Soil Management: Building a Healthy
Soil
| Corn |
Soybeans | Forages
| Cereals | Dry
Edible Beans |
| Spring and Winter Canola
| Other Crops | Soil
Management |
| Soil Fertility and Nutrient
Use | Field Scouting
|
| On-Farm Stored Grain Management
| Weed Control |
| Insects and Pests of Field
Crops | Diseases of Field
Crops | Appendices |
Pub 811:
Agronomy Guide > Soil
Management > Building a Healthy Soil
Order OMAFRA Publication
811: Agronomy Guide for Field Crops
The key to success in building a healthy soil is effective management
of the soil organic matter. As discussed earlier, the organic matter is
made up of three parts: active, moderately stable and very stable. The
active portion is the part that management can have the most influence
on. The organic matter pool continually experiences gains and losses.
If the addition of organic material to the soil exceeds the losses, organic
matter levels increase; if the losses exceed the gains, organic matter
levels will decrease. Table 8-5,
Effects of Different Management Practices on Gains and Losses of Organic
Matter, lists a number of practices and their effect on soil organic
matter.
It is important to keep in mind that soil and its management are part
of the overall crop production system. Soil is also a central part of
the agricultural ecosystem. Changes made in the crop production system
over the years have far-reaching effects on all other systems. When taking
steps to improve soil quality, think about the changes being made and
how they may affect other components of the crop production system.
Adding Organic Material (Residues)
The addition of organic residues is the only sure way to increase soil
organic matter levels. Soils that are well aerated, such as sands, break
down residues quickly, making it more difficult to build soil organic
matter (SOM) levels. Soils with higher clay contents break down residues
more slowly, requiring less organic residues to maintain or increase the
SOM level.
Table 8-6 . Soil Organic Matter Percentage
Levels for Different Soil Textures
|
Soil Texture
|
Targets |
To achieve maximum aggregate stability |
| Sands and sandy loam |
4
|
3
|
| Loam and silt loam |
4-5
|
4
|
| Clay loam |
4-5
|
7
|
| Clay |
4-6
|
9
|
| Source: Ontario Environmental Farm Plan. |
Providing a variety of residue types, such as manure, crop residues, composts,
cover crops, biosolids, etc, will support a diverse group of soil life.
Determining the right organic matter level for a soil depends on the soil
texture and the aggregate stability target. Table
8-6, Soil Organic Matter Percentage Levels for Different Soil Textures,shows
organic matter targets for various soil textures. The targets indicate
soil organic matter percentages to aim for to improve soil productivity.
The levels for maximum aggregate stability were derived from research
(Health
of Our Soils Report, AAFC Ottawa) to determine what levels of
SOM would give aggregates the most resistance to the erosive forces of
water.
Manure
Livestock manure is an excellent source of organic matter for the soil.
Applying manure to the soil will provide other benefits, such as a greater
diversity and activity of organisms and better soil structure. See Table
8-7, Effects of 11 Years of Manure Additions on Organic Matter
Levels.
Consider the following when using manure as an organic matter source:
- Manure will add organic matter but also adds nutrients. Use the information
in Table 9-8, Typical Amounts
of Available Nitrogen, Phosphate and Potash From Different Types of
Organic Nutrient Sources, to help avoid over-application of nutrients
that could lead to loss into the environment.
- The organic matter content of a manure will vary, depending on the
type. Generally, more solids will be added to the soil with solid manure
than with liquid manure. Solid manure from cattle (ruminants) will contain
more forage parts and bedding than liquid manure. See Table
9-9 for a listing of typical manure types and their dry matter levels.
- The application rate will also determine the amount of organic matter
added to the soil.
- Solid manures usually contain more lignin (forage and bedding), which
will have a longer-term effect on organic matter than poultry manure
without bedding.
- Apply manure without compacting the soil.
Table 8-7. Effects of 11 Years of Manure
Additions on Organic Matter Levels
| |
Application Rate (tons/acre/year) |
| None |
10 Tons |
20 Tons |
30 Tons |
| Organic Matter (%) |
4.3
|
4.8
|
5.2
|
5.5
|
| Source: Building Soils for Better Crops, (Magdoff) SARE
Outreach, www.sare.org |
Note: The original organic matter level was 5.2%. The
study was conducted on continuous corn silage on a clay soil adding dairy
manure. The manure application also improved soil aggregation and the
amount of pore space.
The nutrient content of manure is discussed in Manure
Management.
Compost
Applying compost to the soil is another way of adding organic matter.
