Pi

S

D

A

A

R

R

A

K

S

D

T

S

D

S

V

0

d

erformance evaluation of tillage tines operating under different depthsn a sandy clay loam soil

.I. Manuwa *

epartment of Agricultural Engineering, The Federal University of Technology, P.M.B. 704, Akure, Nigeria

Soil & Tillage Research 103 (2009) 399–405

R T I C L E I N F O

rticle history:

eceived 28 June 2007

eceived in revised form 30 August 2008

ccepted 11 December 2008

eywords:

oil bin

raught

ines

oil disturbance

epth

pecific draught

elocity

A B S T R A C T

The study investigated the performance of three model tillage tools (tines). The experimental tillages were

made from flat 8 mm plain carbon steel. They were designated T1, T5, and T20, corresponding to tine widths

of 1, 5, and 20 cm respectively. Experiments were carried out in a soil bin filled with sandy clay loam soil at

average moisture content 11.5% (dry basis) and 600 kPa average cone index. The plastic limit and liquid

limit and plasticity index of the soil are 20%, 31% and 11% respectively. Tests were conducted at forward

speeds of 0.28, 1.0, and 2.5 m/s. Depths of operation considered were 35, 70, 150, 200 and 250 mm. Draught

measurements were made for the different tines and were also calculated using soil mechanics equation.

There was reasonable agreement between measured and predicted draught forces. The effects of depth of

operation on draught force of the tines were studied and evaluated. It was observed that draught increased

at an increasing rate with depth; the relationship was a curvilinear one best fitted by exponential function.

The soil disturbance created as a result was also evaluated and reported in this paper. The parameters used

to define soil disturbance of a single tine were: ridge-to-ridge distance (RRD), maximum width of soil cut

(WFS), maximum width of soil throw (TDW), after furrow depth (df), height of ridge (hr) and rupture

distance (f). They all increased as the depth of operation of the tool increased but less proportionately. The

critical depth of the tines was also estimated.

The results of analysis of variance showed that tool type and operating depth significantly affected

draught at 5% level of significance (p < 0.05) and that, there was interaction between the two factors.

� 2008 Elsevier B.V. All rights reserved.

Contents lists available at ScienceDirect

Soil & Tillage Research

journa l homepage: www.e lsev ier .com/ locate /s t i l l

1. Introduction

Accurate knowledge of draught and energy requirement oftillage implements is essential for proper design of the imple-ments, appropriate matching of the implements with their powersources and the selection of the optimum operation conditions(Ademosun, 1990). The most convenient method to estimate agiven implement’s energy requirement is to measure the draughtrequired to pull the implement under desired operating soilconditions (Ehrhardt et al., 2001). Two mechanisms in particularaffect draft required to move soil (Rosa, 1977). Inertial forces haveremarkable importance for sandy soil (frictional soil). In clay soilthe draft required is not too sensitive to inertial forces, but shearstrength increases substantially with increasing shear rates. AlsoRosa (1977) reported that inertial forces involved in continuouslyaccelerated new masses of soil, as the tool travels are the mostimportant mechanisms in frictional soils when operating speeds

* Tel.: +234 803 415 2976.

E-mail address: sethimanuwa@yahoo.com.

167-1987/$ – see front matter � 2008 Elsevier B.V. All rights reserved.

oi:10.1016/j.still.2008.12.004

increase. Similarly, the strain rate-dependent components are themost important mechanisms for cohesive soils.

Zeng and Yao (1992) developed a soil-cutting model to predictforces on wide and narrow tools. The model incorporated shearrate effects on soil shear strength, soil–metal friction and soilinertial effects. Comparison between prediction and experimentalvalues indicated that results were acceptable.

Stafford (1979) reported that strain rate effects are mostresponsible for changes in soil strength with speed.

Zhang and Kushwaha (1999) reported three mechanismsaccounting for the draft increase with increasing operating depth:soil inertial effect; soil strength rate effect and wave propagationeffect. The wave propagation effect was from the work ofresearchers (Azyamova, 1963; Katsygin, 1969; Vetrov andStanevski, 1972) who noticed when the speed of a tillage toolexceeds some limits; the draft of the tillage tool inverselydecreases. This was attributed to the fact that as the tool speedincreased faster than the wave of stress propagation, theoretically,the plastic zone of soil in front of the tool decreased or evendisappeared, thus the soil-cutting resistance decreased.

