Protecting andNurturing Soils

Chuck Ingels, Farm & Horticulture Advisor

UC Cooperative Extension, Sacramento County

caingels@ucdavis.edu

With contributions from:

Marcia M. Braga, Sierra College

Janet Hartin, UCCE San Bernardino County

Dave Roberts, EcoLandscape California

Protecting andNurturing Soils

Chuck Ingels, Farm & Horticulture Advisor

UC Cooperative Extension, Sacramento County

caingels@ucdavis.edu

With contributions from:

Marcia M. Braga, Sierra College

Janet Hartin, UCCE San Bernardino County

Dave Roberts, EcoLandscape California

Topics to Be Covered

Soil texture and structure Hardpan and compacted soil Protecting, improving, and nurturing soils Organic matter, compost, and mulches Synthetic vs. natural fertilizers Gypsum

The Ideal Soil is Rare!

Important Soil Characteristics

Physical Components

TextureStructure

Physical Properties

Water holdingNutrient holdingWater infiltrationAerationChemical Properties

pHCEC

Soil Texture vs. Structure

Texture – The percent sand, silt, & clay, based on the soil triangle

» e.g., sandy loam, clay loam Structure – The arrangement of primary

particles into secondary units (aggregates)

» Affected by compaction, tillage, and amendments

Soil Texture

Loamy sand LIGHT

Sandy loam

Loam

Silty loam

Clay loam

Clay

Silty clay

Sandy clayHEAVY

Sandy Clayey

Soil Particle Sizes

Sand 2.00 to 0.05 mm

Silt 0.05 to 0.002 mm

Clay 0.002 to <0.0002 mm

Percent Sand

Percent SiltPercent Clay

100 0

100

0

0

100

Clay

Silt loamSandy loam

Clay loam

Silty clay

Silty clay loam

Loam

Silt

Sandy clay loam

Sandy clay

Sand

Loamy sand

Soil Triangle

Soil Texture Affects Soil Moisture

Water Holding Capacity

Permeability

Soil Structure

Structure: the arrangement of soil particles into aggregates

Good structure: holds water (micropore space) and has air space (macropore space).

Poor structure: lacks adequate macropore space.

Soil Structure & Texture Can Be Highly Variable Across Small

Areas

Soil Stratification

Stratified Layer

Loam

Sand

Loam

Sand

Hardpan

Common in many areas

Cemented Hardpan

Primary cementing agent

» In much of Calif. – silica

» In Southwest: (caliche) – carbonates Sand, silt, & clay grains are cemented

together into a hard, impermeable layer of varying thickness

Not always continuous across the landscape

Effects of Grading

Soil Compaction

Soil CompactionEffects on the Soil

Soil structure is destroyed – pore space is severely reduced (great for buildings & hardscapes)

Soil drains slowly and is prone to being anaerobic

Compacted soil physically impedes root growth

Dry and Compacted

Soil

Shallow soil reduces

drought toleranceand anchorage

Poor Drainage, Anaerobic Conditions

Poor Root Health Leads toPoor Plant Health and

Stunting

Phytophthora Root Rot

Protecting, Improving, andNurturing Soils

Protect SoilsAvoid Compaction During Construction

Create Temporary Walkways

Remove and Store Topsoil During Construction

Protect SoilsAvoid Compaction During Construction

Protect SoilsPrevent Erosion

Protect & Nurture SoilsAerate Compacted Soils

Dealing with Compacted Soils and Cemented Hardpan

Rip / Drill Backhoe Trencher

Jackhammer / clay spade / pick ax

Dynamite

Break it up – down to good soil

Use raised planters With walls or barriers Without walls (raised mounds)

Provide drainage Will gypsum or compost break it up? NO

Drainage systems need to be carefully designed and

installed

Subsurface drainage can be improved with

drain lines, but…

(EcoLandscape principle)…maximize soil drainage to minimize off-site

drainage

Ripper

(maybe a little too big for landscapes)

Drill or Trench Soil

Backhoe or Excavate

Jackhammer, clay spade attachment

Or Break it Up Manually

Pick axe

Traditional approach

Use Raised Beds…

…Or Raised Planters

Evaluate Soils and Soil Moisture

Soil sampling tube

Soil probe Soil auger

Key Components of Sustainable Soil Management:

Organic Matter, Compost,and Mulches

Soil Organic Matter

Energy source for soil microbes Stores nutrients for plant use (CEC) Hummus = Organic portion of the soil

remaining after prolonged microbial decomposition

Technically, you cannot add humus to the soil, but adding organic matter helps improve soil

Soil Organic Matter

Energy source for soil microbes Stores nutrients for plant use (CEC) Humus = Organic portion of the soil

remaining after prolonged microbial decomposition

Technically, you cannot add humus to the soil, but adding organic matter helps improve soil

Compost

Considered a soil amendment more than a fertilizer Key benefit: Restores soil biology Well decomposed compost is best

» Reduces tie-up of N» Reduces potential for soil-borne diseases

Typical analysis: N – 1.5 to 2% P – 1.5% K – 1.5%

Helps form soil aggregates» Improved air and water movement» Improved soil structure and soil tilth» Reduced surface crusting and soil erosion» Turns soil into a “sponge” – helps absorb and

infiltrate onsite water Clay soils – increases aeration, water infiltration Sandy soils – increases water holding capacity,

helps hold nutrients

Amending Soil with CompostHow Does it Help?

