Nutrient Management Plan for Organic Systems: Idaho Implementation Guide

This document is an instruction guide for creating and implementing a nutrient management plan (NMP) on certified or transitioning organic lands. An NMP for organically managed lands describes the amount, source, placement, form, and timing of the application of nutrients and soil amendments, generally by field, to meet crop nutrient needs while protecting water quality, improving soil health, and utilizing manure and other organically acceptable byproducts as nutrient sources.

Nutrient Management Plan (590) for

Organic Systems

Idaho Implementation Guide

June 2014
National Center for
Appropriate Technology (NCAT)
Oregon Tilth

Purpose and Objectives……………………………………………. 3
Relevant National Organic Standards……………………. 4
Section 1.
Determining Crop Need for
Nitrogen, Phosphorus, and Potassium…………………… 5
Section 2.
Developing Nutrient Credits……………………………………. 6
Section 3.
Determining Nutrient Application Rates………………. 10
Section 4.
Evaluating Risk of Leaching and Runoff……………….. 12
Section 5.
Calculating Nutrient Application Rates
Based on Risk Analysis…………………………………………….. 13
Appendix A.
Tables…………………………………………………………………………. 14
Appendix B.
Conversion Tables…………………………………………………….20
Appendix C.
References to NRCS Publications
and Other Resources………………………………………………..22

Figure 2. Six-foot-tall fava bean cover crop, Fong Farms,
Woodland, California 2006.

Funded by
a grant from
Research and

Appendix D.
Implementation Requirement Worksheet……………25

Copyright © NCAT and Oregon Tilth 2014

Authors Rex Dufour (National Center for Appropriate Technology), Sarah Brown (Oregon Tilth), and
Denise Troxell (Natural Resources Conservation Service)
Contributors and Reviewers Ben Bowell and Carrie Sendak (Oregon Tilth); Nick Andrews (Oregon State
University); Dennis Chessman, Rich Fasching, Giulio Ferruzzi and Dick Johnson (NRCS); and Jennifer Miller
(Northwest Center for Alternatives to Pesticides)
We thank Dan Sullivan, Extension Soil Scientist, Oregon State University for assistance in presenting methods
for estimating plant-available N release from organic inputs.
Editing and layout Karen Van Epen (NCAT), Robyn Metzger (NCAT)
All photos Rex Dufour (NCAT) unless otherwise noted.
Figure 1. (On front cover) A farmer evaluates soil organic matter. Photo: David Lamm (NRCS)
For more information or questions, contact Ben Bowell at or 503-580-4767

Nutrient Management Plan (590) for Organic Systems

Implementation Guide
Purpose and Objectives
This document is an instruction guide
for creating and implementing a
nutrient management plan (NMP)
on certified or transitioning organic
An NMP for organically managed
lands describes the amount, source,
placement, form, and timing of the
application of nutrients and soil
amendments, generally by field, to
meet crop nutrient needs while
protecting water quality, improving
soil health, and utilizing manure
and other organically acceptable
byproducts as nutrient sources.
Developing an NMP entails:

Figure 3. Cover crop mix of rye and phacilia. Photo: Ben Bowell (Oregon Tilth)

1) Determining a crop’s need for
nitrogen, phosphorus, potassium, and other
nutrients as appropriate
2) Crediting all significant sources of nutrients
in the system such as the nitrogen contribution
of cover crops, the mineralization of nitrogen
based on input history (previous years’ manure/
organic byproducts applications), and any nitrate
that may be contained in irrigation water

3) Determining the target nutrient application rate
(the difference between the crop need and the
nutrient credits)
4) Evaluating likelihood of nutrients moving past
the edge of a field or below the root zone (leaching
and runoff)
5) Calculating the appropriate rate of manure/ organic
product application based on this risk


☞ This icon indicates you should fill in data on the Implementation Requirement Worksheet in
Appendix D, pages 25-29. Alternatively, you may use your state’s NM planning tool to enter the
crops grown.

☞ In the Field and Crop Information section, list the crops in the order they are grown. Check
the box for the current crop. Make additional copies of the form as needed.


