Comparison of two soil quality indexes to evaluate cropping systems in northern Colorado

Transcription

1 University of Nebrsk - Linoln Digitlommons@University of Nebrsk - Linoln Publitions from USD-RS / UNL Fulty USD griulturl Reserh Servie --Linoln, Nebrsk omprison of two soil qulity indexes to evlute ropping systems in northern olordo T.M. Zobek USD-RS.D. Hlvorson USD-RS rin J. Wienhold University of Nebrsk - Linoln, bwienhold1@unl.edu V. ost-mrtinez USD-RS D.L. Krlen USD-RS Follow this nd dditionl works t: Zobek, T.M.; Hlvorson,.D.; Wienhold, rin J.; ost-mrtinez, V.; nd Krlen, D.L., "omprison of two soil qulity indexes to evlute ropping systems in northern olordo" (28). Publitions from USD-RS / UNL Fulty. Pper This rtile is brought to you for free nd open ess by the USD griulturl Reserh Servie --Linoln, Nebrsk t Digitlommons@University of Nebrsk - Linoln. It hs been epted for inlusion in Publitions from USD-RS / UNL Fulty by n uthorized dministrtor of Digitlommons@University of Nebrsk - Linoln.

2 omprison of two soil qulity indexes to evlute ropping systems in northern olordo T.M. Zobek,.D. Hlvorson,. Wienhold, V. ost-mrtinez, nd D.L. Krlen bstrt: Vrious soil mngement or qulity ssessment tools hve been proposed to evlute the effets of lnd mngement prties on soil, ir, nd wter resoures. Two of them re the Soil Mngement ssessment Frmework nd the Soil onditioning Index (SI). This study ws onduted to test the hypothesis tht the Soil Qulity Index () estimted by the Soil Mngement ssessment Frmework n detet more minute hnges in soil mngement thn SI nd to test SI response to other soil qulity (SQ) inditors. These SQ indexes were tested on irrigted ropping systems ner Fort ollins, olordo, tht inluded no-till nd onventionlly-tilled orn (Ze mys L.), nd no-till orn with rottions inluding brley (Hordeum distihon L.), soyben (Glyine mx (L.) Merr.), nd dry ben (Pheseolus vulgris L.) t three levels of nitrogen vrying from to 224 kg N h 1 ( to 2 lb 1 ). oth SQ indexes lerly seprted the plots with very high levels of N from plots with no N. However, for the mid-level of N ws sttistilly the sme s both extreme levels. Sttistil differenes were observed mong ll N levels for the SI. The seemed to mke more detiled differentition mong rop mngement systems thn the SI. The SI seprted the ropping systems into three groups with no overlp mong groups. ll no-till systems hd the sttistilly sme higher SI thn the onventionlly-tilled ontinul orn system. The seprted the ropping systems into three groups with deresing s tillge intensity inresed nd s lower residue rops were introdued into the ropping system. The systems tht inluded tillge nd low residue rop (soyben) hd the lowest. The llowed overlp mong ropping groups not reognized by SI. Seletion of the most pproprite SQ index seems to be trdeoff between dt requirements, resolution required, nd the desired use of the evlution tool. Key words: orgni mtter Soil onditioning Index (SI) soil mngement Soil Mngement ssessment Frmework (SMF) Soil Qulity Index () tillge Vrious soil mngement ssessment tools hve been proposed to evlute the effets of lnd mngement prties on soil, ir, nd wter resoures. The pity of the soil to funtion for speifi purposes hs been lled soil qulity (SQ) (Krlen et l. 1997). The pproprite SQ ssessment tool mesures hnges in soil funtion in response to mngement within the ontext of the soil use (ndrews et l. 24). For exmple, soil tht funtions very well for rop growth my funtion very poorly for wste tretment. There hs been some onern in using the term soil qulity in soil siene (Sojk nd Uphurh 1999), nd tools nd methods to ssess nd monitor SQ re needed (Krlen et l. 26). In this ontext, soil properties re usully used s inditors of SQ. The USD Nturl Resoures onservtion Servie (NRS) hs dopted SQ ssessment tool lled the Soil onditioning Index (SI) to estimte the effets of rop mngement on soil orgni mtter (lso lled soil orgni rbon, SO) (USD NRS 22). The SI ws not designed to determine the urrent SO level but to ssess whether or not SO levels would inrese, derese, or remin stble under the urrent ropping system. Determintion of the SI is required by severl USD NRS riteri of prtie stndrds, inluding the onservtion rop Rottion Prtie Stndrd 328, nd s n dditionl riteri in the Residue nd Tillge Mngement No Till/Strip Till/Diret Seed Prtie Stndrd 329, nd is speified for use in the onservtion Seurity Progrm of the Frm Seurity nd Rurl Investment t of 22. The SI estimtes qulittive hnges in SO in the top 1 m (4 in) of soils bsed on the ombined nd weighted effets of three determinnts of orgni mtter using the following empiril eqution: SI = [OM ()] + [FO ()] + [ER ()], (1) where OM represents the effets of orgni mteril from niml or plnt soures produed nd returned to the soil, FO signifies effets of field opertions inluding tillge nd other field proedures, nd ER orresponds to the influenes of wind nd wter erosion (USD NRS 23). Note tht OM nd FO in eqution 1 eh ount for 4% of the finl SI vlue (totl of 8% ombined), nd wind nd wter erosion represent 2%. The SI ssumes tht field opertions redue SO by stimulting deomposition nd tht mintining orgni residues will mintin nd inrese soil orgni mtter levels. The mount of redution of SO due to field opertions nd erosion depends on the ntive level of rbon tht my be sustined for given site nd region. The SI is usully determined using soil erosion model lled the Revised Universl Soil Loss Eqution (RUSLE2) (USD NRS 