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Methods of Fertilization

PSS 162: Soil Fertility and Management

Spring 2007



Topics of Discussion

Fertilizer Terminology

Building SOM and Fertility

Application Methods

Issues with Fertilizers




Fertilizer

any substance that is added to the soil (orsprayed onto plants) to supply those chemicalelements required for achieving plant growth




Fertilizer material

A carrier (material) that contains at least oneplant nutrient element.




Mixed Fertilizer

a fertilizer that contains two or more of the threemacronutrients (N-P-K). “Complete” mixedfertilizers contain all three macros.




Fertilizer Grade

minimum guarantee of plant nutrient content infertilizer in terms of total N, available P2O5, andavailable K20 in that order




Fertilizer Ratio

the relative amounts of N, P2O5, and K2O infertilizers




Filler

a material added to mixed fertilizers to completethe weight requirement for 2,000 pounds (1 ton)



Methods of Building Fertility in Soil

Organic matter is key factor!



Methods of Building Fertility in Soil

Conserve what you‟ve got… Avoid unnecessary tillage

Add residues to the soil Incorporate cover crops, manures, compost

and crop residues Promote biological activity for soil building over

time



Methods of Building Fertility In Soil

Crop Rotation

Cover Crops

Green Manures

Compost



Crop Rotation

decrease soil nutrient loss from:

runoff

erosion

increases soil organic matter

reduce need for purchasing fertilizer ex. legume crops which fix atmospheric N



Crop Rotation

increases soil biodiversity

increase nutrient cycling capacity

reduces build-up and carryover of soilborne diseases and insect pests



Crop Rotation: Example

Legumes which fixnitrogen

Followed by crops likecereals which neednitrogen



Cover Crops

Protects soil surface from:

Raindrop Impact

Runoff

Erosion



Cover Crops: Strategies

Four Main Strategies

Fallow Cover Crops

Winter Cover Crops

Smother Crops

Inter-seeded



Cover Crops: Fallow

Keeping continuousproduction on the farm

Reduces soil erosionand rain impact damage

Usually pick a plant likeBarseem clover whichdoes not go dormant



Cover Crops: Winter

planted in latesummer or fall

provides soil coverduring the winter

Usually a legume dueto added benefit ofNitrogen fixation



Cover Crops: Smother

Crop grown to suppresspersistent weeds

One of the best isalfalfa which competessuccessfully with manyweeds



Cover Crops: Inter-seeded

Undersowing into astanding cash crop

Get a jump on wintercover crop season

Increase biomassproduction, bettererosion control andSOM enhancement



Cover Crops: Grasses

Winter Rye

Oats

Winter Wheat

Barley, Triticale Ryegrass

Sorghum-Sudan Grass

Japanese Milet



Cover Crops: Legume

Red Clover

White Clover

Sweet Clover

Hairy Vetch Alfalfa

Field Pea

Cowpea

Soybean



Green Manures

a soil building crop

produces organic material forincorporation into the soil

Example: rapid growing summer annuals

like buckwheat and sorghum sudangrassare planted between short season veggiecrops to add organic matter to the soil



Green Manure



Compost

contains macro and micro nutrients often notfound in synthetic fertilizers

slow release



Soil Fertility Building Practices

All intended to add SOM

Subsequently building the fertility of a soil

Will reduce the need for fast release syntheticfertilizers

Contributing factors of maintaining sustainability



Addressing Specific Deficiencies

Fertility building practices are obviouslybeneficial

Still regular soil tests should be carriedout to make sure all nutrient levels are upto par

This will reveal specific deficiencies orexcesses you need to address



Fertilizer Media

Be careful if you have a certified organicoperation

Conventional growers have a wider arrayof fertilizers to address specific issues



Fertilizer Media: Organic Fertilizers

Labels are confusing

Products may contain products prohibited

under organic production synthetic urea

synthetic plant nutrients

sewage sludge

Binding agents & pelleting materials maybe synthetic



Fertilizer Media: Organic Fertilizers

Organic growers can only use approvedproducts:

Compost Uncomposted plant materials

Animal Manures

Wood Ash

Mined Substances limestone, potassium sulfate, gypsum

Fish products

Micronutrient products



Organic Fertilizers

Wood Ashes



Organic Fertilizers

Limestone

Gypsum



Organic Fertilizers

Fish Byproducts



Conventional/Synthetic Fertilizers

Used as a quick fix to address specific nutrient problems

Generally fast released compared to organic fertilizers



Conventional Fertilizers

Can also be calledsynthesized orartificial

Commonly contain thethree primary macro-nutrients (N-P-K)

