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Soil, soil organisms, soil amendments, and their relation to plant health

Thanks to Craig Cogger

Extension Soil Scientist WSU-Puyallup

http://www.puyallup.wsu.edu/soilmgmt

Mineral MatterPore Space

OrganicMatter

Soil Components

The soilecosystem

Residue decompositionNutrient cyclingAggregation and porosityEnhance plant growthBreak down contaminants

•Water MovementHow quickly water moves

through soil

Water Holding CapacityHow much water a soil can hold

available for plant growth

Soil pores and water movement

•Macropores: Infiltration and drainage through soil

•Capillary pores: Available water for plants

•Micropores: Unavailable water (clay)

Soil properties that affect porosity

•Soil texture

•Soil structure

•Compaction and disturbance

•Organic matter

Hand texture technique: clay

Soil StructureAggregation of sand, silt, and clay particles

Structure affects:MacroporosityInfiltrationAeration

Formation of soil structure

•Growth of roots and movement of organisms create pores and aggregates•Soil organisms break down organic

residues, producing glues (glomalin) that stabilize aggregates

•Beneficial fungi provide structural support to aggregates

•Physical, chemical processes also involved

Effects of development on urban and suburban soils

•Increased bulk density•Resistance to root penetration

•Loss of structure•Reduced porosity

•Reduced infiltration•Reduced rooting depth

•Reduced nutrients and water availability

Prescription

•Incorporate organic matter

Expected benefits of organic matter

•Physical: Improved bulk density, structure, porosity, permeability,

•Biological: More activity

•Available water: Increase depends on soil and irrigation regime

•Runoff: Better structure and porosity reduces runoff and erosion

•Nutrients: Significant for some materials

Bacteria, fungi, actinomycetes, protozoa, nematodes, arthropods, earthworms

Pictures courtesy M. Fauci and D. Bezdicek

Soil Organisms

Residue decompositionNutrient cyclingAggregation and porosityContaminant breakdownNitrogen fixationEnhance root functionPathogen Predators

Mary Fauci

Roles of soil organisms

Roots

Detritus

Phytophagousnematodes

Collembolans

Predaciousmites

NematodeFeeding mites

Predaciousnematodes

Omnivorousnematodes

Amoebae

Bacterivorousnematodes

Mycorrhizae

Fungi

Bacteria

Cryptostigmatidmites

Noncrypto-Stigmatid mites

Fungivorousnematodes

Flagellates

Soil food web and nutrient cycling

Organic matter stimulates soil organisms

•Formation of soil structure

•Nutrient cycling

•Plant disease suppression

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Choosing organic

amendments

Why use compost as a source of

organic matter?•Locally produced, recycled material

•Home, farm, or commercial

•Can usually be applied at high rates to increase organic matter benefits

•Hot composting kills pathogens

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Solutions to Compacted Soil

•Research-based science

•Proven effective in horticultural use over many years

•There are three main parts...

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Research Results: Excerpts from Trees, people & the built

environment:Proceedings of the Urban Trees Research

Conference-April 2011

•This is not the research I mean!

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Be careful from whom you take

advice...

•Using Soil : How to Break Up Clay Soil

https://www.youtube.com/watch?feature=player_detailpage&v=_ATpA3bovgE

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“How to Break Up Clay Soil”

Let’s analyze Rick’s recommendations

Gypsum is often recommended for use in clay soils.

Clay in the Kansas City metro area is a species of Smectite clay called montmorillonite, a shrink/swell clay.22

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“How to Break Up Clay Soil”

Montmorillonite clay

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“How to Break Up Clay Soil” by Rick

•Rick recommends 25 pounds of gypsum per 5 sq. ft.

•or 5 lbs./sq.ft.

•or 5,000 lbs./ 1,000 sq.ft.

•A catastrophic amount in soil!24

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Research Results: Excerpts from Trees, people & the built

environment:Proceedings of the Urban Trees Research

Conference-April 2011

•Rooting environment - mycorrhizal fungi

• In one of the earliest arboricultural texts, Wm. Solotaroff (1911) urban forester, states ‘a great deal, if not all of the success in tree growing depends upon the

nature and the preparation of the soil’.This observation has, over time, been proven to be true.

