Turfgrass Science 101 ... nitrogen (N),phosphorus (P), and potassium (K) areamong the most important of the 13

mineral elements essential for plant growth.Elements required by plants in the greatestquantities are designated major nutrients. The dryweight of P (P2O5) in turfgrass clippings is usuallyless than 0.5%, in contrast to 3% to 5% for N andup to 5% for K (K,O) (Turgeon, A.J., 1980).Therelatively low P content in turf plants comparedto N and K, however, should not diminish its roleregarding healthy turf growth and development.

PHOSPHORUS —AN ESSENTIAL PLANT NUTRIENTPhosphate is a key component of ATP (adenosinetriphosphate), an energy-rich organic compoundproduced during the light reaction of photo-synthesis. ATP is the energy currency used byplant cells for various metabolic processes, such asthe synthesis of carbohydrates. You will find thehighest concentrations of P where all the actiontakes place — primarily meristematic regionswhere new cells are produced. Phosphorus is alsofound in seeds, where it is essential for seedlingdevelopment until the turf can develop a root

system more capable of obtaining nutrients fromthe soil solution.

STARTER FERTILIZER —PLACEMENT IS THE KEY TO SUCCESSConsidering the exceedingly small size of acreeping bentgrass seed, for example, it comes asno surprise that the supply of seed-borne P isdepleted quickly during establishment. Symptomsof P deficiency can rapidly develop during thegrow-in unless an ample supply is available inclose proximity to the shallow, immature rootsystem. As a result, general recommendations forturf establishment include a pre-plant applicationof a high-P starter fertilizer at a rate of approxi-mately 1 Ib. of N. For most starter fertilizers, 1 Ib.of N provides about 1.3 to 2 Ibs. of P2O5, whichbecomes very important about 3 to 4 weeksafter seeding when P reserves in the seed areexhausted.

Phosphate is a reactive anion that is relativelyimmobile in the soil. Soluble forms of P, suchas monoammonium phosphate, react rapidlyand form insoluble complexes with iron andaluminum under acid soil conditions and calciumunder alkaline conditions. As a general rule of

Phosphorus from

turf fertilizer is being

blamed for acceleratedeutrophication of

surface water.As as a

result, Minnesota andseveral counties/com-munities in other states

have regulated the sale

and use of fertilizersthat contain this

essential plant

nutrient.

A sign of the

times .. .turf

fertilizer

advertised as

being phosphate

free.

thumb, the only time it is unnecessary to applypre-plant phosphorus is when the soil test valuefor P is already 2 to 3 times more than theamount recommended for established turf. Forexample, if your particular soil test deems 25 ppmof P to be adequate for established turf, then apre-plant application of starter fertilizer is likelyto be beneficial anytime the soil tests less than 75ppm of P.

Reduced overall growth, narrow leaf blades,and dark green color are symptoms of moderateP deficiency. Soils in the upper Midwest with lessthan 25 ppm P (Bray-1) or 18 ppm P (Olsen) areconsidered to be phosphorus deficient. Under

severe deficiency the leaf blades canturn reddish to purple color with tipdiscoloration.

THE PHOSPHORUSCONTROVERSY -A HISTORY LESSONBased on the nature of P to be tightlybound to soils, this nutrient wouldappear to be an unlikely candidate forenvironmental concern. What factorshave resulted in recent statewiderestrictions on fertilizers that containphosphorus in Minnesota and evenmore stringent regulations in DaneCounty, Wisconsin? Let's set the stagewith information gleaned from aninteresting U.S. Geological Survey

publication regarding the history of P controlmeasures in the United States. This compre-hensive document is part of the National WaterQuality Assessment Program initiated byCongress in 1986.

WHITER WHITES ANDBRIGHTER BRIGHTSPhosphorus concerns date back to the '50s, whensynthetic detergents (powdered laundry soaps)were developed to replace bar soap, which wasthe primary cleaning agent used for clothes priorto WWII. ̂ formulated cleaning agents containedup to 15% by weight of P in the form of tripoly-phosphate, a compound that removed hardnessfrom water in the washing machines that werebeing utilized in an increasing number of house-holds at the time. According to the review, at thepeak of phosphate detergent use in 1967, theconsumption of P for making laundry soap wasabout one-tenth the amount used for fertilizer.

Needless to say, a considerable amount ofphosphorus was going down the drain into watertreatment plants and eventually into rivers andlakes.The phosphorus concentration in rawwastewater-treatment-plant effluent nearlyquadrupled from the 1940s to 1970, and overhalf the increase was believed to be caused byphosphates in detergents.

During the same period, synthetic fertilizerproduction and use increased significantly to keeppace with a growing population. Similarly, theincreasing amounts of manure used to fertilizecrops were being recycled into the environment.

