting factor that indicates the seriousness of the P loss potential of that individual site
characteristic. All of the weighted conditions are added together to obtain the P Index.
Current agricultural nutrient management best management practices indicate that a Phosphorus Index
should be determined if the P soil test for a particular field is above 30 ppm. A Phosphorus Index can
still be calculated if the P soil test is below 30 ppm if the farmer feels it is necessary for management
information.
The P Index can impact a nutrient management plan in two separate ways:

• Sets minimum separation distances for nutrient application close to surface water.
• Determines maximum phosphorus application rates in vicinity of surface water.
See also Proficiency Area 3: Phosphorus, Performance Objective 21. For details on calculating a
P Index, refer to OMAFRA Factsheet 05-067, Determining the Phosphorus Index for a Field,
August 2015.

154 PROFICIENCY AREA V - Manure Management

Performance Objective 8
Evaluate the adequacy of the cropland available for spreading manure by
comparing the total annual manure production to the land base.

A number of factors must be considered in order to determine the land base capacity to safely receive
manure. The first step should be to calculate the total N and P generated on the farm (see P.O. 5).
Second, calculate the total land area available to receive nutrients (total farmland minus setback areas
laid out in factor 4 below). Calculate the total nutrient requirements of the crops grown on that land
and the total crop removal. If the manure N or P is greater than the largest of these (requirements or
removal) then there is excess manure.

The OMAFRA computer software program NMAN and corresponding workbook (OMAFRA Publication
818) are tools that help farmers determine values for each of the following factors.

Factor 1: Nutrient Value of Manure to be Applied
The nutrient value of manure varies greatly from one operation to the next. The best way to determine
the nutrient value is to have it analyzed by an accredited lab for N, P and K and dry matter content.
Take liquid manure samples from an agitated tank to obtain an accurate estimate of nutrients. For a
representative solid manure sample, take samples from several locations of a pile. Average manure
nutrient concentrations for a range of livestock types are found in NMAN.

Alternatively, you can create a rough estimation of the nutrient value of the manure produced by
calculating the total Nutrient Units being generated on the farm based on livestock numbers (see Table
5.3). The total Nutrient Units will give you an estimation of the fertilizer replacement value for both N
and P. Note that this method will yield less accurate values than testing the manure.

Table 5.3. Nutrient Unit (NU*) Designations for a Variety of Different Animal Types

Type of Livestock # animals per NU

Large frame dairy cow 0.7

Beef feeders 3

Swine- finishing pigs 6

Lamb feeders 20

Chickens- layer pullets 500

* A NU is equal to the amount of manure needed to give the fertilizer replacement value of the lower of 43 kg of N or
55 kg of P. For example, it takes the manure from 3 beef feeders to get the equivalent of 1 NU.

Factor 2: Planned Crop Rotation
The nutrient requirements of crops vary from one crop to another. The nutrient requirements of the
current crop rotation are calculated and then the extent to which manure can be applied to meet these
requirements should be assessed.

PROFICIENCY AREA V - Manure Management 155

Factor 3: Current Soil Nutrient Levels, Soil Type, and Topography of the Land Base
If soil nutrient levels are already high, nutrient additions from manure could be limited. The best way to
determine the nutrient levels in the soil is to submit a soil sample for analysis. Soil type and topography
can also limit the land base capacity for manure due to the higher risk of occurrence of contaminated
runoff from soil with low soil infiltration and steep slopes.

Factor 4: Proximity to Watercourses or other Environmentally Sensitive Areas
In order to reduce the risk of surface or well water contamination, setbacks for manure application
are used. These setbacks should be considered when calculating how much land remains for manure
application.

Manure Application Setbacks in Ontario
• 330 ft. (100 m) from municipal wells
• 50 ft. (15 m) from drilled wells (minimum depth of 20 metres and a watertight casing to a
depth of 6 metres below ground level),
• or 100 ft. (30 m) from any other well
• 10 ft. (3 m) to 200 ft. (60 m) from the bank of surface water). This setback depends on a
number of factors such as the incorporation method used, the slope near the watercourse and
the P Index value.

Competency Area 3
Crediting the Nutrients in Manure for Crop Production

Performance Objective 9
Use the availability factors for the nitrogen (current and previous applications),
phosphorus and potassium in manure (e.g. published in Agronomy Guide for
Field Crops and NMAN3).

