Soybean Tillage Systems and Physical Changes in Surface Layers of Two Albaqualf Soils

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1 Article Division Soil Use nd Mngement Commission Soil nd Wter Mngement nd Coervtion Soyben Tillge Systems nd Physicl Chnges in Surfce Lyers of Two Albqulf Soils Gerson Meneghetti Srzi Srtori*, Enio Mrchesn(2), Ricrdo De Dvid(3), Reimr Crlesso(4), Mirt Teresinh Petry(4), Núbi Pentido Aires(3), Robson Gicomeli, Bruno Behenck Armburu (3) nd Anelise Lencin d Silv(3) Universidde Federl de Snt Mri, Centro de Ciêncis Ruris, Deprtmento de Fitotecni, Progrm de Pós-grdução em Agronomi, Snt Mri, Rio Grnde do Sul, Brsil. (2) Universidde Federl de Snt Mri, Centro de Ciêncis Ruris, Deprtmento de Fitotecni, Snt Mri, Rio Grnde do Sul, Brsil. (3) Universidde Federl de Snt Mri, Centro de Ciêncis Ruris, Curso de Agronomi, Snt Mri, Rio Grnde do Sul, Brsil. (4) Universidde Federl de Snt Mri, Centro de Ciêncis Ruris, Deprtmento de Engenhri Rurl, Snt Mri, Rio Grnde do Sul, Brsil. * Corresponding uthor: E-mil: gersonmss@yhoo.com.br Received: Jnury 13, 2016 st Approved: Februry 1, 2016 How to cite: Srtori GMS, Mrchesn E, De Dvid R, Crlesso R, Petry MT, Aires NP, Gicomeli R, Armburu BB, Silv AL. Soyben Tillge Systems nd Physicl Chnges in Surfce Lyers of Two Albqulf Soils. Rev Brs Cienc Solo. 2016;40:e Copyright: This is n open-ccess rticle distributed under the terms of the Cretive Commo Attribution Licee, which permits unrestricted use, distribution, nd reproduction in ny medium, provided tht the originl uthor nd source re credited. ABSTRACT: A compcted subsurfce soil lyer cn be limiting fctor for soyben growing, reducing soyben yield. The im of this study ws to evlute the effect of different tillge systems on the physicl properties of two Albqulf soils of the Centrl Pli region in the stte of Rio Grnde do Sul in southern Brzil. Two experiments were conducted: one in Snt Mri, RS, during the 2013/14 nd 2014/15 crop seso, nd nother in Formigueiro, RS, during the 2013/14 crop seson. A rndomized block experimentl design with four replictio ws used. The tretments were: sowing using n offset double disc (T1); sowing using fluted coulter disc (wvy disc with 12 wves) (T2); sowing with knife runner opener (T3); sowing with knife runner opener + press wheel mechnism for ground levelling (T4); sowing using furrow opener upon rised bed (T5); nd chisel plough + sowing using n offset double-disc (T6). In the 2014/15 growing seson, the T4 fctor ws chnged using knife runner opener 0.05 m from the plnting row. A smller reduction in the compcted subsurfce soil lyer ws observed for both T1 nd T2, which exhibited high soil bulk deity vlues for the 2013/14 nd 2014/15 crop seso. Furthermore, T3, T5 nd T6 led to reduction in bulk deity, nd incresing totl porosity nd mcroporosity in the soil, which coequently incresed wter infiltrtion, wter storge cpcity, nd crop yield in res with the presence of compcted subsurfce soil lyer. Keywords: compcted lyer, deep tillge, rised bed, plnter mechnism. DOI: / rbcs

2 INTRODUCTION An increse in cultivtion of soyben in rottion with rice hs been observed in recent crop seso in lowlnd res. This increse cn be explined by the presence of weeds difficult to control in rice cropping res, nd by the need for rurl income diversifiction. The use of crop rottion lso indirectly improves physicl nd chemicl soil conditio (Thoms et l., 2000). The predominnt soil clss in lowlnds of Rio Grnde do Sul is Albqulf (Bmberg et l., 2009) formed inhydromorphic environment (Borges et l., 2004) with limited wter dringe (Mrchezn et l., 2002). When Albqulf soils re cultivted with rinfed crops, s is the cse of soybe, plnt growth nd development my be hindered, minly due to their nturlly unfvorble physicl conditio (Bmberg et l., 2009). During the systemtiztion process of lnd res for irrigted rice, compcted soil lyers cn be found ner the surfce (Nunes et l., 2002; Reichert et l., 2008). Soil compction is mjor cuse of physicl degrdtion of griculturl soils (Mzurn et l., 2013), which indirectly it influences infiltrtion, hydrulic conductivity, temperture, nd ertion of the soil (Borges et l., 2004). The effects of soil compction on ertion cn be evluted by the mount of mcropores (Vlicheski et l., 2012). Soil compction is mnifested by incresed bulk deity nd reduction in totl porosity nd mcroporosity of the soil (Drescher et l., 2011), long with incresed resistnce to penetrtion (Sper et l., 2012). A study conducted by Mentges et l. (2013), evluting hydro-physicl nd mechnicl