A DEAD LAKEWAKES UP THE PUBLICNatural fresh surface water undergoes an agingprocess called eutrophication (eutrophic: fromGreek and German meaning well fed).The processis associated with increased aquatic plant andalgae growth, high nutrient content, a reductionin water clarity, and decreased dissolved oxygencontent. Increased biological activity ultimatelyresults in sedimentation as dead and decayingplant debris sinks and accumulates on the bottomof the lake or pond. In essence, surface water istransformed into a bog. Excessive inputs of Paccelerate the eutrophication process of lakes.

By the end of the 1960s, a serious decline inwater quality was documented for many majorbodies of surface water, especially water adjacentto heavily populated areas of the eastern UnitedStates. The poor water quality of the Great Lakes,particularly Lake Erie, caused the public to standup and take notice. Lake Erie was referred to asa dead lake. Massive blue-green algae bloomsseverely discolored water and gave drinking watera bad taste. Mats of filamentous algae littered thebeaches and affected fish spawning grounds. Thedegradation of water quality had a serious effecton commercial fisheries. In earlier days, blue pikecomprised up to 50% of commercial catches thatsometimes exceeded 20 million pounds. The bluepike population crashed between 1954 and 1958and never recovered. By 1983 it was designated anextinct species.

GOVERNMENT INTERVENTIONPublic outcry about water pollution finallyreached the politicians. The Joint Industry-Government Task Force on Eutrophication wasestablished by Congress in 1967. The goal wasto accelerate research in the hope of finding a

G R E E N S E C T I O N R E C O R D

suitable substitute for phosphates in laundrydetergent that would have minimal impact onthe environment. In 1970 a CongressionalCommittee recommended an end to the manu-facture of phosphate detergents by 1972. NoFederal legislation was passed, while Canadianstook the first significant steps to address theproblem. In Canada, phosphate levels in laundrydetergents were limited to 8.7% in 1970 andfurther reduced to 2.2% in 1972.

In the United States, cities and states began toregulate phosphate detergents. In 1971, five citiesin Illinois passed regulations to limit the amountof phosphates in laundry detergents. Since then,many states have enacted complete or partialdetergent bans, particularly states on the east coastand adjacent to the Great Lakes. By 1994 theindustry found it more cost effective to simplyremove phosphates from all domestic laundryproducts instead of maintaining separate inven-tories of phosphate-free materials.

Interestingly, some states never regulateddetergents and, in general, regulations only affectdomestic detergents, not commercial cleaningagents or dishwashing detergent. However, aquick inventory of cleaning products from mybachelor apartment was made (quick because

there just aren't that many to be found). All weredesignated phosphate free somewhere on the label,including the dishwashing detergent ... an en-lightening exercise, considering some unopenedcontainers of products hidden under the sinkwere likely purchased back in the 1970s.

THE CLEAN WATER ACTThe Federal Water Pollution Control Act arrivedin 1972. Commonly referred to as the CleanWater Act, the statute employs regulatory andnon-regulatory tools to reduce point-source andnon-point-source pollution of the nation's surfacewaters. Point-source pollution consists of effluentdischarges from pipes directly into surface water.Non-point pollution sources include runoff fromconstruction sites, agricultural erosion, feedloterosion, and urban storm sewer discharge. Pollut-ants in runoff or drainage water discharges fromgolf courses would be considered non-pointsources. Incidentally, the Clean Water Act doesnot address issues regarding groundwaterpollution.

First, concerns regarding point sources ofpollution were identified and addressed. Billionsof dollars have been spent cleaning up pollutantsfrom wastewater treatment plant effluent. Water

A thunderstorm canquickly transform a

fairway into a river.Avoid making fertilizer

applications to turf

when heavy rainfall is inthe forecast. On theother hand, be sure to

water-in fertilizer

applications as soon aspossible to move

nutrients off the grassand into the soil.

J U L Y - A U G U S T 2 0 ( 1 5

A narrow strip of

unmowed turf or

shoreline vegetation

can provide an effective

buffer zone between

fairways/roughs and

surface water. Buffer

zones provide habitat

for wildlife and help

reduce nutrient loads

into water during

runoff events.

treatment facilities were upgraded to remove orreduce a variety of pollutants, which sometimesincluded treatments to reduce P concentration ineffluent. Within a relatively short period of time,the serious problems regarding wastewater wereaddressed, particularly at treatment plants adjacentto the Great Lakes.

Since the late 1980s, the focus of the CleanWater Act has shifted to identifying and reducingnon-point sources of pollution. It was a relativelyeasy task to identify and monitor the concentra-tions of pollutants that enter and leave a watertreatment plant. However, identifying, monitor-ing, and reducing sources of non-point pollutionwere, and continue to be, a considerablechallenge.

