Viii. Decomposition And Nitrogen Release Of Turfgrass Clippings 8.1 .
VIII. DECOMPOSITIONAND NITROGEN RELEASE OF TURFGRASSCLIPPINGS8.1 ABSTRACTDecomposition and N release patterns of turfgrass clippings from residentiallawns are not well understood. First-cut clippings of a cool-season turfgrass were placedin litter bags (20 by 20 em) and inserted into the thatch layer of 2 x 2 m experimentalfield plots (l0 per plot). The experiment was arranged as a 2 x 4 factorial in arandomized complete block design with three replicates. The soil at the site was a Paxtonfine sandy loam (coarse-loamy, mixed, active, mesic Oxyaquic Dystrudept).Treatmentsincluded four rates ofN fertilizer (0, 98, 196, and 392 kg N ha" yr") in 3 splitapplications and two clipping treatments (returned vs. removed). Litter bags wereremoved after 1,2,3,4,5,7,9,11, 13, and 16 weeks and samples were analyzed forbiomass, N, and C concentrations, and C:N ratio on an ash-free basis. Nitrogen loss after16 weeks ranged from 88.1 % at 0 kg N ha" to 92.6% at 392 kg N ha ' and from 85.7%when clippings were removed (CRM) to 93.7% when clippings were returned (CRT).Carbon loss ranged from 93.7% at the 0 kg N ha" rate to 95.4% at the 392 kg N ha" rateand from 91.2% with CRM to 96.0% with CRT. Cumulative N release was greater forthe two lower N rates (131 to 132 g N kg" tissue) than for the two higher N rates (120 gN kg -I tissue) and was also higher for CRT (151 g N kg -1 tissue) than for CRM (128 g Nkg" tissue). Grass clippings decomposed rapidly and released N quickly when returnedto turfgrass, which indicates the need for reduced N fertilization when clippings arereturned. Such rapid decomposition suggests that the contribution of grass clippings to. thatch development is negligible.142
1438.2 INTRODUCTIONReturning grass clippings provides a biodegradable source of organic N to theturfgrass ecosystem. The amount of mineralizable N available in such a system has adirect impact on the quality and vigor of the turf. By returning clippings, nutrients arerecycled and N fertilization requirements may be reduced (Busey and Parker, 1992).However, literature reviewed on this topic indicated that there are few published, peerreviewed studies that have examined the effects of returning grass clippings on theturfgrass/soil system. In particular, there are no field studies that have examineddecomposition of turfgrass clippings and the rate of release of clipping N in aturfgrass/soil system.Many studies have reported a high recovery of applied N fertilizer in grassclippings. It is logical to assume that by returning clippings to turfgrass, N fertilizationrates could be decreased due to the N mineralized from the returned clippings. Bowmanet al. (1989) applied 50 kg N ha-l as labeled ammonium sulfate to Kentucky bluegrass(Poa pratensis L.) and recovered 75% ofN in the shoots 5 days after treatment.Bristowet al. (1987) applied labeled ammonium nitrate at 60 kg N ha-l to a perennial rye grass(Lolium perenne L.) under pasture conditions and observed N recoveries in herbage of33,49, and 55% after 28, 111 and 370 days, respectively.During a 2-yr experiment inwhich 196 kg N ha-l yr" of labeled urea were applied to Kentucky bluegrass, Miltner etal. (1996) recovered 35% of the N in clippings. These studies did not, however, examinethe rate at which returned clippings decomposed and released N to turfgrass. Starr andDeRoo (1981) observed that when clippings were returned to turfgrass, approximately
14410% of the N applied as returned clippings was taken up by the turfgrass over a period ofone year, which provided an additional fertilizer equivalent of 40 kg N ha-l.Homeowners and turfgrass managers may remove grass clippings because of abelief that returning clippings increases thatch accumulation.Several studies, however,have shown otherwise. Beard (1976) performed a study that examined potentialproblems associated with returning clippings to turfgrass in relation to the type of mowerutilized. The 12 yr study also examined the role of returned clippings in turfgrass thatchdevelopment and concluded that clippings were not a significant factor in the formationof a problem thatch layer. Visual observations of a Kentucky bluegrass turf fertilized atseven N rates with clippings removed or returned indicated a N response to the return ofclippings 14 d after the clipping treatment began.Haley et a1. (1985) examined the effects of returning clippings to a Kentuckybluegrass turf when conventional and mulching mowers were used. Turf quality, weedencroachment, and thatch accumulation were observed for turfgrass that received threerates of N