Compost will supply relatively low amounts of readily available nutrients
but will release nutrients over time. The composting process partially
decomposes organic matter, so the organic matter added to the soil is
made up of more resistant compounds than in fresh manure. It should not
be the only source of organic matter as soils benefit from fresh residues
as well. Fresh residues will likely stimulate more production of the sticky
material that holds aggregates together than compost will. Similar to
manure, it is important to minimize compaction at application and to avoid
excessive nutrient additions.
Composting of manure and other materials will:
- help stabilize nutrients
- reduce the amount to spread (volume can be reduced by 30%-60%)
- produce a better-smelling final product
Other Organic Materials
Sewage Biosolids
Sewage biosolids, like manure, are another source of organic matter and
nutrients for the farm. As a regulated material, sewage biosolids are
monitored to address environmental quality, food safety and human health
issues. Sewage biosolids are available for application on agricultural
land in many parts of the province. The application rate for a field is
based on the soil test results for the field and crop nutrient requirements.
The amount of organic matter applied will depend on the rate and type
of biosolid.
When applying sewage biosolids, similar to any land operation, ensure
the soil is fit, to avoid soil compaction. Work with the applicator to
ensure the timing fits with your crop production system.
Visit the OMAFRA website at www.ontario.ca/crops
to learn more about biosolids.
Other Agricultural and Non-Agricultural Source Materials
There are a variety of other organic materials that can be applied to
soil to add organic matter. Knowing the dry matter content and nutrient
content of the material will help calculate application rates and provide
an indication of how much organic matter is being added. It is also important
to know the carbon-to-nitrogen ratio of the material to assess any potential
impacts on nitrogen availability. When calculating the rate of application,
consider the physical amount applied and the implications for the rest
of the cropping system.
Applying Organic Materials to the Land
The application of organic materials to the land is done to increase
organic matter levels and also to add nutrients to the soil. To achieve
the maximum benefit and protect the environment, consider how they are
applied. See Considerations When Land-Applying
Organic Materials, for a list of some points to consider.
Considerations When Land-Applying
Organic Materials
Do I have to incorporate the material?
- Incorporate materials with an odour immediately or as soon as possible.
- Incorporate materials containing ammonium nitrogen as soon as possible
to reduce nitrogen losses.
- A certificate of approval or regulation may require incorporation.
- Incorporate nutrient-rich materials on sloping land or flood plains
to prevent loss.
- Leave materials that don't meet the above criteria on the soil surface
to help protect the soil. Earthworms and other soil life will help break
down and incorporate the material.
How much tillage/incorporation is needed?
- Incorporating organic materials with excessive tillage will expose
the soil to erosion and reduce or eliminate the benefits of the organic
matter addition.
- Depending on the material, a minimal amount of tillage will be sufficient
to incorporate most materials. Incorporating some of the material and
leaving the rest on the surface is generally best.
- Full inversion mouldboard plowing will leave a layer of material at
plow depth that will not readily decompose and may affect water movement
through the soil.
Table 8-8. Matching Cover Crop Choices
to Function
|
Cover Crop Function
|
Best Choices for Cover Crops
|
|
Nitrogen production
|
Legumes - red clover, peas, vetch
|
|
Nitrogen scavenging
|
Fall uptake - oilseed radish and other brassicas,
oat
Winter/spring uptake - rye, winter wheat
|
|
Weed suppression
|
Fast growing/shading plants - oilseed radish and
other brassicas, winter rye, buckwheat
|
|
Soil structure building
|
Grasses - oat, barley, rye, wheat, triticale, ryegrass
or fibrous root systems such as red clover
|
|
Compaction reduction
|
Strong tap roots that grow over time - alfalfa,
sweet clover
|
|
Biomass return to soil
|
Fall seeded - oat, oilseed radish
Summer-seeded - millets, sorghum, sudangrass, sorghum sudan
|
|
Erosion protection, i.e., wind, water
|
Winter rye, winter wheat, ryegrass (well-established),
spring cereals seeded early
|
|
Emergency forage
|
Fall - oat, barley, wheat, rye, forage brassicas
Summer - millets, sorghum, sudangrass, sorghum sudan
|
|
Nematode suppression
|
Cutlass mustard, sudans/sorghums (Sordan 79, Trudan
8,) pearl millet (CFPM 101), marigold (Crackerjack, Creole), oilseed
radish (Adagio, Colonel)
Not all cover crops have the ability to suppress nematode
populations; some will even act as hosts. Cover crop activity is
variety- and nematode-specific. To get the most activity, cover
crops should be weed free and may require specific handling.
|
Cover Crops
Growing cover crops is a common soil management practice for many Ontario
farmers. There are a lot of good reasons to grow cover crops but it is
often hard to put a dollar value on the return from growing them. Cover
crops are an important part of a system of soil maintenance - particularly
important on the lighter soils with lower organic-matter or on fields
with short rotations and little return of crop residue or manure. It is
important to know the goal when planting a cover crop and to select the
best one for that job. Table 8-8, Matching
Cover Crop Choices to Function, looks at the various reasons for
including cover crops in a rotation and the potential cover crops that
best meet those goals.
