Diagnosing problems in horticultural soilsDiagnosing problems in horticultural soils

Soil color should be your first clue

Water movement in soils Water movement in soils

Not always down hill!!

Causes of Drainage ProblemsCauses of Drainage Problems

• CompactionCompaction• Excessive Tillage – No organic matterExcessive Tillage – No organic matter

• Lack of topsoil – Exposed parent materialLack of topsoil – Exposed parent material

• Pore size discontinuity Pore size discontinuity

Idealized Kentucky Soil Idealized Kentucky Soil

Pore Space 50%

Soil Minerals(Silt loam)

47%

Organic Matter 3%

Macropores• Include earthworm channels

• Old root channels

• Surface Cracks

Controls soil permeability and aerationControls soil permeability and aeration

Beach sand is almost entirely Beach sand is almost entirely macropores – infiltration is very high, macropores – infiltration is very high, but water holding capacity is very lowbut water holding capacity is very low

Micropores• Very fine pores

• Similar to pores in a sponge or towel

• Hold water against the force of gravity

Much of the water held in micropores Much of the water held in micropores is available to plants, is available to plants, but some is but some is held so tightly that plant roots cannot held so tightly that plant roots cannot use it.use it.

Idealized Kentucky Soil Idealized Kentucky Soil

Macropores 25% Soil Minerals

(Silt loam)47%

Miropores 25%

Organic Matter 3%

Disturbed/Compacted KY Soil Disturbed/Compacted KY Soil

Air5%

Soil Minerals(Silt loam)

72%

Water 20%

Organic Matter 3%

Characteristics of soil with poor internal structure

• Slow permeability

• Very wet natured

• Crust easily

• Poor plant productivity

Once lost, soil structure is very hard Once lost, soil structure is very hard to rebuildto rebuild – – prevention is the keyprevention is the key

Maintaining Soil Structure

• Prevent soil compaction

8 10 12 14 16 18 20 228 10 12 14 16 18 20 22

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Soil Moisture Content (%)Soil Moisture Content (%)

Optimum M.C.=14.3% for a silt loam

Higher Higher Yield Yield Potential?Potential?

Maintaining Soil Structure

• Use roto tiller sparingly

Compaction caused by tillageCompaction caused by tillage

4 – 8”4 – 8”

0.5 – 2”0.5 – 2”

Inaccessible water and nutrients

Slide by: R. PearceSlide by: R. Pearce

Pore Size Discontinuity Pore Size Discontinuity

Coarse Texture Soil

Fine Textured Soils

Pore Size Discontinuity Pore Size Discontinuity

Fine Texture Soil

Coarse Textured Soil

Use mulch to control weeds Use mulch to control weeds and conserve moisture and and conserve moisture and

reduce tillagereduce tillage

Use Cover Crops Use Cover Crops • Turnips and mustard greens

–Grow very good in the fall

–Provide ground cover to prevent erosion

–Have strong tap roots to break compaction and provide future root channels for better infiltration

• Wheat

–Roots provide organic matter

–Improves soil structure

–Reduces winter annual weed pressure

Incorporate Compost or Organic Incorporate Compost or Organic Material when TillingMaterial when Tilling

• Don’t exceed 10% per year

–½ inch mixed into the surface 5 inches

• Stabilized compost is much better

–Fresh manure use very sparingly

–Uncomposted leaves or straw tie up soil nitrogen

• Wood ash is a good sources of nutrients, but doesn’t contain organic matter

Soil MineralsSoil Minerals

Macropores 25% Soil Minerals

(Silt loam)47%

Miropores 25%

Organic Matter 3%

Soil Mineral Phase Soil Mineral Phase • Sand

–Large soil particles – feel gritty and can be seen with the naked eye

• Silt

–Much smaller than sand – feel smooth about the size of flour particles

• Clay

–So small particles can only be seen under a microscope

–Chemically active part of the soil

Changing Soil TextureChanging Soil Texture

• To change soil sand content by 10% To change soil sand content by 10% would require more than 200,000 lbs/a if would require more than 200,000 lbs/a if mixed only in the top 6 inchesmixed only in the top 6 inches

• Its probably better to learn to deal with Its probably better to learn to deal with what Mother Nature gave us.what Mother Nature gave us.

Contractor left us.Contractor left us.

