Minimal soil disturbance sowing in New South

Transcription

Research Library
Resource Management Technical Reports
1-1-1989
Minimal soil disturbance sowing in New South
Wales and its relevance to reducing water erosion in
Western Australia
K J. Bligh
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Part of the Hydrology Commons, and the Soil Science Commons
Recommended Citation
Bligh, K J. (1989), Minimal soil disturbance sowing in New South Wales and its relevance to reducing water erosion in Western Australia.
Department of Agriculture and Food, Western Australia. Report 99, 35p.
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ISSN 0729-3135
1989
Minimal Soil Disturbance Sowing
In New South Wales,
And Its Relevance To Reducing Water
Erosion In Western Australia
K.J. Bligh
Resource Management Technical Report 99
MINIMAL SOIL DISTURBANCE SOWING IN NEW SOUTH WALES
Disclaimer
The contents of this report were based on the best available information at the time of
publication. It is based in part on various assumptions and predictions. Conditions may change
over time and conclusions should be interpreted in the light of the latest information available.
 Chief Executive Officer, Department of Agriculture Western Australia 2001
ii
Summary
A study tour was undertaken investigating minimal-soil-disturbance sowing in New
South Wales, from September 12-28, 1988. Both inexpensive modifications to existing
seeders and “state of the art” new mechanisms were investigated. Narrow—winged
points can readily be fitted to existing tined seeders to immediately reduce water erosion
in Western Australia. Press wheels may improve crop establishment, particularly with
early sowing in this predominantly winter-rainfall region. Front disc coulters may reduce
blockages of tined seeders where low stubble and straw spreading at harvest are
insufficient. Strategies for achieving adoption of minimal-soil-disturbance sowing on
erodible, loamy soils in Western Australia are canvassed.
iii
Contents
1.
Introduction ....................................................................................................1
2.
Minimal-Soil-Disturbance Sowing Mechanisms Used in New South Wales......4
2.1
Narrow-winged opener...........................................................................4
2.2
Spear-point openers ..............................................................................6
2.3
The triple-disc drill..................................................................................7
2.4
The Bioblade® .......................................................................................8
2.5
Associated mechanisms ........................................................................11
2.5.1 Disc coulters................................................................................11
2.5.2 Press wheels...............................................................................13
2.6
3.
4.
Wear of ground tools..............................................................................14
Review of Relevant Developments Elsewhere .................................................16
3.1
Minimal-soil-disturbance sowing ............................................................16
3.2
Stubble Clearance .................................................................................17
Relevance to Reducing Water Erosion in Western Australia ............................19
4.1
Technical relevance ...............................................................................19
4.2
A perspective on prospects for the adoption of minimal-soil-disturbance
for reducing water erosion in Western Australia ...............................................22
5.
Discussion and Recommendations ..................................................................25
5.1
Narrow-winged, and narrow-winged-and-deep-bladed points................25
5.2
Press wheels for seed firming with minimal soil cover ...........................25
5.3
Point wear ..............................................................................................25
5.4
Disc coulters ..........................................................................................26
5.5
The Bioblade® .......................................................................................26
5.6
An integrated minimal-soil-disturbance system......................................26
6.
Acknowledgements...........................................................................................27
7.
References
....................................................................................................28
Appendix 1
Study Tour Itinerary ....................................................................................................34
iv
1. Introduction
Water erosion is a virtually irredeemable form of land degradation. Soil must remain in
place in order to be in a stable condition to sustain production levels. Rates of soil
formation are considered to be less than one millimetre per thousand years in Australia
(Little and Ward, 1980; Walker, 1980; McFarlane and Ryder, 1987). Therefore
comparable erosion rates are required for indefinite maintenance of the soil mass for
sustained productivity.
Soil movement of the order of millimetres has been observed on Western Australian
cropland in single seasons (e.g. Bligh 1987a; 1989; McFarlane and Ryder, 1987). On
the other hand, erosion rates of approximately one millimetre of soil loss per thousand
years have been recorded on pastured land with slope lengths typical of contour bank
spacings in New South Wales (Edwards, 1987). Measurements of suspended sediment
from 4 m2 infiltrometers in Western Australia also suggest similarly low rates of soil loss
in the absence of rill and gully erosion with minimal-soil-disturbance sowing using a
triple—disc drill (Bligh, 1984).
Stubble cover is generally not available on most Western Australian cropland, because
crop—pasture rotations are commonly practiced (Bligh, 1987b; 1988a). Sowing with
minimal soil disturbance minimises soil erodibility during crop years. The principle aim of
minimal-soil-disturbance sowing for reducing water erosion is to eliminate disturbance of
the entire topsoil structure in tillage, by cultivating only a minimal width in the sown rows.
Satisfactory crop yields have been achieved with minimal-soil-disturbance sowing, and
water erosion reduced, in wheat-soybean double cropping rotations in North—Coastal
New South Wales (Desborough, 1983). The Connor-Shea “inverted—T” Coulter Coil
Tine Drill® (after Baker 1976), is used on approximately 50% of cropped land
(Desborough, P.J. pers. comm. 1988) in a newly—developed cropping system, which
was extended to landholders as a package.
In Western Australia, comparable crop yields have been achieved under continuous
cereal cropping whether minimal-soil-disturbance, one, or the traditional three tillage
operations were used in areas receiving greater than 350 mm average annual rainfall
(Jarvis ~ et al 1986). The cropping system in these areas is traditional having been
developed over several generations. Therefore minimal-soil-disturbance sowing cannot
be extended as a new cropping package, as in North-Coastal New South Wales.
The adoption of minimal-soil—disturbance sowing in Australia has been hindered by the
lack of suitable seeding mechanisms (e.g. Quick and Brown, 1984; Sweeting, 1985).
The triple—disc-drill has been generally abandoned for sowing cereals in Western
Australia, largely because of unreliable crop establishment in some seasons (R. Jarvis,
W.A. Dept. of Agric., pers. comm. 1987). Relatively high point wear rates reported using
the seeders such as the Connor-Shea Coulter Coil Tine Drill® and John Shearer Coulter
Drill®, together with their availability in maximum widths of only 2.7 m, have generally
precluded their use in broad-scale cropping. Inexpensive replacement of wearing points,
2
and practical seeders must be developed in order to systemically mitigate water erosion
on cropland by minimal-soil-disturbance sowing in Western Australia.