Swick and Perumpral (1988) reported that soil shear strengthand soil–metal friction increased with increasing shear rates. The

Notationsd depth of tools (m)

df after plough furrow depth (m)

e base of natural logarithm

f rupture distance (m)

hr height of ridge (m)

w width of tool (m)

Cl cone index (kPa)

D draught force (kN)

MC moisture content (% db)

RRD ridge-to-ridge distance (m)

TDW maximum width of soil throw (m)

Wfs maximum width of soil cut (m)

g bulk weight (kN/m3)

Ng, Nc, Na, Nq dimensionless number

c cohesion (kPa)

ca soil-interface adhesion (kPa)

q surcharge

a, d tine rake angle, angle of soil-interface friction (8)

F horizontal draught (kN)

S.I. Manuwa / Soil & Tillage Research 103 (2009) 399–405400

maximum speed they reached was 1.2 m/s and their resultsindicated however that acceleration forces accounted for a largeproportion of the increase in tool force.

However tillage forces vary greatly due to numerous factorsthat influence those forces. It is also known that complicating therelationship is the large number of factors, interactions betweenfactors, and variability of the parameters within a short distance.Hence determining which variable have the greatest influence onthe energy requirement for tillage with the most common tillagetools will greatly enhance the process of matching units to tillageimplements.

The ASAE standard (1999) describes tillage draught as a functionof implement type, implement width, depth and speed. However,depth of operation was found to be the most significant factor whilespeed was often significant. It was reported (Ehrhardt et al., 2001)that most work that has been done on tillage draught focused onspecific draught and has concluded that tillage depth is the primarydeterminant of the amount of power required to pull an implementthrough soil, with speed often having a significant effect.

Draught as an important parameter for measuring and evaluatingtillage implement performance for energy requirements has beeninvestigated by various researchers (Oni et al., 1992; Fielke, 1996;McKyes and Maswaure, 1997; Al-Suhaibani and Al-janobi, 1997;Onwualu and Watts, 1998; Manian et al., 2000; McLaughlin andCampbell, 2004; Mamman and Oni, 2005; Manuwa and Ademosun,2007). Natsis et al. (2002) used tillage force dynamometer tomeasure draught of mouldboard plough in a clay soil.

The specific draught of agricultural tools and implements varieswidely under different conditions, being affected by such factors asthe soil type and condition, ploughing speed, plough bottom,shape, friction characteristics of the soil-engaging surfaces, sharesharpness, and shape, depth of ploughing, width of furrow slice,type of attachments, and adjustment of the tool and attachments. Agreat deal of work has been done in evaluating these variousfactors and investigating possible means for reducing draught.Mathematical methods and models have been developed byresearchers for predicting draught (Reece, 1965; Stafford, 1984).Soil type and condition are by far the most important factorscontributing to variations in specific draught.

Critical depth is the depth below which the amount of soilloosening generated by the tine is minimal and the lateral extent ofthe major soil failure planes to the side of the tine changes littlewith increasing depth (Spoor and Fry, 1983).

According to Spoor and Godwin (1978), there is a criticalworking depth for all rigid tines below which compaction occursrather than effective soil loosening. The critical depth is dependentupon the width, inclination and lift height of the tine foot and onthe moisture and density status of the soil.

Godwin and Spoor (1977) reported that very narrow tines haveworking depths far greater than their widths and the aspect ratio(depth/width) greater than 6.0. According to Payne (1956), narrowtines have working depth far greater than the width, with an aspectratio greater than 1.0, while wide tines have working width fargreater than the depth with an aspect ratio of less than 0.5.

Below the critical depth, soil is not lifted upwards but moveshorizontally around the tools (McKyes, 1978). According to him,critical depth is the point below which soil is moved by a toolprincipally along horizontal lines. Above the critical depth, soilmoves horizontally and upwards. The major implement factorsinfluencing critical depth are aspect ratio and inclination rakeangle (Godwin and Spoor, 1977). For effective soil looseningcrescent failure should occur and therefore the position of thecritical depth influences the maximum useful working depth of atine. Crescent failure will only occur when the shearing resistancefor upward soil flow for any particular depth is less than for lateralflow, the two resistances being equal at critical depth.

A slight decrease in soil disturbance as the working depth of thetool increased indicates that the tine was below critical depth.

Desbiolles (2008) reported that as a rough guide for knifeblades, critical depth values of 8–12 times the blade width may beexpected, in hard brittle sands, and lowering as the soil becomeswetter, less compact and as the clay content increases. In wetplastic clay soils, critical depths at 1–2 times the blade widthvalues can be encountered.