Amend before planting; general guidelines:» Turf: 1-2” compost, till 5-7” deep» Beds: 2-3” compost, till 6-10” deep

Amending Soil with CompostUses and Amounts

Lawn topdressing

»Use mature compost to avoid harming lawn

»Fine (screened) compost, ¼” depth

»Best if lawn is cored before applying Potting mix

»Compost must be mature, fine textured

»Mix no more than 1/3 compost by volume

Amending Soil with CompostLawns and Potting Mixes

Compost vs. Mulch

Mulch = Organic or inorganic material spread on the soil surface

Compost = Mass of rotted organic matter made from decomposed plant material and/or manure

»Thermophilic decomposition (heat)

»Finished compost is not hot

»Usually incorporated into the soil

MulchesPotential Benefits

Prevents raindrops from splashing on the soil surface

↑ water penetration, ↓ erosion Reduces annual weeds Conserves soil moisture ↑ root growth Insulates roots from temp. extremes Protects trees from mechanical injury Improves plant establishment

Mulches Serve Many Purposes and Add Beauty

Mulch Reduces Evaporation from Soil, but Not

Transpiration

Wood Chip MulchReduces Weeds if Deep Enough

May prolong saturation in heavy soils

»Favors root and crown rot Vertebrate pests (moles, voles, mice) May host diseases, insects, nuisance

fungi, and woody plant weed seeds Can’t see soil moisture Some wood chips poor quality Time consuming to spread ($)

Wood Chip MulchPotential Problems

Remove weeds and water before applying Replace grass with mulch under trees Keep mulch 6-12 in. away from the base of

trees & shrubs Application rate: Generally 3-4 in. deep

»Fine = <2 in. Coarse = 4-6 in. Keep mulch on top of soil to prevent N tie-up

Wood Chip MulchApplication Basics

Do Wood Chips Affect Soil Nutrients?

Tie-up of N?

»N immobilization from high C:N mulch

»Generally N tie-up at interface only

»Avoid mulch in planting holes Soil pH – little effect (pine needles acidic)

Do not Make Mulch Mounds around Trunks

Mulch helps retain soil moisture

Prolonged moisture around trunk can lead to cankers and root rot

Mulch can interfere with respiration of cambium, phloem»Limits exchange of CO2 & O2

with air

Landscape Fabric MulchPolypropylene and Polyester

Better weed control than chips alone Slower breakdown of wood chips when

used together Allow water & air movement Do not improve soil quality Most are effective 3-5 yrs. (under chips) Most are not recyclable (landfill!)

Plastic or Fabric Underneath?

Synthetic mulches will usually become exposed and shred, especially on

slopes

Comparison of Fertilizers

FertilizersSynthetic, Quick Release

Provides a fast, short-lived effect Simple, cheap, accurate Petroleum & energy required for production Easy to over-fertilize with N

Greater potential for groundwater pollution

Increased pest potential

Slower, longer lasting; beneficial for most plants Less potential for groundwater pollution Polymer coating breaks down slowly with water

FertilizersSynthetic, Slow Release

FertilizersOrganic

Slower nutrient release Bulkier, harder to transport & store Re-use of a waste product Issues related to animal products?

Humane? Factory farming? Are they better to use?

Philosophical differences Lighter carbon footprint?

Test soil – nutrient analysis Cover crops for N fixation Naturally derived fertilizers

for slow release, e.g.:» Blood meal» Bone meal» Fishmeal

Use timed-releasefertilizers

Protect & Nurture SoilsDetermine Needs, Fertilize Naturally Where

Possible

GypsumCan it Improve Your Soil?

Yes

If soil is impermeable due to excess Na, or due to low Ca:Mg ratio

Probably Not

If soil is impermeable due to fine texture, compaction, or hardpan

Definitely Not

If soil is permeable and water penetrates well

Gypsum

Calcium Sulfate Dihydrate Salt

CaSO4 • 2H2O = Ca++SO4- -

Compound In solution

Does Gypsum Change Soil pH?

Na-clay + Ca++ Ca-clay + Na+

(leached out)

No!

Sulfur and Lime change pH

StopWaste.org / Bay-Friendly Landscaping & Gardening

www.stopwaste.org/home/index.asp?page=8 River-Friendly Landscaping (Sacramento)

www.msa.saccounty.net/sactostormwater/RFL/ Locating Compost and Mulch Facilities

www.calrecycle.ca.gov/Organics/SupplierList/ Composting Is Good for Your Garden and the

Environment

www.anrcatalog.ucdavis.edu

Protecting and Nurturing SoilsResources