The design of reduced and minimal-soil-disturbance seeders have so far been basically
empirical (Baker ~ et al, l979a). Baker et al. (197gb) tested more than 50 combinations
of mechanisms in developing a notched, plain disc with a split, narrow tine and press
wheel mounted on either side, known as the Bioblade® (Baker, C.J., pers. comm. 1988).
Ward and Norris (1982) evaluated 34 mechanisms in the field prior to recommending a
disc coulter—spear point—press wheel combination (Freebairn ~ et al. 1986). Frye and
Lindwall (1986) report a consensus at an international conference on zero—tillage
research priorities, that the physical requirements of the seed zone must be better
defined, to enable objective design. Meanwhile judicious trial-and-error remains the only
available technique for developing minimal-soil-disturbance openers.
After reviewing machinery for cropping with reduced water erosion (Bligh 1987b; 1988a)
and minimal soil disturbance (Bligh 1988b; c), a brief study tour was undertaken
(Appendix 1) to inspect relevant seeder research and its adoption at Cowra, Condobolin,
Gunnedah, Tamworth and Grafton in New South Wales, and to visit relevant machinery
manufacturers in Southern Queensland. The aim of the study tour was to determine
desirable seeder mechanisms for evaluation and demonstration in Western Australia. A
paper reviewing minimal-soil-disturbance seeders was presented at the “Soil
Management 88” Symposium in Toowoomba, Queensland, and at the 1988 Conference
on Agricultural Engineering at Hawkesbury Agricultural College, New South Wales
(Bligh, 1988b; 1988c).
This report documents relevant technical developments, and the adoption of minimal
soil-disturbance sowing in New South Wales and elsewhere. Mechanisms considered
more economically acceptable for adoption in the short term are discussed in greater
detail than newer, more complex mechanisms, in order to facilitate their immediate
evaluation and demonstration in Western Australia.
3
2. Minimal-Soil-Disturbance Sowing Mechanisms Used In
New South Wales
Seeders currently used in New South Wales for sowing with minimal-soil-disturbance
include the narrow-winged point after Baker (1976), spear—point openers (e.g. Kneipp,
1987), the triple disc drill (after Karonka, 1973) and the Bioblade® (Baker et al. 197gb).
Each are reported to provide adequate crop establishment in specific soil and
environmental conditions.
2.1 Narrow-winged Openers
Narrow—winged openers till the soil in the sown row only, leaving the inter-row strip
largely undisturbed.
Some minimum tillage seeder developments in New South Wales were reported by
Mead and Wedd (1982) and Mead (1985). Mead and Chan (1988b) report increased
penetration, and soil fracturing favourable to root development, using 40 mm wide
narrow—winged points, compared with either lucerne points (12 mm wide), or standard
combine seed drill points (100 mm wide) on hard—setting sandy loam soil at Cowra in
Central-Western New South Wales. Planar voids were formed by the passage of the
narrow-winged points, which were not detected by either bulk density or shear strength
measurements in the seedbed (Chan and Mead 1988). Impregnation of the seedbed
mass with epoxy casting resin (after Dexter ~ et al. 1983) revealed their presence.
Wedd (1988) reports that draft forces increased in the order of winged, lucerne and
standard combine points on this undisturbed sandy loam soil. The addition of a deep
front blade protruding 25 mm below the wings (see Plate 1) resulted in the maximum
draft force measured in both undisturbed soil, and soil which had been compacted using
a rubber-tyred roller.
A prototype 80 mm wide winged point, a lucerne point and McKay “Slimline”® combine
point achieved comparable establishment on loamy sand, though not on a red—brownearth in Western New South Wales (Palmer ~ et al. 1988). A Connor-Shea “inverted-T”
opener consistently achieved the highest seedling establishment counts, though still
only 65% of viable seeds sown. The lucerne point required the lowest penetration and
draft forces of the four points tested on the loamy sand at speeds of both 4.0 km h~ and
8.5 km h~ (Palmer, A.L., pers. comm. 1988).
4
Plate 1. The author, holding a 50 mm-wide narrow-winged combine seed drill point
(left), and a similar point equipped with a front blade to cultivate 50 mm below the seed
zone at the wings.
Soil disturbance was increased, with more soil displaced downslope when drilling on the
contour using an “inverted-T” point, than using either a triple-disc or Bioblade® opener
on loamy soils in North-Coastal New South Wales (Baker and Desborough, 1984).
Some smearing of the seed slot occurred using the “inverted-T” and triple-disc openers.
Heavy stubble was satisfactorily handled at row spacings of 250 mm to 350 mm, using
staggered openers on two ranks (Quick and Brown, 1984). Narrow points have been
reported to improve trash clearance because of reduced blockages by clumps of mixed
soil and stubble (Lackie, 1975; Packer and Hamilton, 1984)
5
2.2 Spear-Point Openers
Spear-point openers are typically used on black, clayey soils in Northern New South
Wales (e.g. Kneipp, 1987; Thompson and Elliott, l988a, b), spear points are usually
mounted on a parallelogram linkage sometimes coupled with a disc coulter, with or
without attached rubberized drums for depth control (Plate 2).
Plate 2. A spear point opener close-coupled on a parallelogram linkage, with a disc
coulter with attached rubberized drums for enhanced stubble handling and reduced soil
disturbance with precise depth control
A 20 mm-wide Janke® spear point with a wingspan of 30 mm, or a 30 mm-wide Mason®
spear point with a wingspan of 50 mm, are commonly used in New South Wales and
Queensland. The Connellan® spear point is also commercially available with adaptors
for mounting on either chisel plough or scarifier tines (Ward ~ et al. 1988).
Generally comparable seedling emergence was achieved in Western New South Wales
using Connellan® spear points, lucerne points, standard combine seed drill points and
Connor-Shea “inverted-T” points in untilled loamy sand (Palmer ~ et al 1988). A draft
force of approximately 0.4 kN was required to pull each tine equipped with spear,
lucerne or standard combine points at a speed of 4 km h in the red-brown earth,
compared with approximately 0.9 kN for the “inverted—T” point (Palmer, A.L., pers.
comm. 1988). Draft forces generally increased by 10—20% at 8.5 km h~. The vertical
6
forces required were least for the lucerne point, and greatest for the “inverted-T’~ point,
though all required less than 0.3 kN per tine.