In the rural setting, non-point pollution fromP includes agricultural soil erosion and manuredisposal from concentrated animal feeding opera-tions. In urban settings storm sewer effluent andfertilizer runoff from gardens and turf have beentargeted as sources of P into surface water.

STATEWIDE REGULATIONSFORTHE LAND OF10,000 LAKESLakes abound in Minnesota, particularly inthe heavily populated Twin Cities area. It shouldcome as no surprise that municipalities sur-rounded by lakes would develop various localordinances regulating fertilizer use. A clean,pristine lake has much greater recreational usethan a eutrophic lake choked by weeds andtainted by massive algae blooms. The first waveof P fertilizer use restrictions varied from com-munity to community and resulted in consider-able confusion for lawn-care professionals, home-owners, garden-center professionals, etc. Afterconsiderable debate, statewide fertilizer userestrictions are now in effect for the entire state ofMinnesota (Rose, C. J., and B. P. Horgan, 2005).

Fertilizer restrictions beginning January 1,2005, include:• Only phosphorus-free fertilizer will be used onlawns across the state.

G R E E N S E C T I O N R E C O R D

• Exception: phosphorus can be applied on golfcourses when a person trained in a programapproved by the Minnesota Department ofAgriculture directs their fertilizer use.• Exception: phosphorus can be applied on sodfields, which are considered to be a form ofagricultural production.• Exception: phosphorus can be applied duringturf establishment or when it is based on soil ortissue tests; however, rates need to follow thoserecommended by the University of Minnesotaand approved by the Minnesota Department ofAgriculture.

Note that Minnesota has restricted, notbanned, the use of P fertilizer. Somewhat morestringent restrictions exist currently in DaneCounty, Wisconsin, where the sale/display anduse of P fertilizer are regulated.

WHAT FUELED THEFERTILIZER CONTROVERSY?In essence, turfgrass fertilizer restrictions are acommunity response to actual or perceived con-cerns regarding accelerated, phosphorus-inducedeutrophication of nearby recreational lakes. Itdidn't help the debate when it was discovered that70% to 80% of lawn and garden soils submittedto the University of Minnesota Soil TestingLaboratory tested in the very high range forphosphorus. A similar scenario exists inWisconsin, where many soils on lawns and golfcourse fairways test high for phosphorus.

Until the recent regulations took effect, therewere few, if any, phosphorus-free commercialfertilizers for homeowners. Keeping the lawngreen meant applying fertilizer each season, so theP content of the soil slowly but surely, increased.There is little, if any, noticeable effect on turfquality where high soil P is present, unlike anobvious change in color or surge of growth thataccompanies overzealous nitrogen inputs. Golfcourse turf managers have the option of phos-phorus-free fertilizer. Unfortunately, with someexceptions, fertilizer regulations do not distin-guish between home lawns and golf course turf.

Apparently ignored during the debate wasthe fact that P that reaches a lake in an urbansetting can come from other sources besides turffertilizer. For example, a watershed study inMinnesota that compared treatments of removingvs. not removing leaves from streets during falland fertilizing lawns with P vs. P-free fertilizersshowed that P from decaying leaves had a greater

impact on nutrient loading than the use of Pfertilizers (Shapiro and Pfannkuch, 1973).

Why regulate home lawns and golf coursefertility programs instead of the vast acreage ofagricultural land that obviously has greaterpotential for erosion and runoff than a densestand of turfgrass? From the politicians' point ofview — what do we regulate first, recreational Puse or crop production? The answer should beobvious.

RESEARCH IS THE KEYPolitics aside, can P fertilizers from golf coursesbe found in leachate or runoff water? USGA-

funded research shows that under rather worse-case scenarios, such as a 2" simulated rainfall eventapplied 4 hours after a fertilizer application, P canbe found in the runoff water. However, much lessP was found in the runoff when the fertilizerapplication was watered immediately into theturf — a standard practice employed by respon-sible turf managers (Shuman, L. M., 2002).

In the same study, P was found in the leachateof simulated sand-based greens in the greenhouseunder a heavy irrigation schedule and large simu-lated rainfall event. Less nutrient leaching wasfound at lower irrigation rates. When the study•was conducted outside using field lysimeters tomore closely simulate actual greens, the amountsof nutrients found in the leachate were con-siderably lower than for the greenhouse experi-ments. The take-home message was to use less-soluble sources of P at light rates on sand-basedgreens, and, of course, don't overwater the puttingsurfaces.