chnges in the soil fter eight yers of rice crops grown in conventionl tillge system, showed n increse in bulk deity nd decrese in totl porosity nd mcroporosity. A compcted soil lyer reduces the wter infiltrtion rte (Bonini et l., 2011) nd decreses the lest limiting wter rnge in the soil profile (Kiser et l., 2009). Furthermore, wter vilbility to plnts cn be reduced s the soil structure is one of fctors which directly influence wter vilbility to crops by determining the rrngement of soil prticles nd therefore the distribution of pore dimeters (Klein nd Librdi, 2000). Soil compction increses wter retention but reduces wter vilbility to plnts. Soyben producing res my be dversely ffected fter yers of stress from either lck or excess of wter becuse both retention nd vilbility of wter cn ffect plnt growth nd yield (Cost et l., 2013) by ffecting wter uptke by plnts (Crlesso, 1995). The study of mngement prctices tht improve hydro-physicl properties of the soil becomes essentil to optimize soyben cultivtion in such res. The hypothesis of this work is tht sowing with knife runner opener, sowing using furrow opener upon rised bed nd chisel plough + sowing using n offset double disc improving soil physicl qulity. Thus, the im of this study ws to evlute the effect of different soyben tillge systems on the physicl chrcteristics of the subsurfce lyer of two Albqulf (Plnossolos) soils of the Centrl Pli region in the stte of Rio Grnde do Sul in Brzil. MATERIALS AND METHODS Two experiments were performed: Experiment 1 during the 2013/14 nd 2014/15 crop seson nd Experiment 2 during the 2013/14 crop seson. Experiment 1 ws crried out in the experimentl lowlnd re of the Phytotechnology nd Plnt Science Deprtment of the Federl University of Snt Mri (Universidde Federl de Snt Mri - UFSM), Snt Mri, Rio Grnde do Sul (RS), Brzil, in soil clssified s n Albqulf (Soil Survey Stff, 2014), or Plnossolo Háplico Eutrófico (Sntos et l., 2013). The soil of the surfce lyer where the experiment ws conducted belongs to the silty lom texturl clss (Tble 1). We found 5, 208, nd 547 g kg-1 of cly, snd, nd silt, respectively, in the center of the two lyers, nd the following chemicl properties, 2

3 t 60 dys before sowing, in the m lyer: ph(h2o) (1:1) 5.4; P 18 mg dm-3; K 60 mg dm-3; C cmolc dm-3; Mg cmolc dm-3, nd orgnic mtter (OM) 2.0 % for the 2013/14 crop seson; nd ph(h2o) (1:1) 5.4, P 15.3 mg dm-3, K 44 mg dm-3, C cmolc dm-3, Mg cmolc dm-3; nd OM 2.0 % for the 2014/15 crop seson. The 2013/14 crop seson experiment ws crried in n re which previously contined soyben crop nd the 2014/15 crop seson experiment ws crried out in n re which previously contined irrigted rice. After the preceding soyben nd rice crops were hrvested, the res received 2.0 Mg h-1 of lime nd then disked nd leveled. In the off-seson, ryegrss ws sown in the re, which ws desiccted with glyphoste t rte of 960 g h-1.i.. By the time the experiments were set up, prcticlly no ryegrss remined. A rndomized block experimentl design ws used with four replictio. The tretments were different soyben tillge systems (Figure 1): sowing using n offset double disc (T1); sowing using fluted coulter disc (wvy disc with 12 wves) (T2); sowing with knife runner opener (T3); sowing with knife runner opener + press wheel mechnism for ground levelling (T4); sowing using furrow opener upon rised bed (T5); nd chisel plough + sowing using n offset double disc (T6). In the 2014/15 growing seson, the T4 fctor ws chnged using knife runner opener 0.05 m from the plnting row. Experiment 2 ws crried out in non-systemized re with gently rolling topogrphy in the neighboring municiplity of Formigueiro in soil clssified s n Albqulf (Soil Survey Stff, 2014), or Plnossolo Háplico Eutrófico típico (Sntos et l., 2013). In this experiment, the cly, snd, nd silt found in the soil in the center of the nd m lyers were 360, 252, nd 387 g kg-1, respectively, nd the texturl clss ws silty cly lom in both lyers (Tble 1). At 50 dys prior to sowing, the m lyer hd the following physicl-chemicl properties: ph(h2o) (1: 1) 5.2; P 2.2 mg dm-3, K 112 mg dm-3; C cmolc dm-3; Mg cmolc dm-3; nd OM. 1.6 %. Beef cttle were rised in the experimentl re in the municiplity of Formigueiro, nd prior to the experiment the ntive psture ws desiccted with glyphoste t rte of 960 g h-1.i.. A rndomized block experimentl design ws used, with four replictio. The tretments were the sme s in Experiment 1 during the 2013/14 crop seson, but without the rised bed system. Chisel plough for Experiment 1 ws performed t 45 nd 19 dys before sowing for the 2013/14 nd 2014/15 crop seson, respectively, in frible soil. For experiment 2, deep Tble 1. Prticle size distribution nd soil texturl clss in two soil lyers. Snt Mri nd Formigueiro, RS, Brzil, 2015 Prticle size m m g kg -1 Experiment 1 - Snt Mri Cly Snd Silt silty lom silty lom Texturl clss Experiment 2 - Formigueiro Cly Snd Silt silty cly lom silty cly lom Texturl clss Determined by the pipette method (Dongem et l., 2011). Snd: 2 to 0.05 mm, silt: to 0.05 mm, cly: <0.002 mm. 3