23). The Soil Mngement ssessment Frmework (SMF) is reltively new SQ ssessment tool bsed on the effets of mngement prties on dynmi soil properties nd overll soil funtion (ndrews et l. 22; ndrews et l. 24; Krlen et l. 26). To develop SQ index vlue, SMF pplies Ted M. Zobek is reserh soil sientist t the ropping Systems Reserh Lb, USD griulturl Reserh Servie (RS), Lubbok, Texs. rdell D. Hlvorson is reserh soil sientist t the USD RS, Fort ollins, olordo. rin Wienhold is supervisory reserh soil sientist t the groeosystem Mngement Reserh Unit, USD RS, University of Nebrsk, Linoln, Nebrsk. Veroni ost-mrtinez is reserh soil sientist t the ropping Systems Reserh Lb, USD RS. Dougls L. Krlen is supervisory reserh soil sientist t the Ntionl Soil Tilth Lb, USD RS, mes, Iow. journl of soil nd wter onservtion sept/ot 28 vol. 63, no

3 soil lbortory or field dt for minimum set of soil properties (lled SQ inditors in SMF) to soring urves tht indite the potentil of the soil to funtion for speifi purposes. The SQ soring urves vry from to 1, nd sore of 1 represents the highest potentil funtion nd tht the inditor is non-limiting to pertinent soil funtions nd proesses (ndrews et l. 24). ropping systems re evluted using group of SQ inditors tht represent the properties nd proesses tht hve the gretest sensitivity to the soil funtion under onsidertion. fter ll of the individul inditors used to ssess prtiulr soil mngement system hve been sored, they re ombined into finl index; in this study we ll it the Soil Qulity Index (). The SMF hs been tested in wide vriety of lotions inluding Georgi, Iow, liforni, nd the Pifi Northwest (ndrews et l. 22; ndrews et l. 24), Iow nd Wisonsin (Krlen et l. 26), nd the Gret Plins of the US (Wienhold et l. 26). nlysis of SQ using SMF requires n interprettion step to evlute speifi soil properties (inditors) by ompring mesured vlues to nonliner soring urves s desribed bove (ndrews et l. 24). In n nlysis of severl se studies, ndrews et l. (24) found four generl ptterns of results when ompring sored nd observed soil properties mong tretments (suh s between tillge versus no tillge) using NOVs. Pttern 1 ws hrterized by similr results for the sored nd observed ptterns. The seond pttern found observed nd sored vlues hd opposite results. For exmple, the highest observed tretment vlue ws found to hve the lowest vlue fter soring. In pttern 3, the observed soil property results hd signifint differenes mong tretments, but the sored results showed no signifint differenes mong tretments. The lest ommon pttern, pttern 4, hd no signifint differenes mong tretments for the observed results, but the sored vlues were signifintly different mong tretments. lthough the SI hs been proposed s tool to ssess the effets of soil mngement on SO nd is widely used by USD NRS, its effetiveness in ssessing other resoure onerns hs not been dequtely ddressed. In ddition, few tests of the bility of SI to dequtely desribe the stte of SO hve been performed, nd the results obtined re onfliting. n evlution of SI using nine long-term studies showed tht positive trends in followed positive trends in SI, nd negtive SI trends were ssoited with negtive trends (Hubbs et l. 22). However, reent study of 52 sites in west Texs (Zobek et l. 27) found tht the SI vlues were not strongly orrelted with totl SO. The SI vlues were more strongly ssoited with speifi nd more lbile form of SO lled prtiulte orgni mtter rbon (POM). This study ws onduted to test the hypothesis tht the SMF n detet smller differenes mong rop mngement systems thn SI nd to test SI response to other SQ inditors. Mterils nd Methods Study Site. This study ws initited in 1999 t the griulturl Reserh nd Development nd Edution enter (4 39'6"N, 14 59'57"W) (1,555 m [5,1 ft] bove se level) ner Fort ollins, olordo, in field tht hd been onventionlly tilled (T) nd in ontinul orn prodution for six yers before this study ws strted. The soil ws Fort ollins ly lom (fine-lomy, mixed, mesi ridi Hplustlfs) with 33 g kg 1 (33%) ly nd 41 g kg 1 (41%) snd. The experiment hd rndomized omplete blok design, with three replitions, testing three N rtes within eh of five different ropping systems, inluding T nd no-tillge (NT) tillge systems. This study is prt of lrger study of N nd tillge effets on ropping systems (Hlvorson nd Reule 26; Hlvorson nd Reule 27; Hlvorson et l. 26; Mosier et l. 26). The plot size ws 1.7 by 15.2 m (35 by 5 ft). Unless stted otherwise, the verge vlues listed in this pper refer to dt olleted nnully throughout the five-yer study period 22 to 26, inlusive. The five ropping systems inluded T ontinul orn (Ze mys L.) (T); notillge ontinul orn (NT); no-tillge orn-brley (Hordeum distihon L.) rottion (NT); no-tillge orn-soyben (Glyine mx (L.) Merr.) rottion tht ws hnged to no-tillge orn-dry ben (Pheseolus vulgris L.) rottion (NTS/D) in 25; nd no-tillge orn-soyben-brley rottion (NTS). orn, brley, soyben, nd dry ben were diretly plnted into the previous yer s rop without ny tillge for seedbed preprtion in the NT systems. The orn, brley, soyben, nd dry ben rops were sprinkler irrigted with linermove system s needed during the growing seson eh yer. The mount of irrigtion wter pplied vried with rop (Hlvorson et l. 26; Hlvorson nd Reule 26, 27). The verge totl nnul preipittion during the My through September growing seson ws 148 mm (6 in), nd vried from low of 64 mm (2.5 in) in 26 to high of 181 mm (7.1 in) in 24. The verge irrigtion wter pplied ws 42 mm (15.8 