Godwin and Spoor (1977) reported three specific types of soildisturbance the actual one being dependent on the initial soilconditions and the type and form of the force applied by theimplement: loosening or brittle disturbance where the soil slidesalong a few defined planes and the overall soil density is increased;compacting or compressive disturbance where movement occursalong many planes and the soil density is increased; soil movementwithout any overall soil density change. Tines working abovecritical depth produce a loosening type of disturbance, whereasthose working below cause compaction at working depth. Whenworking at shallow depth (above critical depth), very narrow tinesproduce three-dimensional crescent failure pattern (looseningeffect) but when working below critical depth, the failure patternchange to two-dimensional pattern moving soil both sideways andforward producing a compaction of the soil (Godwin and Spoor,1977).

Payne (1956) observed that narrow tines produce a three-dimensional type of soil failure as the soil from the working depthis brought to the surface in soil wedge, that the soil moves forward,upward and sideways in a crescent, and the end effects aresignificant. Similarly, it was reported that wide tines (blades) causetwo-dimensional type of soil failure moving the soil upward andforward with some end effects, which are normally ignored. Thesoil flows over the tool surface, with some cracking therebyproducing loosening effect.

Sharifat and Kushwaha (1999) studied soil lateral movementunder different soil conditions with a sweep and a furrow opener atspeed from 5 to 8 km/h, and they concluded that different toolscreated different geometries of soil profiles; the parameters of soilprofile were also affected by speed, soil bulk density, and soilmoisture content. McKyes (1985) described the results of a soil

Table 1Physical properties of experimental soil.

Classification Sandy clay loam

Sand (%) 54

Silt (%) 21

Clay (%) 25

Organic matter (%) –

Particle density (kg/m3) 2510

Plastic limit % (H2O) 20

Liquid limit % (H2O) 31

S.I. Manuwa / Soil & Tillage Research 103 (2009) 399–405 401

disturbance study, and indicated that the shape, width and rakeangle of tools strongly influence transporting and mixing of soilparticles; soil throwing to the sides of a tool varied with the squareof tillage speed.

The objectives of this paper therefore were to study theperformance of model tillage tine under different operating depthsand also to evaluate the soil disturbance parameters of the tinesand to model the relationship between depth and draught.

2. Materials and methods

2.1. Experimental tillage tines

Three tines: T1 (very narrow tine), T5 (narrow tine) and T20(wide tine), were used in this study.

The tines were made from flat 8 mm plain carbon steel. Theywere designated T1, T5, T20 corresponding to 1.0, 5.0, 20.0 cmwidths respectively. Tines TI and T5 are very narrow tine andnarrow tine respectively and each of height 50 cm. Tine T20 is awide tine of 15 cm � 20 cm supported by a shank 35 cm long in themiddle. The bottom edge of each tine was beveled at an angle of 158to provide a sharp cutting edge.

2.2. Soil bin facility

Experiments were conducted in the Soil Dynamics Laboratoryof the Department of Agricultural Engineering, The FederalUniversity of Technology, Akure, Nigeria.

The equipment consisted of an indoor soil bin of 9.0 m length,0.85 m width and 0.45 m depth; a soil processing trolley with aleveling blade and compaction roller, a tool carriage, a powertransmission system with a 3.1 kW electric motor as prime mover,a tool mounting frame, a tool vertical and angle adjustment device,a profile meter for measuring soil disturbance parameters, and aload cell (spring dynamometer) for measuring draught (horizontalforce). An overview of the soil tillage dynamics equipment isshown in Fig. 1, with the full details presented in Manuwa (2002).

2.3. Soil description and properties

2.3.1. Physical properties

The soil studied was an Akure sandy clay loam (54% sand, 21%silt, and 25% clay), according to the USDA textural classification ofsoils. The plastic limit, liquid limit and plastic index of the soil are20%, 31%, and 11% respectively. Its organic carbon was 1.3%. It was

Fig. 1. An overview of the soil tillage dynamics equipment used in the study. (1)

Load meter; (2) tool carriage; (3) tool vertical adjustment device; (4) tool angle

measuring plate; (5) tool bar; (6) profilemeter; (7) soil processing trolley frame; (8)

soil leveler; (9) compaction roller; (10) roller vertical adjustment device; (11)

vertical adjustment pipe; (12) winding handle.

one of the prominent agricultural soils of Ondo State, Nigeria. Thesoil was taken from one of the fallow agricultural lands of thecommercial farm of the Federal University of Technology, Akure(78150N, 58150E), and elevation 210 m in the forest-Savanna zone ofsouthwestern Nigeria in 2001. The soil was Oxic paleustalf (Alfisol)or ferric Luvisol (FAO). The site was recovered from 3 years of bushfallow.

Particle size analysis was determined by hydrometer method(Bouyoucos, 1962) in air-dried 2 mm sieved soil samples. Soilorganic C was determined using the dichromate wet oxidationmethod (Nelson and Sommers, 1982). The physical properties ofthe experimental soil are presented in Table 1.

