TurfgrassTurfgrassFertilizationFertilization

Turfgrass fertilization is a function of grass species, turf use, cultural practices and the desires of the turf manager or client.

Fertilization PracticesFertilization PracticesTo Maintain DensityTo Maintain Density

RateRate

TimingTiming

Soil TestingSoil Testing

Rate and timing of fertilizer applications and soil testing are critical components of a turfgrass fertilization program.

Bermudagrass sports fields and golf courses overseeded with ryegrass have a high requirement for nitrogen- typically, 8 to 12 pounds of N per 1,000 sp. ft. per year.

Dormant, non-overseeded bermudagrass appears brown and drab during the winter months. Such golf courses do not attract much play during winter.

Dark green overseeded bermudgrass that is adequately fertilized is much more inviting and attracts heavy play during winter. Thus, great effort is made to produce dark-green turfgrasses through fertilization.

Likewise, sports fields that are not overseeded appear drab druing the dormant period because they lack color appeal.

In contrast, adequately fertilized bermudagrass is attractive during the growing season. Great color and attractiveness are benefits of proper fertilization.

Factors AffectingFactors AffectingFertilizationFertilization

Grass VarietyGrass Variety

Turf UseTurf Use

Soil TestSoil Test

CostCost

Environmental Environmental ConditionsConditions

ManagementManagement

Bermudagrass has the potential to Bermudagrass has the potential to respond to about 1.5 pounds of N respond to about 1.5 pounds of N per month during the summer; per month during the summer;

whereas St. Augustinegrass whereas St. Augustinegrass responds to about 1 pound of N responds to about 1 pound of N and buffalograss about 0.5 lbs N and buffalograss about 0.5 lbs N

per month.per month.

DD JJ FF MM AA MM JJ JJ AA SS OO NN DD

2.02.0

1.51.5

1.01.0

0.50.5

00

Lbs. N/MonthLbs. N/Month

Nitrogen UseNitrogen Use

MonthMonth

St. Augustine Bermudagrass

Nitrogen requirements depend on the use of the grass as well as the species of grass. Golf greens require 10 to 12 lbs N/100 sq ft. per year compared to 3 to 4 lbs N for golf course fairways.

Sports fields have a higher N requirement than lawns. Even sports fields may vary from 4 lbs N to 10 to 12 lbs N depending on soil type, location and use.

Bermudagrass lawns do well with 3 to 4 lbs N per 1,000 sq ft. per year if grass clippings are recycled.

Removing grass clippings with each mowing just about doubles the N requirement of a turfgrass site.

Plant Nutrients Contained in Plant Nutrients Contained in Grass ClippingsGrass Clippings

Plant NutrientPlant Nutrient % of Dry % of Dry WeightWeight

NitrogenNitrogen 3 to 43 to 4

PhosphorusPhosphorus 0.3 to 0.50.3 to 0.5

PotassiumPotassium 1 to 31 to 3

SulfurSulfur 0.5 to 1.00.5 to 1.0

CalciumCalcium 0.1 to 0.60.1 to 0.6

MagnesiumMagnesium 0.1 to 0.50.1 to 0.5A bermudagrass turf produces 6 to 8 thousand pounds of dry matter (dry clippings) per acre per year. At 3 to 4 percent N that amounts to over 200 pounds of N per acre that would be removed with grass clippings.

N

P K

SS

Ca Mg

FeFe

B Cl Cu Mn Mo Zn

Essential Essential Turfgrass Turfgrass NutrientsNutrients

Nitrogen is the nutrient required in the largest amount of the 13 essential nutrients derived from the soil. Carbon is required in larger amounts, but it is derived from CO3 in the air.

NitrogenNitrogen Organic Matter Organic Matter

(O.M.)(O.M.)

FertilizersFertilizersNitrogen is derived from decomposition of organic matter (about 50 lbs N per acre per year). Lightening storms provide another 5 to 10 lbs N. Turfgrasses depend on fertilization for the remainder of their N requirement.

Bermudagrass low in N (less than 2 lbs N per 1,000 sq ft per year) appears chlorotic ( yellow), has an abundance of seedheads and is readily invaded by weeds.

As N fertilization increases color improves, seed heads diminish and growth increases.

Excessive nitrogen fertilization leads to a weaker root system and lush top growth.