The best way of determining the amount of each nutrient from manure is to analyze a sample.
Unfortunately, this is not always possible, as in the case of a new barn. In this case, average values will
provide an estimate of the nutrients available to the crop.

Nitrogen uptake by crops is in the mineral form as either nitrate (NO3-) or ammonium (NH4+). This
means the ammonium portion of the manure is immediately available to the crop while the organic
nitrogen needs to be mineralized before it can be used. For optimum use of the nutrients in manure,
they should be available where and when the crop can utilize them.

156 PROFICIENCY AREA V - Manure Management

Most of the phosphorus in manure is associated with the solid portion and is found in either the
orthophosphate form (PO43-) or in readily degraded organic compounds. This means that, chemically,
the phosphorus in manure does not differ greatly from the phosphorus in fertilizer. Despite this,
phosphorus from manure is assumed to be less available than fertilizer to crops in the year of
application. In Ontario, the availability of manure P, in the year of application, is assumed to be
40% that of fertilizer P. Nutrient management plans in Ontario credit 80% of the total P in the manure
towards building soil fertility. Regular soil testing is the best way to track the actual build-up of soil P in
individual fields.
Essentially all of the potassium in manure is in soluble forms and available to crops.

Ontario Agricultural Planning Tools Suite for Nutrient Management Planning. Courtesy Dale McComb

PROFICIENCY AREA V - Manure Management 157

Table 5.4. Typical Amounts of Available Nitrogen, Phosphate and Potash from Different Types of
Organic Nutrient Sources

Type D.M. Available N Available P205 Available K20
Fall1
Spring2 Spring inject3 3.2 (32)
1.7 (17)
Liquid Materials % kg/1000 L (lb/1,000 gal) 1.4 (14)
1.2 (12)
Hog finisher 7.6 3.1 (30.7) 3.8 (38.2) 4.9 (49.4) 2.1 (21) 2.6 (26)
Hog weaners 3.0 1.6 (15.8) 2.0 (19.9) 2.6 (25.7) 1.3 (13) 3.4 (34)
2.2 1.3 (12.5) 1.5 (14.8) 1.9 (18.9) 0.6 (5.5) 2.6 (26)
Hog SEW 1.9 1.3 (13.0) 1.8 (18.3) 2.4 (24.1) 0.9 (9.2) 2.0 (20)
Hog dry sows 8.4 1.4 (14.4) 1.5 (15.4) 1.9 (19.2) 0.8 (7.7) 2.3 (23)
Dairy liquid ave 14 2.0 (20.1) 2.0 (19.7) 2.4 (24.2) 1.3 (13) 3.6 (36)
Dairy 10%-18% 8.0 1.5 (14.8) 1.6 (16.2) 2.0 (20.2) 0.7 (6.9) 2.2 (22)
Dairy 6%-10% 4.4 1.0 (9.8) 1.2 (11.6) 1.5 (14.7) 0.5 (5.0) 4.6 (16)
Dairy 2%-6% 7.9 1.3 (12.7) 1.4 (13.6) 1.7 (16.9) 0.7 (7.3) 0.9 (9.2)
Beef liquid ave 15 2.0 (19.7) 1.9 (19.1) 2.3 (23.3) 1.2 (12) 16 (32)
Beef 10%-18% 7.8 1.4 (13.5) 1.5 (14.5) 1.8 (18.2) 0.7 (7.2)
Beef 6%-10% 3.8 0.9 (8.6) 1.1 (10.6) 1.4 (13.6) 0.5 (4.5) 0
Beef 2%-6% 0.7 0.2 (2.1) 0.3 (2.7) 0.4 (3.5) 0.1 (1.0) 0
Runoff 0%-2% 11 4.2 (41.8) 5.0 (49.6) 6.4 (63.5) 14 (28)
Poultry liquid ave 2 0.5 (5.0) 0.4 (4.1) 0.4 (4.4) 0.6 (5.5) Available K20
Biosolids aerobic 4.4 1.2 (11.8) 1.2 (11.8) 1.4 (13.8) 1.3 (13)
Biosolids anaerobic Available N 6.0 (12)
Spring2 5.0 (10)
Type D.M. Fall1 Spring inject3 Available P205 5.5 (11)
3.6 (7.2) 8.0 (16)
Solid Materials % 2.1 (4.2) kg/tonne (lb/ton) 5.0 (10)
2.1 (4.1) 4.7 (9.3)
Hog solid average 30 3.1 (6.1) 2.4 (4.8) 4.3 (8.6) 4.3 (8.5) 8.4 (16.7)
1.9 (3.7) 8.5 (17)
Dairy 18%-30% 21 1.7 (3.4) 1.4 (2.8) 2.4 (4.8) 1.5 (3.0) 15 (29)
3.8 (7.5) 17 (33)
Dairy 30% + 39 2.0 (3.9) 9.3 (18.6) 2.3 (4.5) 1.6 (3.1) 1.2 (2.4)
12.7 (25.3)
Beef 30% + 38 2.9 (5.7) 11.3 (22.5) 2.7 (5.3) 3.5 (6.9)
12.3 (25.6)
Beef 18%-30% 24 1.9 (3.8) 1.2 (4.2) 1.5 (3.0)