Relevant National Organic Program (NOP) Regulations
National Organic Program (NOP) regulations section 205.203 should be referenced when assessing nutrient
management in organic systems. The entire NOP regulations, as well as lists of approved and prohibited materials
and other information can be found at the NOP website:

Section 205.203 Soil Fertility and Crop Nutrient Management Practice Standard
(a) The producer must select and implement tillage
and cultivation practices that maintain or improve
the physical, chemical, and biological condition of soil
and minimize soil erosion.
(b) The producer must manage crop nutrients and
soil fertility through rotations, cover crops, and the
application of plant and animal materials.
(c) The producer must manage plant and animal
materials to maintain or improve soil organic matter
content in a manner that does not contribute to contamination of crops, soil, or water by plant nutrients,
pathogenic organisms, heavy metals, or residues of
prohibited substances. Animal and plant materials
(1) Raw animal manure, which must be composted unless it is:
(i) Applied to land used for a crop not intended for human consumption;
(ii) Incorporated into the soil not less than 120
days prior to the harvest of a product whose
edible portion has direct contact with the soil
surface or soil particles; or
(iii) Incorporated into the soil not less than 90
days prior to the harvest of a product whose
edible portion does not have direct contact
with the soil surface or soil particles;
(2) Composted plant and animal materials produced through a process that:
(i) Established an initial C:N ratio of between
25:1 and 40:1; and
(ii) Maintained a temperature of between 131
°F and 170 °F for 3 days using an in-vessel or
static aerated pile system; or
(iii) Maintained a temperature of between
131 °F and 170 °F for 15 days using a windrow
composting system, during which period,
the materials must be turned a minimum of
five times.
(3) Uncomposted plant materials.


(d) A producer may manage crop nutrients and soil
fertility to maintain or improve soil organic matter
content in a manner that does not contribute to contamination of crops, soil, or water by plant nutrients,
pathogenic organisms, heavy metals, or residues of
prohibited substances by applying:
(1) A crop nutrient or soil amendment included on
the National List of synthetic substances allowed
for use in organic crop production;
(2) A mined substance of low solubility;
(3) A mined substance of high solubility: Provided,
That, the substance is used in compliance with the
conditions established on the National List of nonsynthetic materials prohibited for crop production;
(4) Ash obtained from the burning of a plant or
animal material, except as prohibited in paragraph
(e) of this section: Provided, That, the material
burned has not been treated or combined with a
prohibited substance or the ash is not included on
the National List of nonsynthetic substances prohibited for use in organic crop production; and
(5) A plant or animal material that has been chemically altered by a manufacturing process: Provided,
That, the material is included on the National List
of synthetic substances allowed for use in organic
crop production established in § 205.601.
(e) The producer must not use:
(1) Any fertilizer or composted plant and animal
material that contains a synthetic substance not included on the National List of synthetic substances
allowed for use in organic crop production;
(2) Sewage sludge (biosolids) as defined in 40 CFR
part 503; and
(3) Burning as a means of disposal for crop residues
produced on the operation: Except, That, burning
may be used to suppress the spread of disease or
to stimulate seed germination.

Section 1.
Determining Crop Need for Nitrogen, Phosphorus, and Potassium
This section outlines the process and resources to be used
to calculate the demand of a particular crop for N, P, K,
and other nutrients. Sources of information about crop
nutrient needs can be found in Appendix C, Section 1.
It is common for organic farms to grow many different
crops on relatively small acreages and for soil texture
to vary across the farm. In order to develop a practical
nutrient management plan for small plot acreages, it
may be helpful to work with the grower to develop
groupings of crops that have similar growth habits and
nutrient needs, and manage the grouping’s nutrient
needs as a single entity. Crop rotations are required in
organic systems. Growers should have a crop rotation
plan as part of their organic system plan.
Additional information to guide soil sampling strategies
and crop rotations on diverse organic vegetable farms
can be found in Appendix C, Section 1. Some possible
groupings include:
➢ Nitrogen Needs (Ideal): Low/Medium/High N.
See Table 1.
➢ Plant Family: For example, all solanaceous or all
brassica crops
➢ Timing: Early season, mid-season, and late
season plantings. Timing will impact nutrient
availability from soil N mineralization. Early
season crops will be unlikely to pull much from
the soil and should be fertilized accordingly.
➢ Crop Growth: Short-season crops, long-season crops
➢ Crop Type: Grains, legumes, vegetables, fruits
➢ Other: Growers also take other considerations into
account such as irrigation system layout, pest cycles,
and soil type.