in) for orn, 195 mm (7.7 in) for brley, 374 mm (14.7 in) for soyben, nd 299 mm (11.8 in) for dry ben. dditionl detils of the tillge sequene, rops grown, nd other ulturl prties re desribed in Hlvorson nd Reule (26, 27) nd Hlvorson et l. (26). The three N rtes used depended upon the rop nd yer. For orn prodution, the N rtes were, 67, nd 22 kg h 1 (, 6, nd 18 lb 1 ) for levels N1, N2, nd N3, respetively, in 22. The N3 pplition rte ws 224 kg h 1 (2 lb 1 ) in 23 nd 24, nd then inresed to 246 kg h 1 (22 lb 1 ) in 25 nd 26 to ssure dequte N ws vilble to mximize grin yields bsed on NT orn yields reported by Hlvorson et l. (26). For soyben nd dry ben prodution in 23 nd 25, the N rtes were, 22, nd 56 kg h 1 (, 2, nd 5 lb 1 ) for N1, N2, nd N3 tretments, respetively. The N rtes for brley were, 45, nd 112 kg h 1 (, 4, nd 1 lb 1 ) eh yer for the N1, N2, nd N3 tretments, respetively, when brley ws grown in the rottions in 23 nd 25. These N rtes were pplied to the sme plots (N tretments) eh yer, depending on the rop grown. Grin yields generlly were determined in mid-july (brley), mid-september (soyben nd dry ben), nd mid-otober to erly November (orn) eh yer. rley ws hrvested with plot ombine from 18-m 2 (215-yd 2 ) re of eh plot for yield determintion. Soyben nd dry ben yields were determined by hnd hrvesting 4-m 2 (4.8-yd 2 ) re in 23 nd 25. orn yields were determined by hnd hrvesting the orn ers from n 1-m 2 (13.9-yd 2 ) re of eh plot eh yer. The orn ers were shelled with orn sheller to determine grin nd ob weights. rop yields were mesured t physiologil mturity (Hlvorson nd Reule 27; Hlvorson et l. 26). The 22 brley yields in the 33 SEPT/ot 28 vol. 63, no. 5 journl of soil nd wter onservtion

4 NTS rottion were redued by hil storm on July 3, 22, whih redued grin yield potentil bout 4% to 5%. Stndrd moisture ontent yield dt (12% moisture for brley, 15.5% for orn, 14% for dry ben, nd 13% for soyben) ws used to determine SI vlues in RUSLE2. nlysis of vrine ws performed on grin yields expressed on n oven dry bsis by ropping system nd N level. bove-ground orn biomss ws determined in mid-sept. in 22 nd mid- Ot. in other yers by hnd hrvesting 15 whole orn plnts from 1.5-m 2 (1.8-yd 2 ) or lrger re from eh plot. The orn plnts were seprted into grin, obs, nd stover for totl biomss determintion. bove-ground biomss of soyben, dry ben, nd brley ws determined t physiologil mturity from 2-m 2 (2.4-yd 2 ) re of eh plot (Hlvorson nd Reule 26, 27). Soil Smpling nd nlyses. Soil smples were olleted from depths of to 5 nd 5 to 1 m ( to 2 in nd 2 to 4 in) to determine ph, wet ggregte stbility (WS), eletril ondutivity (E), P, mirobil biomss rbon (M), nd β-gluosidse tivity (G) in My, 27. Smples for bulk density (D), SO, soil inorgni rbon (SI), nd POM were olleted using 5-m (2-in) dimeter ore smpler t - to 7.6- nd 7.6- to 15.2-m (- to 3- nd 3- to 6-in) depths in Otober, 26 (D, SO, nd SI) or November, 25 (POM). Sine the SI lultes qulittive hnges in SO in the upper 1 m (4 in) of the soil surfe, soil nlyses were lulted s depth-weighted verges over the to 1 m ( to 4 in) depth for omprisons in this study. ulk density ws determined using the soil ore method s desribed by (lke nd Hrtge 1986). Soil D ws used to lulte SO mss on n re bsis. Soil smples were pre-sreened through 2-mm (8-in) sieve to remove lrge piees of plnt mteril before further grinding with flil type soil grinder to pss through 2 mm (8 in) sreen. Sieved smples were used in the POM nlysis ording to the method of Gregorih nd Ellert (1993). Soil smples olleted for totl soil rbon, SI, nd SO were ground to pss 15 µ sreen (6 in) sreen using roller mill nd were nlyzed for ontent using n Elementr Vrio Mro -N nlyzer (Elementr meris In., Mt. Lurel, New Jersey). Soil inorgni ws determined using the method of Sherrod et l. (22). Soil orgni ws the differene between totl soil rbon nd SI. Smples retined for mirobil nlyses were trnsported to the lbortory in ied oolers nd kept t 4 (39 F) until nlyzed no lter thn two weeks fter smpling. Mirobil biomss ontent ws determined by the hloroform-fumigtionextrtion method using.5 M K 2 SO 4 s n extrtnt (Vne et l. 1987). Eh smple ws duplited, nd results were expressed on n oven-dry bsis. Soil wter ontent ws determined by drying the smple t 15 (221 F) for 48 hours. Enzyme tivity (G) ws ssyed using 1 g (35 oz) of ir-dried soil s desribed in Tbtbi (1994). Soil ph nd E were determined on 1:1 soil:solution rtio using 2 g (.7 oz) of ir-dry soil tht hd been pssed through 2 mm (8 in) sieve. The E ws mesured with n YSI Model 3 ondutivity meter nd ph ws mesured using Thermo Orion Model 42 ph meter. Wet ggregte stbility ws mesured ording to the proedure of mbrdell nd Elliott (1993) nd expressed s the perentge of totl soil with wter-stble ggregtes >25 µm (1 in) in dimeter. Soil P ws determined using the Olsen (NHO 3 ) proedure (Frnk et l. 1998). Soil onditioning Index nd Soil Mngement ssessment Frmework Determintion. Detils desribing the SI nd the SI sub-ftors re found in the USD NRS Ntionl gronomy Mnul, Prt 58 (USD NRS 22). In this study, the SI vlues nd sub-ftors for OM, field opertions, nd erosion were determined using RUSLE2, version 5.8 (De. 25). Wind erosion estimtes re lso needed to determine SI for fields where wind erosion is tive, but it is not estimted in RUSLE2 nd ws estimted using n MS Exel spredsheet progrm (Spori et l. 1998) bsed on the Wind Erosion Eqution (Woodruff nd Siddowy 1965) using the mngement period method. Speifi