Spear points have generally been used to place the seed with minimal soil disturbance,
in order to reduce the evaporative loss of soil moisture in New South Wales (e.g.
Kneipp, 1987). Ward ~ et al. (1988) report beneficial effects on seedling establishment
and vigour using either 50 mm-wide spear points or 100—mm wide “ducksfoot” points,
similar to a low-profile combine seed drill point. They attribute this improved
establishment to better soil tilth in the clayey soils. Seed cover was sometimes inferior
using the spear point, whereas the “ducksfoot” point formed a micro-seedbed of loose
soil.
Water erosion on clayey soils in northern New South Wales occurs mainly during the
summer months (Edwards, 1984, 1987). Therefore, the reduced soil disturbance
achieved using spear point openers may result in less water erosion, because
vegetative cover is increased and soil erodibility reduced in the period before full canopy
development of summer crops. Thompson and Elliott (l988a) advocate paired rows,
sown using spear-point openers 0.12 m apart, with a further spear point for fertilizer
placement located midway in the 0.38 mm space between pairs, in order to reduce soil
disturbance, erosion and soil structural degradation.
2.3
The Triple—Disc Drill
The triple disc drill, has been used extensively as replacement combine seed drill
undercarriages (Plate 3) in the Murrumbidgee Irrigation Area of New South Wales for
sowing rice, usually pre—irrigated, moist soil. It is not generally used for broad-scale
sowing of other crops. Compaction and smearing of the bottom and sides of the slot
under wet conditions may restrict downward root development in dry soils (e.g. Baker,
1976). Depth of sowing was inadequate using the triple disc drill in tight soil conditions in
North-Coastal New South Wales (Baker and Desborough, 1984), where front coulters
0.5 m in diameter were required in order to clear heavy stubble residues encountered in
a double-cropping rotation.
A vertical force of approximately 1 kN per single-row triple-disc assembly was required
to penetrate a red-brown earth soil at Condobolin (Palmer, A.L. pers. comm. 1988).
Draft forces were generally comparable to those required for spear, lucerne or standard
combine points, though the vertical force required was several times less for the points.
Emergence of wheat seedlings using the triple—disc drill was inferior to that achieved
using these points in untilled loamy sand, though comparable in untilled red-brown earth
soil, and in black clayey soil with surface stubble (Palmer et al. 1988). Seedling
establishment using the triple disc was superior to tined assemblies in a sandy loam soil
in Southern Queensland, but was inferior in several clayey soils (Ward ~1988).
7
Plate 3. Rear view of double-disc openers mounted behind the front disc coulters of a
triple disc drill (after Karonka, 1973)
2.4 The Bioblade®
The notched-disc, split-winged point and press-wheel combination, known as the
Bioblade® (Plate 4) was developed for improved stubble handling and reduced wear at
Massey University in New Zealand (Baker ~ et al. 197gb). The Bioblade® was the most
successful of a wide range of direct—drilling mechanisms tested for sowing wheat and
soybeans on non-sticky, sandy loam soils at Grafton Research Station (Baker and
Desborough, 1984; Desborough, 1981a, 1985). Reduced erosion was the principal
reason for selecting the minimal-soil-disturbance Bioblade® opener (Desborough,
1981b). Additional reasons included timeliness of sowing, trafficability, agronomic and
economic factors. Dwyer and Page (1988) also refer to a requirement that fertilizer not
be placed in contact with the soy bean seed.
Draft forces using the Bioblade® averaged 3 kN per opener (Plate 5) on untilled redbrown earth soil at Condobolin - more than double that of any of the other nine openers
tested (Palmer, A.L. pers. comm. 1988). Vertical forces averaged approximately 2kN per
opener. These were approximately double those for the triple—disc drill, which itself
required vertical forces several times higher than those of any other opener tested.
8
Plate 4: The Bioblade® minimal-soil-disturbance seeder with 450 mm-diameter
notched discs, and 50 mm-wide press wheels, used at Grafton Agricultural Research
and Advisory Station since 1982. (Photo, courtesy P.J. Desborough)
Plate 5. Bioblade® openers with 560 mm diameter notched discs and 100 mm wide
press wheels, mounted under a force-measuring tillage dynamometer at Condobolin
Agricultural Research and Advisory Station.
9
A front-wheel-assist 80 kW tractor was required to pull a 14-row, 3.5 m wide “Aitchison
Seedmatic 2000” Bioblade® unit (Plate 6) at typical sowing speeds in sandy loam soil at
Cowra (Mead, J.A. pers. comm 1988). The seeder remained unused at Condobolin
Agricultural Research and Advisory Station from 1985 until viewed in September 1988.
Plate 6. The Aitchison “Seedmatic 2000” Bioblade® seeder
Plant emergence after sowing with the Bioblade® averaged approximately 10 per cent
of viable seeds sown on the red-brown earth soil at Condobolin (Palmer et al. 1988).
Many seeds stuck to the notched disc, became dislodged above ground level and fell
onto the soil surface (Palmer, A.L. pers. comm. 1988). A pin has since been developed
for insertion in the sowing boot, in order to reduce dislodgement of seed from the seed
groove by the disc (Choudhary ~ et al. 1985).
Manufacturing rights for the Bioblade® have recently been acquired by El Al
Agribusiness of Washington State, U.S.A. (Peter Aitchinson, Managing Director,
Aitchison Industries Limited, Wanganui, New Zealand, pers. comm. 1988).Stubblehandling ability (e.g. see Plate 7) appeared to be superior to that ofany other opener
tested in early trials at Washington State University (Hyde, G.M., Associate Professor of
Agricultural Engineering, pers. comm. 1988).
10
Plate 7. Heavy maize stubble typically handled by the Bioblade® seeder at Graf ton
Agricultural Research and Advisory Station (P.J. Desborough, pers. comm. 1988)
2.5 Associated Mechanisms
Devices such as front disc coulters for improved stubble handling, and press wheels to
enhance seedling emergence and establishment are an integral part of some seeders
used in New South Wales.
2.5.1 Disc coulters
Disc coulters are sometimes used in front of tines to cut through stubble and vine weeds
in New South Wales and Queensland. Some straw may merely be pushed into the soil
by the disc, like a hair pin, leaving the ends sticking out. Seeds germinating on
decomposing stubble may then suffer toxicity effects from break-down products,
inhibiting the growth and establishment of seedlings (Baker, 1983).