Table 1. Nitrogen requirement of vegetable
crops based on seasonal nitrogen uptake
Low Total
Medium Total
N Need
N Need
<120 lb/acre <120-200 lb/acre Baby greens Carrot Beans Corn, Sweet Cucumbers Garlic Radish Lettuce Spinach Melons Squashes Onion Peppers Tomatoes High Total N Need >200 lb/acre

— Gaskell et al. 2006, Soil Fertility Management for
Organic Crops

Western states grow a great variety of specialty crops.
Your state cooperative extension has horticulturists and
agronomists who can point you in the right direction
for informational resources about the nutrient needs of
less commonly planted crops. Some specialty crops may
require higher amounts of particular micronutrients,
which if not present will limit quality and yields. Other
crops may be more sensitive to excess micronutrients, such
as citrus sensitivity to boron. If no University recommendations are available for a crop, an acceptable strategy is
to balance N, P and K applied with N, P and K expected
to be removed by the crop.

☞ Enter crop nutrient requirements and yields

under Recommended Nutrients to Meet Yield.

Resources for Nutrient Requirements of Crops
Idaho Cooperative Extension and Idaho Nutrient
NRCS Crop Nutrient Tool:

NRCS Agricultural Waste Management Field
Handbook provides data on N, P and K content of a
wide variety of crops.

Oregon State University Fertilizer/Nutrient
Management Guidelines for Crops:


Section 2.
Developing Nutrient Credits
This section outlines some methods to calculate the
nutrient contributions of:
➣ Soil Organic Matter (SOM) N mineralization
➣ Cover crops
➣ Organic amendments such as manure, compost,
and some specialty fertilizers
The input history of a field is valuable, because many
sources of organic N continue to mineralize over several
years. As part of their organic recordkeeping requirements, organic farmers will have records of their soil
fertility inputs, as well as yield data, and these can help
to make a more comprehensive nutrient management
plan. Transitioning farmers may have no records if they
are early in their transition. Recent soil test information
will provide information about what is present in the
soil. Sources of information about organically acceptable
fertilizers can be found in Appendix A, Tables 4, 5, and 6.

in soil with high P and K concentrations usually do not
respond to P and K fertilizers. When large amounts of
crop biomass are removed at harvest (i.e., alfalfa, or corn
silage) significant amounts of P and K are removed from
the soil. Other crops such as raspberries or blackberries
do not remove large amounts of P and K.

Soil Test Information and Resources

Soil test and leaf test results taken at different times of
year provide valuable data for monitoring the performance
of nutrient management plans. This is especially useful
for refining N fertilizer rates. Pre-Side-dress Nitrate Tests
(PSNTs) can ensure a grower that N levels are sufficient
for the crop. PSNTs are generally done in the late spring
and allow the grower to respond to early spring weather
conditions that impact N mineralization. End-of-season
soil nitrate tests can determine whether N fertilizer rates
were higher than necessary. In most perennial crops, leaf
tests are used to determine crop nutrient status. These
naturally incorporate non-fertilizer nutrients taken up by
the crop.
Mineralization from “native” SOM is generally not
included in NRCS nutrient management plans because
land-grant university recommendations for N fertilizer
application rate assume typical soil N mineralization
already (under conventional management). However
under long-term management with consistently high
organic-N inputs, soil N mineralization may supply a
significant portion of crop N needs.
P and K should be managed by soil tests and attention
to P and K removal through harvest of crop biomass.
P and K fertilization decisions typically do not require
consideration of target yield for the crop. Crops grown

Soil test results can come in either text or graphical
formats. Discuss with the producer which format is
preferred. University nutrient management guides
provide more accurate crop-specific sufficiency levels
than general ranges. Refer to your state’s Conservation
Practice Standard 590 for the required soil tests. A
listing of accredited (NAPT-PAP certified labs) soil
testing labs can be accessed at: www.naptprogram.
org/pap/labs. Tests of plant tissue, water and organic
materials must be conducted by labs that are certified by
organizations noted in the state’s 590 practice standard.
Enter soil test results under the Soil Test
Information section.