Nitrogen RequirementsNitrogen Requirements

GrassGrass Lbs. N/1,000 Lbs. N/1,000 ftft22/Yr/Yr

Common bermudaCommon bermuda 4 - 54 - 5

Hybrid bermudaHybrid bermuda 5 - 65 - 6

St. Augustine (Sun)St. Augustine (Sun) 3 - 43 - 4

St. Augustine (Shade)St. Augustine (Shade) 2 - 32 - 3

ZoysiaZoysia 2 - 32 - 3

Tall FescueTall Fescue 3 - 43 - 4

BuffalograssBuffalograss 1 - 21 - 2

CentipedegrassCentipedegrass 1 - 21 - 2

Recommended nitrogen fertilization rates for lawns with various trufgrasses.

Uniform, timely applications of nitrogen to a bermudagrass sports field. Applications should be distributed throughout the growing season.

Nitrogen SourcesNitrogen Sources

Soluble NitrogenSoluble Nitrogen

Slow Release NitrogenSlow Release Nitrogen

Organic NitrogenOrganic Nitrogen

The relative solubility of nitrogen sources determines the availability of nitrogen. Soluble sourced are immediately available, organic sources are intermediate and slow release sources are slowly available.

Soluble Nitrogen Soluble Nitrogen SourcesSources

UreaUrea

Ammonium SulfateAmmonium Sulfate

Potassium NitratePotassium Nitrate

Ammonium NitrateAmmonium Nitrate

Soluble N-sources are subject to leaching, runoff and denitrification as well as being readily available for uptake by plants (grasses).

Slow ReleaseSlow ReleaseNitrogen SourcesNitrogen Sources

Urea — formaldehyde (UF)Urea — formaldehyde (UF)

Isobutylidene diurea (IBDU)Isobutylidene diurea (IBDU)

Sulfur coated urea (SCU)Sulfur coated urea (SCU)

Polymer coated nitrogenPolymer coated nitrogen

Slow release N-sources may depend on soil microbes or hydrolysis (IBDU) to covert to an available from –NH4

+ or NO3-.

Water soluble nitrogen fertilizers such as illustrated by the top graph produce a rapid greening response, but a short residual response. The effects of a soluble fertilizer last less than four weeks. In contrast water insoluble or slow release fertilizers produce a more gradual but longer lasting green response. This response is general desired in turfgrasses whereas in hay production the soluble fertilizers would be desired.

Organic FertilizerOrganic Fertilizer

A material containing carbon A material containing carbon

and one or more elements other and one or more elements other

than hydrogen and oxygen than hydrogen and oxygen

essential for plant growthessential for plant growth

Example: Natural Based FertilizerExample: Natural Based FertilizerChuck’s GreeneryChuck’s Greenery 100% Natural Based Fertilizer100% Natural Based Fertilizer

14 - 2 - 414 - 2 - 4 81% Natural Organic 81% Natural Organic

7% Natural Inorganic (Mineral)7% Natural Inorganic (Mineral)

Per 100 lbs. by WeightPer 100 lbs. by Weight % of the Nutrients% of the Nutrients

12 lbs. Urea12 lbs. Urea 40% of the N40% of the N

54 lbs. Feather Meal54 lbs. Feather Meal 50% of the N50% of the N

12 lbs. Blood Meal12 lbs. Blood Meal 10% of the N10% of the N

15 lbs. Bone Meal15 lbs. Bone Meal 100% of the P100% of the P22OO55

7 lbs. Sulfate of Potash7 lbs. Sulfate of Potash 100% of the K100% of the K22OO

Factors AffectingFactors AffectingNutrient AvailabilityNutrient Availability

Oxidation = reduction state of the nutrientOxidation = reduction state of the nutrient FE FE +2+2, Fe , Fe +3+3

Concentration of the nutrientConcentration of the nutrient Water content of soilWater content of soil OxygenOxygen TemperatureTemperature pHpH

When developing a fertilizer program the turf manger needs to consider factors affecting the availability of plant nutrients. If the factors affecting availability are favorable nutrients are utilized much more efficiently. For example, saturated and compacted soils common on sports fields often fail to respond to nitrogen fertilization.

NitrificationNitrificationNHNH44

++ + O + O22 NONO22--

NONO22 + O + O22 NONO33--

Concentration of the nutrientConcentration of the nutrient Water content of soilWater content of soil OxygenOxygen TemperatureTemperature pHpH

Nitrification is the conversion of ammonium to nitrate in the soil and requires nitrifying bacteria. Consequently any soil conditions unfavorable to bacteria retard the process. Saturated soils, compacted soils and soils with a low pH fail to respond to nitrogen fertilization because the ammonium in not converted to nitrate. Grasses only use nitrogen in the nitrate form.

