Harold van Es

Fundamentals of Building Soils for Better Crops

Soil Health/Quality is…

… chemically, biologically and physically.

Physical Chemical

Biological

Soil Health

• Good Tilth (structure)

• Physical support for plants

• Aeration

• Soil water storage and movement

• Resistance to soil erosion

• Physical root proliferation and organism movement

• OM decomposition

• Nutrient transformations & access

• Pest suppression, low pest pop.

• Support of microbial community, beneficials, producing plant growth promoting compounds

• Immobilization of toxins

Functional Processes in Soil

• Nutrient storage and release (ion exchange)

• Energy (C) storage

• Salinity/toxicity prevention

The “Limiting Factor Concept”: Perhaps too simplistic?

physical properties

Biological properties

chemical properties

INTERACTION

Soil Health

Plant and Environmental

Health

Examples of Interactions • Hard soil reduces rooting • Compacted soil suppresses beneficial biological

processes • Compaction increases root diseases and

denitrification losses • Organic matter decomposition increases

aggregation • Prolific rooting decreases compaction • Poor drainage reduces rooting and aerobic

biological processes • High sodium contents reduce aggregate

stability, drainage, aeration, beneficial biological processes, and rooting

“Problem” “Solution”

Low N availability Apply N fertilizer

Insect infestation Apply insecticide

Weedy conditions Apply herbicide

Droughty soil Irrigate frequently

Compacted soil Use subsoiler

Current dominant paradigm in Agriculture

Reactive management: short-term response to immediate problems, relies on external interventions.

Are these problems symptoms of a deeper and more fundamental problem … a poorly managed ecosystem?

• Create soil & above ground conditions to promote the growth of healthy crops with enhanced defenses

• Build resiliency and less sensitivity to extreme events

• Enhance beneficials, mutualism and synergies

• Stress pests

Pro-active, long-term management: Enhancing the internal strengths (health)

of a balanced agroecosystem

In the long run, fewer external interventions will be needed, agroecosystem will function more like a natural ecosystem, fewer big problems, higher efficiency and productivity.

Self sufficient

Resilient Efficient

Self regulating Diverse

Natural Ecosystems

Natural Ecosystems should inform Agroecosystem management

• Efficient – energy, nutrients, water, C … all cycle. No “waste” – one organism’s waste is another’s resource.

• Diverse – above and below-ground biological diversity leads to checks and balances

• Self sufficient – only external inputs are sunlight, rain, air… very minimal

• Self regulating – diverse ecological communities, severe disease or pest outbreaks uncommon, populations in flux – dynamic balance

• Resilient – able to bounce back after disturbance/stress (such as extreme weather). They can be damaged, but they come back more easily than a damaged ecosystem

How can we move agriculture closer?

A whole system approach to soil and crop management

Optimal crop yield & quality --

with high positive and low negative

environmental effects

Preventive management — pre-season through planting

time (building internal strengths

into the system)

Post-planting — planned

management

Reactive management (if yield or quality goals not

being achieved)

Healthy plants with minimal pest damage

a) create soil & above ground conditions for

healthy plants with enhanced defenses b) stress pests c) enhance beneficials

2. Build healthy soil

(below ground habitat conservation

& enhancement)

1. Crop/plant selection & planting management;

habitat conservation & enhancement of field

and surroundings 5. Reactive pest

management

6. Reactive soil/nutrient management

Overall Goal

4. In-season management to

Reduce crop stress/ optimize yield

and quality

3. In-season pest

prevention or management

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Soil Health Management Principles & Decision Making in Practice

Do you prefer dense concrete, or well aggregated clay?