Articulated, rippled—disc coulters (see plates 8 and 9) can be fitted to stump-jump
mechanisms, replacing cultivating tines on some combine seed drills (e.g. the John
Shearer “Trash-Culti Drill”®). Satisfactory stubble handling using rippled-disc coulters
has been reported at Cowra, New South Wales (Mead, J.A., pers. comm. 1988; Packer,
I.J., pers. comm. 1988). Disc coulters are also mounted directly in front of the narrow
points on tined seeders in order to slice through the relatively heavy stubble remaining
from the preceeding crop in the wheat-soybean double-cropping rotation commonly
used in North-Coastal New South Wales (Desborough, 1983), and in annual cropping in
Northern Victoria (Steed and Robertson, 1988).
11
Plate 8. A 300 mm diameter, rippled disc coulter with articulated swivel shaft being
held approximately in its operating attitude by Ian Packer, Research Officer at the Soil
Conservation Research Centre, Cowra
Disc coulters 450 mm in diameter were found to be superior in stubble-cutting ability to
those 300 mm in diameter in North-Coastal New South Wales (Baker and Desborough,
1984) and Southern Queensland (Freebairn et al. 1986), though requiring greater
downward force for penetration (L.D. Ward, pers. comm. 1988). Fluted disc coulters
were generally considered marginally beneficial, in clayey soils in Southern Queensland
(Ward ~ et al. 1988). Improved wheat seedling establishment was observed using a disc
coulter and spear point combination than a spear point alone (Norris, 1987).
12
Plate 9. Mountings for articulated disc coulters distributed throughout the tine patter at
250 mm row spacing on this John Shearer “Trash Culti Drill”®. The weight of the entire
seeder, and downward forces of the action of the points, is then available to assist
penetration of the discs.
2.5.2 Press Wheels
Improved wheat seedling establishment and vigour was frequently observed using
smooth or single—ribbed rubber press wheels (Plate 10) to firm soil over and around the
seed on clayey soils in Southern Queensland (Ward et al. 1988). The use of press
wheels is generally recommended for sowing summer crops in well-structured, clayey
soils in northern New South Wales (e.g. Kneipp, 1987; Thompson and Elliott, 1988b;
Esdaile et al. 1989). Wheat seedling emergence was increased using press wheels on a
range of soils in Western New South Wales (Palmer et al. 1988).
Steel V—shaped press wheels have been recommended for sowing wheat in Southern
New South Wales (Hill, 1986), These may be more conveniently mounted with the
capability of varying pressures from the tractor seat through remote hydraulics, rather
than having to stop and adjust spring loadings in order to vary pressures on different soil
types (J. Hill, then Agricultural Mechanization Officer, Department of Agriculture and
Fisheries, Yanco, pers. comm., 1988).
The use of vertical forces equivalent to 15 kg per centimetre width of press wheel has
satisfactorily increased seedling establishment on clayey soils in Southern Queensland
(Ward et al. 1988). However, similar forces on press wheels inhibited plant
establishment and vigour in some soils in some years. Wheat seedling establishment
was increased on coarser-textured soils when forces were reduced. Ward and Norris
13
(1982) considered the use of press wheels superfluous in situations where adequate
plant establishment could be achieved without press wheels.
Plate 10. The various shapes of press wheels used in New South Wales include
single—ribbed (left), loose (so—called “zero pressure”) rubber to minimize clay
adhesion (centre), and steel “V” (right)
2.6
Wear of Ground Tools
Relatively rapid wear rates of narrow-winged “inverted-T” points led to the development
of both the inexpensive “knock-on, knock-off” replaceable narrow winted point (Peter
Aitchison, pers. comm. 1989), and the Bioblade® (Baker et al. 1979). Wear of the
Bioblade® is largely confined to the easily-replaced split-wings (Plate 11).
Spear points are generally of cast steel construction. Depending on the shape of the
spear and its angle of mounting, they may be designed to wear in such a manner that
they remain sharp for consistent penetration. Janke Bros Ltd of Mt Tyson (approximately
40 km west of Toowoomba, Queensland) provide two qualities of cast spear points, one
less brittle for use in stony soils.
Tungsten carbide has been successfully braised onto both pressed and cast steel points
in New South Wales (Packer, I.J., Cowra Soil Conservation Research Centre, pers.
comm. 1988). Cleanliness and care are required in order to achieve good adhesion in
the braising operation. Tungsten carbide has also recently been successfully mounted
on cultivator points using epoxy resin and heat—treated at 200°C (R. Ainge, Hard
Metals Aust. Ltd. pers. comm. 1988).
14
Rolling disc coulters characteristically wear more slowly than fixed openers, particularly
in moist clayey soils. High disc wear rates have been reported on triple—disc drills in
stony soils, (Bligh, 1987). Penetration and scuffing by stones may also cause
deterioration of rubber depth drums, attached to disc coulters for depth control.
Plate 11. The replaceable split wings being demonstrated on a Bioblade® opener
removed from the Aitchison “Seedmatic 2000” seeder by Alan Palmer, Agricultural
Engineer, N.S.W. Dept. of Agriculture and Fisheries, Trangie
15
3. Review Of Relevant Developments Elsewhere
3.1
Minimal-Soil-Disturbances Sowing
Crop establishment using the triple disc drill assembly was inferior to either the
“inverted—T” or more traditional hoe point openers under dryland conditions in New
Zealand (Baker, 1g76; Choudhary and Baker, 1981, 1982; Choudhary et al. 1985;
Choudhary, 1988). Establishment was also unsatisfactory in parts of drill plots in some
seasons in wheat-pasture rotations on loamy soils in Western Australia (R.J. Jarvis,
W.A. Dept. of Agric., pers. comm. 1987).
Baker and Mai (1982) reported indications of greater compaction at the base of triple—
disc grooves than at the sides. Lupin root growth was inhibited after sowing a silt—loam
soil of bulk density 1.32 g cm3 using a triple-disc drill, compared with that sown using an
“inverted-T” opener, though not when the bulk density of the same soil was reduced to
1,04 g cm3.