fertilization and the clipping treatment. In general, turfgrass quality was higherwhen clippings were returned although this effect was lessened at the high N rate (300 kgN ha-l). Thatch accumulation was thought to be from excess organic matter productionrather than from decomposition of clippings.Sartain (1993) performed an experiment in which the effects of clipping return onthatch accumulation in'Tifway' bermudagrass [Cynodon dactylon (1.) Pers. x Cynodontransvaalensis Burtt Davy] and 'Pennant' perennial ryegrass were determined. Visualquality, N content of clippings and clipping yield were increased when clippings werereturned, and mean thatch accumulation in the bermudagrass was not increased by the
"145practice. Johnson et al. (1987) also examined bermudagrass response to fertilization andmowing practices and found that neither fertilizer treatment nor the return of clippingsinfluenced thatch accumulation in 'Tifway' bermudagrass.The reduction in N fertilization that could accompany clipping return has not beenquantified, and the rates at which turfgrass clippings decompose and release N areunknown. Therefore, it was the objective of this research to determine decompositionrates and N release patterns of cool-season turfgrass clippings returned to turf that wasmanaged as a residential lawn. It was a further objective to determine whether thepractice of returning clippings affected clipping decomposition over time.8.3 MATERIALS AND METHODSThe experiment was conducted at the University of Connecticut's Plant ScienceResearch and Teaching Farm (RF) in Storrs, CT during the growing season of 1999 andwas arranged as a randomized complete block design with three replicates. Plot size was2 x 2 m. Experimental treatment was N application rate (0, 98, 196, and 392 kg N ha'yr') in 3 split applications. A mixture of 65% 30-4-4 (urea, methylene urea, ammoniumphosphate and ammonium sulfate-5.2% WIN) and 35% 33-0-0 (NH4N03) fertilizer wasapplied. The soil at the Plant Science Research and Teaching Farm was a Paxton finesandy loam (coarse-loamy, mixed, active, mesic Oxyaquic Dystrudrept).The site had been seeded with a bluegrass-ryegrass-redfescue mixture [35%common Kentucky bluegrass, 35% common creeping red fescue (Festuca rubra L. subsp.rubra), 15% 'Cutter' perennial ryegrass, and 15% 'Express' perennial ryegrass] during thefall of 1995. After establishment, plots were maintained at a typical residential lawnheight of 3.8 em throughout each growing season. Fertilization and clipping treatments-
146began during the growing season of 1997 and continued for two yrs prior to the initiationof the decomposition experiment. The decomposition experiment was conducted from 28May to 21 September 1999 and measurements began on 6 June 1999. Precipitation andtemperature data for the growing season of 1999 are presented in Table 8.1. Totalrainfall during the experimental period was 410 mm and the average temperature was20 C.Decomposition and N release patterns of grass clippings were monitored in thefield using nylon mesh litter bags (20 by 20-cm). Mesh openings were 1.5 by 1.5 mm.Before N application in 1999, first-cutting clippings were harvested from field plots andplaced into litter bags (20 g tissue per bag). Ten litter bags were placed into the thatchlayer of each plot, and the bags were retrieved from the field at 1,2, 3,4, 5, 7, 9, 11, 13,and 16 weeks.The contents of each bag were removed and dried at 70 C until a constant weightwas reached. The contents of each litter bag were weighed and ground in an Udy Mill topass through a 0.5-mm screen. Soil contamination of litter bag contents was accountedfor by ashing a subsample in a muffle furnace at 400 C for 16 hours and converting thedata to an ash-free basis (Cochran, 1991). Samples were analyzed using a LECO FP-2000CarbonlNitrogen Analyzer (Leco Corp., St. Joseph, MI) for the determination of total Nand C concentration. Subsamples of first-cutting clippings were oven-dried at 70 C untila constant weight was reached to obtain initial Nand C concentrations.Initial and final Nand C on an ash-free basis were analyzed using the GLMprocedure of SAS (SAS Inst., 1990) for a randomized complete block design. Using non. linear regression models, the percent of initial Nand C remaining at each sampling
