protecting and nurturing soils chuck ingels, farm & horticulture advisor uc cooperative...
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Protecting andNurturing Soils
Chuck Ingels, Farm & Horticulture Advisor
UC Cooperative Extension, Sacramento County
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
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
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
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 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.
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
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
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
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
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!)
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
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