4 tillge ws crried out t the time of sowing. Tillge depth in both experiments ws bout 0.25 m, nd knives were spced t distnce of 0. m. The knife runner opener, the furrow opener upon rised bed, the offset double disc, nd the fluted coulter disc (wvy disc with 12 wves) system hd working depths of pproximtely 0.18, 0.12, 0.10, nd 0.08 m, respectively. Sowing ws crried out on November 7, 2013 nd November 14, 2014, for Experiment 1. Due to 5 mm rinfll two dys fter sowing during the 2013/14 crop seson, reseeding took plce on November 26, For experiment 2, sowing took plce on November 5, The soyben cultivr used for both experiments ws BMX Torndo t seed deity of 26 seeds m-2 in rows spced t 0.50 m. Sowing of T1, T2, T3, T4, nd T6 ws crried out with MF 407 plnter, weighing pproximtely 2,210 kg. Rised bed seeding (T5) ws performed with KF 8/5 - A seeder, weighing pproximtely 3870 kg. The verge seeding speed for experiments 1 nd 2 ws 3.3 nd 3.5 km h-1, respectively. At sowing the verge wter volume content in the soil ws 26 nd 34 m3 in the m lyer for Experiment 1 nd 2, respectively. The experimentl units were 40 3 m nd 60 3 m for experiments 1 nd 2, respectively, with n re of 15 m2 ech. The properties nlyzed from the soil smples were soil bulk deity (BD), totl porosity (TP), microporosity (Micro), mcroporosity (Mcro), micropore/mcropore rtio, degree of compction (DC), wter content retined t field cpcity, vilble wter, nd mximum soil wter storge. Evlutio were performed t 10 dys prior to sowing during the V6 nd R3 soyben growth stges in both experiments in the 2013/14 crop seson, nd during growth stge R3 in the 2014/15 seson. For soil nlysis, soil smples were collected from the nd m depth lyers in the plnting row using volumetric rings of 4.0 cm height nd 4.8 cm dimeter. After collection, soil smples were sent to the lbortory nd nlyzed using the volumetric ring technique ssocited with tble teion with 0.60-m wter column, following the techniques described by Dongem et l. (2011). We coidered the wter retined t field cpcity of -10 kp nd the permnent wilting point t kp. To determine wter vilbility, the permnent wilting point ws subtrcted from the field cpcity. The degree of compction (DC) ws clculted using the following eqution: DC = (BD/BDref) 100, which reltes bulk deity in the field (BD) to reference deity vlue restrictive to plnt growth. Soil DC ws clculted by using two strtegies to estimte deity reference, nmely: BDc LLWR = cly s proposed by Reichert et l. (2009) in which LLWR (Lest Limiting Wter Rnge) is zero, nd BDc LLWR = cly, ccording to Jones (1983) when coidering restriction to root growth. Wter infiltrtion cpcity ws lso evluted in Experiment 1 in the V6 nd R7 crop stges for the 2013/14 nd 2014/15 crop seso, respectively. The evlutio were performed in the plnting row using the double ring infiltrometer method. Redings were tken over 3-h period, s proposed by Sto et l. (2012). The results were subjected to the test of the ssumptio of the mthemticl model (normlity nd homogeneity of vrinces). Anlysis of vrince ws performed using the F test nd the me of the tretments, when significnt, were compred by the Tukey test t 5 % probbility. RESULTS Experiment 1 Soil physicl properties t ten dys before sowing (Tble 2) indicted the presence of more severely compcted soil lyer t m in both crop seso (2013/14 nd 4