mngement prties nd rop yields for eh N rte, yer, nd replition were entered into the progrms to lulte SI nd the SI sub-ftors. Eight soil properties were seleted nd used s inditors of SQ using SMF: M, TO, G, ph, P, E, WS, nd D. The SMF sored vlues were determined using soring urves tht were relted with the observed soil properties using n MS Exel spredsheet bsed on the method desribed by ndrews et l. (24). The soring urves tke the generl forms of less is better (e.g., D), more is better (e.g., orgni ), nd optiml vlues (e.g., ph) (Wienhold et l. 26). The soring urves used in this study inluded physil (WS using mro-ggregte perentge nd D), hemil (ph, E, P, nd TO), nd biologil (M nd G) soil properties. The SMF soil property index vlues, lled sored vlues, were ombined nd integrted into single tht vried between nd 1, with inditing no SQ vlue nd 1 inditing the highest vlue. Sttistil nlyses were performed using proedures of SS version 9.1 (SS Institute 22). nlyses of vrine (NOV) were performed with Pro Mixed using rndomized omplete blok, with three replitions (four replitions for the T), testing three N rtes within eh of five ropping systems. ll sttistil differenes were evluted t the p = 5 level. Results nd Disussion This study evluted the use of two indexes of SQ for griulturl use, the SI nd SMF, nd ws onduted fter the ropping systems hd been in the field for six yers. The SI lultes qulittive hnges in SO bsed on orgni mteril returned to the soil, field opertions, nd wind nd wter erosion (USD NRS 22) nd estimtes the future trends in SO levels. However, the SMF ombines physil, hemil, nd biologil inditors for n overll ssessment of urrent soil qulity (ndrews et l. 22, 24; Krlen et l. 26). lthough the SI ws intended to estimte only SO, SO is relted to other soil properties tht ffet soil funtion nd eosystems servies. Orgni mtter ts s binding gent for soil prtiles, helps to hold nutrients nd wter in soil, nd provides the energy, substrtes nd biologil diversity to support biologil tivity, whih ffets soil ggregtion nd wter infiltrtion (Frnzluebbers 22). In this study, we evluted these indexes by ompring soil physil (WS nd D), hemil (SO, POM, E, P, nd ph), nd mirobiologil (M nd G) properties with index vlues for five ropping systems (rottions) t three N levels. nlyses of vrine for eh soil property nd index by rottion showed signifint rottion differenes for ll tests (tble 1). The sored vlues re signified by the letter S following journl of soil nd wter onservtion sept/ot 28 vol. 63, no

5 Tble 1 Nitrogen level nd rottion effets on soil properties, rop yields, nd soil qulity indexes. Effets test p > F Nitrogen level Rottion Soure Rottion (R) N-Level (N) R*N NT NT NTS/D NTS T Soil properties Mirobil biomss rbon b b (mg kg 1 soil) Totl soil orgni rbon (%) b 5b b 2b 4b 1.15b β-gluosidse tivity b b b b 13. (mg PN kg 1 soil h 1 ) ph b 7.79b 7.79b Wet ggregte stbility (%) b 58.36b 47.99d 41.94d Phosphorus (mg kg 1 ) b 24.28b 27.6b ulk density (Mg m 3 ) b b 4b 1.32 Prtiulte orgni mtter b.36b.35b.34b rbon (%) Eletril ondutivity (µs m 1 ) b 58.98b b 547b rop properties Yield (Mg h 1 ) b b 6.5b 6.9b 5.45b 7.96 Residue Dry Mss (Mg h 1 ) b b 6.b 5.8b 6.9 Soil qulity inditor sores nd indexes Mirobil biomss rbon sore b 8b Totl soil orgni rbon sore b 1b 2 4 b b b.18b β-gluosidse tivity sore b b b 5 ph Sore b.72b b.73b Wet ggregte stbility sore b.91b 8b Phosphorus sore b ulk density sore b 9b.36b.36b.54 Soil qulity index b.7b b 7b 5 Orgni mtter SI* b b b Soil onditioning index b b 6 3b 6 7 * Orgni mtter subftor of the Soil onditioning Index. 1 = nitrogen; 2 = 67 kg N h 1 for orn, 45 kg N h 1 for brley, nd 22 kg N h 1 for soyben nd dry ben; 3 = 22, 224, or 246 kg N h 1 for orn nd 56 kg N h 1 for soyben nd dry ben, nd 112 kg N h 1 for brley. NT = no-till ontinul orn rottion; NT = no-till orn-brley rottion; NTS/D = no-till orn-soyben/dry ben rottion; NTS= no-till orn-soyben-brley rottion; T = oventionl till ontinul orn study. Mens followed by the sme letter within the sme row nd within nitrogen levels or rottions re not signifintly different t p = 5. the soil property term s listed bove in this mnusript. For exmple, the sored inditor vlue for bulk density is DS. Effet of Nitrogen Level on Soil Properties, Sored Vlues, nd Soil Qulity Indexes. Differenes due to N level were found for the rop grin yields nd residues, for totl SO, G, E, ph nd the totl SOS, GS, OM SI sub-ftor, nd nd SI vlues (tble 1). lthough there were no differenes mong N levels for phs, there ws signifint rottion by N level intertion. The E vlues were not tested beuse the low level of E found in these plots resulted in ll plots hving n ES = 1. mong soil properties tht showed differenes due to N level, inreses in N level generlly resulted in n inrese in the soil property tested (tble 1). The SO nd G were lowest t the N1 level nd were signifintly lower thn the N3 level, where they were the highest. Results t the N1 nd N2 levels were sttistilly the sme. With the exeption of E, eh of the soil properties tht showed differenes due to N level lso hd differenes due to N level for their respetive sored vlue. However, the sored vlues for individul soil inditor properties vried in how the differenes mong N levels were expressed. For exmple, the SOS inresed in the sme reltive diretion nd indited the sme signifine levels s the mesured soil SO vlue. In ontrst, lthough the GS inresed in the sme mnner s the soil G vlue, the GS showed signifint differenes mong ll N levels, while the soil G found no sttistil differene mong the N1 nd N2 levels. Finlly, the phs hd the sme signifine levels s the soil ph, but the phs inresed with N level while the soil ph deresed with N level (tble 1). ll of these generl ptterns were observed nd desribed by ndrews et l. (24) where they disussed four generl ptterns in tret- 332 SEPT/ot 28 vol. 63, no. 5 journl of soil nd wter onservtion

