Turfgrass Fertilization

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

Fertilization Practices
To Maintain Density Rate Timing Soil Testing Rate and timing of fertilizer applications and soil testing are critical components of a turfgrass fertilization program. 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. 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. 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. 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. 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. In contrast, adequately fertilized bermudagrass is attractive during the growing season. Great color and attractiveness are benefits of proper fertilization.

Factors Affecting Fertilization
Grass Variety Turf Use Soil Test Cost Environmental Conditions Management All of these factors affect the fertilization requirements of a turfgrass site.

Bermudagrass has the potential to respond to about 1
Bermudagrass has the potential to respond to about 1.5 pounds of N per month during the summer; whereas St. Augustinegrass responds to about 1 pound of N and buffalograss about 0.5 lbs N per month.

Nitrogen Use Lbs. N/Month Month 2.0 1.5 1.0 0.5
Bermudagrass has the potential to respond to about 1.5 pounds of N per month during the summer; whereas St. Augustinegrass responds to about 1 pound of N and buffalograss about 0.5 lbs N per month. D J F M A M J J A S O N D Month 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. 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
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. 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
Bermudagrass lawns do well with 3 to 4 lbs N per 1,000 sq ft. per year if grass clippings are recycled. 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 Grass Clippings
Plant Nutrient % of Dry Weight Nitrogen 3 to 4 Phosphorus 0.3 to 0.5 Potassium 1 to 3 Sulfur 0.5 to 1.0 Calcium 0.1 to 0.6 Magnesium 0.1 to 0.5 A 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. A 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.

Essential Turfgrass Nutrients
P K S Ca Mg Fe B Cl Cu Mn Mo Zn 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. 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.

Nitrogen Organic Matter (O.M.) Fertilizers
Nitrogen 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. Nitrogen 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. 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 Requirements
Recommended nitrogen fertilization rates for lawns with various trufgrasses. Grass Lbs. N/1,000 ft2/Yr Common bermuda 4 - 5 Hybrid bermuda 5 - 6 St. Augustine (Sun) 3 - 4 St. Augustine (Shade) 2 - 3 Zoysia 2 - 3 Tall Fescue 3 - 4 Buffalograss 1 - 2 Centipedegrass 1 - 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. Uniform, timely applications of nitrogen to a bermudagrass sports field. Applications should be distributed throughout the growing season.

Nitrogen Sources Soluble Nitrogen Slow Release 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 Slow Release Nitrogen Organic 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 Sources
Urea Ammonium Sulfate Potassium Nitrate Ammonium Nitrate Soluble N-sources are subject to leaching, runoff and denitrification as well as being readily available for uptake by plants (grasses). Soluble N-sources are subject to leaching, runoff and denitrification as well as being readily available for uptake by plants (grasses).

Slow Release Nitrogen Sources
Urea — formaldehyde (UF) Isobutylidene diurea (IBDU) Sulfur coated urea (SCU) Polymer coated nitrogen Slow release N-sources may depend on soil microbes or hydrolysis (IBDU) to covert to an available from –NH4+ or NO3-. 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. 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 Fertilizer A material containing carbon and one or more elements other than hydrogen and oxygen essential for plant growth

Example: Natural Based Fertilizer
Chuck’s Greenery 100% Natural Based Fertilizer % Natural Organic 7% Natural Inorganic (Mineral) Per 100 lbs. by Weight % of the Nutrients 12 lbs. Urea 40% of the N 54 lbs. Feather Meal 50% of the N 12 lbs. Blood Meal 10% of the N 15 lbs. Bone Meal 100% of the P2O5 7 lbs. Sulfate of Potash 100% of the K2O

Factors Affecting Nutrient Availability
Oxidation = reduction state of the nutrient FE +2, Fe +3 Concentration of the nutrient Water content of soil Oxygen Temperature pH 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. 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.

Nitrification NH4+ + O2 NO2- NO2 + O2 NO3-
Concentration of the nutrient Water content of soil Oxygen Temperature pH 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. 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 lost from soil by:
Leaching Soil microorganisms Taken up by grass Denitrified Nitrate 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 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. 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.

Denitrification NO3- NO2- N2O N2 Low oxygen concentration
Occurs under the following conditions: Low oxygen concentration High soil moisture Alkaline soils High 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. 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 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
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. 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 quite complex
The nitrogen cycle in turfgrass can be quite complex. Nitrate is taken up through the roots, converted into protein in the leaves, recycled as ammonium as grass clippings decompose and taken up again as nitrate. Nitrogen maybe recycled three to five times during the growing season. Nitrate in the soil is also subject to denitrification, volatilization, leaching and runoff.

Major Nutrients Nitrogen NH4+, NO3- Phosphorus H2PO4- Potassium K+
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+. 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 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 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, H2PO4- Soil minerals Organic matter Fertilizers
Small amounts present in soil Very slowly available readily filled by Ca, Fe, Al & microorganisms Phosphorus 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. Phosphorus 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:
Phosphorus is most available at a pH range of 6 to 7.5. pH Soluble Fe, Al (low soil pH) Soluble Ca (high soil pH) Amount of organic matter Activity 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, K+ Often present in large amounts: Soil minerals
Organic matter In 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. In 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
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. 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
With low levels of K in plant tissue grasses appear chlorotic and weak. Such grasses are subject to severe wear. With low levels of K in plant tissue grasses appear chlorotic and weak. Such grasses are subject to severe wear.

Calcium (Ca++) and Magnesium (Mg++)
Calcium and Magnesium are considered secondary fertilizer nutrients, but are often adequate in soils. Limestone (CaCO3) Dolomite (MgCO3) Gypsum (CaSO4) Calcium and Magnesium are considered secondary fertilizer nutrients, but are often adequate in soils.

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

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

Minor Nutrients Iron, Fe++ Zinc, Za++ Manganese, Ma++ Molybdenum, MoO4
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. Iron, Fe++ Zinc, Za++ Manganese, Ma++ Molybdenum, MoO4 Copper, Ca++ Boron, BO3- Chlorine, Cl- Sodium, 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 micronutrients
Fe++, Ma++, Zn, Ca, Bo, Mo, Cl, Na Soil minerals Organic matter Fertilizers Conditions conducive to micronutrient deficiencies Sandy soils High soil pH Clipping 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. 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 pH Acid soils, pH below 6.5 Alkaline soils, pH above 7.2
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. Acid soils, pH below 6.5 Alkaline soils, pH above 7.2 Nutrient efficiency decreases at pH below 7.0 Micronutrient availability decreases at 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 Recovery Reduced by Soil Acidity
Soil pH affects the availability of major fertilizer nutrients as well as of minor nutrients. Soil pH 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 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. 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. 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. 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.

Turfgrass Fertilization

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