2.3.2. Mechanical properties

Mechanical properties including cohesion, adhesion, internaland external friction angles were determined through laboratorytests. Direct shear test method was used to measure thesevalues of soil shear strength under same moisture and densityconditions as applied in the soil bin experiments. Soil penetrationresistance (cone index) was measured by using a Rimikpenetrometer (model CP 20 ultrasonic, Agridy Rimik Pty Ltd.,Toowoomba, Australia). The penetrometer was comprised of anin-built data logger, a 500-mm long shank, a cone with a base areaof 129 mm2 and an apex angle of 308. The penetrometer waspushed into the soil by hand at a speed of approximately 0–2 mm/s according to the ASAE standards. Core soil samplers were usedto measure soil bulk density and moisture content. All the abovesoil property determination tests were replicated three times andthe means recorded including their standard deviations as shownin Table 2.

2.4. Measurement and prediction of draught forces

Different theoretical models are available for calculating soil-cutting force. In this study, the universal earth-moving equationof the two-dimensional analysis after Hettiaratchi et al. (1966)reported by Stafford (1979) was used to calculate the pullingforce, F:

F ¼ wðgz2Ng þ czNc þ cazNa þ qzNqÞsin ðaþ dÞ (1)

where F is the draught force (kN), w the width of tool (m), z thedepth of tools (m), g the bulk weight (kN/m3), Ng, Nc, Na, and Nq aredimensionless numbers, c the cohesion (kPa), ca the soil-interfaceadhesion (kPa), q the surcharge; a and d are tine rake angle andangle of soil-interface friction (degree), respectively.

The N-factors were estimated from the relationships estab-lished and reported by Hettiaratchi et al. (1966).

2.5. Experimental procedure

2.5.1. Soil preparation and measurements

The experimental soil was dried to the initial moisture contentand crushed to a fine uniform size before it was put into the soilbin. Experiments were conducted first in the driest state and water

Table 2Mechanical property of the experimental soils.

MC (% db) BD (kg/m3) Cohesion

(kPa)

Internal friction

angle (degree)

Adhesion (kPa) Soil/metal friction

angle (degree)

Cone index (kPa)

75 mm depth 150 depth

6.0 (0.2) 1500 (11) 12.1 (1.2) 30.2 (1.1) 0.18 (0.02) 22.3 (1.3) 575 (20) 580 (25)

11.5 (0.1) 1520 (10) 13.3 (1.1) 29.6 (1.2) 0.21 (0.01) 23.6 (1.2) 690 (25) 725 (23)

17.5 (0.2) 1560 (11) 24.5 (1.4) 36.5 (1.2) 0.29 (0.03) 24.7 (1.3) 785 (15) 800 (20)

20.0 (0.1) 1530 (9.5) 22.6 (1.2) 34.5 (1.3) 0.35 (0.02) 23.1 (1.1) 720 (22) 745 (24)

MC = moisture content; BD = bulk density. Standard error in parenthesis.

Fig. 2. Parameters used to define soil disturbance of a single tine: maximum width

of soil throw (TDW); maximum width of soil cut (Wfs); ridge-to-ridge distance

(RRD); height of ridge (hr); after plough depth (df); tool width (w).

Table 3A comparison of the measured and calculated draught force of the experimental

tines.

Depth (cm) Tine Experimental Calculation % prediction

3.5 T1 23 13 �43

T5 90 68 �24

T20 219 273 +24.6

10.0 T1 55 40 �27

T5 180 203 +12

T20 639 812 +27

15.0 T1 100 63 �37

T5 280 315 +12.5

T20 950 1256 +32

+, over-prediction; �, under-prediction; T1, very narrow tine of width 1 cm; T5,

narrow tine of width 5.0 cm; T20, wide tine of width 20 cm.

S.I. Manuwa / Soil & Tillage Research 103 (2009) 399–405402

was added for the consequent runs until the moisture content ofthe soil reached an equilibrium state similar to the procedurereported by Gupta and Surendarnath (1989).

The soil processing trolley was used for processing the soilmechanically in the bin in order to achieve uniform soil conditionas desired for test-run throughout the soil bed.

A reasonable agreement was found in the compaction level atthe different locations along the length of the bin. This wasachieved by rotavating the soil and passing the roller over it for afixed number of times usually between 4 to 6. The conepenetrometer was used to monitor the uniformity of the preparedsoil by comparing the cone indices of the sampled sites. After thesoil processing was over, the test tool was mounted on the tool bar,and the desired depth and rake angle were adjusted appropriately.