Intentional mixeswhich are calledcompound or mixedfertilizers




Anhydrous ammonia

A gas

Can be applied ifabsolutely necessary

Ammonia itself can alsobe applied if incorp-orated into irrigationwater




Superphosphate

Can be synthesized

Can be created naturallyby action of guano or

bird feces




Potassium sulfate

A crude salt which addspotassium and sulfur tothe soil




Once you‟ve decided on your plan for efficientnutrient inputs…

Must choose a technique to apply them




Crops grown

Crop Rotation

Degree of Soil deficiency

Mobility of nutrients in soil

Desired speed of effect

Work force

Equipment available

Fertilizer placement depends on a number of factors:




Pre planting

Broadcast andIncorporation

At planting

Banding

Post emergent

Side dress

Top dress

Fertigation

Foliar feeding

M h d f F ili i B d



Methods of Fertilization: Broadcast

and Incorporation

Nutrient applied uniformly tosoil surface

Incorporated by tilling orcultivating

Only option for applyingfertilizers to existing standsof perennial forage (i.e. N oncool season grasses or K2Oon alfalfa)

used on entire crop fields orbeds

best for large volumes ofmaterials

used on soils that… Are not prone to leaching have significant shortage of

nutrients

M h d f F ili i B d




and Incorporation

Broadcasting

M h d f F ili i B d




and Incorporation

Incorporating



Methods of Fertilization: Banding

Applying fertilizersseveral inches belowand to the side of theseeds or transplant row

* The circles showplacement offertilizer near roots

when banding



Methods of Fertilization: Banding Most efficient fertilizer program for conventional and

especially reduced tillage

Nutrients placed in a position to feed growing plantsystems



Methods of Fertilization: Banding

Pros

More efficient thanbroadcasting

Reduces nutrient lossesbeing placed underground

Improves water-useefficiency

Subsoil moisture moreavailable during summer

Cons

Direct contact of withplant may damage crop

phytoxicity

Increased handing offertilizer and constant

„fill-ups‟



Methods of Fertilization: Side Dressing

Apply along side crop row, often at lay-by (lastcultivation for weed control)

Used mainly to apply Nitrogen



Methods of Fertilization: Top Dressing

Broadcasting/ spinningon fertilizer over theentire crop canopy spinner spreader

Rainfall/dew relied uponfor incorporation



Methods of Fertilization: Fertigation

Application of soluble

fertilizer through theirrigation system




Pros

Reduced labor costs

Simple to install

Even distribution

Consistent application at acontrolled rate

Cons

Time planning system

Equipment needed

Large initial start-up costs



Methods of Fertilization: Foliar feeding

Spray dilute solution ofnutrients onto cropcanopy

Used for:

Nitrogen Magnesium

Micronutrients

Meets emergency crop

needs

Improve cropappearance



Methods of Fertilization: Foliar feeding

Pros

Fast acting

Effective whenappropriate

Cons

Washing off from rain

Foliage burn

Low concentration dueto foliage burn

Rapid drying ofsprayed solution



Application Equipment

A quick gander at what else is out there…



Application Equipment



Issues with Fertilization

Surface Run-off

Groundwater leaching

Excess nutrients can make plantsvulnerable

Volatile gases escape into the atmosphere




Surface run-off

Plants do not metabolize all nutrients instantly

A flush of rainfall can cause nutrients to runright off the surface of the field




Groundwater leaching

Nutrients causeproblems when leached

through the soil andinto ground water

Ex. Phosphorous inwater bodies createsalgal blooms

This is detrimental tofish and other aquaticlife




Excess Nutrients can bedetrimental to crops

Too much Nitrogen canmake plants toosucculent

This stunts growth

Increases pestsusceptibility



Salt Index

High concentration of soluble salts incontact with roots causes injurious effects

This is called plasmolysis

Salt moves H2O out of cell, partially collapsingthe cell

Causes symptoms similar to drought stress

Broadcast and side dressing are effective ways

to avoid salt injury



Nitrate Depression

Adding large amounts of organic matter tothe soil may lead to nitrate depression

Where soluble nitrogen gets incorporated

into the bodies of soil decomposers untilthe carbon of OM is decomposed



References Bierman, P (2005). Nutrient Cycling & Maintaining Soil Fertility.

University of Minnesota Extension Service, RetrievedFebruary 10, 2007, fromhttp://www.extension.umn.edu/distribution/horticulture/M11

93.html Grubinger, Vernon (1999). Sustainable Vegetable Production

From Start- Up to Market . Ithica, New York: NRAES. Havlin, J, Tisdale, S, Beaton, J, & Nelson, W (2005). Soil

Fertility and Fertilizers. Saddle River, NewJersey: Prentice Hall.

Magdoff, F, & Van Es, H (2000). Building Soils for BetterCrops. Baltimore, MD: Sustainable Agriculture Network.

Pulshen, L (2004). Applications of Micronutrients: Pros and Consof Different Application Strategies. Retrieved February 13,2007, from IFA Web site:http://www.fertilizer.org/ifa/publicat/PDF/2004_ag_new_del

hi_pulschen_slides.pdf

http://www.extension.umn.edu/distribution/horticulture/M11





Thank you!

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