6 ment differenes when tretment mens for the sored vlues re ompred with mesured soil properties using NOVs. Our SOS nd GS ptterns followed their pttern 1, where the mesurements tend to fll on the sending portion of the soring urve. They found similr results for SO for Ntionl Resoures Inventory study nd t liforni site. Our phs pttern for differenes mong N levels follows ndrews et l. (24) pttern 2 where the observed nd sored vlues hd opposite results. They lso observed this pttern for ph t liforni test site. This ourred in our study beuse the ph vlues ll ourred in the desending portion of the soring urves where the deresed s ph inresed. lthough the SI mde unmbiguous, non-overlpping distintions mong N levels, some overlpping ourred mong N levels with (tble 1). The inresed with N level, with N1 not signifintly different from N2, nd the N2 level not signifintly different from N3 level, while N3 level ws signifintly greter thn N1 level (tble 1). The SI lso inresed with N level. However, eh suessive inrese in N level produed signifint inrese in SI vlue. This trend in SI seems to follow the inrese in rop yield nd residue (oven dry vlues) with N level. Diret omprison of the SI nd by N level shows lrge seprtion between SI vlues for eh N level nd muh more subtle seprtion mong N levels for the (figure 1). Effet of ropping Systems on the Soil Mngement ssessment Frmework Soil Qulity Index. The soil property vlues nd their SQ sored vlues re listed by rottion in tble 1, nd side-by-side omprison of eh soil property with its sored vlue is shown in figure 2. It is importnt to onsider the rop, tillge, nd residue returned to the soil when onsidering differenes mong ropping systems. Eh grph in figure 2 hs the NT systems on the left side of the horizontl xis nd the T on the fr right. mong the NT systems, there is tendeny for lower residue mounts s other rops re introdued into the system (going left to right in grph in figure 2). There were sttistil differenes in rop residue mong ropping systems with NT, NTS/D, nd NTS hving the lowest residue returned to the soil (tble 1). The two ontinul orn systems (NT nd T) hd the sme Figure 1 Effet of nitrogen level on the soil qulity index nd soil onditioning index. Error brs indite stndrd errors. Index vlue SI Note: rs with the sme letter nd se re not signifintly different t p = 5. but greter mounts of residue returned thn the other systems. Study of the generl ptterns nd trend of the side-by-side omprisons revels three distint ptterns. The first pttern is the most strightforwrd, with the inditors nd sored vlues hving the sme generl trend nd identil sttistil differenes. We see this pttern for SO (figure 2b) nd G (figure 2). Totl SO nd G nd their sored vlues tend to derese with tillge nd s other rops re introdued into the NT system, nd they identify the sme sttistil differenes mong ropping systems. This pttern orresponds to the first pttern desribed by ndrews et l. (24). Enzyme tivities hve been orrelted with SO in the pst (Tbtbi 1994.) In the seond nd most ommon pttern, the soil properties nd the sored vlues hve the sme generl trend, but more differenes mong mngement systems were found for the soil property vlues. Identifying signifint differenes in the soil property vlues despite seeing few or none in the sored vlues is importnt beuse it indites the observed vlues re ourring on n symptote or plteu in the soring urves. This pttern is found for M, WS, nd P (figure 2, 2e, nd 2f, respetively). This pttern is similr to, but not the sme s, the third pttern of ndrews et l. (24). In our pttern, both the soil property nd sored b N level b SQ vlue showed differenes mong ropping systems, but the soil properties showed more differenes thn the sored SQ vlues. For exmple, the mesured M vlue seprted the systems into three overlpping groups, while the MS identified only two slightly overlpping groups. similr pttern ws found for P, nd even greter sttistil differenes mong ropping systems were found for WS. In this se, the WSS hd two overlpping groups while the mesured WS vlue hd four overlpping groups. This degree of sttistil resolution of the WS ompred to the sored vlue is expeted onsidering tht lthough the rnge of mesured WS vlues ws gret nd sttistil differenes were esily diserned, the sored vlues were ll ner the top of the soring urve with little vrition. In the third nd finl pttern observed, desribing the reltionships of the soil property nd sored SQ vlue, the soil properties nd sored vlues showed opposite trends. s ph nd D vlues inresed, the sored phs nd DS vlues deresed (figure 2d nd 2g, respetively). This generl pttern orresponds to pttern 2 of ndrews et l. (24). However, in our study these vlues hd opposite trends for different resons. s disussed erlier, the mesured ph vlues hd opposite trends beuse ll of the sored ph vlues were on the desending portion of bell-shped optimum vlue-type soring journl of soil nd wter onservtion sept/ot 28 vol. 63, no