147period were regressed on time using Deltagraph v. 4.0 software (Deltapoint Inc., 1990).A double, four-parameter model was used with the general form of the equation asfollows (Weider and Lang, 1982):Y I oe-k I t I 1 e -k-r- E rror[1]where Y is the percentage of initial C or N remaining at sampling time t, Po,is the easilydecomposable fraction, 1 1is the recalcitrant fraction (l00- 1 0),k, and k2 are C or Ndecomposition or N release constants, and t is the time in weeks. The double, fourparameter model describes a rapid, initial phase of decomposition followed by a slowerphase (Isaac et al., 2000). Nitrogen release from clippings was calculated for N rate andclipping means by multiplying the initial N content by the percentage estimate of Nrelease from the double exponential decay model equations (Isaac et al., 2000).Treatment effects on model parameters were analyzed using the GLM procedure of SAS(SAS Inst., 1990) for a randomized complete block design.8.4 RESULTS8.4.1 Tissue Chemical CharacteristicsInitial tissue N concentrations and C:N ratios were significantly affected by N rateand clipping treatments prior to decomposition (Table 8.2). Tissue N concentrationsranged from a low of 18.8 g kg-I for the 0 kg N ha-l (0 N) treatment to a high of22.9 gkg -I for the 392 N treatment. Tissue N concentrations were higher when clippings werereturned (Table 8.2). Nitrogen rate and clipping effects observed before decompositionwere likely due to carry-over from previous years' management because experimentaltreatments had been applied to the plots for two years prior to the decomposition study.ITissue C content averaged 446 g kg- across experimental treatments.Carbon to nitrogen
148ratio peaked at 24.0 g g-l at the lowest N rate (0 N) and decreased to 19.6 g g-l at thehighest N rate (392 N). Carbon to nitrogen ratio ,was also higher when clippings wereremoved.Final tissue N content averaged 13.0 g kg" and final tissue C content averaged170 g kg". Final tissue N and C contents were higher when clippings were removed(Table 8.2). Final C:N ratio ranged from a low of 11.8 g g-l at 392N to a high of 14.2 g g1at 196N and averaged 12.9 g g-l across clipping treatments (Table 8.2).8.4.2 Clipping Decomposition PatternsA comparison of double exponential decay model parameters of percentage Nand C remaining revealed significant differences in clipping decomposition models dueto N rate for percentage N remaining (Table 8.3; Fig. 8.1). For percentage N remainingin tissue, significant differences in the fraction of easily decomposable tissue ( 1 0) wereobserved due to N rate and clipping treatment. As N rate increased, 1 0for N remainingtended to decrease and was greater in CRM treatments than in CRT treatments.Significant differences in k2 were also observed for percentage N remaining in tissue dueto N rate as well as clipping treatment (Table 8.3; Figs. 8.1 and 8.2). There were nosignificant differences in percentage N remaining in tissue between values of k2 orfractions of PI , the recalcitrant tissue (l00 - 1 0).For percentage C remaining in tissue, significant differences in ki, the initial,rapid decay constant, were attributed to N rate (Table 8.3). There were no significantdifferences in percentage C remaining in tissue between fractions of easily decomposabletissue ( 1 0)' recalcitrant tissue ( 1 1), or values of k2 due to experimental treatment.
149Most N and C decomposition occurred within the first 4 wks of the experiment(approximately 70%), after which, decomposition occurred at a much slower rate (Fig.8.1A-H). Percentage N loss after 16 weeks averaged 89.7%. Percentage C loss after 16weeks averaged 94.0%. Percentage Nand C loss was higher when clippings werereturned (Table 8.2).8.4.3 Nitrogen Release PatternsConsidering both N fertilization rate and clipping treatment, marked release of Nrelease occurred within the first 4 wks of the experiment (Fig. 8.3A-F). After 16 weeks,cumulative N release was greater for 0 and 98 kg N ha-l treatments (132.4 and 131.4 g kgtissue", respectively) than for 196 and 392 N treatments (both 120.1 g kg-l tissue) (Fig.8.3A-D). Cumulative N release was greater for CRT (150.7 g kg-I tissue) than for CRM(128.1 g kg-l tissue) after 16 weeks (Fig. 8.3E,F).8.S DISCUSSIONThe effect of C:N ratios in the decomposition process is a regulatory one based onthe assumption that N concentrations commonly limit the activity of decomposerorganisms (Swift et aI., 1979). In this experiment, however, C:N ratios for all treatmentswere less than the ratios that are typically considered limiting ( 30: 1). Therefore, weassumed that the decomposition of grass clippings would occur rapidly and limited theexperiment to 16 weeks. Decomposition is highly dependent on air temperature and soilmoisture (Douglas and Rickman, 1992). Although we observed that most tissue wasdecomposed within 4 wks, the hot and dry conditions that prevailed during ourexperiment may have slowed decomposition processes (Table 8.1).
