Growth and Development of Pistachio Seedling Root at Different Levels of Soil Moisture and Compaction in Greenhouse Conditions

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1 Originl Pper Soil & Wter Res.,, 7 (): 6 66 Growth n Development of Pistchio Seeling Root t Different Levels of Soil Moisture n Compction in Greenhouse Conitions Dvou ZAREHAGHI, Mohmm Rez NEYSHABOURI, Mnouchehr GORJI, Rez HASSANPOUR * n Ali BANDEHAGH University of Tbriz, Tbriz, Irn; University of Tehrn, Tehrn, Irn *Corresponing uthor: rzh9@yhoo.com Abstrct Zrehi D., Neyshbouri M.R., Gorji M., Hssnpour R., Bneh A. (7): Growth n evelopment of pistchio seeling root t ifferent levels of soil moisture n compction in greenhouse conitions. Soil & Wter Res., : Soil moisture n compction re importnt fctors for growth n evelopment of plnt root. This stuy ws conucte s neste esign with two fctors n three replictions to investigte the behviour of pistchio seeling roots t ifferent levels of soil compction n moisture in sny lom soil uner greenhouse conitions. The first fctor ws soil compction t four levels of bulk ensity (.5,.5,.65, n.8 g/cm ). The secon fctor ws soil moisture with six levels rnging.7.49 cm /cm. Moisture monitoring t ech tretment ws crrie out by time omin reflectometer evice every two ys. At the en of experiment, root n shoot ry weit, shoot to root weit rtio, root length, n rooting epth were mesure. Results showe tht soil compction n moisture content effects on ll mesure chrcteristics were significnt (P <.). At the bulk ensity of.5 n.5 g/cm n moisture rnges of.4.49 cm /cm (levels 4) the vlues obtine for ll the mesure chrcteristics were the hiest. At the bulk ensity of.65 g/cm the optimum moisture rnge ws.. cm /cm ; t the bulk ensity of.8 g/cm the moisture rnge optimum for root growth n evelopment ws..7 cm /cm. A rop in soil moisture from.49 to.7 cm /cm n concomitnt increse in soil bulk ensity from.5 to.8 g/cm le to severe ecline in root ry weit, shoot ry weit, shoot to root ry weit rtio, root length, n rooting epth by s much s 65, 9, 69, 7 n 66%, respectively. Keywors: ertion stress; bulk ensity; pistchio; rooting epth; wter eficit The invisibility of roots burie in soil hs cuse their vitl role to be frequently overlooke or even neglecte. Root s vegettive orgn is responsible for plnt nchorge in the soil n proviing wter n nutrient for plnt growth. Due to the growing emn for foo in the worl n vrible soil moisture regimens relte to chnging climte ptterns, unerstning the processes n fctors ffecting root growth is very importnt (Glyn Bengou et l. ). Soil compction is one of the physicl forms of soil egrtion tht negtively ffects soil prouctivity. It is estimte tht soil egrtion inuce by soil compction hs ffecte bout 68 million h of the worl s ln (Hmz & Anerson ). Soil compction reuces totl porosity n increses bulk ensity (Pglii et l. ). In ition to reucing the number n size of lrge pores, soil compction lters geometry, morphology, n pore connectivity in soil (Alkukku ). This restricts wter infiltrtion n severely reuces sturte (Hknsson & Meveev 995) n unsturte hyrulic conuctivity (Richr et l. ). When roots encounter compcte soil, their growth ecreses ue to the greter force necessry to move roun the soil prticles. Compcte soil (with hi penetrtion resistnce) limits the vilbility of wter n nutrients to the root system n therefore iminishes the crops yiel. Tylor n Grner (96) in their lbortory works foun tht the cotton 6

