Design of a Soil Cutting Resistance Sensor for Application in Site-Specific Tillage

Senso s 2013, 13, 5945-5957; doi:10.3390/s130505945 senso s ISSN 1424-8220 www.mdpi.com/jou nal/senso s A icle Design o a Soil Cu ing Resis ance Senso o Applica ion in Si e-Speci ic Tillage Juan Agüe a 1, Jacob Ca ballido 1, Jesús Gil 1, Ch is J. Glie e 2 and Manuel Pe ez-Ruiz 3,* 1 Ru al Enginee ing Depa men , Uni e si y o Có doba, Campus de Rabanales, Edi . Leona do da Vinci, C a. Nacional IV- km 396, 14014 Có doba, Spain; E-Mails: jague[email p o ec ed] (J.A.); [email p o ec ed] (J.C.); [email p o ec ed] (J.G.) 2 Biological and Ag icul u al Enginee ing, Uni e si y o Cali o nia, Da is, One Shields A e, Da is, CA 95616, USA; E-Mail: [email p o ec ed] 3 Ae ospace Enginee ing and Fluids Mechanics Depa men , Uni e si y o Se ille, C a. Se illa-U e a km 1, 41013 Se ille, Spain * Au ho o whom co espondence should be add essed; E-Mail: m[email p o ec ed]; Tel.: +34-955-481-389; Fax: +34-955-797-771. Recei ed: 3 Ap il 2013; in e ised o m: 3 May 2013 / Accep ed: 3 May 2013 / Published: 10 May 2013 Abs ac : One objec i e o p ecision ag icul u e is o p o ide accu a e in o ma ion abou soil and c op p ope ies o op imize he managemen o ag icul u al inpu s o mee si e-speci ic needs. This pape desc ibes he de elopmen o a senso equipped wi h RTK-GPS echnology ha con inuously and e icien ly measu es soil cu ing esis ance a a ious dep hs while a e sing he ield. Labo a o y and p elimina y ield es s e i ied he accu acy o his p o o ype soil s eng h senso . The da a ob ained using a hand-ope a ed soil cone pene ome e was used o e alua e his ield soil compac ion dep h p o ile senso . To da e, his senso has only been es ed in one ield unde one g a ime ic wa e con en condi ion. This ield es e ealed ha he ela ionships be ween he soil s eng h p o ile senso (SSPS) cu ing o ce and soil cone index alues a e assumed o be quad a ic o he a ious dep hs conside ed: 0–10, 10–20 and 20–30 cm ( 2 = 0.58, 0.45 and 0.54, espec i ely). Soil esis ance con ou maps illus a ed i s p ac ical alue. The de eloped senso p o ides accu a e, imely and a o dable in o ma ion on soil p ope ies o op imize esou ces and imp o e ag icul u al economy. Keywo ds: soil cu ing esis ance map; si e-speci ic managemen ; soil senso ; GNSS OPEN ACCESS Senso s 2013, 13 5946 1. In oduc ion C op yield a iabili y wi hin a ield depends on soil p ope ies and en i onmen al condi ions. To op imize he managemen o ag icul u al inpu s acco ding o si e-speci ic needs, geo- e e enced in o ma ion abou he si e is equi ed [1]. Spa ial yield a ia ions p o ide oppo uni ies o explo ing he cause wi h si e-speci ic echnology [2]. An impo an aspec o p ecision ag icul u e has been he use o senso da a o ob ain accu a e in o ma ion ha help minimize c op yield a ia ion. This geo e e enced da a is inco po a ed wi h mo e b oadly ela ed in o ma ion such as edaphic, me eo ological, biological, an h opogenic and opog aphic ac o s. Si e-speci ic managemen is ex emely complica ed because all o hese ac o s mus be conside ed. Resea che s and a me s mus o e come se e al challenges, such as simpli ying he complexi ies ha delinea e si e-speci ic managemen zones based on a single ac o ( o example, edaphic p ope ies), and de e mining he yield a ia ion ela ed o his ac o [3]. Mouazen and Ramon [4] in es iga ed he use o an on-line measu emen sys em o soil compac ion, he bulk densi y model, in di e en soil ex u es (i.e., loamy sand, loam, sil loam and sil ). Some soil pa ame e s a y in space and ime. The e o e, logis ical and analy ical cos s a e o en limi ing when add essing spa ial soil a iabili y, especially in la ge-scale applica ions [5]. The adi ional me hod o explo ing ield soil a ia ion is h ough g id sampling, which is ime-consuming, labo -in ensi e and cos ly. Ad anced echnologies and de elopmen s in p ecision ag icul u e applica ions ha e allowed esea che s o sc u inize an on- he-go soil s eng h p o ile senso [6–8]. To de e mine he magni ude o he o e all compac ion o he dep h loca ion o he compac ed laye s, soil s eng h p o ile senso s ha e been de eloped. Hemma e al. [9] e iewed and analyzed soil p o ile senso s ha should be capable o accu a ely mapping bo h spa ial and e ical a ia ion in soil mechanical esis ance. In his wo k, wo di e en app oaches, a ip-based and a ine-based senso , we e used o classi y he soil p o ile senso s. Wi h ip-based senso s, soil compac ion is adi ionally analyzed by measu ing soil s eng h indices such as he cone index (CI). This index is o en measu ed using an Ame ican Socie y o Ag icul u al and Biological Enginee s (ASABE) s anda d cone pene ome e . The o ce pe uni a ea equi ed o push he pene ome e h ough a speci ied small inc emen o soil dep h is measu ed. Howe e , a cone index (CI) is a poin measu emen ha exhibi s high a iabili y, equi es a signi ican amoun o manpowe and is ime-consuming o measu e because la ge amoun s o da a a e needed o map a ield. Cu en guidelines in he ASAE S anda d EP542 [10] ecommend ha he sample size be based upon isible he e ogenei y and ha a sample size o a leas 20 samples be used o cha ac e ize a si e. Geo-s a is ical analysis has p o ed o be use ul o cha ac e izing soil spa ial a ia ion p ope ies [6,11,12]. Wo k a he Depa men o Biological and Ag icul u al Enginee ing a UC Da is has indica ed ha a ia ion in wa e in il a ion a es caused by soil compac ion a iabili y wi hin a p ocessing oma o ield was a majo ac o a ec ing oma o yield [13]. O e he las ew yea s, in e es in applying ine-based senso s o comme cial pu poses has isen. Thei p oposed applica ions can be classi ied in o wo ypes: (1) using an a ay o s ain gauges moun ed on a igid ine [14,15] and (2) mul iple ac i e cu ing edges [16]. An ins umen ed implemen has also been de eloped using a load cell o de e mine soil esis ance in eal- ime o enable ield mapping [17]. This sys em p oduced sa is ac o y esul s bu only a one dep h, which is a majo cons ain . Hall and Rape [18] de eloped equipmen consis ing o a no el senso moun ed on he Senso s 2013, 13 5947 leading edge o a ine and a ecip oca ing d i e o oscilla ing he ine e ically while i mo ed ho izon ally h ough he soil. In his wo k, 30 sensing ips we e used and a wedge index de ined as he measu ed o ce di ided by he a ea o he ip was used o ep esen soil cu ing s eng h. By inc easing he base a ea o he ip om 6.25 o 25 cm2, he slope o he wedge index and he CI ela ed o he base a ea inc eased om 1.52 ( 2 = 0.65) o 2.99 ( 2 = 0.83). These esul s indica e ha a di ec equa ion desc ibing he ela ionship be ween he wedge index and he CI migh no be possible. This was due o empi ical measu emen me hods ha may be a ec ed di e en ly by a ious soil ac o s. Based on p e ious wo k [8], And ade-Sánchez e al. [12] de eloped a soil cu ing o ce p o ile senso ha consis ed o i e 5.1-cm long, ac i e cu ing elemen s di ec ly connec ed o i e cus omized oc agonal ing load-sensing uni s ha could measu e he cu ing esis ance o soil di ec