December 2015

Soils and their Sustainable Management

UME-Baltimore Cityextension.umd.edu/anmp

Plan for today ….•soil composition•soil testing•nutrient sources•soil sustainability (soil health)•nutrient management planning

What is Soil?

• the living skin of the Earth (Ian Pepper, soil microbiologist)

• crucible of terrestrial life (Daniel Hillel, soil physicist)

• the pedosphere • the interface between the lithosphere, hydrosphere

and atmosphere (ecologists)

• a medium for plant growth (edaphologists)

• phenomena of nature (natural bodies) (pedologists)

mysciencebox.org

What are Soils?• reactive, dynamic, three-phase ecosystems composed of

solids, liquids and gases

MineralsAirWaterOrganic Matter

48%

25%

25%

2%

topsoil several days afterrainfall or irrigation

fine texture

medium texture

coarse texture

available water capacity

medium high low

nutrient holding capacity (CEC)

high medium low

infiltration & percolation

slow medium fast

crusting high medium lowcompaction high medium low

Harsh Reality!

•textural groupings set the stage for many physical properties−parent material −time

•management can ameliorate extremes to a certain extent

Do you know the texture of the growing areas you manage? •What is it?

•How did you determine the texture?−soil testing lab reported it (extra $$)−texture by feel−soil map with published information

The Other Soil Solid Material: Organic Matter

Humus

Biomass

Residues &By-Products

75%

10%

15%

Source: USDA

Biomass: What It Does•participates in nutrient cycling−comminute (shred or fragment) plant and animal residues, using what they can utilize and leaving behind what they cannot (meso-and macroorganisms)

•mineralization (microorganisms)−conversion of organic form of an element to an inorganic form−protein to amino acid to ammonium

Biomass: What It Does (cont.)

•creation of biopores−larger organisms (meso and macro) move through soil creating channels or pores• channels promote water infiltration and create

a healthy balance between large and medium pores

−disseminate spores, microbes, nutrients and waste products

Resources about Soil Organisms *

TED Talk – How Bacteria “Talk”http://www.ted.com/talks/bonnie_bassler_on_how_bacteria_communicate.html

Soil Biology Primerhttp://soils.usda.gov/sqi/concepts/soil_biology/biology.html

Residues and By-products:What They Are

•dead stuff − crop residues, dead roots and bodies of soil

creatures

•by-products − materials that plant roots and soil creatures

release or exude into the soil

Residues and By-products:What They Do•fuel and nutrients for soil organisms −energy and nutrient source for most of the soil creatures

•formation and maintenance of soil aggregates (structure or architecture) −sticky and gummy by-products of residue decomposition hold soil particles together in clumps or aggregates

More on By-products (Exudates) *•microbial exudates kill off competing organisms−domestication of soil microbes - antibiotics

•root and microbial exudates solubilize minerals to release nutrient contained therein

•root exudates feed a huge populationof microbes in the rhizosphere

•relatively stable end product of residue decomposition

•composes the majority of organic matter•resists further decomposition (1% per year)•it is not a good nutrient or energy source for soil creatures

Humus

Humus: What It Does

•very small in particle size & high surface area

•charged sites at many locations on the surface

•effective at holding water and nutrients

Mantra

Soil is a living factory of macroscopic and microscopic workers who need food to eat and places to do their work. USDA-NRCS

So, what about the pore space…

• macropores (large pores)− drain quickly after rain or irrigation− allow rapid infiltration of rainfall and

replenishment of oxygen in the root zone• mesopores (medium-sized pores)

− “storage pores”− hold water in a form most plants can use

• micropores (very small pores)− water is held too tightly to be use to most plants− microbes live in water films

Different Pores Perform Different Functions

Soil Aeration – the interplay between water and air

Pore space

residues &by-products

sandsoilsolution

soilair

humus

inorganic solids

organic solids

silt

micro meso macro

biomass

clay layer minerals

oxides

clay

SSSAJ v. 75

What is a fertile soil?