> Since drought, use of winter de-icing salts, lack of nutrients, and attack from disease pathogens are among the main causes of failure of urban trees and lawns (Fini and Ferrini,2007), the

inoculation of urban landscapes with selected, native, competitive and effective mycorrhizal fungi may enhance tree

and turf survival and growth in the urban environment. 25

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•Agriculture and Natural Resources HYG-3305-08

•Mycorrhizae in Urban Landscapes• Nathan M. Kleczewski, Dennis Lewandowski, and Pierluigi (Enrico) Bonello Department of Plant Pathology

The Ohio State University

•Artificial mycorrhizal inoculation may benefit plants when there is no natural and appropriate mycorrhizal inoculum in the soil, the inoculum level is low, or species present are less efficient at aiding the plant host than those being introduced... In principle, highly compacted, organic

nutrient-poor soils in urban environments may also be prime candidates for artificial mycorrhizal inoculation.

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Arbuscular Mycorrhizal Fungi

• An arbuscule of a AM fungus. Photo by M. Brundrett (with permission).

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Ectomycorrhizal Fungi

Highly branched EM root tip. Photo by Nathan Kleczewski.

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Rhizosphere Maintenance•The rhizosphere is the region of soil in intimate contact

with the roots of a plant. The health of a rhizosphere is critical to plant performance. This area contains a complex array of plant-associated communities of microorganisms

vital for soil health (Buée et al., 2009).

•While it is difficult to directly influence the actual rhizosphere, interventions to promote soil ecology and good soil structure will promote rhizosphere health and

simultaneously improve plant performance. It is essential that soil health is on the agenda of those seeking to

establish trees and turf in the urban environment (Buée et al., 2009).

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• Mycorrhizal fungi were tested on newly planted and mature linden (Tilia) trees and horse chestnut trees (Aesculus) growing in a poor, heavily compacted soil and researchers

found that symbiosis was more successful on mature trees, compared to newly planted ones.

• There is research evidence that soil compaction limits root growth and rhizosphere activity (Fini and Ferrini, 2007) and also reduces mycorrhizae

formation (Nadian et al., 1997; Entry et al., 2002). !

Conclusion

• Research results obtained to date showed that the work of selecting, multiplying and inoculating woody species with site- and species-specific mycorrhizal fungi

can result in greater growth and improved physiology.

• That’s part one of the solution!!

•That’s one solution!!

!30

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Plant Growth Stimulators•Application of organic products, such as humates and plant

extracts, at planting have shown only limited benefit to rootor shoot growth of trees and turf. Species vary widely in theirresponse (Kelting et al., 1998a, 1998b; Ferrini and Nicese,

2002; Fraser and Percival 2003; Gilman, 2004; Sammons andStruve, 2004) to the applications of these materials.

•Most commercial plant growth stimulators should be applied by professionals trained in the use of these materials.

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Plant Growth Stimulators•Paclobutrazol, a growth regulator used primarily to reduce

leaf growth on trees and turf, can also stimulate rapid root growth under certain circumstances.

•Paclobutrazol applied at planting doubled root growth on black maple (Acernigrum) in the first season, but not the second. The

lack of root response in the second season is thought to be related to roots being restricted by water deficit, high salt

content of the soil, and reaching planting hole boundaries of compacted soil that roots could not penetrate.

•That’s part two of the solution!!

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Soil Decompaction!•The bulk density of soil is demonstrated to be limiting to tree

growth and turf development; decompaction of the rooting environment has considerable value regardless of landscape

age.

• While a variety of approaches are available to ‘decompact’ soil, the value of some equipment has been questioned. It is now clear that only those

approaches which result in a significant and widespread reduction in soil bulk density throughout the rooting volume have appreciable merit. (Smiley et al.,

1990; Smiley, 1994; Hascher and Wells, 2007).

• High pressure pneumatic soil excavation tools (e.g. Air Spade®,

• Supersonic Air Knife, Soil Pick©) have been demonstrated to achieve this and are capable of cultivating the soil to a depth of 10 - 12 inches (25–

30cm) using compressed air to excavate soil with minimal disturbance or damage to tree roots (Felix, 2004).

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Trees, people and the built environment!Proceedings of the Urban Trees Research Conference

April 2011

• RESEARCHERS found this approach to be particularly valuable when combined with a nutritional amendment in a technique known as Root

Invigoration. Since there is so little damage, larger areas can be excavated, which greatly expands the available area for root growth and development

(Smiley,1999).

• Root Invigoration

• http://www.bartlett.com/root-rx-vid-lg.cfm?rs

•That’s part three of the solution!!34

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Soil Renovation Take Aways• Thanks to Dr. Kim Coder, University of Georgia

• Gardeners must correct compaction and its limitations on plant growth. Compaction must be prevented and actively corrected. Here are some renovation principles derived from research

activities to consider.

