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

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1 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 requires a different apprach than fr hme lawns. While the basic factrs f sil tests, sil texture, grass species present and aesthetic quality desired are the same, ther factrs must be cnsidered in planning fr "utility" turf maintenance. Sme f these factrs are: 1) intensity, time and duratin f use, 2) desired mwing frequency, 3) level f irrigatin and, 4) yur budget. As with all turf situatins, there are minimum fertilizer requirements t maintain a quality utility turf. The nitrgen levels listed in Table 1 assume adequate levels f the ther required turfgrass nutrients. Ptassium and phsphrus must be maintained at ptimum levels in the sil if the turfgrass is t benefit frm the applied nitrgen. The best methd t be sure f adequate sil nutrient levels is t perfrm a sil test. Sil testing shuld be the bench mark fr all fertilizer prgrams. Sil test recmmendatins such as thse in Tables 2 and 3 are intended as guidelines when planning a fertilizer prgram. Sil tests fr nutrients ther than phsphrus, ptassium, calcium and magnesium may be requested but deficiencies f these nutrients are rarely a prblem n turfs in Michigan. Exceptins t this generalizatin include: 1) ccasinal irn (Fe) deficiencies which may be naturally ccurring r induced by excessive sil phsprus levels and 2) micrnutrient deficiencies which may be induced by extremely high r lw sil ph levels. Phsphrus is nt required at levels as high as ther sil macrnutrients t maintain adequate turf grwth. When this nutrient is required t meet recmmended levels, it may be applied in a number f ways. Applicatin timing fr phsphrus is nt as critical as fr nitrgen and ptassium and can be applied with any f the cmbinatin fertilizers r by itself. Phsphate (P20S) carriers are available in a variety f frms including: 1) treble superphsphate (0-46-0), 2) superphsphate (0-20-0) and 3) cmplete fertilizers such as (18-5-9), ( ) and ( ). One applicatin annually will supply the turf requirements fr a much lnger perid f time than similar applicatins f nitrgen r ptassium. Phsphrus related deficiencies f ther nutrients may ccur if fertilizer applicatins greatly exceed recmmended sil phsphrus levels. Phsphrus is a relatively immbile nutrient in the sil s leaching is seldm a prblem unless excessive rates are applied. Ptassium behaves uniquely in sil. There are sme sils that are rarely deficient in ptassium, but these are nt typical in Michigan. Sils with an increasingly sandy nature usually require increased amunts f supplemental ptassium. Lighter-textured sils which receive supplemental irrigatin are particularly prne t ptassium leaching. Table 3 illustrates the sil levels f ptassium based n sil tests required t insure adequate turf grwth. Ptash (K20) may be applied alne r as a part f a cmplete fertilizer. On the sandy sils, ptassium shuld be applied at least twice a year and at least 3 t 4 times annually n intensively maintained turfs. Ptassium surces available are: muriate f ptash (0-0-60), ptassium sulfate (0-0-50), many cmplete fertilizers and sulfur-cated frmulatins which release the ptassium ver lng perids f time in an attempt t decrease 134