ly ahead o he cu ing elemen . This de ice was capable o measu ing soil cu ing esis ance o e he dep h p o ile o 7.5 o 45.7 cm. These load-sensing uni s we e cus om-designed based on hei ela i e loca ion along he dep h and expec ed load a ha dep h o main ain simila sensi i i y le els among all i e sensing uni s. A sub-me e accu acy Di e en ial Global Posi ioning Sys em (DGPS) ecei e ha used a coas gua d beacon di e en ial co ec ion was employed wi h his sys em o p o ide posi ion in o ma ion. In addi ion, ada (model Rada II, Dickey-John Co po a ion, Aubu n, IL, USA) was employed o measu e g ound speed. The e ec o a elling speed on he cu ing o ce was no signi ican be ween 0.65 and 1.25 m·s−1, and he senso ou pu could be exp essed as a unc ion o CI and ope a ing dep h wi h a coe icien o mul iple de e mina ion o 0.985 [8]. The dynamic e ec s o an on- he-go senso mo ing h ough he g ound can include bo h ine ial o ces, due o soil olume accele a ion, and changes in g ound s eng h a a high a e o shea . These e ec s we e s udied in de ail by McKyes [19], who also indica ed ha he e ec o he shea a e was no signi ican in simply ic ional soils bu was signi ican in clay soils and ou weighed he ine ial o ces. The soil o ce on a ool is known o app oxima ely inc ease wi h he squa e o i s speed [20,21]. In he las decade, he in eg a ion o Global Na iga ion Sa elli e Sys ems (GNSS) wi h senso s o o - oad ehicle sys ems and o he pla o ms has p o ided eal- ime sub-me e o cen ime e -le el accu acy and signi ican ly enhanced he spa ial accu acy o da a needed o p ecision ag icul u e [22]. The GNSS ecei e s a e a key pa o he p ecision ag icul u e echnologies, as posi ion in o ma ion is a p e equisi e o si e-speci ic c op managemen . Howe e , esea che s belie e ha no all o he asks ha a e o can be pe o med in p ecision ag icul u e equi e he same le el o GNSS accu acy [22,23]. Some p ecision ag icul u e applica ions, such as yield moni o ing, soil samples o a iable a e applica ions, a e pe o med su icien ly accu a ely wi h di e en ial GPS (DGPS) de ices wi h subme e accu acy. Cu en ly, Real- ime Kinema ic-Global Posi ioning Sys em (RTK-GPS) echnology o e s he possibili y o ansi ioning si e-speci ic echniques om sub-me e -le el p ecision o cen ime e -le el p ecision. Al hough di e en ial co ec ion signals (DGPS) ha e been used o success ully geo-posi ion elec omagne ic induc ion (EMI), ele a ion o compac ion soil measu emen s, accu acies o ±10 cm should be insu icien . Gi en he opog aphy, he a el di ec ion and e ain i egula i ies/inclina ions, senso measu emen s should be co ec ed. Accu a e measu emen s (±2 cm) o he e ain ele a ion o DEM cons uc ion and geo- e e encing geophysical measu emen s allow o senso e o co ec ions. The o e all objec i e o his esea ch was o de elop a soil s eng h p o ile senso equipped wi h RTK-GPS echnology ha could pe o m measu emen s con inuously and e icien ly a a ious dep hs while a e sing he ield. An a icula ed pa allel linkage sys em was used o ansmi he cu ing Senso s 2013, 13 5948 esis ance om he blades o he load cell si ua ed abo e-g ound, which pe mi ed a educ ion in he wid h o he blade and associa ed ene gy equi emen s in soil cu ing compa ed o p e iously epo ed esea ch and makes i possible o use his senso in non- ill a ms. The speci ic objec i es o his esea ch we e: 1. Design and cons uc a ield- eady s eng h p o ile senso . 