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CHEMICAL ENGINEERING TRANSACTIONS
VOL. 58, 2017
A publication of
The Italian Association
of Chemical Engineering
Online at www.aidic.it/cet
Guest Editors: Remigio Berruto, Pietro Catania, Mariangela Vallone
Copyright © 2017, AIDIC Servizi S.r.l.
ISBN 978-88-95608-52-5; ISSN 2283-9216
Evaluation of Traditional and Conservation Tillage Methods
for Cereal Cultivation in Central Italy
Roberto Fanigliulo, Marcello Biocca*, Daniele Pochi
CREA, Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria. CREA-IT, Centro di Ricerca Ingegneria e
Trasformazioni agroalimentari, via della Pascolare 16, 00015, Monterotondo (ROME), Italy
marcello.biocca@crea.gov.it
In Central Italy, traditional soil tillage for winter cereal cultivation is based on medium depth ploughing followed
by soil surface harrowing. Such method may cause undesired effects on soil fertility, surface erosion and
energy costs. These negative effects can be reduced by shifting to conservation tillage methods, such as
reduced tillage, minimum tillage and no-tillage. We performed tests aimed at evaluating the energy demands
of eight implements used for tillage and sowing. We measured: working speed, time and working capacity,
P.T.O. speed and torque, tractor wheel slip, traction force, fuel consumption and energy demands. The study
was conducted at the CREA-IT experimental farm (Monterotondo, Rome), on soil classified as silty-clay
according to USDA textural classification, common in Central Italy. Starting from the data of each tested
implement, we evaluated four traditional tillage methods (CT1: four-furrow plough, rotary harrow, seeder; CT2:
four-furrow plough, disk harrow, seeder; CT3: four-furrow plough, combined seeder; CT4: subsoiler, combined
seeder) and four conservation methods (RT1: subsoiler, disk harrow, seeder; RT2: combined cultivator,
seeder; MT: disk harrow, seeder; NT: pneumatic drill for direct seeding). All tests were performed using a 205
kW instrumented tractor. The results showed that total energy required by traditional methods was 725, 704,
670 and 537 MJ ha
-1 for CT1, CT2, CT3 and CT4, respectively. The conservation methods needed lower
energy inputs: 440, 307, 286 and 77 MJ ha-1 for RT1, RT2, MT and NT, respectively. As expected, the no-
tillage method (NT) gave the best results in terms of energy savings. Finally, we suggested and discussed an
integrated tillage system aimed at optimizing tillage for winter cereals in silty-clay soils.
1. Introduction
Traditional tillage systems, which include intensive and continuous soil tillage, may create undesirable effects,
such as excessive energy requirements (Perfect et al., 1997; Fanigliulo et al., 2016) and costs (Fedrizzi et al.,
2015), deterioration of soil structure, loss of nutrients in the deeper layers and of organic matter in the upper
depths, thus increasing soil erosion (De Laune and Sij, 2012). Such negative effects can be avoided by
replacing traditional tillage with suitable soil conservation tillage operations (El Titi, 2003) that reduce fuel
consumption (Kichler et al., 2011) by decreasing the number of passes and the working depth. This is possible
by utilizing one pass implements consisting of tools with right geometry and optimum working width (Godwin,
2007). Soil management practices, including regular crop rotations and maintenance of permanent soil cover
(leaving at least 30% of the soil surface covered by plant residues), aim to reduce erosion, soil surface
disturbance and compaction, preserving its native fertility (Tebrügge and Düring, 1999). In Central Italy, the
most common tillage method applied to silty-clay soils for preparing the seedbed for winter cereals, is based
on chopping (or rarely burning) the residues from the previous crop, followed by ploughing (0.30-0.40 m) to
bury or incorporate the residues (Valzano et al., 1997; Pezzi, 2005). The operations were followed by
harrowing, generally using either a rotary harrow or a disk harrow. Sometimes, as an alternative, ploughing is
directly followed by sowing with a combined seeder (a machine with work tools operated by the tractor’s
P.T.O. and a pneumatic seed drill), which simultaneously provides surface tillage. The Agricultural Machinery
Test Center at CREA-IT, performed tests on implements commonly used in traditional and conservation soil
tillage and sowing methods. The implements included a four-furrow reversible plough, a rotary harrow and a
combined seeder (considered traditional tillage implements) and an offset disk harrow, a subsoiler, a
DOI: 10.3303/CET1758036
Please cite this article as: Fanigliulo R., Biocca M., Pochi D., 2017, Evaluation of energy requirements of tillage methods for cereals cultivation
in central italy, Chemical Engineering Transactions, 58, 211-216 DOI: 10.3303/CET1758036
211
combined cultivator (conservation implements). Two pneumatic seed drills were employed in sowing
operations in untilled and tilled soil. For each implement, a comprehensive picture of its dynamic-energetic
performances was obtained (Pochi et al., 2013). The data for different implements were combined to
represent eight cultivation methods (four traditional and four conservation), for sowing winter cereals. The
objective of this paper was to compare each one of the studied tillage methods to the traditional method
(CT1), and to obtain the knowledge of the related energy requirements.