•one that provides an adequate supply of all nutrients throughout the entire growing season

•test soil to determine if soil is too acidic and major nutrients are in inadequate supply−lime first, them add other nutrients when needed

What is Soil?

Soil is a mixture of mineral (inorganic) and organic materials found at the Earth’s surface that reflects its parent material, landscape position, climate, vegetation and the time that it has been forming

Growing Mediacommercial growing media−mixes of various organic and, in most cases, inorganic materials that provide mechanical support as well as water retention• peat, coir, compost, bark, perlite, vermiculite

compost−a material that has undergone a thermophilic, aerobic process which changed readily decomposable compounds to more stable compounds

Soil or Growing Medium?

Soil

• 2-5% organic matter

Heavily Amended Soil

• 10-20% organic matter

Growing Medium

• 50-95% organic matter

soil test saturated media extract

(SME)

1

2

3

soil (2.5 g)+

extractant (25 ml)

growing media+

distilled water or DTPA solution to saturation

shake (5 min, 200 os/min)

filter

mix

allow to equilibrate (1 hr)

remove solution

analyze analyze

What is a Management Unit in a Natural Setting?

an area with a similar complex of soils

an area which has been and will be managed similarly− same crops− same fertility regime

How Many Management Units aka Growing Areas or Beds?

•Situation:

stripped sod flat areamapped Glenelg silt

loamrototilled after

amendingcropped to tomatoes

gypsum (5T/A)

+poultry

litter (3T/A)

lime (2T/A)

+poultry

litter (3T/A)

gypsum (5T/A)

+dairy

manure(15T/A)

soil acidity:

the adverse condition in the soil solution in humid regions

Soil Sampling Card

Essential Soil Test InformationpHtexturemagnesium (Mg)phosphorus (P)potassium (K)calcium (Ca)organic matter (OM)*

(*This test is highly advisable but is not strictly essential to get a recommendation.)

Where Can Soils Be Tested?

Regulations require that planners use UME recommendations.

Certain labs’ procedures have been correlated with UME’s procedures.

After a conversion process, UME recommendations can be generated.

Compatible Labs for Commercial Growers

−A & L Eastern Analytic−Agri-Analysis−Brookside−Penn State

See “Comparison of Soil Test Labs” in this chapter.

Labs whose soil test data can be converted to the UME equivalent include:

Spectrum Analytic University of Delaware Waters Agro Lab

Soil test lab comparison

Soil Testing is not Standardized

Soil test results

Soil Tests and Their Interpretation

Soil Test Category Interpretationvery low, low nutrient will likely limit plant

growthmedium nutrient may not be limiting;

addition of nutrient advisablesufficient, optimum or high

nutrient supply is OK; no more is needed

high, very high or excessive

nutrient supply is more than adequate; no more is needed

0-45-0

46-0-0

Blood meal13-0-0

0-0-22

Nutrient Sources•fertilizers−confusing terminology

−“organic” and organic (carbon-backbone)

−commercial (labeled and purchased)

−soluble vs. slow-release

Tyson and Cabrera, 1993, CSSPA

Atmosphericnitrogen

Atmosphericfixation

and deposition

Animalmanures

and biosolids

Industrial fixation(commercial fertilizers)

Crop harvest

Volatilization

Denitrification

Runoff anderosion

Leaching

Organicnitrogen

Ammonium(NH4

+)

Nitrate(NO3)

Plant residues

Biologicalfixation by

legume plants Plantuptake

Input to soilComponent Loss from soil

-

The Nitrogen Cycle

Immobilization

Mineralization Nitrification

Modified from the Potash & Phosphate Institute web site at www.ppi-ppic.org

Mineralization Rates (fmin)

Organic Material

Fraction of original organic N available from N mineralization in each year

Year of application

1 year after application

2 years after

applicationcattle (dairy & beef 0.35 0.18 0.09

blood meal 0.65 0.10 0.05

feather or crab meal 0.60 0.10 0.05

sheep and goats 0.30 0.15 0.05

compost (C/N <25) 0.05 0 0

What is the Nutrient Content of Labeled Fertilizers?Expressed as a percent called the “guaranteed analysis” or

fertilizer grade.

