AND POA ANNUA - THE REST OF THE STORY Wayne R. Kussow, Professor of Soil Science University of Wisconsin, Madison, WI

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1 KUSSOW 17 PHOSPHORUS AND POA ANNUA - THE REST OF THE STORY Wayne R. Kussw, Prfessr f Sil Science University f Wiscnsin, Madisn, WI A mre apprpriate title here is "Anther Chapter in the Phsphrus - Pa Annua Stry." The first chapter f this stry pens with the bservatin f Sprague and Burtn (1937) that Pa annua (hereafter referred t as PA), when grwn alnein pts, exhibited a grwth respnse t P applicatins made t a lw P sil but nt when made t a high P sil. Cmparable greeenhuse studies cnducted by Juska and Hansn (1967, 1969) prduced similar results. They t grew n ther grass species fr cmparisn purpses. Rather, they drew upn earlier research experiences t cnclude that PA des nt differ frm ther bluegrasses in its respnses t N, P, and K (Juska and Hansn, 197). The PA-phsphrus cnnectin was strengthened in 1981 when Dest and Allinsn reprted that PA densities and survival in a glf curse fairway were directly related t the leaf P cntent f PA. They fund leaf P cncentratins f.41 t.6% and cmpared these t P cncentratins f.12 t.24% reprted in the literature fr health Kentucky bluegrass. This gave rise t the idea that PA has an unusually high P requirement that, if satisfied, favrs PA encrachment in turf. Varc and Sartain (1986) demnstrated that maximum PA clipping weights are assciated with high leaf P cncentratins, in the range f.52%. The missing link in the argument that high sil P levels give PA a cmpetitive advantage ver ther turfgrasses is evidence that ther grasses have lwer P requirements. The wrk f Lunt, Brnsn and Clark (1967) suggests that this may be the case. The results f their study shwed that the tissue P cncentratins assciated with maximum grwth rates f ther turfgrasses are apprximately.47% fr cmmn burmuda grass,.45% fr Kentucky bluegrass,.47% fr Highland bentgrass,.32% fr Emerald zysia, and.42% fr Alta fescue. At this pint we leave chapter 1 f the PA-phsphate stry and mve nt the secnd chapter. This chapter begins with the bservatin by several researchers that nutritinal effects n PA encrachment in turf extend beynd just P. These include N (Sprague and Burtn, 1937; Engel, 1977; Engel and Bussey, 1979), K (Waddingtn, et ai, 1978) and S (Gss, 1974; Varc and Sartain, 1986). In ttal, these studies ffer evidence that the effects f P n PA encrachment in turf are dependent n the levels f N, K and S applied with the phsphate. In fact, Dest and Allinsn (1981) cncluded that balanced N-P nutritin is required fr ptimum survival f PA in a mixed Kentucky bluegrassbentgrass glf curse fairway. The cnnectin between N and P seems t be fairly straight frward and may apply t K and S as well. In ne f ur field trails where Kentucky bluegrass was grwn n a sil riginally high in P and fertilized with different N fertilizers cntaining variable amunts f P, leaf P cncentratins bre n relatinship t the amunt f P applied. Rather, tissue N levels

18 GOLF TURF MANAGEMENT accunted fr nearly 98% f the bserved variatin in tissue P cncentratins. In ther wrds, grass utilizatin f P under these circumstances was dependent n the N status f the plant.