2. Materials and Methods
2.1 Test site
The tests were carried out at the experimental farm of CREA-IT in Monterotondo (Rome, Italy; 42°5'51.26"N;
12°37'3.52"E; 24 m a.s.l.), on a flat (< 1% slope), untilled soil. This is classified as silty-clay (clay 543 g kg-1,
silt 434 g kg-1, sand 23 g kg-1) in the USDA soil classification system (USDA, 2014). Before each test, the
following characteristics and parameters were defined to a depth of 0.40 m: water content, dry bulk density
and resistance to penetration (Cone Index). The first two parameters were determined on ten soil samples of
100 cm3 randomly extracted in the test field, by means of a manual soil coring tube, and dried in an oven at
105°C until constant mass. The Cone Index was determined, according to the ASAE standard S313.3 (ASAE,
2004), by means of a hand-operated penetrologger.
2.2 Implements tested and tractor used
The data of the tested implements are shown in Table 1. The implements (Figure 1) were operated by a 4WD
tractor with a nominal power of 205 kW and total mass of 11000 kg. The power take off (P.T.O.) speed was
104.7 rad s-1 corresponding to an engine speed of 206.7 rad s-1. Before the tests, the engine performance was
verified in tests at the dynamometric brake that provided the updated characteristic curves of the engine.
Table 1: Specifications and technical data of the tested implements.
Implement
type
m.u. Plough
Rotary
harrow
Pneumatic
seed drill
Combined
seeder
Combined
cultivator
Subsoiler Disk harrow
Direct
seeding
Working tools -
knife
ploughshare,
mouldboard
vertical
blades,
roller
vertical hoe
opener
vertical
blades
straight
shanks,
notched disks
straight
shanks
notched/plain
concave
disks
single disk
openers
Tools number - 2x4 40 40 24+24 5+10 (Ø 610) 7 18+18 33
Tools spacing mm 1150 245 125 245/125
950 shanks
480 disks
430 230 180
Total mass kg 2560 2910 1930 2680 1730 1670 3465 6380
Figure 1: Tested implements. (1) four-furrow reversible plough, (2) rotary harrow, (3) pneumatic seed drill, (4)
combined seeder, (5) subsoiler, (6) combined cultivator, (7) offset disk harrow, (8) pneumatic seed drill.
2.3 Operating parameters
The main quality and operative parameters of each tractor-implement coupling were determined in tests
performed in accordance with the protocol for the investigation of performance of soil tillage machines,
proposed by ENAMA (National Farm Mechanisation Body). According to these protocol, we measured the
following parameters: width and depth of tillage; working speed, time and capacity; P.T.O. torque, speed and
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power; traction force and power required for tillage; tractor wheel slip and corresponding power losses; fuel
consumption and energy requirements per surface unit and per volume unit of moved soil (ENAMA, 2003).
After field tests, the tractor was connected to the dynamometric brake. Here, with the aim of reproducing the
work conditions, the engine speed was adjusted on the same values adopted at the start of each test. Then,
by means of the brake, the load at the engine was increased until the corresponding speed reduction reached
the average values calculated during the work in field. Such a simulation aimed at evaluating the total torque
and power provided by the engine and the corresponding fuel consumption (Pochi and Fanigliulo, 2010).
Multiplying the total engine power (Wt, kW) by the actual working time (To, h ha
-1), allows calculation of the
energy required per surface unit (Eq(1)), expressed in MJ ha-1.
Eha = 3.6 ·Wt · To (1)
Dividing Eha by the working depth (P, m), gives (Eq(2)) the energy per unit of volume of tilled soil (Evol),
expressed in MJ 10-3 m-3.