2 Soil & Wter Res.,, 7 (): 6 66 Originl Pper roots penetrtion in fine sny lom soil columns significntly ecrese ue to incresing penetrtion resistnce n the penetrtion ws eventully cese t MP resistnce. In fiel experiments, Tylor n Burnett (964) foun tht cotton roots coul not penetrte in Amrillo soil pns with penetrtion resistnce of.5 MP mesure by penetrometer t the fiel cpcity moisture. However, consierble rooting occurre in the pns with resistnce of.9 MP t the sme moisture. Accoring to Brley n Grecen (967), 59% of the roots of pes n bens were ble to penetrte the ense lyer, wheres in whet n brley root penetrtion ws n 6%, respectively. They foun tht plnt species with thicker roots hve better penetrtion into the subsoil tht hs greter penetrtion resistnce becuse they re resistnt to twist. Lipiec et l. (99) reporte tht root length of brley t hi level of soil compction (bulk ensity of.55 g/cm ) compre to the non-compcte soil is reuce by hlf. Atwell s (99) stuies showe tht soil mechnicl resistnce of pproximtely MP or more, reuce root length in ifferent plnt species. Anre et l. (99) foun tht the hi mechnicl resistnce of soil reuces the initil growth of sunflower stlk. Lipiec n Htno () reporte tht incresing soil compction le to reuction in root size n rooting epth n restricte root growth to the upper prt of the soil. This woul ecrese vilble wter, nutrient uptke, n efficiency of fertilizer ppliction in compcte soils. Usul responses of plnt roots system to soil compction inclue reuction in the number n length of roots, restriction of roots penetrtion into the lower lyers, increse in shoot to root ry mss rtio, n reuction in grin yiel (Fgeri et l. 6). Skinner et l. (9) with five levels of soil bulk ensity (.,.,.,., n.4 g/cm ) foun tht incresing the bulk ensity from. to.4 g/cm reuce the rooting epth of Euclyptus lbense n Volpi by bout 77 n 75%, respectively. Grzesik et l. () with three levels of low (. g/cm ), meium (.4 g/cm ), n hi compction (.58 g/cm ) on mize n triticle root growth foun tht in the meium n hi compction tretments compre to low compction, root ry weit ecrese n the rtio of shoot to root increse. Despite mny stuies on these topics, there is still insufficient bsic unerstning of wht soil fctors limit root growth, for wht perios, n uner wht wether n ssocite soil wter conitions. Without this informtion, it is ifficult to mnge soil to enhnce crop prouction. On the other hn, pistchio is known s one of the Irnin griculture crops n its prouction in this country hs long history. In spite of the economic importnce of this crop, there is little informtion bout its moisture nees n root growth response to the stresses such s soil mechnicl resistnce. The im of this stuy ws to evlute the combine effects of soil moisture n compction on the growth n evelopment of pistchio seeling roots. MATERIAL AND METHODS A greenhouse experiment ws conucte to investigte the growth behviour of pistchio seelings t ifferent levels of soil moisture content n compction. Soil smples ( cm epth) were collecte from pistchio gren t the Reserch Center of Agriculture n Nturl Resources, Est Azerbijn province in Irn, n psse throu 4.76 mm sieve. Some physicl n chemicl properties of the stuie soil re given in Tble. The experiment lyout ws neste esign with two fctors n three replictions. The first fctor ws soil compction t four levels of soil bulk ensity (.5,.5,.65, n.8 g/cm ). At ech soil compction level, six moisture levels (Tble ) with three replictes were pplie. At ech compction level 8 pots (5 cm heit n 5.4 cm imeter) n in totl 7 pots (4 compction levels 6 moisture levels replictions = 7) were prepre n rnomly plce on greenhouse bench. Two pistchio (Pistchio ver L.) sees were plnte in isposble continers n were irrigte regulrly for 5 ys to emerge seelings. Seelings with their soil were trnsferre to the prepre pots n regulrly irrigte (every two ys) for week until they were Tble. Severl selecte physicl n chemicl properties of the stuie soil Sn Silt Cly Texturl clss CCE OC (%) (USDA) (%) ph e EC e (S/m) Sny lom CCE clcium crbonte equivlent; OC orgnic crbon; ph e extrction ph; EC e extrction electricl conuctivity 6