5 2014/15). This cn be inferred by the high vlues of bulk deity (BD) nd reduced vlues of totl porosity (TP) nd mcropores compred to the m lyer. In this sme lyer, mcro vlues indicte restriction in ertion with vlues below 0.10 m3 m-3. Moreover, by compring the deity vlues observed with the reference vlues of deity restrictive to plnt nd root growth (Tble 2), these vlues re very close in the m lyer, which indictes mrked degree of compction in this soil lyer in both crop seso. In the m lyer there were distinct respoes rising from the different tillge systems in both crop seso on the hydro-physicl chrcteristics of the soil evluted t different times fter soyben seeding. In the 2013/14 seson (Tble 3), soil wter retention nd vilbility, well s BD nd microporosity (Micro) were not significntly ffected by the tillge systems t the V6 stge in the m nd m lyers. However, T1 (offset double disc system) exhibited lower TP nd Mcro, nd greter micropore/mcropore rtio in the m lyer compred to the other systems. No difference ws found for the vribles evluted in the m lyer. Similr to observtio in the V6 stge, in the R3 stge there ws lower mcroporosity (Mcro) nd TP nd greter micropore/mcropore rtio in T1. For soil wter retention, in systems using n offset double-disc nd (double fluted-counter) wvy disc with 12 wves (T2), there ws higher wter retention compred to the shnk nd rised bed systems in the m lyer, without ny differences in the m lyer. The fluted coulter disc (T2) nd knife runner opener (T3) systems led to greter vilbility of wter in the nd m lyer, respectively. For BD, there ws no significnt difference for the m lyer, where the highest deities were found in soil systems tht used either offset double-disc or fluted coulter disc. Furthermore, low mcropore vlues were found in depths up to 0.2 m in both systems; the highest mcropore vlue ws observed in the rised bed nd knife runner opener system in the nd m lyers, respectively. In the 2014/15 seson (Tble 4), the results were similr to those observed in the 2013/14 seson. In the evlution crried out during the R3 stge, there were no significnt differences mong the systems for wter retention nd vilbility, or for the quntity of micropores in the nd m lyers. Higher BD, lower TP, lower quntity of mcropores, nd higher micropore/mcropore rtio were observed in both lyers for the Tble 2. Soil wter retention t field cpcity (θfc), vilble wter (AW), bulk deity (BD), totl porosity (TP), microporosity (Mi), mcroporosity (M), Mi/M rtio, reference bulk deity vlue restrictive to plnt nd root growth (BDref), nd degree of compctness (DC) in two soil lyers ten dys prior to sowing. Snt Mri 2013/14 nd 2014/15 crop seson nd Formigueiro 2013/14 crop seson Lyer θfc (-10 kp) m AW BD TP Mg m-3 mm Mi M Mi/M m3 m-3 BDref BDref(2) DC Mg m-3 % Snt Mri Experiment 1 (2013/14 crop seson) : : : : : : Formigueiro Experiment 2 (2013/14 crop seson) Snt Mri Experiment 1 (2014/15 crop seson) The methods used were ccording to Dongem et l. (2011). θfc nd AW: determined by Richrds extrctor device (Soils Moisture Equipment); BD: volumetric method; TP: clcultion method with prticle deity; Mi: teion tble method: 0.6 m teion; M: difference between TP nd Mi. BDref nd DC: determined s (2) proposed by Reichert et l. (2009); nd BDref: s proposed by Jones (1983). 5

6 Tble 3. Soil wter retention t field cpcity (ƟFC), vilble wter (AW), bulk deity (BD), totl porosity (TP), microporosity (Mi), mcroporosity (M), nd Mi/M rtio in the tretments t different soil depths. Snt Mri, Brzil. Experiment 1 in the 2013/14 crop seson Tillge system θfc (-10 kp) AW BD TP Mg m-3 mm Mi M Mi/M 2.9:1 m3 m-3 V m c 0.12 b bc 0.14 b 2.7:1 b bc b 2.2:1 b + M b :1 b Rised Bed :1 b bc b 1.9:1 b : m : : :1 + M :1 Rised Bed : : : R m 37 b 25 b c + M Rised Bed 0.49 b 0.38 b 0.11 c 3.5: b c 3.9:1 b bc 2.9:1 b 34 bc b b 0. b 0.18 b 1.9:1 b c 21 b b :1 b 37 b 26 b b bc 2.8:1 b : m 22 b 1.63 b b 2.9:1 b 22 b b 0.06 c 5.7: c :1b + M b 1. c b 2.1:1 b Rised Bed 22 b 1.40 bc b 2.1:1 b 21 b 1.30 c b 2.2:1 b : : no significnt t p Me not followed by the sme letter in the column differ by the Tukey test t 5 % probbility. Plnt development stge. The methods used were ccording to Dongem et l. (2011); θfc nd AW: determined by Richrds extrctor device (Soils Moisture Equipment); BD: volumetric method; TP: clcultion method with prticle deity; Mi: tble method: 0.6 m teion; M: difference between TP nd Mi; M: press wheel mechnism for ground leveling. 6

7 double disc system. Use of the knife runner opener ner the plnting row led to lower BD nd greter TP in the m lyer, which is lso the lyer with the gretest mount of mcropores in the deep tillge system. Furthermore, the systems tested in this study influenced mximum wter storge in the soil in the m lyer, nd wter infiltrtion cpcity in both crop seso. The offset double disc nd the fluted coulter disc systems led to lower wter storge cpcity in the V6 nd R3 stge (Figure 2). In the knife runner opener, rised bed, nd chisel plough systems, there ws wter storge cpcity of 8, 9, nd 6 mm, respectively, which is higher thn the verge of the double disc t V6, which ws 11, 12, nd 11 mm, respectively, which, in turn, ws higher thn the cpcity of the offset