7 Figure 2 omprison of soil property vlues with soil property sored vlues for () mirobil biomss rbon (M), (b) soil orgni rbon (SO), () ß-gluosidse tivity, (d) ph, (e) wet ggregte stbility (WS), (f) soil phosphorus (P), nd (g) bulk density. M (mg Kg 1 soil) β-gluosidse tivity (mg PN kg 1 soil h 1 ) WS (%) ulk density (Mg m 3 ) M b M sore b β-gluosidse t. β-gluosidse t. sore b b WS % b b ulk density b b WS sore d ulk density sore b d () () (e) (g) M sore β-gluosidse tivity sore WS sore ulk density sore SO (%) ph Vlue Soil P (ppm) SO % SO sore b b b b ph vlue ph sore b b ontinuous orn NT P ppm b orn-brley NT P sore b orn-soybens/dry bens b orn-soybens-brley ontinuous orn T (b) (d) (f) SO sore ph sore Soil P sore ontinuous orn NT orn-brley NT orn-soybens/dry bens orn-soybens-brley ontinuous orn T Notes: Error brs indite stndrd errors. rs with the sme letter nd se re not signifintly different t p = SEPT/ot 28 vol. 63, no. 5 journl of soil nd wter onservtion

8 Figure 3 omprison of soil property vlues with soil qulity index () nd soil onditioning index (SI) vlues for () mirobil biomss rbon (M), (b) soil orgni rbon (SO), () ß-gluosidse tivity, (d) ph, (e) wet ggregte stbility (WS), (f) phosphorus, (g) bulk density, nd (h) prtiulte orgni mtter rbon (POM). M (mg Kg 1 soil) β-gluosidse tivity (mg PN kg 1 soil h 1 ) WS (%) M b b SI () β-gluosidse tivity SI b b Wet ggregte stbility SI D b D b () (e) Index vlue Index vlue Index vlue SO (%) ph vlue Soil P (ppm) SO ph P SI b SI b SI b b b b (b) (d) (f) Index vlue Index vlue Index vlue ulk density (Mg m 3 ) ulk density SI b b ontinuous orn NT orn-brley NT orn-soybens/dry bens orn-soybens-brley ontinuous orn T (g) Index vlue POM (%) ontinuous orn NT POM % SI b b orn-brley NT orn-soybens/dry bens orn-soybens-brley (h) ontinuous orn T Index vlue Note: Error brs indite stndrd errors. rs with the sme letter nd se re not signifintly different t p = 5. journl of soil nd wter onservtion sept/ot 28 vol. 63, no

9 Tble 2 ropping system yields, erosion estimtes, nd soil onditioning index sub-ftors by nitrogen level. Erosion estimtes ropping Yield Residue WEQ RUSLE2 Soil onditioning index ftors system* N level (Mg h 1 ) (Mg h 1 ) (Mg h 1 ) (Mg h 1 ) SI OM FO ER STIR NT (.15) 5.44 (.15) () 3 () 3 (2) (4).97 () () 2.6 () NT (1) 6.76 (1) () 1 () 1.15 (4) (.1).97 () () 2.6 () NT (.19) 8.68 (.19) () 1 () 7 (2) 1.71 (4).98 () () 2.2 () NT () 4.68 () 7 (7) 4 ().93 (4).98 (9).96 () (7) 4.5 () NT (.77) 5.91 (.77) () 2 () 5 (6) 8 (.14).96 () () 4.5 () NT (.7) 7.65 (.7) () 1 () (2) 2.56 (5).96 () () 4.5 () NTS/D (4) 5.35 (4) () 2 () 6 (5) 7 (.12).97 () () 2.6 () NTS/D (9) 6.16 (9) () 1 () 3 (3) 1.11 (7).97 () () 2.6 () NTS/D (1.11) 6.48 (1.11) () 1 () ((3) 1.53 (8).97 () () 2.6 () NTS (.7) 4.23 (.7) () 2 () 1.14 (7) 1 (.18).96 () () 4.5 () NTS () 5.18 () () 2 () 7 (4) 1.71 (9).96 () () 4.5 () NTS (8) 5.84 (8) () 1 () 1.36 (5) 1.94 (.12).96 () () 4.5 () T (.18) 5.5 (.18) 9.69 (6).31 (2) 1 (4).73 (9).38 ().75 () 14 () T (.17) 7.5 (.17) 9.63 ().19 ().31 (1) 1.53 (3).38 ().73 () 141 () T (4) 8.15 (4) 9.63 ().15 ().5 (1) 1.99 (2).38 ().72 () 142 () Note: Stndrd errors re in prentheses. * NT = No-till ontinul orn rottion; NT = No-till orn-brley rottion; NTS/D = No-till orn-soyben/dry ben rottion; NTS= no-till orn-soyben-brley rottion; T = oventionl till ontinul orn study. 1 = nitrogen; 2 = 67 kg N h 1 for orn, 45 kg N h 1 for brley, nd 22 kg N h 1 for soyben nd dry ben; 3 = 22, 224, or 246 kg N h 1 for orn nd 56 kg N h 1 for soyben nd dry ben, nd 112 kg N h 1 for brley. WEQ = wind erosion eqution; RUSLE2 = revised universl soil loss eqution. SI = soil onditioning index vlue; OM = SI orgni mtter sub-ftor; FO = SI field opertions subftor; ER = SI erosion subftor; STIR = SI soil tillge intensity rting. urve. The D omprison of mesured nd sored vlues hd opposite trends beuse the D soring urves represent the less-is-better effet nd SQ inresed with deresing D. In ddition, lthough these ptterns re similr in their generl trend, they differed in the sttistil resolution of the prmeter. For exmple, there were more sttistil differenes identified with the phs vlues thn the mesured ph vlues. onversely, there were more sttistil differenes identified by the D vlues thn by the DS vlues. omprison of sored vlues mong ropping systems shows tht the T hd signifintly lower sored vlues thn NT, with the exeption of DS (tble 1). The NT systems hd higher observed D tht produed lower DS thn the T system. The signifint differenes mong ropping systems vried with the sored vlues tested. For exmple, the T hd the sme sored vlue s the NTS for the MS nd the phs (figures 2 nd 2d, respetively); the T hd the sme sored vlue s the NTS/D nd NTS for the WSS nd the PS (figures 2e nd 2f, respetively); nd the T hd the sme sored vlue s the NT, NTS/D nd NTS for the SOS (figure 2b). So using n pproh on individul soil properties my led to different outomes depending upon the sored vlue seleted for omprison. For this reson, n importnt step in the determining n index of SQ using SMF is to ombine the individul inditor sores into single vlue tht desribes the overll ondition of the soil, without the distrtion of (potentilly) onfliting individul soil property inditor sores (ndrews et l. 24). The omprison of the integrted vlues is shown in figure 3. The seprted the ropping systems into severl groups with deresing with inresing tillge nd deresing residue s lower residue rops re introdued to the ropping system. The NTS nd T systems hd the lowest. The highest ws mesured in the NT, NT, nd NTS/D