In all the tests, the mean moisture content was about 11.5%(db), the rake angle was held constant at 908, and the mean coneindex was 600 kPa. Moisture content of the soil was determined bygravimetric method. The five levels of operating depth tested were35, 70, 150, 200 and 250 mm respectively.

2.5.2. Calibration of load cell

To ensure the accuracy of measurements of draught, the loadcell was calibrated in advance of being used for force measure-ment. The dead weight method was used for the calibration in therange of force experienced in the draught measurements.

2.5.3. Experimentation

For all the experiments, the soil moisture content was heldconstant at an average of 11.5% (db). After the soil processing wasover, the test tool was mounted on the tool bar for experimenta-tion. In each of the three blocks, the forward speed and rake anglewere kept constant but the depth was varied in five levels. Thefixed rake angle was 908 for all the treatments while the toolcarriage was towed at the fixed forward speeds V1, V2, V3corresponding to 0.28, 1.0 and 2.5 m/s respectively for the threeblocks. During the test, the load cell measured draught. Data werecollected and mean values of three replicates were used forcomputation and analysis. A profile meter similar to that describedby Spoor and Godwin (1978) and meter scale were used to measurethe soil-disturbed surface after each test. Soil disturbanceparameters were subsequently defined and evaluated.

For the purpose of analysis, the general form of soil disturbancewas quantified by the parameters shown in Fig. 2. The parametersused to describe soil disturbance include: maximum width of soilthrow (TDW); maximum width of soil cut (WFs) also referred to aswidth of crescent; the ridge-to-ridge distance (RRD); the height ofthe ridge (hr); after plough furrow depth (df) and the tool width(w).

Another parameter of the soil disturbance measured but notshown in Fig. 2 is rupture distance (f), defined as the distanceahead of the tine at which the distinct shear plane broke thesurface (Godwin and Spoor, 1977). Some of these parameters havebeen used to assess soil disturbance of tillage implements byresearchers (Willat and Wills, 1965; Godwin and Spoor, 1977;Spoor and Godwin, 1978; Taniguchi et al., 1999).

3. Results and discussion

3.1. Comparison between measured and predicted draught forces

The measured draught forces were recorded after the procedureexplained under experimentation. On the other hand, thepredicted forces were calculated using Eq. (1). The values of themeasured draught forces, the corresponding predicted values andthe percentage over or under prediction are shown in Table 3.Eq. (1) was more appropriate to predict draught forces with narrowtines than very narrow tines or wide tines.

3.2. Effect of depth of operation on draught

The effect of depth of operation on draught of tines is presentedin Figs. 3–5. The best relationship between draught (D) andoperating (d) was a curvilinear one from regression analysis, and isof the form:

D ¼ aebd (2)

where a and b are coefficients of the exponential function. Theregression equations and the coefficients of determination are

Fig. 3. Effect of depth on draught at forward speed of 0.28 m/s. DT1, draught of tine

of width 1.0 cm; DT5, draught of tine of width 5.0 cm; DT20, draught of tine of width

20 cm.

Fig. 4. Effect of depth on draught at forward speed of 1.0 m/s. DT1, draught of tine of

width 1.0 cm; DT5, draught of tine of width 5.0 cm; DT20, draught of tine of width

20 cm.

S.I. Manuwa / Soil & Tillage Research 103 (2009) 399–405 403

shown in the respective figures. In these figures, draught increasedat an increasing rate with increase in operating depth. The reasonbeing that at higher depths more soil volume is considered, soilbecomes stiffer and denser (due to overburden pressure and sostrength properties vary. It should be noted that the exponentialmodes best fitted the relationships, with R2 (coefficient ofdetermination) values ranging between 0.9784 and 0.9975. Thiscurvilinear relationship is similar to that reported by Al-Suhaibaniand Al-janobi (1997), Grisso et al. (1996) and Nicholson et al.(1984). An increase in specific draught (draught per maximumwidth of soil cut), was observed with an increase in tillage depth forall the tools tested. This also agrees well with the work reported byAl-Suhaibani and Al-janobi (1997) and Ademosun (1990).

Generally specific draught increased with width of tine but lessproportionately. This agreed with the findings reported by McKyes

Fig. 5. Effect of depth on draught at forward speed of 2.5 m/s. DT1, draught of tine of

width 1.0 cm; DT5, draught of tine of width 5.0 cm; DT20, draught of tine of width

20 cm.

and Maswaure (1997). The increase became higher as the depthincreased due to the increase of bulk density with depth.