Holistic soil management is • knowledge intensive • requires an understanding of soil processes and

system functioning

Soil Processes

Soil Management

Soil Constraints

Download the pdf from http://www.sare.org/publications/soils.htm

Building Soils For Better Crops, 3rd Edition by Fred Magdoff

and Harold van Es

I. Organic Matter – the key to healthy soils

II. Physical Properties and Nutrient Cycles

III. Ecological Soil Management

IV. Putting it all Together

The Soil Health Management Toolbox

1. Organic/chemical amendments

2. Crop rotation

3. Growing cover crops

4. Reducing or modifying tillage

General Options for Managing Constraints

Resource: Magdoff and van Es. 2009. Building Soils for Better Crops

Soil

heal

th

years

reduced tillage

cover cropping

reduced tillage, cover cropping

reduced tillage, cover cropping, perennial forage rotation crop, manure/compost

Combining management practices can have an additive effect

Green manure cover crop

Strip tillage

Roles of the three “types” of organic matter in soils

Living: 1. soil organisms that play important roles in making nutrients available, suppressing disease, producing plant growth promoting hormones, creating humus, aggregating soils…

2. plant roots

Dead: recently dead soil organisms and crop residues provide the food (energy and nutrients) for soil organisms to live and function.

Very Dead: well decomposed organic materials, also called humus. Humus contains very high amounts of negative charge (holds nutrients) and has high water-holding capacity, and stores C

Coexisting, but progressing in time

A well aggregated soil has a range of pore sizes

large pore – Important for drainage, aeration and rooting

Intermediate pore- Important for water retention and biological functions

small pore – important for long term moisture retention

Aggregate (crumb)

Organic Matter Provides Good Soil Water Relations

Building a Healthy Soil for Healthy Crops – Managing Organic Matter –

• GOALS to balance:

Regularly add diverse types of organic matter (manures, composts, cover crops, crop residues, leaves, biochar? …)

Rotate crops Decrease organic matter losses from decomposition and erosion

Need OM to decompose nutrients “glue” for aggregates food for microbes

Need OM to accumulate Water storage C-storage Nutrient retention

Why add different kinds of organic matter?

Different types of organic matter perform different important roles • Nutrient release (N if

low C:N ratio) • Aggregation • Water and nutrient

retention through accumulation of OM

• Balanced effects (overapplication can be a problem)

Which cover crop will you choose for your multiple constraints?

Reduce compaction

increase aggregation

Types of Cover Crops - Legumes

• Fix nitrogen from the atmosphere and add it to the soil. • Legumes such as hairy vetch or crimson clover that produce a

substantial amount of growth may supply over 100 pounds of nitrogen per acre to the next crop. Other legumes, such as field peas and red clover, usually supply only 30 to 80 pounds of available nitrogen.

• Legumes also provide other benefits including attracting beneficial insects, helping control erosion, and adding organic matter to soils.

Common Grass Cover Crops

• Very useful for scavenging nutrients—especially N—left over from a previous crop.

• Tend to have extensive root systems, and some establish rapidly, and can greatly reduce runoff and erosion.

• annual cereals: rye, oats, wheat, barley • annual or perennial forage grasses: ryegrass, and warm-season

grasses such as sorghum-sudangrass.

Other Cover Crops Buckwheat • summer annual that is easily killed by frost.

Grows better than many other cover crops on low-fertility soils.

• Grows rapidly and completes its life cycle quickly, taking around six weeks from planting into a warm soil until the early flowering stage.

• Suppresses important root pathogens. Brassicas (mustard, rapeseed, and forage radish). • Increasingly used as winter or rotational

cover crops in vegetable and specialty crop production

• Forage radish has gained a lot of interest because of its fast growth in late summer and fall. It develops a large root that can break through compacted layers.

Incorporation of cover crops as green manures against Pratylenchus penetrans.

0 250 500 750 1000 1250 1500 1750 2000

Hairy Vetch

Alfalfa

White clover

Rye grain

Alsike clover

Phacelia

Radish

Crown vetch

Red clover

Wheat

Oats

Buckwheat

Mustard

Ryegrass

Rapeseed

Sudex

Number of P. penetrans/ g bean root

SELECTING A COVER CROP 1. OBJECTIVES

• Add organic nitrogen • Catch excess nitrogen • Add large amounts of organic residue • Create surface cover (living or mulch) • Control erosion • Relief compaction • Suppress weeds • Suppress diseases • Combinations of the above……..