Nitrogen (N)
Nitrogen in organic systems is often tied up in organic
matter, and not in a form that is immediately available
to plants. Most organically acceptable sources of N have
lower N concentrations than chemical fertilizers, and
typically release less of their total N in the first cropping
season. In contrast, PAN for chemical fertilizers such as
urea, ammonium sulfate, and others, is 100%. That is,
the N is available to the plant shortly after application as
either nitrate (NO3 —this is the form most plants take
up N), or ammonium (NH4+). Possible sources of N for
organic systems include compost, manures, cover crops,
organic matter mineralization, organic approved fertilizers (fish meal, feather meal, etc.), and irrigation water.
In some locations, irrigation water can have significant
levels of nitrates, so it’s a good idea to have the irrigation
water tested. The nitrate contribution from irrigation water
should be taken into account when developing nutrient budgets, but there are many variables to consider:
uptake by plant, irrigation water going beyond root
system, and nitrate variability in water during the season.
Table 12 provides conversions to calculate parts per
million to lbs/acre inch.

PAN Plant-Available Nitrogen —
Nutrient Source: Soil N Mineralization
This is the process whereby the stock of N that is “stored”
in SOM decomposes to release plant-available nitrogen
(PAN). Because organic farmers typically apply more
organic matter than conventional farmers, PAN provided
by soil N mineralization generally increases under organic
management. The most recent organic inputs have the
most influence on PAN release from soil organic matter.
Most University nutrient management guides account for
some background soil N mineralization, but not usually
the high levels often found on established organic farms.
The potential rate of soil N mineralization is a function of
temperature, tillage, type of soil, and other factors. Any
figures developed for PAN from soil N mineralization
must be considered approximate.
While organic growers are required to record applications
of materials, they might not have the nutrient analyses
they need to do a calculation. Approximate numbers can
be used in this situation.

How to Estimate Soil N Mineralization
1. Organic amendments (composts, manure, cover
crops, fertilizers, etc.) applied to the soil will continue
to provide PAN in subsequent years, but in ever-smaller
quantities. Organic fertilizers such as blood meal,
and feather meal, which are higher in N, will provide
roughly 75% of their N in the first year and up to 50%
of their N within a week of application (Gaskell, 2007).
Assuming some materials have been applied, first calculate total N application per year. To determine the PAN
for the current year, refer to Tables 7-9. The estimation
rule for PAN available in years 1, 2, and 3 post-application
are 8%, 5%, and 3% of total N applied, respectively. See
Table 2, below. Although a soil with more organic matter contains more total N, SOM levels are not a good

indicator of PAN as soil temperature, moisture, and
many other soil management factors are not considered.
Laboratories that estimate PAN based on SOM typically
do not have calibration data to support their estimates
(Horneck, 2011).
2. If previous organic input history is not available,
then credit 50 lbs N/acre if the field received substantial
organic inputs (i.e. cover crops and manure or compost)
for at least three consecutive years.

PAN Plant-Available Nitrogen —
Nutrient Source: Manures and Compost
To determine PAN from manure and compost products
you must first analyze the nitrogen content. Table 7,
Appendix A, based on Oregon State University’s Organic
Fertilizer and Cover Crop Calculator (Andrews, et al.),
identifies the PAN % or pounds after four weeks for
manure, compost, and other organic amendments. In
Idaho, the University of Idaho Cover Crop Calculator is
available and applicable for southern regions of the state
In order to obtain the full N benefits of manure,
applications should be incorporated immediately.
Significant amounts of ammonia-N can be lost within
one to two days of application through volatilization
(see Table 5 Appendix A). Significant amounts of N may
also be lost if manure is applied too far in advance of the
period of rapid N uptake by the crop, even if the manure
is incorporated. For fall manure applications, up to
half of the N may be lost by the time of greatest crop
demand the following year (Magdoff, 2009).
Poultry litter is a popular organic amendment because of
high N and P levels, but it may be high in arsenic, copper
and zinc due to additives in their feed. Analysis of poultry
litter should include Zn, Cu, and As to ensure that soil is
not being contaminated.