double disc t R3. Similr results were found in the 2014/15 seson (Figure 2c) in the evlution t R3 in the knife runner opener, rised bed, nd chisel plough systems, where the soil exhibited wter infiltrtion cpcity of 12, 6, nd 7 mm, which is higher thn in the offset double disc system. Wter infiltrtion cpcity (Figure 2d) ws highest for the chisel plough system, followed by the knife runner opener nd rised bed systems (2013/14 seson). These systems incresed infiltrtion cpcity by 97, 31, nd 15 %, respectively, compred to the verge of systems using offset double disc nd fluted coulter disc. In the 2014/15 seson, the increse ws 173, 57, nd 18 % for these sme systems. Overll, compring the verge vlues of ll tillge systems in both seso nd evlution periods with offset double disc vlues in the m lyer, there ws n overll 10 % Tble 4. Soil wter retention t field cpcity (θfc), vilble wter (AW), bulk deity (BD), totl porosity (TP), microporosity (Mi), mcroporosity (M), nd Mi/M rtio in the tretments t different soil depths. Snt Mri, Brzil. Experiment 1 in the 2014/15 crop seson Tillge system θfc (-10 kp) AW BD TP Mg m-3 mm Mi M Mi/M m3 m-3 R m b c 5.9: b 2.3:1 b 1.31 b b :1 b b b 2.1:1 b Rised Bed 1.34 b b 2.1:1 b b b 1.7:1 b : c c 4.5: b 0.39 bc bc 3.0:1 b c b 2.3:1 b bc 0.43 b bc 2.7:1 b m Rised Bed bc 0.41 bc bc 2.8:1 b bc 0.45 b :1 b : : no significnt t p Me not followed by the sme letter in the column differ by the Tukey test t 5 % probbility. Plnt development stge. The methods used were ccording to Dongem et l. (2011); θfc nd AW: determined by Richrds extrctor device (Soils Moisture Equipment); BD: volumetric method; TP: clcultion method with prticle deity; Mi: tble method: 0.6 m teion; M: difference between TP nd Mi; knife runner opener 0.05 m from the plnting row. 7

8 reduction in soil BD compred to the offset double disc system, s well s 13 % increse in porosity nd 76 % increse in soil mcroporosity compred to the offset double disc. In the m lyer, BD decresed by 11 % compring the verge of ll systems with the offset double disc. In ddition, there ws n increse of 11 % in TP nd % in Mcro in the verge of ll systems compred to the offset double disc. As result, the offset double disc hd the lowest grin yield, with n verge yield of 4082 nd 3759 kg h-1 in the 2013/14 nd 2014/15 crop seson, respectively, compred to the knife runner opener rised bed, nd chisel plough systems, where the grin yield vlues were 4405, 4345 nd 4484 kg h-1 for the 2013/14 seson, respectively, nd 4327, 4013, nd 4749 kg h-1 for the 2014/15 seson, respectively (, 2015). Experiment 2 Soil physicl properties (Tble 2) lso indicted the presence of compcted soil up to the depth of 0.2 m, which ws more evident in the m lyer. Noteworthy is the high vlue of BD, over 1.6 Mg m-3, nd the low mcroporosity, less thn 0.05 m3 m-3, in both lyers. Moreover, in both lyers evluted ( nd m), the deity vlues observed were higher thn the restrictive reference deity vlues for plnt nd root growth (Tble 2), which cn lso be observed by the degree of compction (DC) higher thn 100 %. This experiment did not show ny differences in soil wter retention nd vilbility nd microporosity in the soil during the V6 stge (Tble 5). During the sme period of evlution, there ws lower BD nd micropore/mcropore rtio for knife runner opener nd chisel plough systems. Moreover, these systems led to n increse in Mcro nd TP compred to the offset double disc nd fluted coulter disc systems in the m lyer. In the m lyer, the knife runner opener system cused the gretest reduction in BD nd the micropore/mcropore rtio, s well s (b) (c) (d) (e) (f) 0.05 m () 1+ Sowing line (g) Figure 1. Tillge systems used for soyben: sowing with offset double disc (); sowing with fluted coulter disc (b); sowing with knife runner opener (c); sowing with knife runner opener + press wheel mechnism for ground levelling (d); sowing with knife 0.05 m from the plnting row (e); rised bed system (f); nd chisel plough + sowing using n offset double disc (g). Arrow indictes position in which the soil press wheel mechnism for ground levelling ws plced. 8