Also in the range of depth considered, the increase in specificdraught became higher as the tine, width increased. This is becausethe amount of soil displaced by narrow tines is considerably lowerthan that disturbed by wide tines. Inertial forces are moresignificant for wide tines than narrow tines. The specific draughtof the tines T1, T5 and T20 ranged from 5 to 6.1, 8.6 to 12.2 and 6.8to 13.2 N/cm respectively within the range of depth considered. Inthe range of depth of operation tested, under this condition, thespecific draught increased by about 21.2%, 42.0% and 92.18% for T2,T5 and T20 tines respectively.

Although draught force increased with width, it was less thanproportionately. Specific draughts of different widths of tinesoperating at the same depth were relatively higher per unit fornarrower tines. This is due to the shear area, which is smaller per unitwidth for narrower tines. This is in close agreement with the findingsof McKyes and Ali (1977). The numerical values of these parameterswould provide valuable information in the design of tillage tines.

3.2.1. Analysis of variance tests

Analysis of variance (ANOVA) was also performed on theinteraction of tool type (T) and operating depth, d—the sources ofvariation. For all the three levels of speed the results showed thattool type and operating depth affected the draught of tinessignificantly at 5% level of probability (p < 0.05). The interactionbetween the two factors was also statistically significant at 5% levelof probability (p < 0.05).

Moreover, draught increased as the forward speed of a tineincreased. This is mainly because of the acceleration of the soil.Greater forces provide this acceleration and since they alsoincrease the reaction at the interface, a higher sliding resistanceresults. The increased sliding resistance contributes most to theincreased draught force (Spoor, 1969).

3.3. Soil disturbance parameters

The effect of depth of operation of the tines (T1, T5, and T20) onsoil disturbance was observed for a forward speed of 1.0 m/s(3.6 km/h), 908-rake angle, average cone index of 600 kPa andmoisture content of 11.5% (db) with the results presented inTable 4. As the tool moved through the soil in the soil bin, the soilwas disturbed as it was cut and thrown to the sides of the tool. Thesoil disturbance generated was observed, assessed and analyzed.The shape of the ridge profile was very close to an isosceles triangleat the speed of 3.6 km/h. This finding was similar to that reportedby Liu and Kushwaha (2006). The width of the tool stronglyinfluenced the soil disturbance parameters as they all increased asthe working depth increased but less proportionately. This wasalso similar to the findings reported by McKyes (1985).

This is because the major factors that control the nature of soilfailure or disturbance are the aspect ratio (depth/width ratio) andthe rake angle. Tines with small aspect ratio causes cause a surfacecrescent-like failure (Payne, 1956). As the depth/width ratioincreased, the nature of soil failure changed. The inertial forcesinfluenced the distance that the sol was thrown away from the toolpath. For all the three levels of speed, the furrow level was filled toan upper level mostly with pulverized soil that fell back, thisinfluenced the after furrow depth.

3.4. Estimation of critical depth of experimental tines

The critical depth of the experimental tillage tines was estimatedbased on the procedure described by Desbiolles (2008), which ofcourse was referred to as a rough guide. The results are presented inTable 5.

Table 4Effect of depth of operation on soil disturbance.

Parameters

of soil disturbance

Depth (cm)

T1 T5 T20

3.5 10 15.0 3.5 10 15.0 3.5 10 15.0

RRD (cm) 5 10 15 12 13.5 16.5 26 30 33

Wfs (cm) 6 10 16.5 10.5 20 23 28 32 34

TDW (cm) 9.5 12.5 17.5 25 27.5 33 39 43.5 46

df (cm) 2 7.5 10.5 1.5 5.5 7.0 1.9 3.5 6.2

hr (cm) 0.8 1.5 1.6 2.5 4.5 6.0 2.5 3.0 4.5

f (cm) 5.5 11 15 9.5 18 21 17.5 23 25

Draught (N) 23 (4) 55 (6) 100 (10) 90 (11) 180 (14) 280 (25) 219 (21) 639 (59) 950 (69)

Sp. draught (N/cm) 3.8 5.5 6.06 8.57 9.00 12.17 7.8 19.96 27.94

a = 908; v = 1.0 m/s; MC = 11.5% db; f = rupture distance

Standard error of draught in parenthesis.

Table 5Estimated critical depths of the experimental tillage tines.

Consistence/soil condition Tine type Tine width (cm) Critical depth (cm) Moisture status

Friable T1 0.01 8–12 Moist

T5 0.05 40–60

T20 0.2 160–240

T1 is very narrow tine of width 1 cm; T5 is narrow tine of width 5.0 cm; T20 is wide tine of width 20 cm.