150A double exponential decay model (Weider and Lang, 1982) was successfullyused to describe percent Nand C remaining in the grass clippings. Douglas and Rickman(1992) also found that a two-stage decomposition model was appropriate for buriedresidues. Considering parameter estimates for decay models ofN, we found significantdifferences in k2 decay constants and Poin relation to N fertilization and clippingtreatment. Although a logical trend in k2 values in relation to N treatment was notapparent, Po tendedto decrease as N rate increased indicating that there was a greateramount of easily decomposable tissue N at lower N fertilization rates. In relation toclipping treatment, Powas greater for CRM than for CRT and k2 was greater for CRTthan for CRM. The higher k2 value for CRT treatments indicates that the practice ofreturning clippings increased the rate of decay and N cycling of previously returnedclippings during the second, slower phase of the decomposition process. For C models,we found significant differences in k, decay constants attributable to N rate but a logicaltrend was not apparent.Direct comparisons of model parameters that we determined to those of otherstudies are difficult because we were unable to find published work on the decompositionof turfgrass clippings. Comparisons may be made, however, to decomposition studies ofother grasses. Kochy and Wilson (1997) compared litter decomposition and nitrogendynamics in aspen forest and mixed-grass prairie. Using a three-parameter, exponentialdecay model, they determined a k rate of 0.03 wk-I for mixed prairie grass. It is difficultto make direct comparisons to their study because we used double exponential decaymodel, however, Kochy and Wilson's (1997) k rate was comparable to k2 decay constantsthat we observed.
151Hendrix and Parmelee (1985) examined the influence of herbicide upondecomposition of Johnsongrass [Sorghum halepense (L.) Pers.] in a fallow field. DriedJohnsongrass was treated with varying rates of atrazine, paraquat and glyphosateherbicide solutions and monitored for decomposition over time. Hendrix and Parmelee(1985) stated that they were unable to use double exponential decay models due to a lackof data during the initial, rapid decomposition phase, however, they were able to performlinear regressions on data from the second phase of decomposition.Their observed krates averaged 0.03 wk-l and were comparable to the k2 decay constants that we observed.8.6 CONCLUSIONSThe rapid decomposition of grass clippings we observed supports the conclusionsof Beard (1976), Haley et al. (1985), and Johnson et al. (1987) that thatch accumulation isnot increased by the practice of returning clippings to turfgrass. Further research isnecessary, however, to determine decomposition and N release rates of different grassspecies under varying management conditions when clippings are returned. This studyclearly shows, however, that the decomposition of grass clippings provides rapidlyreleased N within the thatch layer of turfgrass. It is reasonable to assume that some, ifnot all, of that N will become available to the turfgrass during the growing season.Therefore, N fertilization rates should be reduced when clippings are returned to turfgrassmanaged as a residential lawn.8.7 REFERENCESBeard, J.B. 1976. Clipping disposal in relation to rotary lawn mowers and the effect onthatch. 1. Sports Turf Res. lnst. 52:85-91.