9 b b DD bc + + ife lp lo ug h Kn ise Ch Fl u et fs Of b Infiltrtion cpcity (mm h-1) b (d) 2013/14 crop seson 2014/15 crop seson 18 b M ife Kn rd isc ) co ul te (D D b c d di sc b te lp Be lo d ug h + DD M 20 R bc 8 c c 6 b b 4 b b b DD Ch ise lp lo ug ise h + Be d d fe R co ed Kn i isc ul te sc di e Fl ut bl Of fs e td ou lp ise Ch rd (D D) DD + gh lo u ise d Be d 1 ife R Kn fe isc Kn i rd ul te ed Fl ut bl e co di sc (D D) 2 ou td fs e V6 R3 c b se se Ch i et fs Of Mximum wter storge (mm) (c) Of (b) d + R i Kn Kn ife b * bc b c b bc Mximum wter storge (mm) V6 R3 do ub le () ife do ub le Fl di ut sc ed (D co D) ul te rd isc Mximum wter storge (mm) Tillge systems Figure 2. Mximum wter storge in the soil t m s function of tillge systems in V6 nd R3 plnt growth stges in Snt Mri, 2013/14 () nd 2014/15 (c) crop seso; nd Formigueiro 2013/14 crop seson (b). Wter infiltrtion cpcity in soil in Snt Mri, Brzil (d). Experiment 1, 2013/14 nd 2014/15 crop seso. Brs followed by the sme letters do not differ significntly by the Tukey test t 5 % probbility. incresed TP nd Mcro of the soil. In stge R3, in both the nd m lyers, the offset double disc nd fluted coulter disc systems showed the highest BD vlues nd micropore/mcropore rtio. In ddition, these systems exhibited incresed micropores in the m lyer. For the knife runner opener nd chisel plough systems, there ws reduction in BD, n increse in TP nd Mcro, nd reduction in the micropore/mcropore rtio. 9

10 Tble 5. Soil wter retention t field cpcity (θfc), vilble wter (AW), bulk deity (BD), totl porosity (TP), microporosity (Mi), mcroporosity (M), nd Mi/M rtio in the tretments t different soil depths. Formigueiro, Brzil. Experiment 2 in the 2014/15 crop seson Tillge system ƟFC (-10 kp) AW BD TP Mg m-3 mm V6 Mi M Mi/M b 5.1:1 b 0.04 b m3 m m + M + M b b 1.27 b bc b + M b 0.46 b R m 32 b 0.42 b 1.38 b 22 c 0.43 b 1.38 bc 30 b m 1.28 b 31 b + M b b 26 b b 1.29 b b 1.43 b bc 1.28 c 1.21 c b 1.22 b bc b b b 0.40 b 0.07 b b b m b c b b 0.19 b 0.20 b b 0.04 b :1 2.4:1 b 2.1:1 b 2.3:1 b 4.1: :1 5.6:1 2.1:1 b 2.3:1 b 2.9:1 b 3.6: :1 6.9:1 2.0:1 1.7:1 b 1.7:1 b :1 10.6:1 2.3:1 b 2.2:1 b 2.5:1 b 5.4:1.7 : no significnt t p Me not followed by the sme letter in the column differ by the Tukey test t 5 % probbility. Plnt development stge. The methods used were ccording to Dongem et l. (2011); θfc nd AW: determined by Richrds extrctor device (Soils Moisture Equipment); BD: volumetric method; TP: clcultion method with prticle deity; Mi: tble method: 0.6 m teion; M: difference between TP nd Mi; M: press wheel mechnism for ground leveling. Furthermore, the shnk nd deep tillge systems showed greter wter storge in the soil compred to the offset double disc system. These systems showed n increse of 11 nd 5 mm in V6, nd 18 nd 17 mm in R3 in wter storge, respectively, compred to the offset double disc system. In the m lyer, coidering the verge vlues for fluted coulter disc, knife runner opener, knife runner opener + press wheel mechnism for ground levelling, 10

11 nd chisel plough systems in both evlution periods, there ws 7 % reduction in BD in reltion to the offset double disc system. Moreover, in the double disc system, the TP nd mcropores in the soil were 8 nd 93 %, respectively, which is lower thn the verges of the other systems. These systems in the m lyer reduced BD by 11 % when compred to the offset double disc system, nd showed n increse from 15 to 132 % in TP nd Mcro. Therefore, grin yield in the offset double disc system hd the lowest verge, with n verge yield of 2642 kg h-1, compred to the knife runner opener system, which ws 2970 kg h-1, nd the chisel plough system, which ws 2698 kg h-1 (, 2015). DISCUSSION The soils on which the experiments were preformed hve lyer of high BD ner the soil surfce. The m lyer in Experiment 1 nd the m lyer in experiment 2 stnd out minly becuse of their higher BD vlues (Nunes et l., 2014), which resulted in poor ertion porosity (Gubini et l., 2014; Nunes et l., 2014). This my be relted to the fct tht, in Experiment 1, the re ws used for growing irrigted rice, where decompction of the soil occurred s deep s 0.07 m, minly due to the tillge prctice of discing (Munreto et l., 2010). This prtilly expli the lower deity of the surfce lyer ( m) in the re of Experiment 1. The incresed BD vlues in the m lyer my be ssocited with the fct tht the res in which Experiment 1 took plce were systemtized in both crop seso. In study crried out by Nunes et l. (2002) in Albqulf soils in the municiplity of São João do Polêsine bout 40 km northest from the town of Snt Mri, reserchers found tht systemtiztion incresed soil subsurfce deity, due to the trffic of hevy mchinery. Similrly, Prfitt et l. (2014) found tht the verge BD of 1.60 Mg m-3 (prior to systemtiztion) chnged to 1.67 Mg m-3 s result of the systemtiztion process nd mchine trffic. Thus, deer soil lyer in the res of Experiment 1 my lso be ssocited with the systemtiztion process of the re. In ddition, the