systems. The NTS/D nd NTS systems hd the sme (sttistilly) but overlpping vlues for the NT, NT, nd NTS systems. Effet of ropping Systems on the Soil onditioning Index. The SI is determined on the bsis of rop nd tillge mngement, orgni mtter returned to the soil, nd estimted erosion. The sub-ftors representing the effet of OM, FO, nd ER re shown in tble 2. Very little vrition mong replitions ws found for the SI sub-ftors so only mens re presented. Sttistil nlyses reveled differenes mong ropping systems for SI nd the OM sub-ftor (tble 1). In ll ropping systems, the OM sub-ftor (representing orgni mteril returned to the soil) inresed with inresing N level. This result ws due to the inresed grin yield (tble 1). The STIR is the soil tillge intensity rting estimted in RUSLE2 nd is bsed on 336 SEPT/ot 28 vol. 63, no. 5 journl of soil nd wter onservtion

10 the frequeny nd type of opertions used to produe the rop (USD NRS 27b). The rting inreses with inresing soil disturbne. lthough the STIR vlues re very similr, the NT nd NTS/D systems hve slightly lower STIR vlues thn the NT nd NTS systems tht inlude brley in the ropping systems due to slight differenes in the plnter speified in the model. The T system hs fr greter STIR vlue (>3 to 5 times greter) thn the other systems nd produed the only negtive FO vlues. ggressive tillge exposes the soil nd inreses its vulnerbility to wind erosion. Sine the plots were level, estimtes of wter erosion were miniml. The high wind erosion estimtes resulted in negtive ER sub-ftor vlues for the T system plots (tble 2). Diret omprisons of the SI with soil properties, s done bove for, ws not possible beuse the SI is not bsed on observed soil properties but rther on model output using soil, limte, rop mngement, nd grin yield dt. However, grphil omprison of the SI vlues with the soil properties used to determine the n show how SI reltes to importnt soil property inditors not diretly used to develop the index (figure 3). The SI vlues seprted the ropping systems into three groups with no overlp mong them (figure 3). The NT nd NTS hd the highest SI; the NT nd NTS/D hd signifintly lower SI; nd the T hd the lowest SI. None of the NOVs for the soil properties tested seprted the ropping systems into three groups with no overlp. lthough most of the soil properties identified t lest three different groups, most of the nlyses indited overlp mong ropping systems. lthough the SI ws developed to indite qulittive hnges in SO, the SOS ws more suessful in seprting the ropping systems bsed on SO ontent. The SOS in figure 2b mde the sme seprtions of ropping systems s the mesured SO ontent vlue. However, the SI filed to ssoite the NT, NTS/D, nd NTS systems with the T s suggested by the SO ontent vlue (figure 3b). The RUSLE2 simultions of SI showed tht NT hd signifintly greter SI thn T. These results lso show nd SI differed in their bility to detet differenes mong rop mngement systems. lthough both nd SI seprted the NT nd T, the identified signifint differene between NT nd NTS not reognized by SI (figure 3). Thus, we ept the hypothesis tht the produed by SMF n detet smller differenes mong rop mngement systems thn SI. The results of this study seem to onflit with reent study of semirid soils in west Texs (Zobek et l. 27). In the west Texs study, SI ws more losely ssoited with POM thn with totl SO. However in this study of soil in northern olordo, the SI ws more losely orrelted with SO (r =.52, p < 1) thn POM (r = 7, p =.16) (dt not shown). In ddition, the SOS ws very highly orrelted with SO (r =.99) nd not well-orrelted with POM (r = 8, p = 57). The high orreltion of the SOS with SO is expeted beuse SOS ws developed using soring urves developed from SO dt sets tilored to speifi soils nd limte dt sets. omprison of the nd SI with POM is shown in figure 3h. Zobek et l. (27) lso found onsiderble vrition in SI estimtes in ropping systems tht were lssified s the sme system by soil onservtionists nd so suggested buffer of plus or minus for SI determintions. onsidertion of this buffer would suggest tht ording to the lulted SI vlues, ll ropping systems in this northern olordo study would hve positive SI vlues nd meet the SI qulifition for government progrms requiring positive SI vlue. Summry nd onlusions The SI nd SMF provide n evlution of the soil for griulturl use nd mngement. However, they hve different dt requirements nd differ in the resolution they provide in differentiting mong ompeting mngement systems. The SI ws designed to estimte the onsequenes of rop mngement on SO nd uses informtion on soils, limte, nd rop mngement s required by RUSLE2 nd the Wind Erosion Eqution. Field smpling of the soil is not required. onsiderble trining in the use of the models is required to ensure proper results. The estimted through SMF uses set of soil mesurements to determine the urrent SQ bsed on soring urves of properties inditive of soil funtions onsidered importnt for griulturl use nd mngement. The SMF requires informtion bout the soil, limte, nd rop type, but detiled informtion bout rop mngement is not required. However, lbortory nlyses of field soil smples re required. The dt input is strightforwrd, nd it is now possible to input the dt vi the Internet (USD NRS 27). oth indexes seemed to differentite mong three levels of N in this study. The lerly distinguished the plots with very high level of N from plots with no N. However, the mid-level of N ws sttistilly the sme s both extreme