S.I. Manuwa / Soil & Tillage Research 103 (2009) 399–405404

4. Conclusion

The performance of model tillage tines was evaluated in a soiltillage dynamics laboratory at the Federal University of Tech-nology, Akure, Nigeria. The mechanical background and soilmechanics theory were used to explain certain aspects of theperformance of the tines. It was observed that depth of operationaffected draught of the tools. Draught increased with depth ofoperation at an increasing rate. There was reasonable agreementbetween measured and predicted draught forces. The relationshipwas a curvilinear one best fitted by an exponential function. Soildisturbance parameters were also evaluated for the sandy clayloam soil. The soil disturbance parameters all increased with depthand also with width of tool but less proportionately. The criticaldepths of the tines were also estimated.

Acknowledgement

The author is grateful to the Federal University of Technology,Akure for the University Research Grant No. URG/MINOR/98/105which partly funded this project.

References

Ademosun, O.C., 1990. The design and operation of a soil tillage dynamics equip-ment. The Nigerian Engineer 25 (1), 51–57.

Al-Suhaibani, Al-janobi, 1997. Draught requirements of tillage implements operat-ing in sandy loam soil. Journal of Agricultural Engineering Research 66, 177–182.

Azyamova, E.N., 1963. Studies of dynamics of deformation of soil. Trudy (TSNII-MESKH) Minsk 1, 131–139 (Translated by W.R. Gill, National Tillage MachineryLaboratory, USDA, ARS, Auburn, AL).

American Society of Agricultural Engineering Standards, 1999. Agricultural Machin-ery Management Data. ASAE, St. Joseph, MI, USA.

Bouyoucos, G.J., 1962. Hydrometer method improved for making particle sizeanalysis of soils. Agronomy Journal 54, 464–465.

Desbiolles, J., 2008. http://www.google.com/search?hl=en&q=%27+soil+failure+with+tillage+tool%27+%27pdf%27&start=10&sa=N,250708.

Ehrhardt, J.P., Grisso, R.D., Kocher, M.F., Jasa, P.J., Schinstock, J.L., 2001. Using theveris electrical conductivity cart as a draft predictor. ASAE Paper No. 011012 atSacramento Convention Center, Sacramento, CA, July, 29–August 1, 2001.

Fielke, J.M., 1996. Interaction of the cutting edge of tillage implements with soil.Journal of Agricultural Engineering Research 63 (1), 61–72.

Godwin, R.J., Spoor, G., 1977. Soil failure with narrow tines. Journal of AgriculturalEngineering Research 22, 213–228.

Grisso, R.D., Yasin, M., Rocher, M.F., 1996. Tillage implement forces operating insilty clay loam. Transactions of the American Society of Agricultural Engineers19 (6), 1977–1982.

Gupta, C.P., Surendarnath, T., 1989. Stress field in soil owing to tillage tool inter-action. Soil and Tillage Research 13, 123–149.

Hettiaratchi, D.R.P., Whitney, B.D., Reece, A.R., 1966. The calculation of passivepressure in two-Dimensional soil failure. Journal of Agricultural EngineeringResearch 11 (2), 89–107.

Katsygin, V.V., 1969. Relation of Draught of Agricultural Machines toOperating speeds. Voprosy Sel’skohozyaistvennoi, section 2, vol. XII.National Tillage Machinery Laboratory, Auburn, AL, pp. 96–119 (Translatedby W.R. Gill).

Liu, J., Kushwaha, R.L., 2006. Modeling of soil profile produced by a single sweeptool. Agricultural Engineering International: the CIGR Ejournal, Manuscript PM06 008, vol. VIII, May 2006.

Mamman, E., Oni, K.C., 2005. Draught performance of a range of model chiselfurrowers. Agricultural Engineering International: the CIGR Ejournal, Manu-script PM 05 003, vol. VII. November 2005.

Manian, R., Rao, V.R., Kathirvel, K., 2000. Influence of operating and disk parameterson performance of disk tools. Agricultural Mechanization in Asia, Africa, andLatin America 31 (2), 19–26 38.

Manuwa, S.I., 2002. Development of equipment for soil tillage dynamics andevaluation of tillage parameters. Unpublished Ph.D. Thesis in the Departmentof Agriculture Engineering, The Federal University of Technology, Akure,Nigeria.

Manuwa, S.I., Ademosun, O.C., 2007. Draught and soil disturbance of model tillagetines under varying soil parameters. Agricultural Engineering International: theCIGR Ejournal, Manuscript PM 06 016, vol. IX, March 2007.

McKyes, E., 1978. The calculation of draught forces and soil failure boundaries ofnarrow cutting blades. Transactions of the ASAE 21 (1), 20–24.