Evol = Eha10 ·P (2)
The power losses for slip (Ws, kW) was estimated on the basis of the tractor self-dislocation power (Wsd, kW),
by means of the relation presented in Eq(3).
Ws = s ·(Wtr + Wpto + Wsd) (3)
where s is the tractor wheel slip, Wtr is the traction power and Wpto is the P.T.O. power.
In addition to power loss due to wheel slip, we also considered the power lost in the transmission of motion
between engine and wheels (Wtrs, kW), that differently affects the final energy balance depending on the
machines used. They were not directly measured, but estimated adopting a transmission efficiency coefficient
equal to 0.87, as indicated in literature for 4WD tractors (Biondi, 1999), with reference to the total engine
power (Wt, kW).
2.4 Measurement equipment and data acquisition system
The instrumental system used for no active implements consisted of the following sensors: (1) a digital
encoder, mounted on the axis of one of the tractor’s rear drive wheel, allowing slip calculation during work; (2)
two mono-axial load cells, having a full-scale of 98 kN (plough, subsoiler and combined cultivator tests) and 49
kN (rotary harrow, disk harrow, seed drills and combined seeder tests), respectively, for the measurement of
traction force. The load cell is lodged in a drawbar connecting the tractor-implement system to a traction
vehicle. The tractor-implement system is pulled, with gear in “neutral”, by the traction vehicle at the same
working speed recorded during the actual operation. Each traction test is made both with the implement
working and raised, to calculate the net traction force as the difference between the two observed values. In
addition, two torque meters were applied at the tractor’s P.T.O. for the tests with rotary harrow and combined
seeder (full scale: 3 kNm) and with the pneumatic seed drills (full scale: 500 Nm). These sensors measure the
P.T.O. torque and speed during the work, required for P.T.O. power calculation. The signals from the sensors
were recorded at a scan rate of 10 Hz and collected by an integrated data acquisition system based on two
units, a field unit and a support unit (Fanigliulo et al., 2004), fully assembled at CREA-IT. The field unit is
represented by the tractor (equipped with the above sensors, a computer with a PCI card for real time data
acquisition and a LCD control monitor) and a photocell system, placed in the test field, indicating the length of
the test basis and the start and stop of the data acquisition. The support unit is represented by a van equipped
as a mobile laboratory. The PC of the support unit communicates with the field unit’s PC by means of a radio-
modem system, exchanging data and allowing to monitor, in real time, the behaviour of critical parameters and
the efficiency of the transducers and of the data acquisition system. Preliminary tests were conducted to find
the most correct adjustment of each tractor-implement system considering soil characteristics and workability.
Working speed and depth were set according to the values commonly adopted in central Italy for each
implement type. The plough was set in the in-furrow configuration. Three replications were made for every
test. All measurements were referred to a 100 m reference distance.
2.5 Tillage treatments
The energy requirements data of each implement were collected for eight tillage methods. Four traditional
methods were considered. The first method (CT1) consisted of a main tillage at medium depth, performed by
a four-furrow reversible plough, followed by a soil refinement with a single pass of a rotary harrow. In the
second method, CT2, the refinement after the ploughing was obtained by double pass of the offset disk
harrow. The third method (CT3) consisted of a single pass of the combined seeder after ploughing. In the
fourth traditional method (CT4), the plough was replaced by the subsoiler, followed by a single pass of the
combined seeder. As to conservation methods, two were based on reduced tillage: the first method (RT1)
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consisted of a main tillage at medium depth with subsoiler, followed by refinement with a single pass of the
offset disk harrow; the second (RT2) consisted of a single pass with the combined cultivator. The third
conservation method was minimum tillage (MT) and which was two passes of the offset disk harrow. The last
was a no-tillage method (NT) with cereal direct sowing by means of a pneumatic seed drill. The above
mentioned dynamic and energetic variables can be referenced to a surface unit area (hectare), providing
information on both each single implement and on the combination of implements forming each tillage method.
The values of actual and operative working time, fuel consumption per hectare, energy requirement per
hectare and energy losses for slip and transmission, used for each tillage method resulted as the sum of
values measured for each of the implements employed. As to the slip, for each implement, the average values
of each replication were used to calculate power and energy losses.