2. Pe o m labo a o y and p elimina y ield es s o op imize he senso o eliable ope a ion. 3. Ob ain geo e e enced soil mechanical esis ance om comme cial ield and p oduce soil s eng h p o ile a iabili y maps. 2. Ma e ials and Me hods We ha e designed and buil a senso ha quan i ies he soil cu ing esis ance ee om he in luence o he ic ion o ce exe ed by he g ound upon s eel blades. The cu ing o ce was simul aneously ob ained a di e en dep hs. These measu emen s we e pe o med by making a con inuous cu h ough he soil wi h ou s eel blades posi ioned one behind he o he . Each s eel blade was a a di e en dep h wi h na ow cu ing wid hs. In his wo k, he sensing mechanism, which u ilized an RTK-GPS ecei e o loca e he soil cu ing esis ance da a, was pulled by a con en ional ac o and was success ully ope a ed in he labo a o y and in a comme cial ield in Spain. This senso was speci ically designed o be economically easible o a iable- a e managemen compa ed o a cone pene ome e g id-sampling senso [24]. 2.1. Senso Desc ip ion Fou blades we e each equipped wi h load senso s (Figu e 1(a,b)) simila o he p o o ype de eloped by Sie ken e al. [25], excep he load cells ha suppo ed he blades we e si ua ed abo e g ound. An implemen ame was designed, de eloped and assembled o ensu e ha he s eel blades we e o ien a ed e ically du ing he ope a ion. The cu ing blades we e loca ed be ween wo ho izon al pla es (1) o he ame. Ve ical suppo ba s (6) we e moun ed on each side o he cu ing blades (2), (3), (4) and he ic ion blade (5) acco ding o Adamchuk e al. [15] and allowed quad ila e al a icula ion. Each blade module consis ed o ou e ical ba s, wo on each side, hus p o iding mechanical s eng h. The blades we e cham e ed a ound hei edges; he e o e, he cu ing a ea was oblique (45°) o he soil su ace wi h a blade wid h o 100 mm. Each blade was 100 mm longe han he p eceding blade, excep o he las blade. We selec ed he wid h o he blade as 10 mm o p o ide minimum soil dis u bance and ene gy consump ion (minimum cu ing wid h). The blades we e a ached o he implemen ame using a shea bol mechanism, and he implemen was a ached o he ac o wi h a h ee-poin hi ch. In he wo king posi ion, he ame is ho izon al, and he i s blade is a a dep h ha posi ions i s op mos oblique on cu ing edge a he soil su ace. Senso s 2013, 13 5949 Figu e 1. The soil s eng h p o ile senso . (a) (b) 2.2. Idealized Fo ce and Momen Balance on he Cu ing Blade The po ion o he s eel blade below he g ound su ace is subjec ed o a esul an o ce (FR) ha o igina es om wo di e en mechanisms when he sys em is mo ed o wa d: 1. The cu ing esis ance is caused by shea ing soil agg ega es. This o ce is dis ibu ed along he cu ing edge. Thei esul an (FC) is a ho izon al ec o and is loca ed a a dep h ha is in e media e be ween bo h ends. FC would be loca ed a he midpoin jus when he soil exe s a uni o m shea h oughou he cu edge p o ile. 2. F ic ional o ce is caused by soil pa icles p essing on he sides o he blade. The ic ional o ce (FF) will be a ho izon al ec o and is loca ed a a dep h ha depends on he dis ibu ion o hese elemen al o ces. Fo a uni o m dis ibu ion, he o ce ec o will be a a dep h ha di ides he exposed su ace o he blade in o wo equal po ions. The FR is in opposi ion o he ad ancemen o he blade and will be loca ed a a dep h ha esul s om he dis ibu ion o bo h componen s. In addi ion, his dis ibu ion may di e acco ding o he loca ion wi hin he plo o in e es . The eac ion o ce (FM), which coun e ac s he FR, was measu ed by a load cell (model LFH-71/0280 model, Senso ec, Columbus, OH, USA). As shown in Figu e 2, he dis