Table 2. PAN Credits.
PAN, Percent of Total N
(general rule)
45% x total N lbs/acre
8% x total N lbs/acre
5% x total N lbs/acre
3% x total N lbs/acre

Years After
current year

Manure and Compost
Refer to page 4 for additional National Organic Program
regulations related to the use of manure and compost on
organic farms. It should also be noted that manure and
compost inputs from non-organic sources are allowed as
long as there is no risk of contamination.


PAN Plant-Available Nitrogen —
Nutrient Source: Cover Crops
Cover crops and green manures provide both nitrogen
and organic matter to the soil. The amount of N and
organic matter provided will depend on the cover crop
species, or mix, crop biomass, and growth stage when
killed. These same factors will influence how rapidly the
cover crop will decompose, and whether it will release,
or immobilize PAN. Most PAN is released in four to six
weeks after cover crop termination. For a comprehensive
guide on this topic see ‘Estimating Plant Available
Nitrogen Release from Cover Crops, PNW 636’. In
this publication we will review the shortcut method as
outlined in that document.
PAN from any cover crop is minimal when the cover
crop is very small. For solo cover crops, the best time to
terminate the cover crop to maximize PAN depends on
whether the cover crop is a legume or a non-legume.
➣ PAN from a robust stand of legumes (Figure 4)
peaks at budding growth stage. PAN declines slowly
as reproductive growth continues.
➣ PAN from cereal residues is positive early in the
spring (through tillering, mid- to late March). As stem
elongation proceeds (jointing), PAN from cereal residues declines. By the time the flag leaf (uppermost
leaf) emerges (Feekes growth stage 8 or Zadoks 37),
PAN from cereal crop residue is near zero. When
cereal heads are visible, PAN from cereals is negative.
To maximize PAN, kill cereal cover crops early, but
wait until bud stage to kill legumes. In cereal/legume
mixtures, the best crop growth stage for maximum
PAN benefit depends on the percentage of legume in the
stand. Figure 4 illustrates how PAN changes over time
in solo and mixed cover crop stands.
➣ When the cover crop is mostly legume, it behaves
much the same as does a pure legume cover crop—
the PAN from crop residue increases until cereal boot
stage. (Feekes stage 10; Zadoks stage 45). After pure,
or majority cereal stands reach jointing stage, PAN
➣ When a cover crop has more cereal than legume
(25 percent legume line in Figure 4), it follows a
similar PAN curve as a solo cereal crop, but negative
PAN is usually not seen until the cereal reaches boot
stage (around mid-May).
Seeding legume/cereal mixes instead of a solo cereal
crop allows greater flexibility in timing of cover crop

Figure 4. Effect of kill date on typical plant-available N (PAN)
release from cereal, legume, or mixed stands. Based on
compilation of field data from Willamette Valley cover crop
trials. Figure from PNW 636, Estimating Plant-available
Nitrogen Release from Cover Crops (Sullivan and Andrews,
2012), ©Oregon State University. Used by permission.

termination without consequences of negative PAN.
Cover crop mixes also combine the N fixation benefits of
legumes with weed suppression and soil benefits of cereals.
The percent N in cereals varies with field history. Fields
that have a history of manure/compost application and/or
legumes in rotation often have higher percent N in cereal
than do fields with a history of only N fertilizer application.
Biomass determination. The first step in estimating PAN
from a cover crop is determining how much cover crop
biomass is present. Visual estimates of cover crop biomass
are not very accurate, especially for multi-species cover
crop mixes. Cutting and weighing cover crop biomass is
the preferred method to estimate PAN. Generally, cover
crop roots are not included in this calculation. Harvest
the above-ground cover crop with quadrats or a sickle bar
mower (see Sullivan et al. 2012, Appendix C, Section 5 for
additional sampling instructions). Any harvest method can
be used that gives you a clean plant sample with a known
harvest area.
To determine the PAN you’ll need to estimate the percent
dry matter (DM; Tables 3 and 9). You will need to either
use a ballpark estimate of DM or oven dry the sample
that has been collected. Mixed, vegetative cover crop DM
will usually be between 12 and 18%. Very wet clover
samples are usually 10 to 12 % DM. Cereals after head
emergence are usually 20 to 25% DM.