Baker (1976) reported greatly increased seedling establishment using an “inverted T”
narrow—winged opener with 14 mm wide shanks and a maximum width at wing
extremities of 38 mm at very low speeds, than using either “U” and “V” shaped slots
formed by traditional hoe points and triple-disc openers, respectively, A shallow Ushaped zone of crumpled soil is formed above the seed placed at the bottom of the slot
in unstable soil conditions, using narrow-winged openers at speeds in excess of 5 kmh~
(Choudhary and Baker, 1982). “Inverted T” openers have been manufactured in New
Zealand by Aitchison Industries Ltd of Wanganui since 1970 (P. Aitchison, Managing
Director, pers. comm. 1989).
Wheat seedling emergence was superior using the Bioblade® at a ground speed of 5
km h~ in a silt—loam soil, than using a hoe opener in one out of nine, and a triple—disc
opener in two out of nine sequential sowings at two—week intervals in New Zealand
(Choudhary and Baker, 1982). Sub—surface seedlings survived under dry conditions
when sown with the Bioblade® in a further two sowings, when no seedling emergence
occurred after three weeks in any of the three treatments. Emergence following use of
an early-model Bioblade® without a seed-locating pin was inferior to that using tripledisc and “inverted-T” or hoe openers on silt loam and sandy soils (Choudhary ~ 1985).
The insertion of the pin behind each opener blade beside the central disc controlled the
depth of sowing, resulting in emergence comparable with the other two treatments.
Wheat seedling emergence increased when pressures of 35 kPa and 70 kPa were
applied directly over the seed using hoe or triple-disc openers, before covering with a
bar harrow (after Baker, 1970), in a fine sandy loam with soil moisture close to wilting
point, but not after covering (Choudhary and Baker, 1981). All openers were operated in
undisturbed turf blocks in tillage bins at very low speed. Seedling emergence was 58.4%
using a narrow-winged opener, 31.3% using a hoe opener, and 10.5% using a tripledisc. The low emergence using the hoe opener was attributed to reduced germination,
whereas seeds mainly germinated after sowing with the triple disc, but subsequently
16
died. The narrow-winged and hoe openers gave similar emergence counts when sowing
into initially moist soil (mean, 68.8%) and the triple—disc, 42.0%.
Krall and Dubbs (1979) report higher yields using a triple-disc drill than a disc coulterhoe opener combination. Minimal soil-disturbance sowing resulted in less germination of
weeds between the rows in continuous cropping than using furrow openers.
A narrow-winged point with a deep front blade is available from Ralph McKay Ltd. in
either “Nok—on” or bolt—on fittings for combine seed drills, in order to cultivate up to 50
mm below the seed zone located at the 55mm wide wings. Draft forces at 4 km h~ in a
sandy loam soil at 21—26% moisture content were comparable to those required for a
narrow-winged point, a lucerne point and Baker “inverted—T” point. Soil disturbance
was significantly less than that using a similar point with a blade at the same depth
enclosed at the back, (particularly at 8 km h~ (Riley, T.W., South Australian Institute of
Technology, pers. comm. 1988). Both types of narrow winged-and-deep-bladed points
required higher draft forces at 8 km h~ than at 4 km h~, increasing from 388 N to 480 N
for the front-bladed point, and from 587 N to
640 N for the enclosed-bladed version. Lower rhizoctonia-disease levels have been
reported in wheat by Dr A. Rovira (CSIRO Soils Division, Adelaide), using deep,
enclosed-bladed points (Sweetingham, M., W.A. Dept. of Agric. pers. comm. 1987).
Draft forces required for the other openers did not increase significantly at 8 km h1
compared with 4 km h1, remaining in the range of 350 N to 395 N. Draft and vertical
forces also remained relatively constant at field speeds for a range of tined and disked
furrow openers in Canada, (Sheaf et al. 1979).
Vertical forces in the range 101-120 N per opener were required for both deep-bladed
points, which were approximately double those of the Baker point. The Lucerne point
required vertical forces of 353 and 370 N per opener at 4 and 8 kin h1, and the narrowwinged point, 453 and 401 N per opener, which was significant at the 5% level.
3.2 Stubble Clearance
Cereal stubbles were reported to be readily passed through tines more widely—spaced
that four times the mean stubble length in New South Wales (Quick, 1985). An
“arrowhead” configuration of tines proved superior to a “reverse arrowhead” pattern,
though disc coulters were required in the heaviest stubble conditions. Allen (1988)
reported that wheat stubble of 3.5 t ha~ appeared to be close to the limit of clearance for
a hoe—press drill.
Disc coulters mounted directly in front of each tine have been reported to assist in slicing
through stubble (e.g. Anon, 1986; Freeborn et al. 1986). Kushvaha et al. (1986) found
that discs with a diameter of 460 mm, cut stubble better than 300 mm or 600 mm, with
little difference between plain and fluted discs. Morrison and Allen (1988) detailed
several combinations of disc coulter-tine combinations used in Texas.
Mead (1985) and Krall and Dubbs (1979) observe that disc coulters should be mounted
in such a manner as to allow separate break-out action in stony soils, for reasonably
17
trouble-free operation. Net vertical forces were downward when disc coulters were set at
depths less than those of following conventional points at the Agricultural Machinery
Research and Design Centre of the South Australian Institute of Technology (Anon.
1986). Draft forces increased rapidly when the disc coulters were set deeper than the
points, with little increase when set shallower. Soil disturbance was reduced using the
disc coulters though the self-cleaning action of the tine was reduced.
Baker et al. (1983) commented that a front disc coulter seldom improves stubble
clearance. Baker (1983) observed that uncut but “hair-pinned” stubble poses a danger to
germinating seedlings from fatty-acid decay products in wet soils.
The practicality of punch—planting, in which the seed is placed in a hole punched in the
soil, was investigated by Srivastava and Anibal (1981). They reported that the concept
has merits if the wheel on which the punches are mounted is powered with positive slip,
and the seed is propelled aerodynamically rather than under gravity alone. They also
reported that seeds should be accurately graded for size.
An experimental punch seeder reported by Rogers and Baron (1987) operated with
pneumatic seed and fertilizer delivery. Punches mounted on a rotating wheel required
about 0.25 kN load to penetrate 30 mm into a stubble field in Canada. The wheel hub
was being re-designed to minimise bounce of the seeds onto the surface after the punch
leaves the soil. Low draft and accurate sowing—depth control are reported using this
innovative seeder.
Stubble handling begins at the harvest of a preceding crop. Harvesting height and straw
choppers mounted on harvesters affect the amount of loose stubble (Porritt, 1987) and
its distribution behind the harvester. Several harvester fittings for chopping and
spreading straw and chaff residues are described by Butt and Quick (1986). An
experimental, second knife to reduce the height of standing stubble without increasing
through-put through the harvester and therefore, reducing speed, is described by
Robotharn and Ward (1984).