ance be ween bo h o ces gene a es a momen ha mus be coun e ac ed so ha he sys em is in balance. The balance condi ion causes o que o be exe ed on he hinge poin s o he e ical a ms o he blades. The a m loca ed a he on , acco ding o he o wa d di ec ion, exe s a o ce on he blade e ically upwa ds (FBD), while he ea a m exe s a downwa d e ical o ce (FBT). Bo h mus be equal bu in opposi e di ec ions o cause a momen equal o he p oduc o FBD by he dis ance ha sepa a es hem. Equa ion (1) illus a es he ho izon al o ces in balance: (1) Fu he mo e, o main ain he momen balance, he o que gene a ed by he ho izon al o ces should be equal and opposi e o ha gene a ed by he e ical o ces. This indica es ha he o ce measu ed by (2) (3) (4) (5) Cu ing blades F ic ion blade (1) (6) RM FF    Senso s 2013, 13 5950 he load cell FM will always equal o he sum o he cu ing and ic ion componen s, ega dless o he dep h a which i s ac ion is loca ed wi hin he line. The o igin is he momen gene a ed by he equal and opposi e e ical o ces, FBD and FBT, he magni ude o which a ies acco ding o FR and d1: (2) Figu e 2. Dis ibu ion o FR, FM and he dis ances on he cu ing blade. The load cell suppo ing he blade was si ua ed abo e g ound, he eby educing he incidence o complica ions compa ed o i s placemen below g ound le el. The no el y o his senso is he unique load cell-media ed as ening o he s eel blade o i s ame suppo . This allows he load cell o expe ience ho izon al h us while suppo ing he blade, hus emo ing he need o co ec he load cell eadings o de e mine he o al soil esis ance. To de e mine bo h FC and FF, a special kni e- ool ( ic ion blade) was used. This ic ion blade does no cu when mo ing h ough he soil. I only mo es inside he space p e iously opened by cu ing blades and he e o e is only subjec ed o FF. The o ce measu ed by he load cell o his blade, di ided by he g ound con ac su ace, yields he FF pe uni a ea. The FF alue can be applied o he cu ing blades, conside ing i s con ac su ace, e ealing wha pa o he o al o ce, as measu ed by he load cell, co esponds o he ic ion and which pa co esponds o he soil cu ing. E alua ing bo h o ces is an impo an inno a ion o his no el s eng h p o ile senso . Fo si e-speci ic illage applica ion, only he cu ing o ce is ele an . Howe e , he ic ion o ce auxilia y measu emen is essen ial o co ec ing he o al o ce FM ob ained by each load cell a ached o he h ee cu ing blades. 2 d d FF 1 RBD  Senso s 2013, 13 5951 2.3. Labo a o y Tes s and Ini ial Field Tes s Labo a o y es s we e pe o med o compa e he o ces exe ed on he blades and he load cell ha we e ins alled in he main ame wi h he o ce measu ed by a e e ence load cell (SM-5000 N model, In e ace Inc., Sco sdale, AZ, USA). The e e ence load cell was connec ed o he blades h ough ension locks wi h hook and eyele a achmen s. Bo h load selec ions we e based on he size and design o he sensing elemen and on p e ious expe ience gained h ough ob aining he expec ed maximum soil esis ance alues wi h he soil cone pene ome e . Fo ce da a o each load cell we e condi ioned and eco ded by a da a acquisi ion sys em (DEWETRON, G az-G ambach, Aus ia). This sys em is a po able uni compa ible wi h plug-in signal condi ioning modules wi h selec able anges and an analogic il e ha acili a es a sui able signal- o-noise a io. Load cell and o he senso s, such as an accele ome e and he mocouples, can be di ec ly in e aced wi h he da a acquisi ion sys em. The labo a o y es s we e pe o med in ou eplica es. Each blade