Table 3. Estimated plant-available N (PAN) release from decomposition of crop residues in soil
at 4 and 10 weeks
Total N
4 wk
10 wk
4 wk
10 wk
% N, dry wt
PAN, % of residue total N
lbs PAN/dry ton
Cereals after head emergence
<0 -8 <0 2 20 5 20 2 8 Cereals, tillering/jointing 3 13 35 40 21 24 50/50 Cereal/Legume Mix or Flowering Legumes 4 10 50 55 40 44 Legumes, vegetative Adapted from OSU Extension publication EM9010-E (2010): Nutrient management guide for sweet corn (western Oregon). See “Biomass determination” on page 8 for a discussion of estimating the percent of dry matter. Negative PAN values indicate immobilization of N by cover crop residue. With a good stand and cover crop kill near bud or head emergence stage of plant development, the typical cover crop PAN credit is 50 lb N/acre for cereal legume mixtures, and up to 100 lb PAN/acre for legumes. Shortcut method. Harvest and measure cover crop biomass and use typical values for cover crop DM and percent N (Table 3) to estimate PAN. See Table 9 for information and sample calculations about how to estimate cover crop contributions to PAN. More accurate estimations can be made with lab analysis (Sullivan & Andrews, 2012). ☞ Enter figures for PAN available from previous applications of manure, compost and cover crops under Nutrient Sources section. Alternatively, use the rates established in your state’s Nutrient Management Planning tool. Phosphorus (P) In nature, most plants, except brassicas, receive much of their phosphorus through mycorrhizal interactions with the soil. This is particularly true in perennial systems. In organic systems, with regular cover crops, this interaction may be more prominent than in conventionally managed systems because organically managed soils can provide better conditions for mycorrhizal survival. If manures, or composted manures, have been regularly applied at rates to meet a crop’s N needs, this may result in more P (and K) than the crop requires. After many years, this can result in over-accumulation of P and K, and any solution requires some combination of reduced applications and/or increased uptake and removal of these nutrients. Potassium (K) Potassium is available as a positive ion, or cation, and soils with a high cation exchange capacity (CEC) will generally have more capacity to store K. Most soils with high clay content, high organic matter levels (>3%), or both will

Figure 5. Assessing the biomass of a cover crop.

have high CEC. There are thousands of pounds per acre
of potassium in an average, non-sandy soil, but most
of that is unavailable to plants—usually only 1-2% is
available. Repeated applications of manures can lead to
over-abundance of K (as well as P) in the soil.

Secondary Macronutrients and
Micronutrients are important to plant health, and can
be limiting factors for both yield and quality in some
production systems, or, when present in excessive
amounts, can reduce availability of other nutrients or
have a negative impact on plant health. Soil tests should
provide information on the levels of the secondary
macronutrients Calcium (Ca), Sulfur (S), and Magnesium (Mg), as well as micronutrients, such as Manganese
(Mn), Iron (Fe), Zinc (Zn), Copper (Cu), and Boron (B).
Documented soil deficiency, either through soil or tissue
tests, is required per NOP regulations prior to applying
any synthetic micronutrients.

Section 3.
Determining Nutrient Application Rates
Determining nutrient application rates consists of taking
your crop’s nutrient needs and subtracting any credits
from the system. If the credits are less than the crop’s
nutrient need, the grower will need to apply supplemental
nutrients in order to achieve the desired yield. Not all of
the N applied this year will be available to the crop in
the first year. A balanced nutrient program will supply
sufficient PAN, P2O5, K 2O, and other nutrients while
avoiding excesses. The example below demonstrates this

Assume that after all the nutrient credits are subtracted,
the values for the Nutrients Recommended for Yield are:
80 lbs PAN, 40 lbs P2O5, and 60 lbs K2O per acre.
The manure analysis is 3% N, or 60 lbs total N per dry ton.
According to Table 7, PAN Estimates for Uncomposted
Manure, at 10 weeks PAN released is about 30% of the product, or 18 lbs PAN per dry ton. This material is 60% dry matter
(therefore, 40% water), so to make consideration for this:
18 lbs PAN x 0.60 = 10.8 lbs PAN per “as is” ton
80 lbs PAN/ac ÷ 10.8 lbs PAN/Ton = 7.4 T/ac
This is the application rate that meets the crop’s
nitrogen need.
The manure also contains 20.6 lbs P2O5/dry ton (reported
on a dry basis this time) and 37.8 lbs K2O/dry ton according
to the analysis.