18
4. Relevance To Reducing Water Erosion On Cropland In
Western Australia
4.1
Technical Relevance
Severe water erosion typically occurs on tilled cropland in Western Australia (Bligh,
1989). It was estimated in 1975, that contour banking was required to reduce erosion of
tilled cropland on up to 45% of the 16 million ha of agricultural land in Western Australia
(Anon., 1978). Contour banks have been constructed on only a small proportion of
erodible land to date.
Erosion of tilled cropland typically occurs within weeks of the initial tillage operation in
this predominantly winter-rainfall region, frequently before appreciable settlement of
tilled soils has occurred. Increased infiltration and reduced suspended sediment
mobilisation have been observed under reduced tillage and, particularly, triple-discdrilling on sandy loam and loamy sand soils (Bligh 1g84). Contour farm planning with
contour working and strategic diversion banks would still be required to discharge
concentrated flows with a minimum of erosion, however.
Long-term cereal yields have been maintained using triple-disc drills on loamy soils in
medium (~ 325 mm average annual) rainfall areas, compared with a tillage operation
approximately 50 mm deep at sowing, or three tillage operations per season (Jarvis
et/al. 1986). Therefore minimal-soil—disturbance sowing is a potentially viable method
of reducing water erosion on cropped loamy soils in Western Australia.
Though typically 70% to 80% of soil losses occur in the first three months of the year at
Cowra (Edwards, 1987), signs of water erosion were evident on sloping cropland in
September 1988 (Plates 12 and 13) following relatively high winter rainfall. Severe rilling
occurred even on direct-frilled-sandy-loam soils at the Soil Conservation Reseach
Centre at Cowra, for example (Plates 12 and 13). Conservation Research Centre
photographed in September 1988
Packer (1988) reported significantly reduced runoff under simulated rainfall on 0.8 m—
square plots after five years continuous cropping to cereals in Central Western New
South Wales. Traditional tillage (four tillage operations each year) resulted in the highest
runoff, followed by reduced tillage (two) and direct drilling (one tillage operation1 at
sowing). The presence of 3 t ha~ of stubble significantly decreased runoff under reduced
tillage and ~ treatments, though not under traditional tillage and ungrazed direct-drilling.
Sediment loss was significantly reduced in the same order as runoff. Significant
reductions in soil movement were observed when stubble of 3 t ha~ was applied under
traditional and reduced tillage, but not under either the grazed or ungrazed direct-drilling
treatment. Packer cautions against stubble retention alone on degraded soil, advocating
stubble retention with minimal-soil-disturbance sowing to optimally reduce runoff and
water erosion.
19
Plate 12. An erosion nil looking down a contour-worked slope at Cowra Soil
Conservation Research Centre photographed in September 1988
20
Plate 13. Rilling and erosion debris looking upslope in the vicinity of the trees at the top
of Plate 12
Packer and Hamilton (1988) comment on the overriding effects of good soil
management over tillage level for reducing water erosion. Machinery selection,
herbicides, weeds, stock management, stubble, alternative crops and deep ripping are
included in good soil management. Trends in runoff and sediment loss for all
conservation tillage treatments were significantly different from those for traditional
tillage at two intensively sampled sites in the Cowra area. Multiple regression analyses
indicated that decreased runoff resulted mainly from the development of stable biopores,
particularly those larger than 0.75 mm in diameter in a sandy-loam soil. On a loamy soil,
decreased runoff resulted from increased total porosity (i.e. reduced bulk density) rather
than specific pore sizes. Plant establishment was significantly reduced on the sandy
loam soil when surface crusting developed. Organic matter increased with reduced
tillage, depending on organic litter or stubble more than on degree of soil disturbance.
They advocate maximum retention of stubble for soil conservation in long—term
cropping in arid cereal-growing areas.
Grain yields generally increased when soil physical conditions stabilised after three or
more years of conservation tillage (Packer and Hamilton, 1988). Mead and Chan
(1988b) observed reduced wheat seedling vigour with tillage level following five years of
pasture. They advocated reduced rather than minimum tillage in the initial years of
continuously cropping hard—setting sandy loam soils, with timely cultivation to minimise
soil erosion and recompaction. Mead believes that direct—drill yields in Southern New
South Wales, are limited chiefly by biological factors, which are evidently ameliorated by
tillage (pers. comm. 1988).
Row spacings used for cereals in New South Wales are typically 200 mm — 300 mm
compared with 150 mm to 180 mm in Western Australia, where yield reductions have
21
been demonstrated at wider spacings (Burch and Perry, 1986). The greater space and
reduced expense per unit width of seeder, allows the use of more complex mechanisms
in New South Wales, such as parallelogram linkages and depth and press wheels for
improved depth control and seed-soil contact on minimal—soil—disturbance seeders’.
Water erosion typically occurs during summer months in the winter cropping areas of
Southern New South Wales (Edwards, 1987). Minimal-soil-disturbance sowing is even
more relevant in Western Australia, where erosion typically occurs shortly after the
sowing when soil erodibility is high. A perspective on its prospective adoption may be
obtained from experience in other parts of the world, particularly in the United States of
America where documentation is more complete.
4.2 A Perspective on Prospects for the Adoption of Minimal-SoilDisturbance Sowing for Reducing Water Erosion of Cropland in
Western Australia
Soil movement of the order of millimetres depth has been measured in several recent
seasons in Western Australia (McFarlane and Ryder, 1987; Bligh, 1987; 1989),
compared with soil formation rates estimated at less than one millimetre per thousand
years. Shallow soils are more vulnerable to productivity losses than deeper soils,
because water storage and fertility become more limiting with erosion.
Average annual soil erosion on cropland in United States was 20 t ha~ in 1982 (Lee,
1984), equivalent to approximately 1.6 mm depth on cropland, and approximately 1.5
mm on all agricultural land. However, soil loss tolerances are considered to be 1 mm per
year for many soils in the United States. Depending on the depth of fertile soil available
to be “mined” in this way, the relative erosion risk to sustained productivity may be more
severe in Western Australia, where soil formation rates are extremely low, than in the
United States.