2 leaching lsses. Nitrgen, almst withut questin, is the mst frequently needed nutrient t attain and maintain a healthy turf. The rate and timing f nitrgen applicatin is usually determined by several factrs. The species f grass present will partially determine the ttal punds per year (N/I000 sq ft) required. The intensity and timing f turf use playa primary rle in deciding yearly nitrgen rates and the timing f applicatin. Table 4 illustrates pssible rates and timing f nitrgen applicatins n sme utility turfs. Nitrgen is available in several frms. Nitrgen can be purchased in fast-release frms such as urea (45-0-0), ammnium nitrate (33-0-0) r ptassium nitrate ( ). Slw release nitrgen carriers, which prduce an extended grwth respnse, include sulfur-cated urea, IBDU, Milrganite, and several carriers based n urea frmaldehyde. Scheduling f nutrient applicatins must be dne with cnsideratin f the previusly mentined factrs. Table 5 illustrates an example fertilizatin schedule fr a fall-use athletic turf in the suthern ne-third f Michigan. The purpse f this tw part table is t shw hw sil test recmmendatins are used and just ne example f pssible fertilizer carriers and ntes which can be used t meet the sil test recmmendatins. The recmmended nitrgen, phsphrus, and ptassium recmmendatins n the tp half f the table have been taken frm Tables 1,2, and 3, respectvely. A slw-release nitrgen surce was applied in June t insure adequate turf density befre the summer stress perid begins yet t minimize mwing. A 1/2# N/I000 ft2 applicatin in early Octber will keep the turf actively grwing, fr the balance f the seasn and a mid-nvmeber (late seasn) applicatin will supply nitrgen required fr sme fall recvery and spring grwth t rebuild the turf frm the fall damage. Fr mre nrthern sites, the late seasn applicatins wuld need t be applied at an earlier date. As in the example f table 5, use f cmplete fertilizers can partially r fully satisfy phsphrus and ptassium requirements, while minimizing labr input. The annual ttal applicatin f phsphrus at 0.7#/1000 ft2, is smewhat shrt f the recmended 1#/1000ft2 as nted in the tp half f Table 5. The difference between recmmended nutrient rates and actual rates applied, is ften acceptable if the difference is nt large because the rates recmmended are just that, recmmended rates. Supplementary irrigatin is recmmended fr intensively used turfs t maximize the effectiveness f the fertilizer prgram. In summary, while every turfgrass site has its wn particular requirements, the planning and scheduling f a fertilizer prgram requires cnsideratin f the same basic factrs t be successful. The manager must knw which nutrients are limiting and what amunts are needed t insure gd turf. He must knw when t apply these nutrients and at what rates. Finally, the manager must be able t d all these things within the cnstraints f his budget. 135

3 Table 1. Annual nitrgen requirements fr general turfgrasses in Michigan. Grass Species Level f Use /tn/1000 ft2/yr "Imprved" Kentucky Bluegrass Medium - lw 2-3 "Imprved" Kentucky Bluegrass High 4-5 Fine Fescue Medium 2-3 Perennial ryegrass Medium - high 3-5 Minimum maintenance turfs Lw 1-2 Table 2. Annual phsphate (P205) applicatins based n sil tests (Bray PI Extractable) at the M. S. U. Sil Testing Lab. Punds phsphate (p?o~) recmmended Sil test General turf High maintenance turf a Per Per Per (lbs P/acre) 1000 sq. ft. acre 1000 sq. ft. a - 14 (very lw) (1m\') (medium) (high) a a (very high) a a a a High maintenance turf wuld include intensively used athletic fields, glf greens and tees, tennis curts, and fr establishment recmmendatins. 136

4 Table 3. Annual ptash (K20) applicatins based n sil tests (neutral nrmal ammnium acetate extractable) at the M. S. U. Sil Testing Lab. Punds f ptash (K20) _~_e_c m_m_e_n_d_e_d _ Sil test General turf High maintenance turf a Per Per Per (lbs K/acre) 1000 sq. ft. acre 1000 sq ft - 49 (very lw) (lw) (medium) (med. - high) (high) 0 a (very high) 0 a 1 New tuctd a High maintenance turf wuld include intensively used athletic field, glf greens and tees, and tennis curts. b Place up t half f this amunt in the seedbed at higher rates recmmended, applying the rest during the grwing seasn. 137

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6 Table 5. Athletic Field Fertilizer Scheduling Example. USE: Intensive (ftball, Aug. I-Nv. 15) IRRIGATION: Supplemental, during stress perids SOIL TYPE: Sandy Lam GRASS SPECIES: Kentucky Bluegrass Nutrient ph Nitrgen Phsphrus Ptassium Sil Test Level lbs/a 125 lbs/a Recmmendatin Ibs/l000 sq. ft/yr N lime required FERTILIZING SCHEDULE FOLLOWED Nutrient Punds nutrient applied per 1000 sq ft. applied June l Aug2 Sept) Oct L Nv4 Ttal Annual Nitrgen Phsphate Ptash Applied 3.8 punds/looo sq. ft f cntaining sme slw release nitrgen and 1.0 pund Applied 2.5 punds/looo sq. ft. f cntaining sme slw release nitrgen 3 - Applied 5.0 punds/looo sq. ft. f cntaining sme slw release nitrgen 4 - Applied 4.5 punds/looo sq. ft. f cntaining slw release nitrgen and 1.7 punds