Add up all the PAN nutrient credits from the
previous applications of manure, compost, cover
crops, as well as what can be expected from the
irrigation water for this season’s crop. This total
should be subtracted from the total Nutrients
Recommended for Yield.

To calculate how much P2O5 the 7.4 T/acre manure
application rate will provide:
Application rate: 7.4 T/ac x .6 (60% dry matter) x 20.6 lbs P2O5/
dry ton = 91.5 lbs P2O5/ac
91.5 lbs P2O5/ac is being applied with the 7.4 T/ac manure.
Note that this is over twice as much P2O5 as is required by the
crop. What are some other fertilizer options that would supply
sufficient N, but less P2O5?
To calculate how much K2O the 7.4 T/acre manure
application rate will provide:
Application rate: 7.4 T/ac x .6 (60% dry matter) x 37.8 lbs K2O/
dry ton = 168 lbs K2O/ac
168 lbs K2O/ac is being applied with the 7.4 T/ac manure. This is
nearly three times as much K2O/ac as is required.
What are some other fertilizer options that would supply
sufficient N and P, but less K2O/ac?
Refer to Tables 4-6 for additional organic fertilizer

Please note: Calculations here use lbs N/ton or PAN/ton because litter and compost are commonly delivered by the ton.

Enter planned NPK applications to the
right of line 7 (Manure), line 8 (Compost), or
line 9 (Specialty Fertilizers) in the appropriate
nutrient column.


Timing and Application Method
The timing, application, and incorporation methods
of nutrients is most important relative to conserving N
and P. Manure applications can provide significant N to
the soil if they are incorporated within 12 hours of application. If the manure is broadcast and left on the surface, between one half and two thirds of the available
N can be lost to volatilization after one week (see Table
5, Appendix A). Even in reduced-till systems, application
close to the time of planting will decrease the likelihood
of loss by runoff or erosion. Manures are generally best
applied just before soil tillage, but diligence is needed to
ensure that National Organic Program harvest-interval
regulations related to manure applications are followed.
N mineralized from manures during a rainy period may
leach N into the water table or, if eroded, may carry into
surface waters. Fall applications of manure on annual row
crops do risk considerable N loss, even if incorporated
in regions with significant winter/spring precipitation.
The ammonium is converted to nitrate, and then is subject
to leaching and denitrification before the N is available for
next year’s crop (Magdoff & Van Es, 2009). Denitrification
is the microbial conversion of nitrates to nitrous oxides,

and mostly occurs in soils that become anaerobic due to
high water tables, poor drainage, or surface sealing. But
regardless of the mechanism of N loss, the loss of N to
water or air should be minimized through applications of
N appropriate to plant needs. The forms of N applied, as
well as its time of application can influence the percentage
N taken up by plants, and lost to leaching or the atmosphere. The goal of N management is to have minimal
nitrate-N present in soil that could be leached through
rainfall or irrigation or denitrified. This may allow for
fall manure applications with low risk of N leaching
due to winter rains. Manures mixed with large amounts
of high-carbon bedding (straw or wood shavings) may
immobilize N during the early stages of decomposition,
and should be composted prior to application, or be
applied long enough prior to planting to reduce the risk
of immobilization.
Cover crop incorporation can be considered a fertilizer
application and as Figure 6 shows, the peak PAN generally
occurs after four weeks. That may be two or more weeks
before the crop has its highest demand for N. Attempting
to plant too soon after cover crop incorporation risks pest
and pathogen problems associated with the decomposing
cover crop.

Figure 6. Timing of nitrogen (N) mineralization from cover crop residue in relation to crop N uptake (adapted from Gaskell et al., 2006). From
Gaskell, M., and R. Smith. 2007. “Nitrogen Sources for Organic Vegetable Crops.” HortTechnology October-December 2007 vol. 17 no. 4, 431441) Note: S


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