Napier (1988) observes that erosion-control programmes carried out to date in the
United States are difficult to justify in terms of on—site costs, and that off—site costs are
not borne by landholders at present. A similar situation also pertains in Western
Australia, where water erosion reduction has historically depended on the goodwill of
offending landholders. The availability of satisfactory techniques for reducing water
erosion may therefore be a necessary if not sufficient condition for their adoption by
landholders.
The profit—maximising desire of landholders may be expected to result in earlier sowing
in order to achieve higher yields in Western Australia. Weed control under minimal—
soil-disturbance sowing will necessarily depend more on adequate weed seed-set
control in the previous season, through the use of cereal—legume rotations or pasturetopping. Weed control by tillage in the cropping season is then likely to be less critical.
The prospective use of press wheels may increase the reliability of early establishment
through increased seed—soil contact in generally drier, early—season conditions.
22
Landholders may still choose to reduce their weed risk through tillage, because water
erosion is not an appreciable current cost in Western Australia. Risks may be less using
a systems approach to weed seed-set with appropriate rotations and pasture topping,
though improved management may be required. Hurley et al. (1985) found that Victorian
farmers were aware of benefits, but worried both about new investment costs in
machinery, and risks of yield reductions.
The 50% adoption of a minimal-soil-disturbance cropping system in North-Coastal New
South Wales for reducing water erosion, suggests that farmers are amenable to a
demonstrated, credible systems approach. Emphasis should therefore be placed on a
minimal-soil-disturbance systems approach which minimises weed control and crop
establishment fears, in extension of minimal—soil—disturbance sowing for reducing
water erosion in Western Australia. McGowan and Associates (1988), for example, have
recommended increased tax write—offs for approved conservation seeders together
with contour farm practices for reducing water erosion in the Avon Valley of Western
Australia.
Indices of rainfall erosivity are several times higher in North-Coastal New South Wales,
than in South-Western Australia (Mcrarlane and Clinnick~. 1984). Suitable minimal—
soil-disturbance seeders were also at first unavailable for use in this cropping system.
The Connor-Shea “Coulter Coil Tine Drill”® (sometimes known as “The Bean Machine”),
and other seeders utilizing the “inverted—T” concept (after Baker, 1976), and
subsequently the Bioblade® (Baker and Desborough, 1984) were then developed in
acceptable sowing widths, in order to enable the ready adoption of minimal-soildisturbance sowing. Cropping, then a new land treatment in the area (Desborough,
198lb), was effectively extended as a “package” which included direct-drilling as an
integral part of the system.
A similar situation pertained in extension of direct-drilling in the lupin phase of wheatlupin continuous cropping rotations in Western Australia. Wheat stubble is required on
the soil surface in order to reduce “brown spot” infection of the succeeding lupin crop.
Either traditional prior tillage is typically carried out in the wheat phase, or the soil
receives full tillage at sowing using a combine seed drill or air seeder equipped with
overlapping, conventional points.
The fact that tillage is still typically carried out in the wheat phase of wheat—lupin
rotations in Western Australia, supports evidence that farmers favour least—risk
techniques (e.g. Napier and Camboni, 1988; Napier, 1988). No-till farming has been
developed and extended by scientists primarily to reduce water erosion (Van Es and
Notier, 1988). Water erosion has usually been given a minor consideration in
landholders’ reasons for it’s adopting on 1.5 million ha of cropland in the United States
(Christiansen and Norris, 1983). Napier (1987) suggests that the “carrot” is likely to soon
be replaced by the “stick” in the United States Government’s dealings with farmers
regarding water erosion. He suggests that it is therefore in farmers best interests to
adopt conservation techniques on erodible land before they are forced to, by possibly
unpalatable methods.
23
Plate 14. Minimal—soil-disturbance seed grooves formed by narrow-winged-and-deep
bladed points on a combine seed drill at Chapman Valley Research Station near
Geraldton, Western Ausralia in 1988
24
5. Discussion And Recommendations
5.1
Narrow-winged, and Narrow-winged-and-deep-bladed Points
Most detailed seed-groove investigations have involved towing openers in undisturbed
turf or annual pastures, either at very low speeds in tillage bins (e.g. Choudhary and
Baker, 1981), or at more representative speeds of 4.0—8.5 km h’ in field situations (e.g.
Choudhary and Baker, 1982; Palmer et al. 1988). Groove formation may be different at
higher speed in soils with negligible or dead vegetation. For example, grooves formed
using the McKay narrow—winged-and-deep—enclosed-bladed point appear to resemble
more a generalised “U” or “V” shape depending on soil texture and moisture content
(Plate 14) than the “dagger” shape of the point (Plate 1 right) in Western Australia.
Further establishment trials are suggested following superior wheat yields at four out of
five sites than those achieved with full tillage on loamy soils using similar points in the
1988 growing season (C. Henderson, Department of Agriculture, Western Australia,
pers. comm. 1989; Bligh, unpublished, 1989). Narrow—winged points without a deep
blade should also be tested, particularly on sandy loam and clayey soils, where deeper
cultivation may not be required for adequate establishment (R. Belford, Department of
Agriculture, Western Australia, pers. comm. 1988).
5.2
Press Wheels for Seed Firming with Minimal Soil Cover
Considerable loose soil cover appears to be thrown into grooves formed by front tines
by adjacent following tines (Plate 14). It is therefore difficult to arrange a machine
configuration so that pressure can be applied by press wheels to seeds before covering
(after Choudhary and Baker, 1980). Press wheels would have to be mounted
immediately behind each time, and in front of adjacent tines, in order to minimise soil
cover before pressing. Space limitations usually prevent the use of such a configuration
(Bligh, 1g87b). Rear-mounted press wheels could be tested with a finger harrow
immediately in front to remove excess soil, with a further finger-harrow following the
press wheel to provide loose soil cover. Alternatively bar harrows (after Baker, 1970)
could be considered for trailing behind the seeder if press wheels are not required, and
their operation is not hindered by obstacles such as stones or stubble collecting in front
of the bars.
Pressures of approximately 35-70 kPa appear desirable (after Choudhary and Baker,
1981). Difficulties of measuring pressures in field soils suggest that its expression as its
static equivalent, in kilograms per centimetre width of press wheel, is preferable for
extension purposes (after Ward and Norris, 1982; Ward et al. 1988). Pressures as low
as that provided by a mass of 3 kg per centimetre width of press wheel are suggested
by Riethmuller (Agricultural Engineer, W.A. Dept. of Agric., pers. comm. 1988).