McKyes, E., 1985. Soil cutting and tillage. Elsevier Science Publishing Company Inc.,New York, NY10017, USA.

McKyes, I.E., Ali, O.S., 1977. The cutting of soil by narrow blades. Journal ofTerramechanics 14, 43–58.

McKyes, E., Maswaure, J., 1997. Effect of design parameters of flat tillage tools onloosening of a clay soil. Soil and Tillage Research 43, 195–204.

McLaughlin, N.B., Campbell, A.J., 2004. Draft-speed-depth relationships for fourliquid manure injectors in a fine sandy loam soil. Canadian Biosystem Engi-neering 46 (2), 1–25.

Natsis, A., Papadakis, G., Pitsilis, I., 2002. Experimental investigation of the influenceof the foreploughshare and the disk coulter on the tillage quality and the tractorfuel consumption. Agricultural Engineering International: the CIGR Journal ofScientific Research and Development. Manuscript PM 02 002, vol. IV, December2002.

Nelson, D.W., Sommers, L.E., 1982. Total carbon, organic carbon and organic matter.In: Page, A.L., Miller, R.H., Keeney, D.R. (Eds.), Methods of Soil Analysis, Part 2.ASA, Madison, WI, pp. 539–580.

Nicholson, R.L., Bushford, L.L., Miclke, L.N., 1984. Energy requirements for tillagefrom a reference implement. American Society of Agricultural Engineers (ASAE),Paper No. 84-1028, ASAE, St. Joseph, MI.

Oni, K.C., Clark, S.J., Johnson, H.W., 1992. The effects of design on the draught ofunder-cut sweep tillage tools. Soil and Tillage Research 22, 117–130.

S.I. Manuwa / Soil & Tillage Research 103 (2009) 399–405 405

Onwualu, A.P., Watts, K.C., 1998. Draught and vertical forces obtained from dynamicsoil cutting by plane tillage tools. Soil and Tillage Research 48, 239–253.

Payne, P.C.J., 1956. The relationship between the mechanical properties of soil to theperformance of simple cultivation implements. Journal of Agricultural Engi-neering Research 1 (1), 23–50.

Reece, A.R., 1965. The fundamental equation of earth-moving mechanics. In: EarthMoving Machinery Symposium, vol. 179 (3F), Institution of Mechanical Engi-neers, London.

Rosa, U.A., 1977. Performance of narrow tillage tools with inertial and strain rateeffects. Ph.D. Thesis. Department of Agricultural and Bioresource Engineering,University of Saskatchewan, Saskatoon, Canada.

Sharifat, K., Kushwaha, R.L., 1999. Lateral soil movement by tillage tools. ASAE PaperNo. 991003. ASAE, St. Joseph, MI.

Spoor, G., Godwin, R.J., 1978. An experimental investigation into the deep looseningof soil by rigid tines. Journal of Agricultural Engineering Research 23, 243–258.

Spoor, G., 1969. Design of soil engaging implements. Farm Machine Design Engi-neering 3, 22–26.

Spoor, G., Fry, R.K., 1983. Soil disturbance generated by deep-working low rakeangle narrow tines. Journal of Agricultural Engineering Research 28, 217–234.

Stafford, J.V., 1979. The performance of a rigid tine in relation to soil properties andspeed. Journal of Agricultural Engineering Research 24, 41–56.

Stafford, J.V., 1984. Force prediction models for brittle and flow failure of soil bydraught tillage tools. Journal of Agricultural Engineering Research 29, 51–60.

Swick, W.C., Perumpral, J.V., 1988. A model for predicting soil–tool interaction.Journal of Terramechanics 25 (1), 43–56.

Taniguchi, T., Makanga, J.T., Ohtomo, K., Kishimoto, T., 1999. Draft and soil manip-ulation by a moldboard plow under different forward speed and body attach-ments. Transactions of the ASAE 43 (6), 1517–1521.

Vetrov, Y.A., Stanevski, V.P., 1972. The investigation of the factors of the speed ofcutting soils. Mining Construction and Highway Machines 8, 21–26 (Translatedby W.R. Gill, National Tillage Machinery Laboratory, Auburn, AL).

Willat, S.T., Wills, A.H., 1965. A study of the trough formed by the passage of tinesthrough soil. Journal of Agricultural Engineering Research 10, 109–113.

Zeng, D., Yao, Y., 1992. A dynamic model for soil cutting by blade and tine. Journal ofTerramechanics 29 (3), 317–327.

Zhang, Z.X., Kushwaha, R.L., 1999. Operating speed effect on the advancingsoil failure zone in tillage operation. Canadian Agricultural Engineering 41(2), 87–92.