was es ed indi idually and a di e en dep hs ( i s blade a 10 cm; second blade a 10 and 20 cm; hi d blade a 10, 20 and 30 cm). Readings o each blade and i s dep h we e collec ed indi idually. The e e ence load cell was linked o he blades h ough ension locks wi h a hook and a 50-cm-long eyele . One end o he ension lock, a s eel “S” as ene was used as an adap e o he cu ing and ic ional blades. A he o he end, a 20-cm-long ension lock was a ached o a me al pole wi h su icien bea ing capaci y. Inc eases o 490 N we e achie ed by manually igh ening he enso lock. Simple ield examina ions we e pe o med on a comme cial ield loca ed in he Sou h o Spain o assess adequa e senso pe o mance (Figu e 3(a)). Two ypes o moni o s we e used: a hand-ope a ed soil cone pene ome e (CI) and he ield- eady soil s eng h p o ile senso (SSPS). Soil mois u e was measu ed in ield on he es day. SCPS da a a h ee dep hs (0–10, 10–20 and 20–30 cm) we e collec ed wi h a 10-m ansec spacing a 40 m in leng h (11 No embe 2010). The ansec spacing was se acco ding o he shape and dimensions o he ield. The soil o he ield es , a loamy- ex u ed allu ial soil (45% sand, 45% sil , 10% clay), was classi ied as a Typic Xe o lu en [26]. Figu e 3. (a) The yellow ci cles ep esen he geospa ial loca ion o each six se o cone pene ome e measu emen s and he ed ack he s aigh s eng h senso measu emen ansec . (b) Implemen senso a he wo king loca ion wi h a GPS an enna. (a) (b) Senso s 2013, 13 5952 On a 10-m in e al along each ansec , six CI p o iles we e ob ained wi h a hand-ope a ed soil cone pene ome e equipped wi h a s aigh ci cula s ainless s eel cone a an angle o 30° ixed on a s ainless s eel ba acco ding o he ASAE S313.3 s anda d. Ope a ing pa ame e s we e se acco ding o he ASAE EP542 s anda d, and he pene a ion speed was se o app oxima ely 3 cm/s. The i s eading was collec ed when he cone base was e en wi h he su ace o he soil. The epo ed CI alue was he mean alue o he p essu e (MPa) iden i ied by he cone as i was inse ed in o he soil. A load cell measu ed he o ce wi h which he soil opposed pene a ion, and a po en iome e measu ed he displacemen a e o de e mine he exac dep h loca ion o he o ce da a. The hand-ope a ed soil cone pene ome e was e o i ed wi h an RTK-GPS ecei e (model AgGPS 332, T imble Na iga ion L d., Sunny ale, CA, USA). This GPS ecei e was in e aced o a ield compu e (model AgGPS 170, T imble Na iga ion L d.) o eco d he loca ion o each sampling poin . Thi y measu emen s we e ob ained wi h he hand-ope a ed soil cone pene ome e in clus e s o i e along o he cu ing line. Figu e 3(b) illus a es he eco ding o soil s eng h measu emen s wi h he implemen senso ha is being pulled by a ac o . All o he passes we e pe o med a a eloci y o 5.7 km/h. To a oid eadings in luenced by g ound b eakage e ec s, measu emen s we e aken app oxima ely 0.3 m om he cu ing line o he senso . To analyze he da a, he 15 s eng h senso measu emen s ha we e ob ained close o he measu emen s collec ed a he cone pene ome e measu emen loca ions we e used o in es iga e he ela ionship. 