3 Originl Pper Soil & Wter Res.,, 7 (): 6 66 Tble. Six rnges of soil moisture (cm /cm ) mintine t ech levels of soil compction uring the experimen. Compction levels (g/cm ) Moisture rnges well estblishe. The pots were then thinne to one seeling per pot. At this stge, the esire moisture levels (Tble ) were pplie to ll pots n mintine till the en of the experiment. A time omin reflectometer (TDR) (Soil Moisture Equipment Corportion; Snt Brbr, USA) evice ws use to monitor soil moisture content in pots. The 45 cm TDR wve guie ws verticlly inserte into pots n its position permnently fixe in the soil uring the whole experimentl perio. Soil moisture ws mesure once every two ys. When the moisture content in the pots ecrese to the low limit of the specifie rnge (Tble ), wter ws e to the pots to rise moisture to the upper limit of the esire rnge. The volume of wter require ws clculte from Eqution. V = D (θ V θ V ) () where: V volume of wter require (cm ) D, epth (45 cm) n cross-section re (8. cm ) of the pots θ V upper limit of the selecte moisture rnge (cm /cm ) θ V moisture content (cm /cm ) t the time mesure by time omin reflectometer After estblishing of the moisture levels, the experiment continue until pistchio seelings roote out from the bottom of the pots with soil bulk ensity of.6 g/cm. This event (rooting out of the pot) occurre fter weeks. At this time the pots were plce in buckets of wter to esily remove the root system from the pot soil. Roots length ws mesure by Tennnt (975) metho. Seprte shoot n roots prts were plce in pper pocket n ovenrie t 7 C for 48 h. Dry weit of roots n shoots ws etermine by weiing blnce (±. g). A vrince nlysis ws one using SPSS softwre (Version., ) n the mens were compre by Duncn s test t the % probbility level. Soil penetrtion resistnce ws mesure by electronic cone penetrometer (Mobtkern Corportion, Tbriz, Irn) with cone ngle of, bottom imeter of 6 mm, n constnt penetrtion spee of mm/ min. Soil texture ws mesure by hyrometer (Gee & Buer 979), soil orgnic mtter content by wet oxition metho (Nelson & Sommers 996), percentge of equivlent clcium crbonte by ci neutrliztion n titrtion metho (Jckson 958). Electricl conuctivity (EC) n ph of soil in sturte pste extrct ws etermine by the EC-meter (Testo4; Keison Proucts, Chelmsfor, UK) n ph-meter (Hch EC, Loveln, USA), respectively (Richrs 969). RESULTS AND DISCUSSION The results of the nlysis of vrince for the five chrcteristics of pistchio shoot n root growth re given in Tble. Effects of soil compction n soil moisture on ll the chrcteristics were hily significnt (P <.). Tble. The nlysis of vrince for the five shoot n root growth chrcteristics Source of vrition 6 f Men squres RDW SDW S/R RL RD Compction 8.8** 45.8**.74** ** 4.8** Moisture within compction.45** 8.7**.6** 78 7** 76.** Experimentl error f egrees of freeom; **significnt t % level; RDW root ry weit; SDW shoot ry weit; S/R shoot to root ry weit rtio; RL root length; RD rooting epth

4 Soil & Wter Res.,, 7 (): 6 66 Originl Pper Root ry weit (g/pot) Moisture rnge Moisture rnge Moisture rnge Moisture rnge 4 Moisture rnge 5 Moisture rnge 6 b b bc c-f -g bc b-e c-g fg g fg bc c-g -gefg g Soil compction levels (g/cm ) Figure. Root ry weit (g/pot) t ifferent levels of soil compction n moisture content There ws no significnt reuction for the mesure root chrcteristics t bulk ensities of.5 n.5 g/cm n in the moisture rnges of to 4 (Figures 5). Seemingly t.5 n.5 g/cm the plnts were not encountere either with ertion stress or wter eficit. At the mentione bulk ensities, the soil ws loose enou n the e wter esily rine off n i not le to ertion limittion. By continuing moisture reuction n reching to the rnges of level 4 n 5 (below 4% moisture content), the plnt fce with severe wter eficit stress leing to reuction in root n shoot growth n evelopment. Another fctor tht my ffect the growth is the penetrtion resistnce of soil. The ssume criticl vlue of soil penetrtion resistnce is bout MP (Tylor et l. 966; Atwell 99; Silv et l. 994); in our experiment t the bulk ensity levels of.5 n.5 g/cm, the penetrtion resistnce of the soil ws much lower thn MP (Figure 6) n therefore the root growth ws not reuce. At the bulk ensity of.65 g/cm n moisture rnge of level, plnts were fcing ertion stress, n t low moisture content (moisture levels of 4 6) with wter eficit stress n soil penetrtion resistnce limittion the growth n root evelopment ecline (Figures 5). At this bulk ensity (.65 g/cm ) the moisture levels of n (moisture content of %) were optimum promoting the hiest growth n root evelopment. At the bulk ensity of.8 g/cm, the best moisture level ws (moisture content of 7%). As mentione erlier, t hi moisture rnge (rnge ) the ertion stress, n t low moisture rnges (levels 6), wter eficit stresses n/or penetrtion resistnce (Figure 6) reuce the mesure chrcteristics. A ecrese in soil moisture level (from to 6) n concomitnt increse in soil bulk ensity level (from to 4) le to severe ecline of s much s 65, 9, 69, 7, n 66% in root ry weit, shoot ry weit, shoot to root ry weit rtio, root length, n rooting epth, respectively. 7 Moisture rnge Moisture rnge Moisture rnge Moisture rnge 4 Moisture rnge 5 Moisture rnge 6 Shoot ry weit (g/pot) b b bc ef efg bc bc bc c f f h e f f f Soil compction levels (g/cm ) Figure. Shoot ry weit t ifferent levels of soil compction n moisture content 6