2.6 Statistical analysis
The probability of statistically significant differences among tillage methods in terms of dynamic and energetic
parameters was assessed by one-way analysis of variance (ANOVA) and subsequent multiple pair-wise
comparisons, performed by the HSD-Tukey’s test. The significance of comparisons (α = 0.05) among
treatments was determined after the Bonferroni correction. The statistical procedure was computed with the
software R (R Core Team, 2013).
3. Results and discussion
Soil characteristics were similar in all tests, with the following mean values: moisture content equal to 19.5 %
(± 0.5 Standard Deviation); dry bulk density equal to 1445 kg m-3 (± 172 SD); Cone Index equal to 1.74 MPa
(± 0.12 SD). The tests provided data that accurately describe the performance of each machine and, properly
combined, of the eight tillage methods. Table 2 shows the mean values resulting from the measurements of
the main dynamic and energetic parameters referred to each tractor-implement coupling. Considering the
single operations, Table 2 shows that the highest requirement of energy per surface unit area (MJ ha-1) was
observed for the plough and the rotary harrow (mostly due to low working speed).
Table 2: Average and standard deviation values of the dynamic and energetic parameters referred to the
tested machines.
Implement
State of the soil
m.u.
A
untilled
B
ploughed
C
ploughed
D
ploughed
E
tilled
F
untilled
G
untilled
H
untilled
I
untilled
Actual work. speed km h
-1
4.31 3.36 6.33 5.03 7.94 5.12 5.40 7.46 7.21
SD 0.06 0.03 0.04 0.05 0.04 0.07 0.07 0.01 0.01
Working width m 2.50 5.03 3.92 3.00 5.00 2.45 3.00 3.92 5.94
SD 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.01 0.02
Working depth m 0.41 0.15 0.19 0.10 0.04 0.37 0.35 0.16 0.04
SD 0.02 0.01 0.02 0.01 0.01 0.01 0.02 0.01 0.01
Actual working time h ha
-1
0.94 0.60 0.42 0.67 0.25 0.81 0.65 0.36 0.24
SD 0.01 0.01 0.002 0.01 0.001 0.01 0.01 0.001 0.003
Operative work. time h ha
-1
1.44 0.69 0.69 0.89 0.38 1.10 0.81 0.63 0.37
SD 0.01 0.01 0.002 0.01 0.001 0.01 0.01 0.001 0.003
Fuel consumption kg ha
-1
29.4 20.2 10.3 20.2 3.3 21.7 20.2 9.6 5.3
SD 1.57 0.38 0.31 1.04 0.11 0.05 0.53 0.15 0.36
Traction force kN 60.5 11.9 19.0 19.1 9.7 43.5 52.7 30.0 16.5
SD 6.94 2.00 1.96 3.48 1.50 4.40 4.79 1.21 2.26
Traction power kW 73.4 11.1 33.4 26.7 21.4 61.8 78.9 62.1 33.1
SD 8.08 2.47 4.30 5.00 3.56 6.53 7.32 3.05 2.87
P.T.O. speed rad s
-1
- 107.2 - 108.1 97.2 - - - 104.4
SD - 0.60 - 1.12 0.42 - - - 0.27
Torque at the P.T.O. Nm - 860 - 659 36 - - - 70
SD - 51.40 - 33.79 0.47 - - - 1.0
Power at the P.T.O. kW - 92.2 - 71.3 3.6 - - - 7.3
SD - 5.36 - 4.92 0.79 - - - 0.80
Energy/surface unit MJ ha
-1
403 284 131 267 39 267 270 124 77
SD 3.30 1.00 4.52 3.44 1.20 3.15 5.88 2.34 1.43
Energy/volume unit MJ10-3m-3 99 191 68 268 - 73 76 77 -
SD 4.94 2.89 3.01 3.82 - 2.47 4.02 3.66 -
Tractor wheel slip % 28.9 3.6 7.7 5.9 3.1 14.8 11.0 8.8 1.4
SD 1.43 0.29 0.48 0.55 0.29 1.03 0.99 0.19 0.19
Energy losses MJ ha
-1
125 38 21 39 6 62 55 23 10
SD 5.81 0.22 0.62 0.36 0.08 0.97 2.70 0.42 0.34
Legend: Implement: A: reversible plough; B: rotary harrow; C: offset disk harrow; D: combined seeder; E: pneumatic seed drill; F: combined
cultivator; G: subsoiler; H: offset disk harrow; I: pneumatic seed drill for direct seeding.