study crried out by Pedrotti et l. (2001), evluting the compction of n Albqulf soil under different mngement systems, found tht ll of the tillge systems evluted hd soil mechnicl resistnce to penetrtion vlues higher thn 2.0 MP, especilly in the m lyer, nd mximum resistnce vlues were observed in the mngement system with continuous irrigted rice crops. According to the sme uthor, conventionl tillge contributes to physicl degrdtion of the soil due to incresed soil mechnicl resistnce to penetrtion. In Experiment 2 of this study, beef cttle were rised in the re prior to the experiment; due to cttle trmpling, the higher deity lyer ws concentrted closer to the soil surfce. A study conducted by Cpurro et l. (2014) found higher deity in the 0.09 to 0.12 m lyer nd ssocited this result with ccumultion of pressures imposed by niml trmpling. Another study by Vzzotto et l. (2000), lso evluting the chnges in physicl properties of n Albqulf soil subjected to cttle trmpling, found reduced porosity nd incresed BD in the top 0.05 m lyer. The effects of tillge systems in reducing soil compction in plnting rows were more expressive in the deeper lyer ( m). This my be ssocited with the presence of higher orgnic mtter content in soil surfce, greter microorgnism ctivity nd wetting nd drying cycles tht contribute to differentition between the soil lyers (Drescher et l., 2011), nd higher root volume, which do not llow significnt chnges in BD (Cpurro et l., 2014). In ddition, from the uppermost soil lyer to pproximtely 0.07 m in depth, the effect of tillge equipment on the soil is greter (Munreto et l., 2010), which contributes to reduction in soil compction. The double nd notched disc tillge systems hd the lest impct on reduction in BD in the soyben crop in the plnting row, nd this cn be explined by less ction in depth nd lterl soil movement in the plnting row of these systems compred to the knife runner opener rised bed, nd chisel plough systems. 11

12 However, the fluted coulter disc, by hving lrger contct re, could lso be n importnt tool for soil decompression in the plnting row. A study conducted by Sntos et l. (2010) found tht notched discs ffected the soil less thn flt bldes. According to these uthors, these results my be due to the fct tht there is no dditionl lod on the equipment to increse its penetrtion in the soil. In this regrd, Mion nd Benez (2008), evluting the efforts of five furrow opening mechnisms (even discs, corrugted discs, undulted discs, double discs, nd shnks) with vrition in verticl lod, found tht the shnk promotes greter soil mobiliztion with less horizontl effort, reching higher work depths becuse only the tip of the shnk promotes resistnce. As for the discs, ccording to the Mion nd Benez (2008), more power is needed for them to penetrte, cut through soil nd strw, nd overcome rolling resistnce nd friction on the sides of the discs. These uthors found tht the wve disc showed the gretest lterl force vlues in reltion to other mechnisms for verticl lods of 1500, 2250, nd 3000 N. Coidering the verge of ll verticl lods in bsolute numbers, the soil re mobilized by the corrugted disc ws second only to the shnk. Thus, in our study the reduced impct of the fluted coulter disc system cn be prtilly explined by the lck of lod on the seeder to provide greter penetrtion nd decompression effect on the compcted soil lyer. Offset double disc nd fluted coulter disc were less effective in reducing BD nd incresing Mcro, s observed in both experiments. In contrst, shnk, rised bed, nd chisel plough systems hd positive effects in terms of reducing BD nd incresing the percentge of mcropores nd TP. This respoe my be ssocited with the different working depths of the systems. The soil depth for the shnk ws pproximtely 0.18 m t the time of sowing, 0.12 m for the rised beds, nd 0.25 m for the chisel plough system. The depth of the offset double disc nd fluted coulter disc in soil ws pproximtely 0.1 nd 0.08 m, respectively. The lower effect of the offset double disc my be ssocited with its performnce t shllower soil depths (Drescher et l., 2011). The our results re in greement with those obtined by Kokoski et l. (2007), wherein the breker type knife system promoted, on verge,.3 % increse in soil porosity compred to the offset double disc system. Incresing the depth of ction of the shnks (0.17 m) increses the volume of soil fvorble to root growth, due to the reduction of the compcted lyer in the plnting row (Nunes et l., 2014). These uthors found tht use of the shnk leds to incresed