152Bowman, D. C., J. L. Paul, W. B. Davis, and S. H. Nelson. 1989. Rapid depletion ofnitrogen applied to Kentucky bluegrass turf. 1 Am. Soc. Hort. Sci. 114:229-233.Bristow, A. W., 1C. Ryden, and D. C. Whitehead.intervals of1989. The fate at several time15N -labeled ammonium nitrate applied to an established grass sward. J.Soil Sci. 38:245-254.Busey, P. and J.H. Parker. 1992. Energy conservation and efficient turfgrassmaintenance. p. 473-500. In D.V. Waddington, et aI. (eds.). Turfgrass. Agron.Monogr. 32. AS A, CSSA, SSSA, Madison, WI.Cochran, V.L. 1991. Decomposition of barley straw in a sub-arctic soil in the field.BioI. Fertil. Soils. 10:227-232.Deltapoint, Inc. 1990. Deltagraph user's guide. Version 4.0. Deltapoint, Inc., Monterey,CA. U.S.A.Douglas, C.L. Jr., and R.W. Rickman. 1992. Estimating crop residue decompositionfrom air temperature, initial nitrogen content, and residue placement.Soil Sci. Soc.Am. 1 56:272-278.Haley, lE., DJ. Wehner, T.W. Fermanian, and AJ. Turgeon. 1985. Comparison ofconventional and mulching mowers for Kentucky bluegrass maintenance.HortSci.20:105-107.Isaac, L., C.W. Wood, and D.A. Shannon. 2000. Decomposition and nitrogen release ofprunings from hedgerow species assessed for alley cropping in Haiti. Agron. J.92:501-511.Johnson, BJ., R.N. Carrow, and R.E. Bums. 1987. Bermudagrass response to mowingpractices and fertilizer. Agron. J. 79:677-680.
Kochy, M., and S.D. Wilson. 1997. Litter decomposition and nitrogen dynamics inaspen forest and mixed-grass prairie. Ecology 78:732-739.Miltner, E.D., B.E. Branham, E.A. Paul, and P.E. Rieke. 1996. Leaching and massbalance of 15N-Iabeled urea applied to a Kentucky bluegrass turf. Crop Sci.36:1427-1433.Sartain, J.B. 1993. Interrelationships among turfgrasses, clipping recycling, thatch, andapplied calcium, magnesium, and potassium. Agron. J. 85:40-43.SAS Institute. 1990. SAS/STAT User's Guide. Version 6. 4th Ed. Cary, NC. U.S.A.Starr, lL., and H.C. DeRoo. 1981. The fate of nitrogen applied to turfgrass. Crop Sci.21 :531-536.Swift, M.J., o.w. Heal, and J.M. Anderson.1979. Decomposition in terrestrialecosystems. University of California Press, Berkeley and Los Angeles, CA.Weider, R.K., and G.E. Lang. 1982. A critique of the analytical methods used inexamining decomposition data obtained from litter bags. Ecology 63: 1636-1642.
154Table 8.1 Thirty-yr normal (Storrs, CT) and 1999 precipitation and temperature on]199930-yrDeviationmmnunMay100101 1.014.013.7 0.3June91.933.0-58.920.523.2-2.7July102149 47.023.221.4 1.8August97.545.0 52.518.120.6-2.5September91.4212-12118.016.1 1.9October99.8124-24.29.7010.0-0.3November11280.5 31.57.635.0 2.6t Total deviation from 30-yr normal mean precipitation and temperature.
t55Table 8.2 Chemical characteristics of turf grass clippings before and after decomposition.TreatmentN ConcentrationC ConcentrationInitialInitialFinalkg N ha-lFinal % LossC:N ratioFinalInitialFinalNCg 46.411220.9212.885.791.9NS**NS**NS***ClippingF Test*, **, ***, NS Significant at the 0.05, 0.01, and 0.001 probability level and nonsignificant, respectively.t CRM-clippings removed.tCRT-clippings returned.
156Table 8.3 Mean parameter estimates for double exponential decay models of percentageNand C remaining across N rates and clipping treatments.CarbonNitrogen 1 otkJ 1»§k2 1 0kJ S****NSCRM#49.01.6155.60.0847.91.3251.30.16CRT eatmentkg N ha-1ClippingF*, **, NS Significant at the 0.05 and 0.01 probability levels and nonsignificant, respectively.of easily decomposable tissue.:j: Decomposition constant.§ Fraction of recalcitrant tissue. Decomposition constant.# CRM-clippings removed. CRT-clippings returned.t Fraction
157 010o'(]).s:Z asCI"'N"0 MC\J1I'lto";'1I'l15'?(])1I'l('jVII·m·Z .::l 2eoenen0 0 0 .6 VII - '"c:enOJ):::00.09-0U 0enenNro .9(])";'ass:zCI"'"to1I'l N'"0 :::·eo;.coVII'"c: 0 '(])asCI"'co"0 C\JV1I'l ;;:')I(]) 0u'iVII·m·eo6VIICI"'C)"C\!C'JC'JII0o 1)"0:::OJ)::: c aE . 1):c0c:0VQ.,u.J '-' . .IC l;:::0.D Q) ."0c0c 0 1)I '-'"00E ;.0 1)U:::roo::: l;::::::OJ)0 o::!lC\J.··c.,66N0 0 eo!::cC/)IIVII00 1) .o cv'"c:00co0 00V0C\J(%) 6u!u!ewa ua6oJl!N0000co0 00V0C\J(%) 6u!u!ewa uoqJeJ0***E 1)eno . 1) 1) 0. .0 0 - rr00E0 to t:'?(])0CoEro(])Z-0;;;0c,roo0 0 00 0c0u9s:j::0NasECII - '"c:";' Cii0s: Q)0ZIi)Q)Q)0 6";'OJ)OJ)C\J1I'l::lo::!lU;.C0N0-2
(58CRTlC)c'c'(6EY 36.0e-2.71100 CRM63.5e-0.121Y 49.0e-·1.61 55.6e-0.081R2 0.960***8060 Llc:::c LlC)0I- oJZ402000481216Decompositiono481216Time (Weeks)Figure 8.2. Percentage nitrogen remaining in decomposing grass clippings when clippingswere returned (A, CRT) or removed (B, CRM). ***Significance of model fit at P O.OOI.
