SOIL FERTILITY MANAGEMENT IN PASTURESEquine Environmental Stewardship Program

Soil Fertility• The status of soil with respect to its ability to

supply the nutrients essential to plant growth. (Soil Science Society of America)

• In other words….- Are the correct nutrients available in the soil in order

for the crops to grow? - Is the soil too acidic for the crops to grow?

• Make adjustments (apply fertilizer and lime) to meet the crops’ demand - Appropriate time and amount

How do you begin learning about your

pasture’s soil fertility?

• Provides current fertility status of the soil

• Provides fertility recommendations

Soil Test

Soil Testing: Step 1Purchase Soil Testing Kits– Available at your local Penn State Extension

Office

– Approximately $10 per sample depending on location

– Kit includes:• Sampling instructions• Data collection form• Plastic bag for soil• Mail - in envelope

Soil TestingDetermine # of Samples–Based on:• Soil type (clay vs. sandy)• Use (pasture vs. exercise lot)• Management (fertilization, manure spreading,

etc.)• Size of testing area (10 - 20 acres for each test)

– If these factors differ, take another test

Soil Testing: Step 2Collect soil sample– Goal is to obtain a representative sample– Take at least 15 - 20 cores from random spots• Avoid abnormal areas

– One sample should not represent more than10 - 20 acres

– Sample to a depth of 3 - 4 inches–Mix cores together, remove about 1 cup for testing– Air dry and remove any stones, roots and other

material

Soil Testing

Take multiple, randomly selected sub-samples from the area to be

tested

3-4”

Soil Testing

Soil Testing: Step 3Complete Data Collection Information– Agronomic Crops Form (Yellow)– Personal Information– Identify area sampled (“Back Field”)– Crop Information (Grain Group)

• Established Pasture or Renovating Pasture (Code)

• Yield Goal

• Future Rotation Plan

SAMPLE

Soil Testing: Step 4• Mail Soil Sampling Kit

–Don’t forget to include information form and soil sample bag

– If mailing several samples:

• Match the serial # on the information form, sample bag, and envelope

–Wait 1 - 2 weeks

Soil Results

Interpreting Test Results• Existing nutrient levels and corresponding

fertility category– Below Optimum = Fertilize to build soil level based on

expected crop response

– Optimum = Fertilize to maintain soil level and amount equivalent to crop removal

– Above Optimum = No fertilizer

• Existing pH level–Numerical value

–Verbal description

Soil Recommendations

Interpreting Test Recommendations

• Fertilizer and limestone recommendations are based on cropping information provided– Crop to be grown– New stand to be planted or maintenance of existing stand– Expected yield– Future rotation plans

• Recommendations for fertilizer and limestone amendments to meet current plant requirements and to improve existing soil fertility status over three-year period are provided

… Now what?

• Address and correct nutrient deficiencies and pH through the application of fertilizers and limestone

• Helpful and necessary to understand: – Fertilizer and Liming

Materials

After the Results

Fertilizer BasicsWhat are fertilizers?

– Any organic or inorganic material added to the soil to supply certain elements essential to plant growth

• Organic (plant or animal origin)– Ex: manure, compost, blood meal

• Inorganic (synthetic or processed)– Ex: commercial fertilizers such as urea,

potassium chloride, etc.

Fertilizer Basics• Most fertilizers supply the three main essential plant

nutrients:

– Nitrogen (N)

– Phosphorous (P)

– Potassium (K)

Fertilizer Basics: Nitrogen

• Nitrogen is abbreviated as “N”

• Critical component of plant proteins

• Required for vegetative growth

• Produces lush, dark green coloration

• Most forms do not remain in the soil, rather they have high soil mobility

• N must be annually applied and in methods that reduce environmental problems

Fertilizer Basics: Phosphorous

• Phosphorus is abbreviated as “P”

• Vital role in plant reproduction

• Essential for root growth and seedling development

• Supplied as P2O5

• Limited soil mobility

Fertilizer Basics: Potassium

• Potassium is abbreviated as “K”

• Important in many chemical processes in plant growth

• Important for disease resistance, overall plant health, and winter hardiness

• Supplied as K2O

• Little soil mobility

• Grades of fertilizer are identified by three numbers, for example:

10 – 10 – 10

• Numbers represent the percentage, by weight, of N, P2O5, and K2O, respectively

Nitrogen

Fertilizer Basics: Grades

Phosphorus Potassium

Fertilizer Basics: Grades• Multiply the total weight of fertilizer material by the

percentage to determine nutrient content

– For example, a 50 pound bag of 10-20-30 fertilizer contains:

10/100 = 0.1 x 50 = 5 lb. of N

20/100 = 0.2 x 50 = 10 lb. of P2O5

30/100 = 0.3 x 50 = 15 lb. of K2O

0.20 lb. of P2O5 x 200 lb./A = 40 lb. of P2O5/A

• Urea (46-0-0) – Dry material– Instant availability • Rapid N loss due to

volatilization

– Best if incorporated into soil or applied right before rain

• Ammonium Sulfate (21-0-0-24S)– Dry material–More stable than

Urea• No volatilization

Nitrogen Fertilizers

• Triple Superphosphate (0-46-0) – Dry granular

material

– Direct application

• Muriate of Potash (0-0-60)– Dry material

– Direct application

Phosphorus and Potassium Fertilizers

pH Basics

• Soil acidity or alkalinity– Measured by pH– The pH scale is from 0 to 14

• 7.0 = Neutral• < 7.0 = Acidic• ≥ 7.0 = Alkaline or Basic

• Crops have specific soil pH requirements for optimum growth– Most pasture grasses and legumes

prefer a pH range of 6.5-7.0

pH Basics

pH Basics• Low pH conditions can cause:

– Aluminum toxicities

• Toxic to roots

– Reduced availability of soil

nutrients

• Deficiencies of calcium and/or

magnesium

– Poor conditions for soil microbes

– Poor soil structure

–Weeds to proliferate

• Limestone is an amendment used to reduce soil acidity (raise pH)

• Limestone contains carbonates and oxides of calcium and magnesium

• Expressed as CaCO3 or MgCO3

pH Basics: Limestone

pH Basics: Limestone• Limestone quality and neutralizing ability

– Limestone recommendations based on 100%

CCE

• Calcium Carbonate Equivalent

• The measure of the quality of limestone, based on the

amount of calcium carbonate

– Can vary from less than 60 to more than 125 CCE

– Higher CCE requires less lime

– Lower CCE requires more lime

(100*recommendation rate)/% CCE = amount to apply in lbs/A

(100*2,000 lbs/A)/80 = 2,500 lbs/A

pH Basics: Limestone

• Limestone particle size affects rate of

neutralization

– Finer materials react faster

– Standard mesh sizes

• 20 = Coarse (95%)

• 60 = Medium (60%)

• 100 = Fine (50%)

Pasture Fertility Management

• Different recommendations will be made:

– If the intention is to seed a new field or to fertilize

an existing field

– Depending on the type of pasture species

– Depending on the current fertility levels

Pasture Fertility Management

• New Seeding - Establishment– This may be the last chance to build nutrient

levels into the optimum range throughout the rooting zone• At this time, tillage and cultivation may be used to

incorporate fertilizers and limestone into the soil• This is particularly important if the soil pH or

phosphorus level is very low

– If required, fertilizer is usually broadcast onto the field and disked or tilled into the soil prior to seedbed preparation

Pasture Fertility Management

• Established Pastures - Maintenance

– Decide if there is enough good quality forage in the pasture to warrant fertilizer. Don’t just fertilize weeds and bare ground.

– Depending on current soil fertility levels and the type of pasture species being grown……..• The amount of N, P2O5, and K2O recommended will differ• N rates for pastures containing legumes will be lower than

pastures that are primarily grasses• Low growing grasses, such as Kentucky bluegrass, will

require different fertilizer rates and application timings than tall growing grasses, such as tall fescue and orchardgrass

Pasture Fertility Management

• Established Pastures - Nitrogen– Apply or not to apply?

• This depends on whether the pasture contains legumes or is primarily grass• If the pasture contains 75% or more legumes, no nitrogen

should be applied – Legumes such as clovers and alfalfa are able to fix

atmospheric N and utilize it for their growth, as well as provide some to neighboring grasses

• If the pasture contains primarily grasses and some legumes, N should be applied as recommended

Pasture Fertility Management

• Established Pastures - Grasses– Nitrogen

• Application rate - based on expected yield–Generally 50 lb N/acre per ton of yield is

recommended– Equivalent to approximately 100 to 125 lb N/acre

annually

• Timing - split– Early Spring (green up)– Early May– Late summer (August/early September)

• Phosphorus and Potassium

– Recommendations are provided on soil test

– Don’t apply without soil testing

Pasture Fertility Management

Conclusions• Soil testing is the foundation for sound soil fertility

management• Timely applications of lime and plant nutrients will

provide pasture plants with optimum fertility conditions

• Proper management is essential to reduce environmental risks or degradation

• Soil fertility is one piece of the puzzle for maintaining lush and dense vegetative pastures

Donna Foulk Alicia Spanglerdlf5@psu.edu ajs5201@psu.edu (610) 746 -1970 (724) 548-3447

Penn State EquineExtension.psu.edu/animals/equine

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