Horses average 37 1.5 (3.0) 1.6 (3.1) 1.4 (2.8)

Sheep average 34 3.2 (6.4) 4.5 (8.9) 2.6 (5.2)

Poultry layers 34 8.7 (17.4) 11.3 (22.5) 8 (16)

Poultry pullets 48 12.2 (24.5) 14.5 (28.9) 13 (25)

Poultry broilers 68 10.8 (21.6) 12.4 (24.7) 13 (25)

Biosolids dewatered 32 11.3 (22.6) 13.7 (27.3) 12 (24)

1. Late fall application or early application with cover crop.
2. Spring application incorporated within 24 hours.
3. Injection or immediate incorporation, assumes good coverage.

Chart source: Agronomy Guide for Field Crops, Publication 811, 2009, p.164.

158 PROFICIENCY AREA V - Manure Management

Worksheet for Calculating Available Nutrients from Spring-Applied Manure Using a Manure Analysis

Keep the same units throughout the calculation. Some reports will provide ammonium-N contents in ppm (mg/kg, mg/L),
while the other numbers are in percentages. The convert ppm to percentage, divide by 10,000.

Available Nitrogen1 Available Phosphate2 Available Potash2

A. Total Nitrogen H. Total Phosphorus K. Total Potassium

B. Ammonium-N I. Available Phosphorus L. Available Potassium
(H x 0.4) (K x 0.9)

C. Organic N3 J. A vailable Phosphate M. A vailable Potash
(A-B) (I x 2.29) (L x 1.2)

D. A mmonium Losses
(B x factor from Table 9-10
on page 165)

E. Available Ammonium For values in percent:
(B-D)
To get: multiply by:
F. Available Organic N
(C x factor for Table 9-11 kg/1,000 L 10
on page 166)

G. Total Available N
(E+F)4

1. Available nitrogen is determined by subtracting the ammonia losses to the air from the ammonium-N applied and adding the mineralization from the organic N
portion of the manure.

2. C alculate reductions in fertilizer phosphate and potash by determining the available portion of the total P and K in the manure (40% for phosphorus and 90%
for potassium) and multiplying by a factor to convert from elemental form to the oxide form (fertilizer nutrients are expressed in the oxide form). In the year of
application, 40% is available; another 40% is available in the follow year.

3. O rganic N will also give an N credit for several years after application: 10% in 2nd year, 5% in 3rd year, x 2% in 4th year.
4. T o estimate the available N from summer or fall applications of manure, multiply the Total N content by the appropriate factor in Table 9-12, Estimate of Available

Nitrogen from Late Summer- and Fall-Applied Manure, on page 166.