levels. The SI vlues identified ler differenes mong ll N levels. These differenes were the sme s those found for the differenes mong N levels for rop yields nd residue returned to the soil. However, the seemed to mke more detiled differentition mong rop mngement systems ompred with SI. The SI seprted the ropping systems into three groups with no overlp mong groups. The NT nd NTS hd the highest SI; the NT nd NTS/D hd signifintly lower SI; nd the T hd the lowest SI. This result seemed ontrolled by the emphsis of tillge intensity nd estimted erosion used in this index. The lso seprted the ropping systems into three groups with deresing with inresing tillge nd deresing residue s lower residue rops re introdued into the ropping system. The ropping systems tht inluded tillge (T) nd the low residue rops (NTS) hd the lowest. The llowed overlp mong ropping groups not reognized by SI. Sine SI ws primrily developed to lulte the onsequenes of mngement on SO, perhps more preise test would be to ompre the SI with the bsed only on the SO inditor. In omprison of the SI nd the SOS, the SOS ws more suessful in seprting the ropping systems bsed on SO. The SOS mde the sme sttistil differentitions mong ropping systems s the SO soil property vlues, seprting the systems into brod but overlpping groups. Seletion of the most pproprite SQ index seems to be trdeoff in dt requirements, resolution desired, nd expeted use of the index vlue. lthough previous reserh hs shown tht the SI does seprte reltively smll differenes in mngement in some ropping systems, in this study the journl of soil nd wter onservtion sept/ot 28 vol. 63, no

11 provided more resolution to distinguish mong mngement options but requires field smpling nd lbortory nlysis. The SI requires only soil mngement nd site dt but lso requires expert knowledge of the models to ensure the orret result. re must be tken when interpreting the output of either SQ model tested. It is very importnt to understnd the history of the site when using tool like SMF to mke n pproprite interprettion of the results. The SMF is developed from mesured soil properties tht my or my not be relted to urrent soil mngement. The ropping systems used in this study were in the field for six yers, nd we ssume the results represented stedy stte ondition. However, if the soil mngement hs reently hnged, the mesured results my represent the former mngement system nd not the urrent mngement. onversely, the SI estimtes the effets of the urrent mngement on future SQ nd does not neessrily reflet urrent soil onditions. In this study, the SI ws orrelted with SO, but it did not mth the pttern of differenes mong ropping systems s well s the. knowledgements The uthors re indebted to Den Holder, urtis Reule, Ptti Norris, nd rdley Floyd (USD RS) for tehnil ssistne with field work nd lbortory nlysis; nd Monty Dollr (retired USD NRS gronomist) for tehnil ssistne with SI lultions. This publition is bsed upon work supported by the USD griulturl Reserh Servie under the USD RS GREnet Projet. The uthors re grteful for the helpful omments suggested by nonymous reviewers. Dislimer Mention of trde nmes or ommeril produts is solely for the purpose of providing speifi informtion nd does not imply reommendtion or endorsement by the USD RS. Referenes ndrews, S.S., D.L. Krlen, nd.. mbrdell. 24. The soil mngement ssessment frmework: quntittive soil qulity evlution method. Soil Siene Soiety of meri Journl 68(6): ndrews, S.S., D.L. Krlen, nd J.P. Mithell. 22. omprison of soil qulity indexing methods for vegetble prodution systems in Northern liforni. griulture, Eosystems, nd the Environment 9(1): mbrdell,.., nd E.T. Elliott rbon nd nitrogen distribution in ggregtes from ultivted nd ntive grsslnd soils. Soil Siene Soiety of meri Journl 57(4): lke, G.R., nd K.H. Hrtge ulk density. In Methods of Soil nlysis. Prt 1. ed. E. Klute, gronomy Monogrph No. 9. Mdison, WI: merin Soiety of gronomy nd Soil Siene Soiety of meri. Frnk, K., D. eegle, nd J. Denning Phosphorus. In Reommended hemil Soil Test Proedures for the North entrl Region, ed. J.R. rown. North entrl Publitions No. 221 (Revised). olumbi, MO: University of Missouri griulturl Experiment Sttion. Frnzluebbers,.J. 22. Wter infiltrtion nd soil struture relted to orgni mtter nd its strtifition with depth. Soil nd Tillge Reserh 66(2): Gregorih, E.G., nd.h. Ellert Light frtion nd mroorgni mtter in minerl soils. In Soil Smpling nd Methods of nlysis, ed. M.R. rter, o Rton, FL: Lewis Publishers. Hlvorson,.D., nd.. Reule. 26. Irrigted orn nd soyben response to nitrogen under no-till in northern olordo. gronomy Journl 98(5): Hlvorson,.D., nd.. Reule. 27. Irrigted orn nd brley response to nitrogen under no-till in northern olordo. gronomy Journl 99(6): Hlvorson,.D.,.R. Mosier,.. Reule, nd W.. ush. 26. Nitrogen nd tillge effets on irrigted ontinuous orn yields. gronomy Journl 98(1): Hubbs, M.D., M.L. Norfleet, nd D.T. Lightle. 22. Interpreting the soil onditioning index. In Mking onservtion Tillge onventionl: uilding Future on 25 Yers of Reserh, ed. E.V. Snten, Proeedings of 25th nnul southern onservtion tillge onferene for sustinble griulture. Speil Report No. 1. lbm griulturl Experiment Sttion nd uburn University. Krlen, D.L., M.J. Musbh, J.W. Dorn, R.G. line, R.F. Hrris, nd G.E. Shumn Soil qulity: onept, definition, nd frmework for evlution. Soil Siene Soiety of meri Journl 61(1):4-1. Krlen, D.L., E.. 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