Choosing a Cover Crop
There are often several cover crop options for any one goal or function.
Consider specific farm needs and management style to select the best cover
crop for a farming system. Table 8-9, Choosing
a Cover Crop, gives examples of
the questions that should be posed when considering a particular cover
crop.
Characteristics of Cover Crops
Information on the most commonly used cover crops is provided in Table
8-10, Characteristics of Cover Crops Grown in Ontario. More
information about specific grass and legume cover crops can also be found
in Chapter 3, Forages.
Grass Crops
Grasses have fine, fibrous root systems that are well suited to holding
soil in place and improving soil structure. Suitable grass species for
cover crops are fast growing and relatively easy to kill, either chemically,
mechanically or by winter weather. Grasses do not fix any nitrogen out
of the atmosphere but can accu-mulate large quantities from the soil.
Grasses are often referred to as either bunch grass or a spreading grass.
Bunch grasses generally do not have rhizomes or stolons, just a simple
root system supporting the plant. The species with rhizomes or stolons
have the ability to send up new shoots from nodes on these structures,
allowing the grass to spread and form a sod.
Spring Cereals
Spring cereals are well suited for late-summer and early-fall plantings.
Under good growing conditions, spring cereals will produce the greatest
amount of crop biomass, making them valuable for feed or ground cover.
Once well established, spring cereals are relatively tolerant of frost;
do not attempt to establish them late in the fall, as the growth will
be disappointing.
Winter Cereals
Winter cereals are highly versatile cover crops. They can be planted
in summer and will tiller and thicken due to their need for vernalization
or a cold treatment before reproduction, or they can be planted in fall
for soil cover. Winter cereals will generally over-winter well, providing
winter and spring erosion protection. These grasses can be used to create
spring wind barriers, residue mulch or killed early to minimize residue
cover at planting.
Table 8-9. Choosing a Cover Crop
|
Consideration
|
Comment
|
| Growth habits |
- What kind of growth habit is needed?
- When is the growth required - lots of vigorous growth in late
fall or rapid growth in early spring?
- Is deep rooting important?
|
| Overwintering |
- Does the cover crop need to survive overwinter?
- Would it suit the cropping schedule and soil type if the cover
crop winter-killed and dried out by spring ?
|
| Control options |
- Will the cover crop become a weed concern?
- How is it controlled?
- What options are there for control?
|
| Sensitivity to herbicides |
- How sensitive is the cover crop to herbicide residues from other
crops in the rotation?
|
| Seed cost and availability |
- What is the seed cost and is the seed available in your area?
|
| Establishment |
- What is the best way to plant the seed?
- Is different equipment required?
- How easy is it to establish?
- Will it create a solid cover?
- Good establishment is critical to the success of the cover
crop.
|
| Nutrient management |
- Is it a nitrogen producer or does the cover crop require nitrogen
to grow well?
- What is the nitrogen cycle and timing of nitrogen release?
- Does it scavenge well for nitrogen?
|
| Pest management |
- What crop family is the cover crop in?
- Is it related to other crops in the rotation?
- Are there pest concerns?
|
Warm-Season Grasses
Warm-season grasses such as sorghum and millet are best suited for planting
into the warmer soils of late June, July and early August. They are very
sensitive to frost. Root growth is extensive and the top growth lush.
Be prepared to mow these grasses to keep stalks tender and prevent heading
out. Do not mow closer than 15 cm (6 in.) to ensure regrowth. Some nitrogen
may have to be applied to achieve optimal growth.
Legume Broadleaf Crops
Legume cover crops can fix nitrogen from the air, supplying nitrogen
to the succeeding crop. Legumes will take up residual soil nitrogen or
nitrogen from manure applications. They are approximately 80% as effective
as non-legumes in nitrogen uptake from soil. Legumes also pro-tect the
soil from erosion and add organic matter. The amount of nitrogen fixed
varies between species, although generally, more top growth equals more
nitrogen fixed. Some legume species such as alfalfa and sweet clover have
aggressive tap roots that can break up subsoil compaction, but this requires
more than one year's growth.