Nitrate (NO3-) is lostNitrate (NO3-) is lostfrom soil by:from soil by:

LeachingLeaching

Soil microorganismsSoil microorganisms

Taken up by grassTaken up by grass

DenitrifiedDenitrifiedNitrate is highly mobile in the soil and subject to leaching, denitrification (volatilization) and fixation by soil microbs as well as uptake by plants.

Nitrate is readily leached through sandy soil profiles commonly used on golf greens and sports fields. For example nitrate concentrations approach 300 parts per million in the leachate from golf greens following application of a soluble fertilizer. A slow release or organic fertilizer greatly reduces leaching loses.

DenitrificationDenitrificationNONO33

-- NONO22-- NN22OO NN22

Occurs under the following conditions:Occurs under the following conditions:

Low oxygen concentrationLow oxygen concentration High soil moistureHigh soil moisture Alkaline soilsAlkaline soils High temperaturesHigh temperatures

Denitrification is the conversion of nitrate to elemental nitrogen or other gaseous forms of nitrogen. Compacted or saturated soils, soils with a high pH and high temperatures contribute to excessive losses of nitrate.

Volatilization is the conversion of nitrate to ammonia (NH3) and is enhanced by thatchy conditions. High temperatures and high pH also contribute to

volatilization losses.

Volatilization resulted in the death of ryegrass on this golf green. Ryegrass is very sensitive to ammonia and died within hours after applying a nitrogen fertilizer to this golf green. At the time of application of fertilizer temperatures were in the 90’s and soil pH was above 8. This could have been prevented by lowering soil pH or by applying during cooler temperatures.

The nitrogen cycle in turfgrass can be The nitrogen cycle in turfgrass can be quite complex. Nitrate is taken up quite complex. Nitrate is taken up

through the roots, converted into protein through the roots, converted into protein in the leaves, recycled as ammonium as in the leaves, recycled as ammonium as grass clippings decompose and taken up grass clippings decompose and taken up

again as nitrate. Nitrogen maybe again as nitrate. Nitrogen maybe recycled three to five times during the recycled three to five times during the

growing season. Nitrate in the soil is also growing season. Nitrate in the soil is also subject to denitrification, volatilization, subject to denitrification, volatilization,

leaching and runoff.leaching and runoff.

Major NutrientsMajor Nutrients

NitrogenNitrogen

NHNH44++, NO, NO33

--

PhosphorusPhosphorus

HH22POPO44--

PotassiumPotassium

KK++

The major fertilizer nutrients include nitrogen, phosphorus, and potassium. In the fertilizer analysis nitrogen is always expressed as percent elemental nitrogen, phosphorus as percent HPO, and Potassium as percent K+.

Phosphorus is rarely limiting in turfgrass production, however in sandy root zones under irrigated conditions it can become limiting. Turfgrasses do not respond to

excessive application of phosphorus in terms of color or growth. Excessive phosphorus can lead to deficiencies of minor elements, especially iron.

Phosphorus deficiency would appear as weak, thin turf and may display a purple pigmentation. This color symptom is often apparent in newly seeded bermudagrass that is planted too early or that is watered excessively. Phosphorus is not available to the grass under saturated soils or under low temperatures. Phosphorus levels of .3 to .5 percent in plant tissue are adequate.

Phosphorus, HPhosphorus, H22POPO44--

Soil mineralsSoil minerals Organic matterOrganic matter FertilizersFertilizers

Small amounts present in soilSmall amounts present in soil Very slowly availableVery slowly available readily filled by Ca, Fe, Al & readily filled by Ca, Fe, Al &

microorganismsmicroorganismsPhosphorus is made available to the plant through decomposition of soil minerals and organic matter and as fertilizers supplement. Phosphorus tends to accumulate in fertilized turfgrasses since it is not subject to leaching or volitalization.

P availability influenced by:P availability influenced by:

pHpH

Soluble Fe, Al (low soil pH)Soluble Fe, Al (low soil pH)

Soluble Ca (high soil pH)Soluble Ca (high soil pH)

Amount of organic matterAmount of organic matter

Activity of microorganismsActivity of microorganisms

Phosphorus is most available at a pH range of 6 to 7.5.