5 Originl Pper Soil & Wter Res.,, 7 (): 6 66 S/R.5.5 b b b Moisture rnge Moisture rnge Moisture rnge Moisture rnge 4 Moisture rnge 5 Moisture rnge 6 b b b b b b bc b.5 c c c c c c c c c Soil compction levels (g/cm ) Figure. Shoot to root ry weit t ifferent levels of soil compction n moisture content Oxygen eficiency uner ertion stress increses ethylene biosynthesis in roots n sens bscisic ci to shoots. Plnt responses to these hormones re lef curling, prevention of root n shoot growth, n leves flling (Drew 99; He et l. 996). Reuction in growth n evelopment of corn roots ue to soil compction hs been reporte by Tubeileh et l. () n Grzesik (9). In whet, hevily compcte (bulk ensity of.7 g/cm ) soil lyers significntly ecrese ry shoot mss, root ms ensity, n root length ensity (Noslevicz & Lipiec 4). Soil moisture reuction ecreses wter potentil n soil hyrulic conuctivity, leing to shrp ecline in wter vilbility prticulrly in course texture soils. In this conition both root imeter n volume ecrese enhnces root ging. The lter reuces root hyrulic conuctivity n eventully root soil contct surfce. Also, uner wter eficit stress, the number of root hirs ecrese significntly n thereby reuce wter n nutrients uptke. As seen in Figure 6, soil mechnicl resistnce hs increse with rise in bulk ensity n with soil moisture ecrese. At hi bulk ensities soil mechnicl strength restricts or even my prevent root growth n evelopment in the soil (Noslevicz & Lipiec 4). In this conition, roots encountere hr n impenetrble soil, n were not cpble of sufficient infltionry pressure to move soil prticles roun n penetrte throu them (Chn & Weil ) n consequently soil volume expose to the root system reuce n efficiently restricte wter n nutrients uptke s well s root n shoot growth (Figures 4). Further, increse in soil bulk ensity les to significnt reuction in totl porosity, especilly of lrge pores, which my le to root ertion stress n oxygen problem, n further reuces root growth n evelopment. Mullins et l. (99) reporte reuce root growth t. MP mtric potentil ue to soil mechnicl strength rther thn low soil wter energy level. Root length (cm/plnt) b b Moisture rnge Moisture rnge Moisture rnge Moisture rnge 4 Moisture rnge 5 Moisture rnge 6 bc ce bc bc bc bc ef efg j ce ce ef h ce f f f Soil compction levels (g/cm ) Figure 4. Root length t ifferent levels of soil compction n moisture content 64

6 Soil & Wter Res.,, 7 (): 6 66 Originl Pper Rooting epth (cm) b b b Moisture rnge Moisture rnge Moisture rnge Moisture rnge 4 Moisture rnge 5 Moisture rnge 6 b b b b c c c ij e e f g ij ef hi ij j Soil compction levels (g/cm ) Figure 5. Rooting epth t ifferent levels of soil compction n moisture content 6 compction level 4 Mechnicl resistnce (MP) 5 4 compction level compction level compction level Moisture rnges Figure 6. Soil penetrtion resistnce t vrious moisture n compction (bulk ensity) levels. The horizontl line elinetes the criticl vlue for root growth ( MP) Thus it is speculte tht the suppressive effect of soil moisture on root growth often my be inirect throu the soil penetrtion resistnce (Shrp et l. 988). In ition to soil mechnicl impence inuce by wter eficit, other intercting effects ssocite with het, isese, low nutrients sttus, n even hypoxi shoul be tken into ccount (Whitmore & Whlley 9). CONCLUSION Effects of soil compction n moisture significntly (P <.) ecrese root n shoot ry weit, shoot to root ry weit rtio, root length, n rooting epth. The hiest vlues for ll mesure chrcteristics were obtine t the bulk ensities of.5 n.5 g/cm n moisture rnge of.4.49 cm /cm. At the bulk ensity of.65 g/cm, the optimum moisture levels were.8. cm /cm n..8 cm per cm, n t the bulk ensity of.8 g/cm, the moisture level of..7 cm /cm ws optimum for root n shoot. Menwhile, the soil moisture rnge reuction from.49 to.7 cm /cm n the soil ensity level increse from.5 to.8 g/cm le to ecrese of bout 65, 9, 69, 7, n 66% in root ry weit, shoot ry weit, shoot to root ry weit rtio, root length, n rooting epth, respectively. References Alkukku L. (): Soil Compction. Compcting Soil Degrtion. Helsinki, University of Helsinki. Finln, 8: 7. Anre A., Wolfe D.W., Fereres E. (99): Lef expnsion, photosynthesis n wter reltions of sunflower plnts on compcte soil. Plnt n Soil, 49: Atwell B.J. (99): Response of roots to mechnicl impence. Environmentl n Experimentl Botny, : 7 4. Brley K.P., Grecen E.L. (967): Mechnicl resistnce s soil fctor influencing the growth of roots n unergroun shoots. Avnces in Agronomy, 9: 4. Chn G., Weil R.R. (): Penetrtion of cover crop roots throu compcte soil. Plnt n Soil, : 4. 65

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