2 18 GOLF TURF MANAGEMENT accunted fr nearly 98% f the bserved variatin in tissue P cncentratins. In ther wrds, grass utilizatin f P under these circumstances was dependent n the N status f the plant. This cncludes the secnd chapter in the PA-phsphate stry and leaves us with the ntin that high sil P levels r applicatins f high P rates alne d nt autmatically signify rapid encrachment and survival f PA in turf. Our third chapter begins with the assertin that N is mre crucial than P when it cmes t PA invasin f bent grass turf. In 1977, Engel reprted research results frm which he cncluded that the key t minimizing encrachment f PA in bentgrass is minimal use f N. He als demnstrated that time f N applicatin has a significant effect n the rate f invasin f bentgrass by PA. Cntinuatin f this research by Engel and Bussey (1979) further supprted the bservatin that N rate has a dminating effect n PA encrachment but als depends n the N carrier applied and when N is applied. Nitrgen rate, carrier and scheduling effects n PA ppulatin f bentgrass have als been reprted by Sprague and Burtn (1937), Waddingtn, et ai, (1978), Dest and Allinsn (1981), Snaydn and Hwe (1986), and Dest and Guillard (1987). What is s striking abut the wrk f Engel and Bussey (1979) and Dest and Guillard (1987) is the magnitude f changes in PA ppulatins assciated with N fertilizatin f intensively managed turf. These changes match and in many cases surpass by a cnsiderable amunt the rates f PA encrachment and grass species ppulatins shifts arising frm variatin f the P supply. The furth chapter in this PA-phsphate saga fcuses n the wrk f Snaydn and Hwe (1986). They applied an eclgical apprach in designing a study t determine whether it was abve-r belwgrund cmpetitin that cntrlled invasin f varying densities f perennial ryegrass by Paa annua, P. trivialis and Festuca rubra and the nature f that cmpetitin. They bserved that in the case f PA in particular, the cmpetitin was belw-grund and increased markedly with increasing ryegrass density (i.e. decreasing size f invasin gaps). Applicatin f N alleviated the rtzne cmpetitin between PA and the ryegrass while P and K applicatins had little effect n PA seedling survival. This research prvides a lgical explanatin fr the bservatin by Dest and Guillard (1987) that the PA ppulatin in a bentgrass turf decreased with increasing bentgrass density and declined as much as 34% ver a 3-year perid when the annual N rate was reduced frm 8 t 2 t 3 lb/m. This furth chapter in ur stry leads us t the cncept that rapid invasin f turf by PA requires the presence f invasin gaps and adequate supplies f N t vercme rt cmpetitin between the PA seedlings and the existing turfgrass plants. This des nt preclude applicatin f P and ther essential nutrients frm having an influence as well when their supplies are less than ptimal with respect t N. Thus, given the right circumstances, ne might be able t demnstrate that applicatin f anyne f the essential plant nutrients favrs PA encrachment int pre-existing turf. The idea that the presence f invasin gaps is a prerequisite fr encrachment f turf by PA is certainly nt new. Sprague and Burtn cncluded in 1937 that bentgrass density at the time f PA seed prductin is the cntrlling factr in the effects f different N fertilizers n the abundance fpa Cincidence between bentgrass density and the time fpa seedset may well accunt fr Engel's (1977) bservatin that late August and fall N applicatins encurage PA encrachment in bentgrass. With these thughts in mind, we established a field study t see what effect different sil test P levels and fur N carriers, each applied at three rates, have n the invasin f a new stand f creeping bentgrass. The intent was t give the bentgrass a year t acclimate t the N treatments and then verseed with PA. Natural invasin by PA, mst likely in August f the first full year f the study, thwarted this plan, but allwed bservatin f treatment effects n PA invasin by August f the secnd year f the study. The fllwing spring, a well-intentined glf curse emplyee treated the plts with benefin plus trifluralin. This dramatically reduced the PA ppulatins that spring and prmpted.verseeding ne-half f each plt with PA the fllwing August. Thrugh this series f events, we were able t bserve N treatment effects n natural invasin by PA and the reestablishment f PA ppulatins frm the natural invaders and the natural invaders plus the intrduced PA seed. In August f 1988, ppulatins fpa were cunted at the peak f inflrescence. Sil test P levels at that time ranged frm 111 t 28 1b/A. Ppulatin cunts were made again in May, 199, by which time cntinual applicatins f activated sewage sludge and clipping remval had altered the range in sil test P levels t 65 t 245 lb/a. Under these cnditins, there were n significant relatinships

KUSSOW 19 between sil P levels and natural PA ppulatins in 1988 (Figure 1) r PA ppulatins in 199 frm the nn-verseeded (Figure 2) r PA-verseeded plt areas (Figure 3).

3 KUSSOW 19 between sil P levels and natural PA ppulatins in 1988 (Figure 1) r PA ppulatins in 199 frm the nn-verseeded (Figure 2) r PA-verseeded plt areas (Figure 3). Wide ranges in bentgrass verdure due t the N treatments and the casual bservatin that there was decidedly mre earthwrm activity in the activated sludge plts where PA ppulatins were ntably greater, prmpted examinatin f the PA ppulatins in relatin t bentgrass verdure and earthwrm activity recrded as numbers f casts in the plts. This analysis revealed that these tw factrs accunted fr nearly 85% f the extent f natural invasin f PA in the plts by August f As shwn in Figure 4, PA ppulatins increased almst linearly with the numbers f earthwrm casts present. Increases in bentgrass verdure partially ff-set the apparent enhancement f PA establishment by the presence f large numbers f earthwrm casts. The respnse surface shwn in Figure 4 suggests that lw bentgrass verdue prevented invasin by PA Actually, this is indirect evidence that the lw N rates that led t lw verdure were insufficient t vercme rtzne cmpetitin between PA seedlings and bentgrass fr N. In May f 199, bentgrass verdure and earthwrm cast numbers accunted fr 79% f the variatin in the numbers f PA plants per plt. But in this instance, the influence f earthwrm activity was nearly cnstant while bentgrass verdure was the dminant factr cntrlling PA ppulatins (Figure 5). Virtually n PA was fund at verdure levels abut 1.35 gldm 2 Changes in PA ppulatins between August, 1988, and May, 199, (Figure 6) were largely accunted fr by bentgrass verdure and earthwrm cast numbers averaged ver this perid f time (R 2 =.857). Intermediate verdure, in cmbinatin with a high level f earthwrm activity, was mst effective in sustaining high PA ppulatins. Lw verdure and n earthwrm activity r very high verdure actually led t reductins in the PA ppulatins. In the case f lw verdure, the effect is presumed t be that f strng rtzne cmpetitin fr N that reduced PA seedling survival. The effect f high verdure was likely the creatin f a situatin in which there were few invasin gaps wherein PA culd becme established. Des this research cnstitute the "rest f the stry" regarding phsphrus and Pa annua? Undubtedly nt. As with any field study, the results may well be site specific and certainly d nt apply t sites inhspitable t earthwrms. On the ther hand, the results d cnfrm t what I see as ur current understanding f hw fertilizatin influences PA encrachment in bentgrass. The prerequisites fr PA encrachment are the existence f invasin gaps, particularly when PA seed supplies are ample, adequate levels f all nutrients in the sil, and sufficient fertilizer N t vercme bentgrass rt cmpetitin with the emerging PA seedlings.