The typical appearance of a seedling bermudagrass showing phosphorus deficiency.

Potassium, KPotassium, K++

Often present in large amounts:Often present in large amounts:

Soil mineralsSoil minerals

Organic matterOrganic matterIn clay or clay loam soils, potassium is usually present in adequate quantities. In sandy root zones, potassium is a limiting nutrient. Fertilizer applications provide the major source of potassium to turfgrasses.

Turfgrasses appear chlorotic and thin under low potassium levels. Such grasses are also subject to severe wear and weed invasions. Potassium levels are adequate at 1.5 percent or greater. However, on sports fields or high traffic areas 2 percent potassium in plant tissue is desirable. Once the potassium level is adequate grasses do not respond in terms of color or growth to additional potassium.

With low levels of K in plant tissue grasses appear chlorotic and weak. Such grasses are subject to severe wear.

Calcium (CaCalcium (Ca++++) and) andMagnesium (MgMagnesium (Mg++++))

Limestone (CaCOLimestone (CaCO33))

Dolomite (MgCODolomite (MgCO33))

Gypsum (CaSOGypsum (CaSO44))

Calcium and Magnesium are considered secondary fertilizer nutrients, but are often adequate in soils.

Calcium deficiencies appear as chlorotic, thin turf. Calcium can be provided by limestone or gypsum.

Magnesium deficiencies appear similar to calcium. In sandy soils magnesium deficiencies are not uncommon.

Minor NutrientsMinor Nutrients

Iron, FeIron, Fe++++

Zinc, ZaZinc, Za++++

Manganese, MaManganese, Ma++++

Molybdenum, MoOMolybdenum, MoO44

Copper, CaCopper, Ca++++

Boron, BOBoron, BO33--

Chlorine, ClChlorine, Cl--

Sodium, NaSodium, Na++

Minor nutrients are required in very low concentrations in plant tissue. Iron is the minor nutrient most often found deficient in turfgrasses. Iron deficiencies are

common in central and south Texas in St. Augustine lawns.

Trace nutrients or micronutrientsTrace nutrients or micronutrientsFeFe++++, Ma, Ma++++, Zn, Ca, Bo, Mo, Cl, Na, Zn, Ca, Bo, Mo, Cl, Na

Soil mineralsSoil minerals Organic matterOrganic matter FertilizersFertilizers

Conditions conducive to micronutrient Conditions conducive to micronutrient deficienciesdeficiencies

Sandy soilsSandy soils High soil pHHigh soil pH Clipping removalClipping removal

Minor (or trace) nutrients are provided from soil minerals and organic matter as well as fertilizer applications. Conditions conducive to micronutrient deficiencies include sandy soils, high pH and clipping removal. Such conditions are common on golf greens and turfgrasses growing on sandy soil.

Soil pHSoil pH

Acid soils, pH below 6.5Acid soils, pH below 6.5

Alkaline soils, pH above 7.2Alkaline soils, pH above 7.2

Nutrient efficiency decreases at pH Nutrient efficiency decreases at pH below 7.0below 7.0

Micronutrient availability decreases Micronutrient availability decreases at pH above 7.5at pH above 7.5

Soil pH is the property that has the greatest impact on minor nutrient availability. At pH’s above 7.5 most minor nutrients become deficient.

Plant Nutrient RecoveryPlant Nutrient RecoveryReduced by Soil AcidityReduced by Soil Acidity

0

10

20

30

40

50

60

70

7.0 6.0 5.5 5.0 4.5

Nitrogen Phosphate Potash

Soil pHSoil pH

Nu

trie

nt

Rec

over

y %

Nu

trie

nt

Rec

over

y %

Soil pH affects the availability of major fertilizer nutrients as well as of minor nutrients.

Iron deficiency in St. Augustinegrass appears as bright yellow (chlorotic) irregular patches in lawns. Such conditions are common under the dripline of trees since tree roots are much more efficient at extracting iron from the soil.

Iron deficiencies appear first in new leaves since iron is not mobile within the plant. Upon close examination the veins in the grass tissue often remain green giving the leaf a stripped appearance.

High phosphorus fertilizers contribute to iron deficiencies in turfgrasses. The grass on the left shows severe iron deficiency as a result of high phosphorus levels in the soil.

Iron deficiencies can be corrected by application of numerous iron containing fertilizers. Here Ironite was applied to a three foot stripe in the center of this lawn to demonstrate its affect on greening. Most products only last three to four weeks.