159o kg N ha-1140 -------------- 98 kg N ha-112010080604020O -- -- -- -- A392 kg N ha-1196 kg N ha-1140 -------------- 12010080604020O -- -- -- -- cCRTCRM160 -------------- 14012010080604020O -- -- -- -- Eo481216DecompositionFigure 8.3. CumulativeFo4Time(Weeks)8nitrogen release from decomposing1216grass clippings at 0 (A), 98(B), 196 (C), and 392 (D) kg N ha-l and with clippings removed (E, CRM) or returned(F, CRT).
CLIPPINGS 8.1 ABSTRACT Decomposition and N release patterns of turfgrass clippings from residential lawns are not well understood. First-cut clippings of a cool-season turfgrass were placed in litter bags (20 by 20 em) and inserted into the thatch layer of 2 x 2 m experimental field plots (l0 per plot). The experiment was arranged as a 2 x 4 .
Nitrogen Cycle The atmosphere is the largest reservoir of nitrogen on Earth. It consists of 78 percent nitrogen gas. The nitrogen cycle moves nitrogen through abiotic and biotic compo-nents of ecosystems. Absorption of Nitrogen Plants and other producers use nitrogen to synthesize nitrogen-containing organic
2.1. Singular Value Decomposition The decomposition of singular values plays a crucial role in various fields of numerical linear algebra. Due to the properties and efficiency of this decomposition, many modern algorithms and methods are based on singular value decomposition. Singular Value Decomposition of an
The ENB 45 Pneumatic Nitrogen Booster provides the capability of boosting remaining lower pressure Nitrogen from supply bottles to the required pressure, up to 4,500 psi. The Nitrogen Booster is driven by compressed air or nitrogen. It cycles automatically to boost low-pressure nitrogen to high pressure.
A mission decomposition diagram is built to represent a hierarchical structure among the mission tasks. Different decomposition techniques (e.g., functional decomposition, goal decomposition, terrain decomposition) generally re
mineralization from organic matter decomposition, nitrogen cycling, and nitrogen losses through leaching, runoff, or denitrification. Organic matter . cycle typically begins with nitrogen in its simplest stable form, dinitrogen (N 2) in air, and foll
3.1.3 Data analysis 8 3.2 Calculation of NPCFs 9 3.3 Modelling of non-protein nitrogen 10 3.4 Assessment of risk of bias and certainty of evidence 11 4 Results 12 4.1 Literature review 12 4.2 Analytical methods for nitrogen, amino acid and protein content in foods 14 4.2.1 Methods to determine total nitrogen content in foods 14
existing or future chemical and water flow models to predict nitrogen movement from the soil-water system to ground water bodies, lakes, streams, and the atmosphere. The hydrological and agricultural signifi cance of nitrogen prediction models becomes more evident upon examination of some nitrogen problems. Problems Associated With Soil Nitrogen
Zrunners-repeaters-strangers-aliens [ (RRSA) (Parnaby, 1988; Aitken et al., 2003). This model segments inputs of demand from customers (in this case, the requests from researchers for data cleared for publication) and uses the different characteristics of those segments to develop optimal operational responses. Using this framework, we contrast how the rules-based and principles-based .