SELECTING A COVER CROP 2. GROWING CONDITIONS

• Which cover crops grow in our climate? • When and how should you plant the crop? • When should the crop be killed or incorporated into the

soil? • Should I consider cover crop mixtures?

Interseeding and Living Mulches

A wide cover-free strip and living mulch, which is also used for traffic.

Penn State Interseeder and Applicator

Cover Crop Termination

• mowing (most annuals are killed that way) once they’ve flowered

• naturally by winter injury • plowing into the soil • with herbicides • rolling and crimping

Rodale Steve Groff

Cover Crop MANAGEMENT CAUTIONS

Cover crops can cause serious problems if not managed carefully. They can • deplete soil moisture • become a weed • aggravate disease problems • when used as an intercrop — they can

compete with the cash crop for water, light and nutrients

Thick mulched cover crops make good habitat for some undesirable species like rats, mice, and snakes

Effect of incorporated cover crops on root rot severity of beans (NYSAES greenhouse). Lower rating means better disease suppression

1 2 3 4 5 6 7 8 9

White clover ' New Zealand'

Check

Hairy vetch

White mustard 'Mantegena'

Alfalfa 'Iroquois'

Ryegrass 'Pennant'

Oats

Sudangrass

Rye grain

Wheat 'Geneva'

Crown vetch

Rapeseed

Root Rot Severity (1-9)

Cover crop

Dr. George Abawi

Crop Rotation: Soil Improvement and Degradation

Crop Rotations and Active Rooting

Crop Sequence Problems and Opportunities (Mohler and Johnson, 2009)

D: disease, I: insects, W: weeds, C: cultivation N: nitrogen, S: soil structure

Following: Preceding:

Pea

Lettuce

Potato

Tomato

Pea XXXX D, C-

Lettuce D XXXX D D, C-

Potato D XXXX D, I

Tomato D D, I XXXX

Real Organic Farm Rotations- Field Crops

Mohler and Johnson, 2009

Real Organic Farm Rotations - Vegetables

Mohler and Johnson, 2009

Tillage Addiction: Downward Spiral in Soil Health

Compaction

Reactive management: Increased tillage

Declining OM

Unhealthy microbial communities

Reduced soil aggregation

Poor drainage

Downward spiral to poor soil health

nitrogen losses Stressed plants

Reactive management leads to:

Stressed plants Increased pest

pressure

Increased pest pressure

Stressed beneficials

Tillage Addiction: Downward Spiral in Soil Health

Compaction

Increased tillage

Declining OM

Unhealthy microbial communities

Reduced soil aggregation

Poor drainage

Downward spiral to poor soil health

Intervention Points -

Preventive management needed to intervene

Soil Compaction Causes: OM losses (multiple reasons) Excessive loading Effects: Water Relations Infiltration Percolation Aeration

Rooting Biological activity Crop growth

Preventing or Lessening Plow Layer Compaction

• Tillage is a problem, but sometimes can be a temporary solution • Cover crops • OM additions (manure, compost to lesser extent) • Reduced, gentle tillage, or restricted (targeted tillage) • Better attention to traveling on soil

– Wetness – Controlled traffic lanes

Controlled Traffic requires equipment adjustments

works best with RTK GPS technology

Tramlining (narrow-row crops)

Reducing Equipment Loads

Tracks

Duals

Flotation Tires

Remediating Subsoil Compaction

Don’t plow when soil is wet!

Drainage

Reduce tillage Deep tillage/subsoiling

Deep-rooted crops

More is Not Always Better…. • Over-application of manure may generate excess

leaching and denitrification losses • Excess vegetative vigor and reduced quality can

result from too high a supply of soil N and/or soil water.

• The sensorial traits of wines are generally enhanced by mild water stress and reduced root growth in the early summer

Some Information Resources

soilhealth.cals.cornell.edu