Nutrient content always appears in this order:

- % total nitrogen

- % available phosphate or phosphoric acid

- % soluble potashTraditionally, phosphorus and potassium are expressed as their

oxides (P2O5 and K2O).

What Does a Fertilizer Guarantee Mean?

This bag contains: 5% nitrogen--10% phosphate--15% potash

or 2.5 lbs. nitrogen 5 lbs. phosphate 7.5 lbs. potash

Ag-Gro-Pro 5-10-15

50 lbs.

Unlabeled Organic Sources

• published tables of nutrient content−OK for homeowner

•collect a representative sample−essential for commercial grower

•obtain a nutrient analysis (“manure” analysis)

Characteristics of a Sustainably Managed Soil (Healthy Soil)

•fertile but not excessive in nutrient status•holds adequate water for plant growth•allows rainfall or irrigation to infiltrate yet provides adequate aeration

•has good tilth•has surface protection•contains adequate beneficials/minimal pathogens

Protect the Soil Surface –How?

•protect soil from direct impact of rainfall−encourage a complete crop

canopy−mulch

•plant a cool season cover crop

•minimize bare soil all seasons of the year!

Protect the Soil Surface – Why? •minimizes erosion & runoff−strip cropping, contour planting, intercropping, grassed waterways

•protects soil aggregates

•conserves moisture

•moderates soil temperature

Soil Tilth

•a soil property that assesses the suitability of soil to support plant growth

•a physical condition of a soil that relates to its ease of tillage, the impedance of seedling emergence and root penetration

Practically speaking, what does good tilth look like? •compaction is absent in the entire root zone

•soil does not crust after a rain•soil is firm when dry and friable (crumbly) when moist

•drains well after rainfall

Tips for Maintaining Good Tilth•add organic matter−food for most soil creatures (heterotrophs)−amendments −cover crops**

• warm and cool season choices•use mulch−moderates temperature and moisture content−protects soil from crusting and erosion

•minimize extreme tillage−rototilling

Are you managing your growing areas sustainably? •Are the major macronutrients in the optimal range based on soil test?

•Is it friable and crumbly when moist? •Is root growth restricted in the subsoil? •Does water pond after significant rainfall?

•Do rills form during rainfall?

Let’s talk about nutrient management….

Who Needs a Plan?

Any agricultural operation or farm that

•tills, crops, pastures animals, or produces an agricultural product, and

•has a gross annual income of $2,500 or more or 8 animal units (1 animal unit = 1000 lbs. of live weight).

What Information Must Be Provided?

•soil tests for each field and pasture•crops •manure or compost analysis•type and number of animals •amount and type of bedding•days or hours per day on pasture vs. confinement

•farm map −Google −hand drawn is acceptable

•tax account ID numbers−from tax bill or assessment

What Information Will I Be Asked to Provide? (cont.)

What is a Nutrient Management Plan?•a written, site-specific plan

•specifies the amount, placement, and timing of all nutrient applications (manure, fertilizer, or other nutrient sources)

Duration of Plans•Most plans are updated annually; however, plans can be written to cover a three-year period under some conditions.

•Soil tests & nutrient source are the limiting factors− a soil test is considered current for 3 years−organic nutrient sources are tested each year−nitrogen credits are taken for 2 years after application of organic sources

Where Can I Get a Nutrient Management Plan?

•Certified Nutrient Management Consultants −private-sector consultants−public-sector consultants (University of Maryland

Extension advisors)•Certified Farmer Operators (CFOs)−Winter schedule of Farmer Training and Certification

is online

Questions? Comments?

Compaction

•bulk density high enough or pore space low enough to negatively impact plant growth

•bulk density >1.6 grams per cubic centimeter or pore space <40% will restrict root growth

•information on either is difficult to obtain

Many subsoils in Maryland’s Piedmont are high in bulk density and low in porosity