Available Nitrogen Available Phosphate Available Potash

A. Total Nitrogen 0.65 H. Total Phosphorus 0.2 K. Total Potassium 0.3
0.27
B. Ammonium-N 0.35 I. A vailable Phosphorus 0.08 L. Available Potassium 0.32
(0.2 x 0.4) (0.3 x 0.9)
32
C. O rganic N 0.30 J. Available Phosphate 0.18 M. A vailable Potash
(0.65 – 0.35) (0.08 x 2.29) (0.27 x 1.2)

D. A mmonium Losses 0.13
(0.35 x 0.38)

E. Available Ammonium 0.22
(0.35 – 0.13)

F. Available Organic N 0.06
(0.30 x 0.20)

G. T otal Available N 0.28
(0.22+0.06)

Nutrients lb/1,000 gallons 28 18

An electronic version of this worksheet can be found in the OMAFRA NMAN software or as a spreadsheet at www.gocorn.net.

Worksheet source: Agronomy Guide for Field Crops, Publication 811, 2009, p.168.

PROFICIENCY AREA V - Manure Management 159

Performance Objective 10
Describe how to credit the phosphorus and potassium in manure for the crop
requirements recommended by soil tests using the nutrient recommendations of the
Ontario Soil Management Research and Services Committee (OSMRSC) and how
to adjust manure spreading rates accordingly for each field.

Table 5.5: Calculating Available Phosphorus and Potassium from Manure

Most labs in Ontario report the raempoourtnetdoafsav%aiPlaabnledP%2OK5 .anIfdthKi2sOofcrocmursm, yaonuurwe,ilbl ut
occasionally you see a sample

have to convert the figures to match the units of the fertilizer recommendation.

Total P to available P2O5
% P x 2.29 = % total P2O5
% total P2O5 x 0.40 = % available P2O5 in application year
% total P2O5 x 0.80 = % available P2O5 for soil build-up

Total K to available K2O
% K x 1.20 = % total K2O
% total K2O x 0.90 = % available K2O

Chart source: Soil Fertility Handbook, Publication 611, 2006, p.107

Table 5.6: Conversion from Percent to Units of Weight

% available nutrient to unit of weight
% available nutrient x 10 = kg/t
% available nutrient x 20 = lb/ton

% available nutrient x 10 = kg/1,000 L = kg/m3
% available nutrient x 100 = lb/1,000 gal (Imperial)

Chart source: Soil Fertility Handbook, Publication 611, 2006, p.107

The long-term availability of phosphorus
(P), potassium (K), magnesium, zinc
or manganese from previous manure
applications is best estimated by soil
testing. Application of large quantities of
manure over time can result in high levels of
available P and K in soils.

Manure Application. Courtesy Christine Brown
160 PROFICIENCY AREA V - Manure Management

Performance Objective 11
Evaluate the strengths and weaknesses of each tool listed below and the situations
in which it is appropriate to use each tool:

a. pre-plant soil nitrate test (PPNT);
b. pre-sidedress soil nitrate test (PSNT);
c. chlorophyll meter;
d. post-season stalk nitrate.

Pre-plant Soil Nitrate Test (PPNT)
The pre-plant test measures the amount of residual or carryover nitrate in the root zone before planting.
The pre-plant test allows farmers to adjust nitrogen applications to meet the needs of each specific field.
Cropping sequence significantly affects the amount of nitrogen in the soil available to corn. The pre-
plant test is most useful in continuous corn, second-year corn fields, and fields with a history of manure
applications.

The pre-plant test is most useful on medium- or heavy-textured soils and during years when precipitation
is normal or below normal. Below normal precipitation in autumn and winter leads to higher spring
pre-plant soil nitrate levels.

The pre-plant nitrate test does not measure nitrogen from manure applied or alfalfa plowed down the current
spring. Therefore, the test may not reflect all the nitrogen available to first-year corn grown after alfalfa.

Only corn and spring barley have a PPNT soil test calibration.

Pre-Sidedress Soil Nitrate Test (PSNT)
Sampling when the corn is 15-30 cm (6-12 in.) tall, before the application of sidedress nitrogen,
has increased in popularity. This is referred to as the pre-sidedress nitrogen test (PSNT). By delaying
sampling past the busy planting season, the PSNT allows more time for sampling and receiving results
from the laboratory. More importantly, considerable evidence indicates that nitrogen recommendations
based on this later sampling time are superior to those based on a planting time sample. This is
particularly true when there are organic sources of nitrogen, such as manure or legumes, in the
cropping system.

Sometimes the fertilizer recommendations based on the nitrate-nitrogen soil test need to be modified.
The nitrogen in manure or legumes applied or plowed down just before sampling will not have
converted into nitrates and will not be detected by the soil test. Information will be provided with the
test results on how to make appropriate adjustments.