Non-Legume Broadleaf Crops
These broadleaf crops cannot fix nitrogen out of the air but may absorb
large quantities from the soil. Most of these crops are not winter-hardy,
so additional con-trol measures are not normally required. They should
not be allowed to go to seed, as the volunteer seed can become a significant
weed problem.
New and Emerging Cover Crops
Every year new crops are tried as cover crops. Often these species are
from different parts of the globe and may not be well adapted to Ontario
growing conditions. For more information on new and well-known cover crop
species, see the OMAFRA website at www.ontario.ca/crops
or the Midwest Cover Crop Council at www.mccc.msu.edu/.
Crop Rotation
Crop rotation is an integral part of the crop production system. The
greatest benefit to a good crop rotation is increased yields. A well-planned
crop rotation will help with insect and disease control and aid in maintaining
or improving soil structure and organic matter levels. Using a variety
of crops can reduce weed pressures, spread the workload, protect against
soil erosion and reduce risk. Legume crops in the rotation have become
more valuable with the increased cost of nitrogen. Research and experience
have proven that a good crop rotation will provide more consistent yields,
build soil structure and increase profit potential.
Table 8-10. Characteristics of Cover
Crops Grown in Ontario
| Species |
Seeding Rate
kg/ha
|
Normal Seeding Time |
Minimum Germination Temperature
°C
|
Nitrogen Fixed or Scavenged (F or S)1 |
Over-Wintering Characteristics |
|
Grasses
|
| Spring cereals |
100-125
|
Mid-Aug- Sept |
9
|
S
|
Killed by heavy frost |
| Winter wheat |
100-130
|
Sept-Oct |
3
|
S
|
Over-winters very well |
| Winter rye |
100-125
|
Sept-Oct |
1
|
S
|
Over-winters very well |
| Sorghum sudan |
50
|
June-Aug |
18
|
S
|
Killed by frost |
| Pearl millet |
4
|
June-Aug |
18
|
S
|
Killed by frost |
| Ryegrass |
12-18
|
April-May or
Aug-early Sept
|
4.5
|
S
|
Annual, Italian partially survive;
Perennial over-winters |
|
Broadleaves - Legumes
|
| Hairy vetch |
20-30
|
Aug |
15.6
|
F/S
|
Over-winters |
| Red clover |
8-10
|
March-April |
5
|
F/S
|
Over-winters |
| Sweet clover |
8-10
|
March-April |
5.5
|
F/S
|
Over-winters |
| Soybeans |
40-50
|
Aug |
8
|
F/S
|
Killed by frost |
| Field peas |
40-100
|
Aug |
5
|
F/S
|
Killed by heavy frost |
|
Broadleaves - Non-Legume
|
| Buckwheat |
50-60
|
June through Aug |
10
|
S
|
Killed by first frost |
| Oilseed radish |
10-14
|
Mid-Aug-early Sept |
7
|
S
|
Killed by heavy frost |
| Other brassicas, i.e., forage radish |
Varies with species
|
Mid-Aug-early Sept |
5-7
|
S
|
Species dependent, many killed by heavy frost |
| 100 kg/ha = 90 lb/acre |
1 Oilseed radish, buckwheat
and the grasses do not fix nitrogen from the air but are scavengers
of nitrogen from soil and manure applications.
2 Clover legumes make good feed or grazing, however feeding
pure legumes can cause bloat.
|
| Species |
Building Soil Structure |
Weed Suppression |
Grazing Potential |
Quick Growth |
Root Type |
|
Grasses
|
| Spring cereals |
Good |
Good |
Very good |
Very fast |
Fibrous |
| Winter wheat |
Good |
Good |
Very good |
Fast |
Fibrous |
| Winter rye |
Very good |
Very good |
Very good |
Very fast |
Fibrous |
| Sorghum sudan |
Good |
Good/Fair |
Very good |
Very fast |
Coarse fibrous |
| Pearl millet |
Good |
Good/Fair |
Good |
Fast |
Coarse fibrous
|
| Ryegrass |
Very good
|
Fair/poor |
Good |
Slow to establish |
Fibrous |
|
Broadleaves - Legumes
|
| Hairy vetch |
Good |
Fair/poor |
C2 |
Slow to establish |
Tap with secondary fibrous |
| Red clover |
Good |
Fair |
C2 |
Slow to establish |
Weak tap/ fibrous |
| Sweet clover |
Good |
Fair |
C2 |
Slow to establish |
Strong tap |
| Soybeans |
Poor |
Good/fair |
C2 |
Fast |
Tap |
| Field peas |
Poor |
Good/fair |
C2 |
Fast |
Weak tap/fibrous |
|
Broadleaves - Non-Legume
|
| Buckwheat |
Poor |
Very good |
Poor |
Fast |
Weak tap/fibrous |
| Oilseed radish |
Fair |
Very good |
Good |
Fast |
Moderate tap |
| Other brassicas, i.e., forage radish |
Fair |
Very good |
Good |
Fast |
Moderate tap |
| 100 kg/ha = 90 lb/acre |
1 Oilseed radish, buckwheat and the grasses
do not fix nitrogen from the air but are scavengers of nitrogen from
soil and manure applications.