Mcro nd TP nd BD nd resistnce to penetrtion of the compcted lyer in the plnting row, corroborting the results found in this study. This reduction in BD nd coequent increse in TP re relted to incresed Mcro. Except for Experiment 1 during the 2013/14 crop seson, in the offset double disc system, mcro ws under 10 %, which my be criticl since gs flow nd wter movement in the soil re closely relted to Mcro to eure root oxygention (Silv et l., 2005). This my be relted to the mintennce of high levels of BD; soils with lower deity hve higher porosity (Gubini et l., 2014). Soyben tillge systems howed less effect on wter retention nd vilbility compred to other vribles, possibly becuse these properties re more influenced by soil properties. Soils with finer prticles (cly or silt) nd higher orgnic mtter content hve higher wter retention, becuse orgnic mtter is importnt for wter vilbility nd retention (Reichert et l., 2009b). Furthermore, Klein nd Librdi (2000) report tht the soil structure nd texture, type nd mount of cly, nd orgnic mtter content re the fctors tht ffect wter vilbility to crops. Soil microporosity (Micro) ws lso little ffected in either experiment by the tillge systems evluted, corroborting results found by Drescher et l. (2011), in which Micro did not respond to soil mngement prctices, becuse it is soil chrcteristic. 12

13 An importnt effect of the tillge systems on the soil ws incresed wter infiltrtion cpcity, especilly for the chisel plough nd knife runner opener systems. This cn be explined by greter reduction in BD in the deepest soil lyer studied ( m) for these systems, nd coequent increse in hydrulic conductivity (Cmr nd Klein, 2005). The chnges cused by griculturl use on pore distribution, mechnicl properties, nd wter nd gs trport processes within the soil re relted to BD (Gubini et l., 2014). In ddition, n increse in BD decreses soil wter content (Gubini et l., 2015). Incresed soil mcroporosity with the use of chisel plough, knife runner opener, nd rised bed systems my hve contributed to incresed cpcity for wter infiltrtion becuse wter infiltrtion cn decrese when there re compcted lyers, due to reduced Mcro (Bonini et l., 2011). These results re coistent with studies from Cmr nd Klein (2005), in which soil tillge to n verge depth of 0.25 m incresed the wter infiltrtion rte. Incresed infiltrtion cpcity for chisel plough, knife runner opener, nd rised bed systems my explin why these systems hd greter soil wter storge potentil. The greter quntity of mcropores fcilittes dringe nd contributes to wter storge in the soil lyers underlying excess wter which infiltrtes the tillge lyer (Kunz et l., 2013). Finlly, bsed on the results obtined in the two experiments, chisel plough, knife runner opener nd rised bed systems reduce BD in the plnting row. These systems improve the hydro-physicl chrcteristics of the soil, such s BD, TP, Mcro, infiltrtion cpcity, nd wter storge in the soil, resulting in higher grin yield in Albqulf soils with the presence of compcted lyer ner the soil surfce. The offset double disc nd fluted coulter disc systems showed less effect on BD reduction in the plnting row under the conditio simulted by these experiments. CONCLUSIONS Soyben tillge systems with the use of offset double disc nd fluted coulter disc showed less effect of tillge nd mintined higher bulk deity lyer in the plnting row. Chisel plough, rised bed, nd knife runner opener systems reduce soil bulk deity in the plnting row, thus incresing totl porosity, mcroporosity, nd grin yield. Chisel plough nd the use of knife runner opener increse wter infiltrtion rte nd storge in the soil. ACKNOWLEDGMENTS We would like to thnk the Coordenção de Aperfeiçomento de Pessol de Nível Superior (CAPES) for providing the first uthor with fellowship. We lso wish to cknowledge the Coelho Ncionl de Desenvolvimento Científico e Tecnológico (CNPq) for providing reserch fellowship to the second uthor nd doctorl studies grnt to the first uthor, s well s the Fundção de Ampro à Pesquis do Estdo do Rio Grnde do Sul (FAPERGS) for providing scholrship to the third uthor. REFERENCES Bmberg AL, Puletto EA, Gomes AS, Timm LC, Pinto LFS, Lim ACR, Silv TR. Deidde de um Plnossolo sob sistems de cultivo vlid por meio d tomogrfi computdorizd de rios gm. Rev Brs Cienc Solo. 2009;: doi: /s Bonini AK, Secco D, Sntos RF, Reinert DJ, Reichert JM. Atributos físico-hídricos e produtividde de trigo em um Ltossolo sob estdos de compctção. Cienc Rurl. 2011;41: doi: /s

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