The nitrate-nitrogen soil test has not been adequately evaluated for:
• legumes or manure plowed down in the late summer or fall;
• legumes in a no-till system; and,
• s oil samples taken prior to planting before the soil has warmed up significantly
(i.e. in mid- to late April)

In these circumstances, use the nitrate-nitrogen soil test with caution. Only corn has a PSNT calibration.

PROFICIENCY AREA V - Manure Management 161

Chlorophyll Meter
Nitrogen is closely associated with leaf chlorophyll; thus, chlorophyll-meter readings of corn leaves
provide information about the N status of the corn plants. The early season chlorophyll meter test
consists of taking meter readings of corn leaves when plants are between the six- and eight-leaf stages
(when plants are about 10 to 20 inches tall), which allows time to sidedress if necessary.

Currently, two methods exist for using the chlorophyll meter in corn. The preferred method is to establish
a high-N reference plot that has been adequately fertilized with N fertilizer early in the season in each
field to be tested. Readings are taken from this reference area and the rest of the field. Additional N is
required for optimum corn yield if the average meter reading of the field is less than 95% of the high-N
reference value.

Fields that have a history of manure application or the first year after forage legume (alfalfa, alfalfa/
grass, clover) do not require the establishment of a high-N reference plot. An alternate method is
to take readings at the six-leaf stage and, if the readings are very high (>46), no sidedress N is
recommended. If the readings are very low (<42), a sidedress N recommendation can be made using
the meter reading and other field information. For fields where the readings fall between very high and
very low, a second reading is taken a week later to determine if and how much sidedress N is needed.

Advantages of the early season chlorophyll meter test:
• Chlorophyll meter readings are quick, easy, and provide instantaneous values.
• No samples need to be collected, processed, and sent to a laboratory for analysis.
• Cost of sampling involves only labor costs.
• Nitrogen recommendations are accurate (comparable to the pre-sidedress soil nitrate test).

Disadvantages of the early season chlorophyll meter test:
• Initial expense is high (the meter costs about $1,500).
• E arly season corn leaf chlorophyll levels are affected by hybrid characteristics and
environmental stresses; therefore, for best results, establish high-N reference plots.
• T his test is not applicable to fields that have received a pre-plant or an at-plant N fertilizer
application beyond about 15 pounds per acre of starter N.

Post-season Stalk Nitrate
The post-season stalk nitrate test allows growers to conduct a “post-mortem” evaluation of the adequacy
of their nitrogen program for the current growing season. The test is described as “post-mortem”
because stalk samples are taken after the grain is physiologically mature. Given that this is a very late
season test, the interpretation of the results offers no assistance in fine-tuning nitrogen management for
the current year, but rather provides insight into N management options for coming years.

The basis for the test lies in the fact that corn plants deficient for nitrogen will usually remobilize stored
N from the lower portions of the stalk and leaves to the developing grain; resulting in lower stalk
nitrogen concentrations at the end of the season. Plants that take up excessive amounts of soil nitrogen
(more than is needed for maximum yields) will store excessive amounts in the lower stalk sections by the
end of the growing season; resulting in higher stalk nitrogen concentrations.

The stalk nitrate test is probably best suited for identifying fields/situations where soil nitrogen uptake was
excessive (no yield benefit) and, thus, costly to the grower and possibly the environment. Typical situations
where N uptake may be excessive include manured fields or fields following alfalfa that received
additional (and possibly unnecessary) nitrogen fertilizer applications for the subsequent corn crop.

162 PROFICIENCY AREA V - Manure Management

REFERENCES

4R Nutrient Stewardship, Split Fertilizer Application Helps Optimize Nutrient Management, retrieved
from: http://www.nutrientstewardship.com/implement-4rs/article/split-fertilizer-application-helps-
optimize-nutrient-management#print.

Bagg, J., Sulphur on Alfalfa, Ontario Ministry of Agriculture, Food and Rural Affairs, 2014.

Ball, B., Ball, B., Validating Sulphur Rates and Sources for Alfalfa in Ontario, Ontario Ministry of
Agriculture, Food and Rural Affairs, 2014.

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