Cation Exchange Capacity Cation Exchange Capacity

CaCa++++

Plant Root

HH++

KK++HH++

KK++

-----

- - --

-

-

-

- - -

-

HH++NHNH44++CaCa++++

CaCa++++

HH++

HH++

KK++

KK++

MgMg++++

MgMg++++

CaCa++++

CaCa++++CaCa++++

CaCa++++

MgMg++++

MgMg++++

MgMg++++

HH++HH++HH++

KK++

KK++

HH++

KK++

CaCa++++

CaCa++++

NHNH44++

NHNH44++

NHNH44++

Clay

ClayClay

Clay

Soil SolutionSoil Solution

Soil pHSoil pH is is the most the most important important soil test soil test conductedconducted

azaleasazaleas VegetablesVegetables

A handheld pH meter is a good investmentA handheld pH meter is a good investment

Forestry Suppliers IncForestry Suppliers Inc~$76.00~$76.00

Also needed buffers for Also needed buffers for calibration and distilled calibration and distilled water water

Estill County Soil Test Results Estill County Soil Test Results

Elemental Sulfur Reduces pHLime Increases pH

Gypsum Has No Effect

Gypsum Has No Effect??Gypsum Has No Effect??

Dunn, 2002, Cotton Study Southeast Missouri

Material Tons/a Ca:Mg pH Plant Ca

CaSO4 5.6 11.7 6.3 2868

CaSO4 3.7 11.6 6.2 2572

CaSO4 1.7 10.5 6.4 2502

Untreated 0 10.2 6.2 2472

MgSO4 1.7 7.5 6.1 2322

MgSO4 3.7 7.0 6.2 2389

MgSO4 5.6 4.0 6.3 2128

MgSO4 7.4 3.8 6.1 2086

MgSO4 9.3 3.8 6.5 2149

LSD (0.05) 316

What About Gypsum’s Effects on Bulk Density and Compaction??

• Mark Schonbeck. 2000. Soil Nutrient Balancing in Sustainable Vegetable Production, In Organic Farming Research Foundation Project Report No 99-05.

• Five locations in Virginia and eastern Tennessee for three years with three replications.

Vegetable Study (Cont)

• Low and high Ca treatment– Low Ca:Mg = 2.64– High Ca:Mg = 4.00

Created using Calcitic and Dolomitic limestone

Measured effects of ratio on soil physical properties and soil biological properties.

Soil Physical Properties

What About Gypsum’s Effects on Biological Properties??

Positive Effects of Gypsum

• Used to replace sodium on soil Used to replace sodium on soil exchange sitesexchange sites

• Does increase infiltration if soil is Does increase infiltration if soil is saturated with sodium. saturated with sodium.

• Only used to reclaim soil in arid Only used to reclaim soil in arid regions or salt spills. regions or salt spills.

Soil Testing - Nitrogen

• Nitrogen is the fertilizer needed most in KY Nitrogen is the fertilizer needed most in KY soilssoils

–Very little soil nitrogen is in the plant available Very little soil nitrogen is in the plant available form so soil testing is not generally form so soil testing is not generally recommendedrecommended

–Soil testing can be used to diagnose Soil testing can be used to diagnose excessive fertilizer applicationsexcessive fertilizer applications

–Plants take up inorganic (NOPlants take up inorganic (NO3 3 and NHand NH44) )

nitrogen – nitrogen – Organic sources must be Organic sources must be mineralized before they are plant availablemineralized before they are plant available

Fertilizer Recommendations Fertilizer Recommendations Soil Testing is the only way to know for sure how Soil Testing is the only way to know for sure how much phosphorus and potassium is needed. much phosphorus and potassium is needed.

If soil test phosphorus is above 100 lbs/a PLEASE DON’T apply any more phosphorus

Fertilizer Recommendations Fertilizer Recommendations Soil Testing is the only way to know for sure how Soil Testing is the only way to know for sure how much phosphorus and potassium is needed. much phosphorus and potassium is needed.

Potassium has no negative environment effects

Fertilizer AnalysisFertilizer Analysis

34-0-0 34% N – 0% P2O5 – 0% K2O5-5-5 5% N – 5% P2O5 – 5% K2O

Analysis Nutrient Concentration

Fertilizer recommendation is for 1 lb N per 1000 sq ft how much 34-0-0 or 5-5-5 is needed?

1 lb N/1000 sq ft0.34 lb N/lb material

3 lbs 34-0-0 per1000 sq ft

Nutrient Content of ManureNutrient Content of Manure

Other Essential ElementsOther Essential Elements

Sulfur, Calcium, Magnesium, Zinc, Sulfur, Calcium, Magnesium, Zinc, Iron, Copper, Manganese, Boron, Iron, Copper, Manganese, Boron, Molybdenum, and ChlorineMolybdenum, and Chlorine

Are almost always adequate if soil pH is adjusted for the crop

Questions ???Questions ???