4 11 GOLF TURF MANAGEMENT PA = Sil P C\l. r 2 =.4 l 3 " Sil P - lb/a Figure 1. Relatinship f sil test P level t numbers f Pa annua plants in creeping bentgrass turf in August f 1988.

5 KUSSOW Nt Overseeded 5 4 PA = Sil P r 2 = Sil P - lb/a 25 Figure 2. Relatinship f sil test P level t numbers f Pa annua plants in creeping bentgrass turf in May, 199, when nt ver seeded with Pa annua the previus August.

6 112 GOLF TURF MANAGEMENT 199 Overseeded C\l 6 PA = Sil P r 2 =.529 1O t- 4 ""-. g Q ;j Q 2 Q Sil P - lb/a 25 Figure 3. Relatinship f sil test P level t number f Pa annua plants in creeping bentgrass turf in May, 199, after verseeding with Pa annua the previus August.

7 KUSSOW Figure 4. Respnse surface shwing the influence f number f earthwrm casts and verdure n the natural invasin f creeping bentgrass bypaannua in 1988 (R 2 =.849). ---

8 114 GOLF TURF MANAGEMENT 199 N..J t Figure 5. Respnse surface shwing the influences f numbers f earthwrm casts and verdure n the Pa annua ppulatin in creeping bentgrass in 199 resulting frm natural invasin and verseeding f Pa annua the previus year (R2 =.792).

9 KUSSOW 115 Pa change: 1988 t j..) C 5 =' C 2-1 Figure 6. Respnse surface shwing the influence f average number f earthwrm casts and verdure n the change in the Pa annua ppulatin in creeping bentgrass frm 1988 t 199 (R2 =.857).

10 116 GOLF TURF MANAGEMENT LITERATURE CITED 1. Dest, W.M. and D.W. Allinsn Influence f nitrgen and phsphrus fertilizatin n the grwth and develpment f Pa annua L. (annual bluegrass). Prc. 4th Int. Turfgrass Res. Cnf. p Dest, W.M. and K. Guillard Nitrgen and phsphrus nutritinal influence n bentgrass - annual bluegrass cmmunity cmpsitin. J. Amer. Sc. Hrt. Sci. 112(5):n Engel, R.E Annual bluegrass: Friend r fe? Glf Superintendent. July. p Engel, R.E. and C.W. Bussey The effect f fertilizatin n annual bluegrass. Glf Curse Management. Sept./Oct. p Gss, R.L Effects f variable rates f sulfur n the quality f putting green bentgrass. Prc. 2nd Int. Turfgrass Rec. Cnf. p Juska, F.V. and A.A. Hansn Factrs affecting Pa annua cntrl. Weeds. 15(2): Juska, F.V. and A.A. Hansn Nutritinal requirements f Pa annua L. Agrn. J. 61: Juska, F.V. and A.A. Hansn Nutritinal requirements f Pa annua. Glf Superintendent, March. p Lunt, L.O., R.L. Brnsn and S.B. Clark Respnse ffive grass species t phsphrus n six sils. Calif. Turfgrass Culture 17: Snaydn, R.W. and C.D. Hwe Rt and sht cmpetitin between established ryegrass and invading grass seedlings. J. App. Eclgy 23: Sprague, H.B. and G.W. Burtn Annual bluegrass (Pa annua L.) and its requirements fr grwth. N.J. Agr. Expt. Sta Bull Varc, J.J. and J.B. Sartain Effects f phsphrus, sulfur, calcium hydrxide and ph n grwth f annual bluegrass. Sil Sci. Sc. Am. J. 5: Waddingtn, D.V., T.R. Turner, J.MN. Duich and E.L. Mberg Effect f fertilizatin n Pencrss creeping bentgrass. Agrn. J. 7:

DESIGNING FERTILIZER PROGRAMS FOR YOUR TURF. Shawn BcBurney and Paul E. Rieke Department of Crop and Soil Sciences Michigan State University

DESIGNING FERTILIZER PROGRAMS FOR YOUR TURF Shawn BcBurney and Paul E. Rieke Department f Crp and Sil Sciences Michigan State University Planning a fertilizer prgram fr athletic fields, parks, and cemeteries