•Principle 1 -- Soils do not “come back” from compaction. Soil must be actively renovated.

•Principle 2 -- A garden is a composite of many compaction events over many years, all needing remediation.

•Principle 3 -- Management activities should concentrate on increasing aeration space and reducing soil strength, rather than trying to recover

past ecological history by topically adding amendments.

•Principle 4 -- Estimate soil compaction now as a bench-mark for gauging effectiveness of any treatment.

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Soil Renovation Take Aways

Principle 5 -- Measure compaction using any or all approximations, such as bulk density, penetration force, oxygen diffusion rates, and plant available water. (Laboratory analysis)

Principle 6 -- Alleviation of soil compaction is part of a good garden soil health management plan.

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Soil Renovation Techniques

Once the general principles of working with compacted soils are digested, the next requirement in garden soil health care is to identify general

techniques for renovating compacted soils.

•The two main objectives are:

1) remove enough soil volume from compacted soil to make a significant difference in soil bulk density and fracture hardpan layers; or

2) pierce the soil enough to significantly impact gas exchange with the atmosphere.

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•Soil Renovation TechniquesThanks to Dr. Kim Coder, University of Georgia

Technique 1 -- Defend the ecological “foot print” of a garden rooting area. Select working conditions (dry, dormant season, surface mulch, etc.) that minimize compaction in a rooting area.

Technique 2 -- Carefully design garden growth areas using “biology-first” design processes rather than the common (and damaging) “aesthetics-first” design processes.

Technique 3 -- Try to soften and distribute any new compaction forces applied to garden soil by using temporary coarse, thick organic mulch, plywood, or rubber planting pads.

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Soil Renovation Techniques

Technique 4 -- Restart or improve the detritus energy web in soil, including the addition of composted organic matter, living organisms, essential nutrients in short supply, and water (supply & drainage).

Technique 5 -- If tree roots are not present on-site, use deep tilling to fracture and aerate soil before other activities are begun for installing garden plants.

Technique 6 -- Utilize porous paving materials, soil binding materials, or root aggregation structures, where possible, to avoid further compaction.

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Soil Renovation TechniquesTechnique 7 -- Use core (not punch) aerators designed for compacted areas which reach 8-14 inches in depth. These are large hydraulic powered core aerators, not shallow surface aerators as used in turf culture.

Technique 8 -- A derivation of core aerators is the use of compressed air probes. High pressure air is used to fracture soil. Materials added could be either liquid or granular, and include fertilizers, organic matter, biologics, and porous solids for holding soil fractures apart.

Technique 9 -- Use soft excavation techniques like air guns to cultivate (stir-up) soil in selected areas under trees (Bartlett renovation technique). Composted organic matter and other soil and growth materials can be incorporated during this operation.

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Soil Renovation TechniquesArboriculture & Urban Forestry 37(6): November 2011

Evaluation of a Soil Decompaction and Amendment Process for Urban TreesKelby Fite, E. Thomas Smiley, John McIntyre, and Christina E. Wells

Abstract. Researchers investigated the effects of a soil decompaction and amendment process (AFM) and its individual components (air tillage, fertilizer, and mulch) on soil properties at four urban sites. At each site, 50 red maples (Acer rubrum) were growing on compacted and/or nutrient-poor soils. The AFM treatment significantly reduced soil strength relative to control at all sites... Overall, AFM was effective in improving soils beneath established trees, and mulching was the most beneficial of the individual treatments.

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Soil Renovation TechniquesArboriculture & Urban Forestry 37(6): November 2011

Evaluation of a Soil Decompaction and Amendment Process for Urban TreesKelby Fite, E. Thomas Smiley, John McIntyre, and Christina E. Wells

CONCLUSIONSA program of air tillage, prescription fertilization, and mulch improved a suite of physical and chemical properties in urban soils.... In the field, practitioners should experiment with specific materials, techniques, and treatment frequencies to best address the needs of individual sites. Nonetheless, it is clear that a multi-pronged approach to soil remediation gives arborists an effective means to improve compacted soils beneath established urban trees.

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J. Paul Getty Museum Garden - Malibu, California

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Contact InformationBill Nolde, MSConsulting Arborist   member, American Society of Consulting Arborists

ISA Certified Arborist, Cert. #MW5326-Amember, International Society of Arboriculture

Consulting Agronomistmember, American Society of Agronomy

Consulting Soil Scientistmember, Soil Science Society of America

Nolde and AssociatesDirect: 816-820-3262Email:  nolde.arborist@gmail.comWebsite: www.treecaretoday.info