Soil Fertility and

Pasture Fertilization

Les Vough

Forage Crops Extension Specialist Emeritus

INAG 116

Causes of low pasture productivity:

Lack of adequate fertilization.

Poor grazing management.

Unproductive species.

Adequate Fertilization

Soil test every 2-3 years.

Lime and fertilize according to soil test recommendations.

Soil Testing

If no-till seeding, sample from 2 depths -- surface to 2 inches and surface to 8 inches or normal plow layer if pasture has ever been plowed.

If tilled soil seeding, sample from surface to 8 inches or the plow or tillage depth.

Correct Fertility Deficiencies

Do not attempt seeding unless willing to apply the recommended amounts of lime and fertilizer.

pH affects availability and plant utilization of minerals.

P critical for seedling development.

K critical for maintaining legumes.

Apply 1 – 3 years before seeding.

Pasture Soil Fertility Pasture Soil Fertility ManagementManagement

Daniel Kluchinski County Agent & Assistant

Director

Rutgers University

Mid-Atlantic Equine Pasture InitiativeMid-Atlantic Equine Pasture Initiative

Paul H. CraigDauphin County Cooperative

Extension Agent

Penn State University

pH Basics

Soil acidity or alkalinity is

measured by pH

o 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

Low pH conditions can cause:

o Aluminum toxicities

o Reduced availability of soil nutrients

o Poor conditions for soil microbes

o Deficiencies of calcium and/or magnesium

o Poor soil structure

pH Basics: Limestone

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

Quality and neutralizing ability

o Depends on origin or source of limestone

o Limestone recommendations are based on Calcium Carbonate Equivalent (CCE)

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

o The actual amount of limestone to be applied will differ from material to material due to different CCE values for each

pH Basics: Limestone

Limestone particle size affects rate of

neutralization

o Finer materials react faster

o Pulverized > ground > granular

Ag lime must meet minimum standards and

the label must provide a guaranteed analysis

CCE value

Fertilizer Basics

Most fertilizers are products that

supply:

o Nitrogen (N)

o Phosphorous (P)

o Potassium (K)

Fertilizer Basics: Grades

Grades of fertilizer are identified by three numbers, for example:o 10-10-10o 5-10-5o 46-0-0

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

Fertilizer Basics: Nitrogen

Nitrogen is abbreviated as “N” Listed as the first number in fertilizer grade

o 10-10-10 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 Can be fixed by legumes

Fertilizer Basics: Phosphorous

Phosphorus is abbreviated as “P” Listed as the second number in fertilizer

gradeo 10-10-10

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” Third number in fertilizer grade

o 10-10-10 Important in many chemical processes

in plant growth Important for disease resistance,

overall plant health, and winter hardiness

Supplied as K2O Little soil mobility

Fertilizer Basics: Grades

Multiply the total weight of fertilizer material by the percentage for each nutrient to determine actual nutrient contento For example, an 80-pound bag of

10-10-10 fertilizer contains 8 lb. of N

8 lb. of P2O5

8 lb. of K2O

Fertilizer Basics: Grades

Fertilizer recommendations are

provided based on pounds of

nutrients needed for the given crop

based on the soil test levels and

expected yields

Application timing and method will

be provided in the recommendation

Fertilizer Basics: Manures

Manures are a source of nutrients o Typical nutrient composition of

horse manure (per ton) 12 lb. of N

5 lb. of P2O5

9 lb. of K2O

o A manure analysis will provide data on specific nutrient concentrations

Fertilizer Basics: Manures

Manure should be applied to fields only if fertility levels justify their application.

Manures can be composted to reduce their volume as well as any pathogens contained within.

Pasture Fertility Management

Soil testing data and recommendations should be followed to develop a fertility and pH management plan

Recommendations differ, depending upon:

o New seeding or established stand

o Grass and legume species

o Current fertility levels

Pasture Fertility Management

Establishing New Seedingso Last chance to build nutrient levels into

the optimum range throughout the rooting zone At this time, tillage may be used to incorporate and mix lime and fertilizer into the soil

This is particularly important if the soil pH or phosphorus level is very low

o Fertilizer and lime usually broadcast onto the field and disked or tilled into the soil prior to seedbed preparation

Pasture Fertility Management

Establishing New Seedings o Different application procedures are

used depending on the amount of lime or fertilizer to be applied

If large amounts are recommended, apply as a split application -- plow down ½ the amount and surface apply the remaining ½

If small amounts are recommended, apply the entire amount on surface

Pasture Fertility Management

Maintenance of Established Pastures

o Amount of N, P2O5, and K2O recommended depends on current soil fertility levels and the type of pasture species being grown.

o N not recommended for pastures containing >25% legumes.

o Heat sensitive grasses such as Kentucky bluegrass and timothy require different fertilizer rates and application times than less sensitive grasses such as tall fescue and orchardgrass.

Pasture Fertility Management

N -- Established Grass Pastureso Rate based on expected yield

– Generally 40 lb N/acre/ton of expected yield is recommended

– Equivalent to approximately 100 to 250 lb N/acre annually

o Timing – split applications

– Late winter/early spring (green up)

– Mid- to late May

– Late Aug/early Sept

Pasture Fertility Management

P and K --Established Grass Pastures

o Application rates based on soil nutrient levels

and expected yields

– Generally 10 - 20 lb P2O5 and 45 - 60 lb K2O

removed/ton of forage

o Timing

– For low fertilizer rates, timing not critical – High rates should be split for maximum

efficiency »½ in mid- to late May»½ in late Aug/early Sept

Pasture Fertility Management

Long-Term Management

o Recommended fertilizer applications should be followed for a 2- to 3-year period.

o Soil should be retested every 2 to 3 years to determine:

Soil pH and fertility status

If any change in fertilization and pH management is necessary

Pasture Fertility Management

Long-Term Managemento All soil test reports should be kept on file

for historic referenceo All application records should be retained

for future reference Include a field-by-field inventory Record lime and fertilizer analyses and rates Record manure applications

o Reference this information and follow the recommendations to improve and maintain soil fertility

Conclusions

Optimum production of pasture plants depends on optimum pH and fertility management

Soil testing is the foundation for sound soil fertility management

Timely applications of necessary lime and plant nutrients will provide pasture plants with optimum fertility conditions

Proper management is essential to reduce environmental risks or degradation