In a perfect world, turf managers would be ableto apply just enough fertilizer nutrients to supplythe exact needs of the plants — no excess and

Make an extra effort

to clean equipmentin an environmentally

responsible manner.Modern equipment-

cleaning facilities areequipped with trapsthat separate grass

clippings from waste-

water, thereby reducingthe nutrient load into

storm sewers and

surface water.

no deficiencies. Judicious soil testing and tissuetesting help us make more cost-effective andenvironmentally responsible choices regardingfertilizer inputs.

Then again, if the world were perfect wewould all be able to eat just enough to maintain aconstant, ideal weight ... so it's obvious the worldis not perfect. In fact, we apply fertilizer to thesoil, where transformations occur and elementsmove in and out of dynamic equilibrium withthe soil solution. Some of the nutrients are takenup by the roots and utilized by the turf; some areimmobilized or transformed by soil microbes, andso on. Some nutrient loss through leaching andrunoff is to be expected, and responsible manage-ment practices help keep these losses into theenvironment negligible.

Knowing the concentration of phosphorus inrunoff or leachate is important because it helpsfine-tune our management practices. Moreimportant, however, is the total load of P thatreaches lakes near golf courses — a number con-siderably more difficult to determine. A trickle ofwater with a P concentration of 5 ppm that exitsa drain tile of a green after a heavy rainfall eventposes less risk of accelerated eutrophication than astream flowing into the lake that has a P concen-tration of 2 ppm. The total load is a function ofthe P concentration and the volume of water thatenters the lake.

A better view of the big picture can be seenin a study that measured the concentrations ofnutrients upstream and downstream from twogolf courses. Water was sampled on a regularschedule and after five heavy runoff events. Therewas no difference in the upstream and down-stream levels of P concentrations found in regularsampling. Golf course 1 had a slightly higher Pconcentration in water downstream on a fewoccasions after runoff events. In contrast, up-stream levels of P were always higher than down-stream after all runoff events at course 2. Theauthor suggests that the presence of a buffer stripalong the stream at course 2 was the reason whywater leaving the course had less P than waterentering the course, even after heavy rainfallevents. Long-term enrichment of streams associ-ated with runoff from the golf courses was notfound (Soli, A. M., and W. O. Lamp, 2004).

USGA-funded research to develop models fornitrogen and phosphorus runoff and leaching isbeing conducted currently at the University ofGeorgia. Buffer strips, nutrient losses from turf,

and water quality monitoring are being studied atother universities as well.

SUMMARY -- EASY DOES ITLighten up is a good attitude to take regardingphosphorus use. Soil test surveys indicate thatmany soils on golf courses and home lawnsalready have ample and often excessive supplies ofP. Make an extra effort to obtain soil tests on aconsistent schedule to monitor P levels, but avoidcomparing test results between labs because Pvalues vary according to the method ofextraction.

The most important time to ensure adequate Pis during establishment. Adequate soil test valuesfor established turf may not supply enough P forshallow-rooted seedlings.

Apply light, frequent applications of P to sand-based greens and avoid overwatering to minimizeloss of P through leaching. Water-in fertilizerapplications immediately, but avoid makingfertilizer applications when heavy rainfall eventsare forecast.

Eliminating unnecessary P use from your turfprogram will ultimately benefit the environmentand the operating budget. Monitor nutrient levelsthroughout the course consistently and you'll bebetter prepared for any unexpected regulationsdown the road.

REFERENCESLitke, D. W. 1999. Review of phosphorus control measures inthe United States and their effects on water quality. U.S.Geological Survey. Water-Resources Investigations Report99-4007.

Rosen, C.J., and B. P. Morgan. 2005. Regulation of phos-phorus fertilizer application to turf in Minnesota: historicalperspective and opportunities for research and education.Accepted for publication. International Turfgrass ResearchJournal.

Shapiro,J., and H. Pfannkuch. 1973.The Minneapolis Chainof Lakes: A Study of Urban Drainage and its Effects, 1971-1973. Interim Report No. 9. Limnological Res. Ctr. Univ. ofMinn. 248 pp.

Soli, A. M., and W. O. Lamp. 2004. Pesticide and fertilizercontamination of streams adjacent to golf courses and theresponse of the benthic macroinvertebrate community.USGA Turfgrass and Environmental Research Online3(5): 1-18. http://usgatero.msu.edu/v03/n05.pdf.

Shuman, L. M. 2002. Nutrient leaching and runoff from golfcourses. USGA Turfgrass and Environmental ResearchOnline 1 (17): 1 -9. http://turf.lib.msu.edu/tero/v01/nl7.pdf.

Turgeon,A.J. 1980.Turfgrass Management, Prentice Hall,New Jersey.

BOB VAVREK is the senior agronomist in the North-Central Region. He is happy to report that Lake Erieis alive, well, and supplying fish to interested parties.