5.3
Point Wear
Excessive wear rates of narrow—winged McKay points reported by a Western
Australian farmer Peter Copestake in 1988, may be reduced by the attachment of
tungsten carbide tips. Aitchison Industries’ “knock-on, knock-off” winged points appear
25
to warrant trial use in this regard, with the possible added advantage of depth separation
of seed and fertiliser delivered through separate tubes. Deep front blades currently
manufactured for separate replacement where wear rates exceeds those of the narrowwings, (W.M. Johnson, Concept Engineer, Ralph Mckay Limited, pers. comm. 1989),
also warrant investigation for possible economic use on existing combine seed drill
tines.
5.4
Disc Coulters
The mean length of stubble should be reduced to less than one quarter of minimum
distance between tines on a rank (after Quick, 1985), either at harvest or prior to sowing,
in order to facilitate the passage of seeders without disc coulters. Evaluation of disc
coulters in front of tines appears warranted where heavy stubble or vine weeds still
collect between widely—spaced tines (after Baker and Desborough 1984; and Morrison
and Allen, 1988). A disc diameter of 400—460 mm appears to adequately trade off
stubble-clearing ability with downward force requirements for penetration. From
evidence reported in the literature, there appears to be little to choose between plain,
rippled and fluted discs in their ability to cut a path for tines through stubble, though
rippled discs are reported to be more self—sharpening than plain discs (Morrison and
Allen, 1988). The reduced soil disturbance of front disc coulter-tine combinations, and
reported, though unexplained improved establishment compared with tines alone
(Norris, 1983), may also be useful in contributing towards their adoption for reducing the
erodibility of cropland by minimal-soil-disturbance sowing and stubble retention.
5.5
The Bioblade
The Bioblade® has reportedly achieved excellent plant establishment in heavy stubble
in North-Coastal New South Wales, the North-Western United States, and in some soils
in New Zealand. Disappointing results in moist, relatively sticky soils in Western New
South Wales, and in some soils in New Zealand, suggest that the Bioblade® may be a
relatively soil-specific minimal-soil-disturbance seeder mechanism. A watching brief
appears warranted on the commercial development of this complex seeder mechanism
in the United States.
5.6
An Integrated Minimal—soil-disturbance System
A satisfactory systems approach with emphasis on weed control and adequate crop
establishment should be developed and extended with contour farm planning as a
conservation package, in order to achieve a reduction in water erosion through minimalsoil-disturbance sowing in Western Australia. Narrow—winged and narrow-winged-anddeep-bladed points appear to have the potential to maintain crop yields, particularly if
used in combination with press wheels for reliable early sowing, and front disc coulters,
if found to be satisfactory for clearing stubble and surviving summer vine-weeds.
26
6. Acknowledgements
Numerous officers gave generously of their time in discussion and inspections, during
the study tour in New South Wales, particularly Alan Palmer, Ashley Mead, Peter
Desborough and John Kneipp of the NSW Department of Agriculture and Fisheries, and
Ian Packer, Lindsay Ward and Greg Elliott of the Soil Conservation Service of New
South Wales. The assistance of Greg Hamilton, (Principal Soil Conservation Officer,
Department of Agriculture, Western Australia) in facilitating the study tour is gratefully
acknowledged. Bill Johnson (Concept Engineer, Ralph McKay Ltd.), Greg Haydon
(Engineering Manager, Chamberlain John Deere Pty. Ltd.) and Peter Aitchison
(Managing Director, Aitchison Industries Ltd.) also assisted with relevant, helpful
discussion. Glen Riethmuller and Ed Blanchard (Agricultural Engineers, Department of
Agriculture, Western Australia) made helpful suggestions on the manuscript.
27
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32
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33
Appendix 1 Study Tour Itinerary
Monday. September 12
Fly to Sydney, and drive to Cowra.
Tuesday. September 13
a.m. Discussions with Ian Packer, Brian Murphy
and Evan Thomas (Research Officers) at Cowra Soil Conservation Research Centre.
Inspect machinery, tillage practices trials and the former runoff and soil loss plot sites.
Tuesday September 13
p.m. Discussion with Ashley Mead (Research
Officer) at Cowra Agricultural Research Station. Inspect trial sites and seeders.
Wednesday September 14
Discussions with Alan Palmer (Agricultural
Engineer) and Neil Fettell (Research Officer) at Condobolin Agricultural Research and
Advisory Station. Inspect tillage and sowing machinery, and cropping and chemical
fallow trials.
Thursday September 15
a.m. Travel to Gunnedah p.m.Tour of the
Gunnedah-Breeza area of the Liverpool Plains with John Kneipp (District Agronomist,.
Dept. of Agriculture and Fisheries), then visit Gunnedah Soil Conservation Research
Centre for discussion with Col Rosewell (Research Officer).
Friday September 16
a.m. Discussion with Lindsay Ward
(Conservation Farming Officer, Soil Conservation Service), at Tamworth
p.m.Discussions with Col Rosewell. Greg Elliott and Bob Crouch (Research Officers)
Gunnedah Soil Conservation Research Centre. Inspect an experimental twin—row
seeder and the former contour bay trial and runoff and soil loss plot sites.
Saturday September 17
Drive to Brisbane via Inverell
Sunday September 18
Travel to Toowoomba
Monday September 19
Darling Downs
Attend Soil Management 88 Symposium at the
Institute of Advanced Education, presenting a
paper entitled “A review of machinery for seeding with minimal soil disturbance.
Conserva—til Ltd.
late p.m. Inspect spear-point seeders at Mason
Thursday September 22
am. Travel to Janke Bros. Ltd., Mt. Tyson to
inspect and discuss seeders and associated components with Noel Klease (Sales and
Development Manager).
Friday September 23
Travel to Grafton Agricultural Research and
Advisory Station, New South Wales for discussion with Peter Desborough (Research
Agronomist). Inspect minimal—soil—disturbance seeders and trial sites.
34
Saturday September 24
Travel to Karuah, en route to Sydney
Sunday September 25
a.m. Travel to Sydney
p.m. Attend pre-conference tour, and the
Agricultural Engineering Conference of the Institution of Engineers, Australia at
Hawkesbury Agricultural College.
late p.m. Fly to Perth.
35

Minimal soil disturbance sowing in New South

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