2 Clover legumes make good feed or grazing, however feeding
pure legumes can cause bloat.
|
The basic rule of crop rotation is that a crop should never follow itself.
Continuous cropping of any crop will result in the build-up of diseases
and insects specific to that crop, and cause a reduction in crop yields.
The more often the same crop has been grown in the field in the past,
the greater this impact will be. For example, the practice of growing
two or more years of soybeans is becoming increasingly common. Perhaps
the greatest impact of back-to-back years of soybeans has been the accelerated
spread of soybean cyst nematode (SCN). For more information and potential
yield reductions, see Soybean Cyst
Nematode. The increased number of years of soybeans in the rotation
is also increasing the susceptibility of Ontario's soils to erosion.
Table 8-11. Corn Yield Response to Rotation
|
Rotation1
|
Corn Grain Yield2 |
Loam
(1990-95)
|
Clay Loam
(1990-93)
|
| t/ha (bu/acre) |
| Continuous corn |
8.84 (141)
|
6.59 (105)
|
| Soybean-corn |
9.78 (156)
|
7.40 (118)
|
| Soybean-wheat-corn |
9.47 (151)
|
7.90 (126)
|
| Soybean-wheat (RC)3-corn |
10.23 (163)
|
8.47 (135)
|
| Soybean-wheat (RC)-RC3-corn |
10.35 (165)
|
8.28 (132)
|
| Source: Vyn, University of Guelph |
1 On a Toledo loam near Chatham, Ontario,
and on a Brookston clay loam near Maidstone, Ontario.
2 All corn treatments were fertilized with 179 kg/ha (160
lb/acre) of N.
3 Red clover plowdown was underseeded into wheat. "Wheat
(RC)-RC" indicates that underseeded red clover was not plowed
under but harvested for seed the following year and then fall plowed.
|
In fact, the structure of soils in corn-soybean rotations can actually
be poorer than that of soils that are in continuous corn production. For
example, a recent study found that erosion following an intense June rainstorm
in first-year corn following 2 years of soybeans was twice as high as
following corn, wheat underseeded with red clover or alfalfa. Relatively
poor soil structure after 2 years of soybeans not only increased erosion
susceptibility but also reduced soil porosity, which resulted in less
rainwater infiltration. Reduced rainwater infiltration increases the likelihood
of erosion, yield-reducing water ponding and/or soil moisture deficits;
all of these effects can reduce crop productivity, particularly in years
with weather-related stress.
The greatest benefit from crop rotation comes when crops grown in sequence
are in totally different families. The two families are grasses (monocots)
and broad-leaves (dicots). The grasses include forages grasses, cereals
and corn. Soybeans, white beans, alfalfa and canola are examples of broadleaf
crops. Table 8-11, Corn Yield Response to Rotation,
provides an example of the type of response to crop rotation that is possible.
The fibrous root systems of cereal and forage crops (including red clover)
are excellent for building soil structure. Studies have shown that the
benefits of including wheat, and especially wheat plus red clover, may
persist beyond just the following year. Underseeding red clover into wheat
resulted in yield increases every year for 3 consecutive years compared
to when red clover was not included in 4-year rotation systems.
In choosing which crop to grow, consider the economics of the entire
rotation instead of a single crop in isolation. See Publication
60, Field Crop Budgets, for cost estimates, or visit the OMAFRA website
at www.ontario.ca/agbusiness.
Also, be aware of any potential insect or disease problems that could
affect crops later in the rotation. Cover crops in the rotation may also
have an impact on diseases and pests, either positive or negative (see
Cover Crops,for potential impacts of
various cover crops). Table
8-12, Management Considerations for Various Crop Rotations,
displays various crop rotations that are recommended, cautioned against
or not recommended, depending on their impact on the crop production system.
It is not a comprehensive listing of crop problems but does highlight
the main issues to be aware of. More information is provided in each crop
chapter.