2.4. Da a Analysis The pe o mance o he soil s eng h senso was e alua ed using labo a o y and ield es s. In labo a o y es s, he mean and s anda d de ia ion (SD) o simula ed soil esis ance om he e e ence load cell o each blade and dep h we e de e mined. A eg ession analysis was pe o med o in es iga e he o ce ansmission sys em (a icula ed pa allel linkage sys em) when he cu ing o ce changed along he blade. In a comme cial ield es , a non-pa ame ic one-sided Wilcoxon-Mann-Whi ney p ocedu e was used o compa e he soil esis ance among independen samples. The ield ial da a was i s co ec ed in o de o ob ain he cu ing o ces, ee om he in luence o he ic ion o ces, using o ha he da a om he ic ional blade. The ela ionship be ween he cone pene ome e measu emen s and cu ing o ces was de e mined using he leas immed squa es eg ession [27]. Analysis o he da ase was pe o med wi h R so wa e [28]. A obus Ellip ic Plo using he Replo unc ion was used o de ec and s udy ou lie s [29]. A geos a is ical me hod o in e pola ing spa se da a o andom spa ial p ocesses was used o achie e he cu ing esis ance maps (o dina y k iging). The o iginal o mula ion o k iging is he mos obus me hod and is o en used in p ecision ag icul u e [30]. 3. Resul s and Discussion 3.1. Labo a o y Tes Eigh y sepa a e s a ic o ce measu emen s we e collec ed o each blade and o he e e ence load. The means and SDs o he s a ic o ce exe ed on he blades by he load cell we e calcula ed in inc emen s o 490 N om 0 o 4413 N. The a e age SDs o s a ic o ce o he i s , second, hi d and ou h blades we e 4%, 5.3%, 3.4% and 5.2%, espec i ely. These SDs displayed accep able Senso s 2013, 13 5953 pe o mance indices o his me hod. An SD o 5% o less indica es adequa e me hod pe o mance, whe eas an SD o 10% o highe indica es p oblema ic pe o mance. The labo a o y es s demons a ed ha he s eng h senso design pe o med success ully based on an a icula ed pa allel linkage sys em and sepa a ed s eel blades. This indica ed ha he applica ion poin o he cu ing o ce is independen o he cell load measu emen s. Figu e 4 displays he eg ession h ough he o igin ha was employed, whe e Y alues a e he cu ing o ce applied and X alues a e he load cell measu emen s on he hi d s eel blade. The es ima ed eg ession unc ions a e: Figu e 4. Sca e plo and i ed eg ession h ough he o igin o he hi d s eel blade. Le el 1 (0–10 cm) in ed ci cles, Le el 2 (10–20 cm) in blue ci cles, Le el 3 (20–30 cm) in g een ci cles. The equa ions and eg ession plo s o he s eel blade (1), (2) and (4) we e simila . Howe e , we obse ed minimal slope di e ences in all o he blades. The end indica es ha when he suppo is a he om he esul an o ce (i.e., a a g ea e dep h), he esponse is smalle . S a ed ano he way, he same F R applied o he blade gene a es less o ce on an uppe suppo ha is mo e dis an om he suppo . This is caused by ic ion a quad ila e al a icula ion. This ic ion is p opo ional o he axial s ess ha suppo s he quad ila e al a ms, which is p opo ional o he o que momen ha mus be balanced. Al hough he o ce applied on he blade is he same, he g ea e he dis ance om he eac ion (uppe suppo ), he g ea e he ic ion o ce abso bing a icula ions, which wi hs ands less o ce o main ain balance. The e o e, his es is no jus a simple calib a ion bu also a way o quan i y he in luence o ic ion phenomena in he ini ial heo e ical model ha we e no aken in o accoun . 3.2. Simple Field Examina ion A simple ield es was conduc ed o analyze he pe o mance o he senso as i a e sed he g ound. The main objec i e o his b ie ield es was o demons a e an adequa e pe o mance, wi h pa icula a en ion o p oblems wi h ope a ing he equipmen (mechanics and elec onic componen s), in eg a ing echnology sys ems and collec ing and managing s eng h o ce da a. The senso measu emen s we e compa ed wi h he hand-ope a ed soil cone pene ome e measu emen s. Equa ion (3) p o ides insigh in o he soil cu ing o ce equi emen o his senso . I