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The energy required per volume unit of moved soil (MJ 10-3 m-3) was higher for the combined seeder and the
rotary harrow (due to the higher power required by the tractor P.T.O.). The highest values of fuel consumption
per surface unit area (kg ha-1) were observed for the plough, due to high operative working time, and
subsoiler. The average traction force required for tillage ranged from a minimum of 11.9 kN for the rotary
harrow, to a maximum of 60.5 kN for the four-furrow plough, depending on the high variability of working width
and depth. The width varied from 2.45 to 5.03 m as the depth varied from 0.10 to 0.41 m. The highest values
of tractor wheel slip were obtained by the plough and the combined cultivator, due to the high working depth.
All described parameters play a role in the energy balance of the system and can be managed with the aim of
reducing power requirements and losses, also for optimizing the coupling between tractor and implement
(McLaughlin et al., 2008). Based on the values reported in Table 2, it has been possible to quantify the overall
values resulting for each of the traditional and conservation tillage methods described above. Statistical
analysis showed significant effects in each of the examined parameters. Consequently, it was possible to
perform, for each parameter, the Tukey-HSD post-hoc test and to separate the averages. These results are
shown in Table 3.
Table 3: Comparison of the total amount of the main dynamic and energetic parameters for each method. The
averages followed by the same letter do not differ significantly according to HSD-Tukey’s test.
Parameters m.u. CT1 CT2 CT3 CT4 RT1 RT2 MT NT
Actual working
time
h ha
-1
1.79 b 2.05 a 1.61 c 1.32 d 1.33 d 1.07 e 0.97 f 0.24 g
Operative working
time
h ha
-1
2.51 b 3.20 a 2.33 c 1.69 e 1.88 d 1.49 g 1.63 f 0.37 h
Fuel consumption kg ha
-1
52.9 a 53.4 a 49.6 a 40.4 b 33.9 c 25.0 d 22.5 d 5.3 e
Energy
requirement
MJ ha
-1
725 a 704 a 670 b 537 c 440 d 307 e 286 e 77 f
Average tractor
slip
%
11.9 b 11.8 b 17.4 a 8.5 cd 7.3 cd 9.0 c 6.9 d 1.4 e
Energy losses MJ ha
-1
168 a 172 a 163 a 94 b 82 bc 67 c 52 d 10 e
Figure 2 shows the percent variations in energy requirements, referred to the values reported in Table 3,
obtainable moving towards to less intensive methods, compared to CT1, assumed as the reference traditional
tillage method. Figure 2 shows also that NT requires about 90% less energy than CT1. Moreover, MT and
RT2 allow the highest savings of working time and energy. CT2 shows an energy requirement lower than CT1,
despite the fact that this method requires three operations. This is explained by the lower energy demand for
disc harrow compared to other implements. The CT4 method has a high slip value as it combines the work of
two high-slip implements.
Figure 2: Percent reduction of the main dynamic and energetic parameters from traditional to conservation
tillage methods (the method “CT1 = plough + rotary harrow + seed drill” was assumed as the reference
method).
215
4. Conclusions
The spreading of conservation tillage methods can contribute to reduce the energy requirements on farming
activities, keeping productivity at satisfactory levels. The correct application of each tillage method depends on
soil characteristics, which determine the choice of the most suitable implements and, therefore, the effects on
energy and labour savings. The study, carried out on compact soils, which are commonly found in Central
Italy, showed that three methods, NT, MT and RT2, allow to achieve significant energy savings. Medium and
long-term observations are needed to achieve comprehensive information on the effects of long application of
conservation methods on compact soils. Potential problems linked to cereal cultivation, such as difficult weed
management and reduced deep-water infiltration, could be prevented by alternating different conservation
methods over the years. In the hypothesis of a three-years period, the application of the RT2 method during
the first year would allow, in a single pass of the combined cultivator, to disrupt compacted subsurface layers
and to incorporate crop residues and biomass into the soil. In the second year, a no-tillage method could be
applied, improving energy savings. Finally, in the third year, the minimum tillage (MT) would contribute to bury
excessive biomass and residues left after the no-tillage method, and to reduce the application of
agrochemicals. In conclusion, according to the needs and the characteristics of each farm, the choice of the
most suitable cultivation method has the potential to significantly reduce the level of the interventions on soil
and, consequently, the incidence of the related costs.
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