Sowing guidelines

Seed supplies of most native grasses are so limited that hand sowing of small   plots followed by hand raking to cover the seed are very common methods of   establishing small scale trials. Often, much larger scale trials would be   preferred, but sufficient seed simply does not exist for many species and   varieties and so there is no alternative.

The number of species with smooth seeds that will readily flow through a   standard small seed box on agricultural sowing equipment is limited (see Species quick reference). Australian native grass seeds tend to   clump together and clog up standard seed boxes. As a result, much effort has   been expended in designing specialised equipment that will handle fluffy seeds   or seeds with scabrid or twisted awns.

A further complication is that some species have specific requirements for   successful germination in the field and for survival of the seedlings for   successful recruitment. There have been many trials in which germination has   been satisfactory but the seedlings have failed to survive to maturity. This   highlights the importance of appropriate post-sowing management. The main   obstacles to successful field establishment of native grasses for major climatic   zones are shown in Table 5.2.

Table 5.2. Obstacles to the successful establishment of native   grasses in the major climatic zones in southern Australia. (Source: Scholz, G.   (1996). Practical Guide to Rangeland Revegetation in New South Wales: Using   Native Grasses. Technical Report No. 33. Department of Land and Water   Conservation)

Rainfall regime characterised   by:> 500 mm reliable soil   moisture>350 mm reliable rainfall   events<250 mm unreliable   rainfall
Establishment problemsExisting pasture and weed competitionMaintaining soil moistureHarvesting and maintaining soil moisture
Methods to overcome limitationsControl existing pasture and weeds with spraying, cultivationReduce run-off; increase infiltrationPonding water; controlling run-off; increase infiltration
Technology usedBand seeder; cultivatorDiscing; pitting; press wheelsPonding banks; contour furrows

Below 500 mm annual rainfall the most critical factor is adequate soil   moisture, but in higher rainfall areas, competition from annual and perennial   weeds presents the most serious challenge to successful establishment of native   grasses.

Generally two or more wet days will result in germination when other   conditions, such as soil temperature are satisfactory. However it is the   occurrence of follow-up rains, within 4–6 weeks of germination, that is required   for successful establishment. The rate at which the soil surface dries out is   critical not only for germination but also for establishment. Ideally, under   cloudy conditions for several days, the soil surface will not dry out. Good   follow-up rains will allow seedlings to develop adventitious (secondary roots)   which can supply sufficient moisture for later seedling growth. More than any   man-imposed management practice, it is the occurrence of these moisture   conditions that will result in successful establishment.

Drilling

Conventional small seed boxes are satisfactory for sowing native grass seeds   that are either naked caryopses (Caryopsis - The indehiscent fruit of most grasses with a single seed, the testa (seed coat) of which is fused with the pericarp (outer wall)) or are shed with smooth ancillary structures so that the dispersal units will   flow easily. The seeds of these species generally germinate better when buried   beneath the soil surface, but the number of species with these characteristics   is relatively small. The dispersal units of some species (e.g. T.   triandra and Austrodanthonia spp.) can be cleaned and separated   into a form that can be sown using this equipment, although this is not the case   for many other species of native grasses such as M. stipoides.

Specialised drilling equipment

Much ingenuity has been expended in the design of seedboxes for sowing fluffy   or chaffy seeds by the farming community and a number have been manufactured on   a small scale in farm or local workshops. The Landcare movement has provided   much of the funding for these efforts but few of the seedboxes have been   subjected to detailed study of their effectiveness in sowing untreated dispersal   units of a range of difficult native grasses.

Specialised seed boxes

The B & S seed box was designed and built by B & S Industries, Oakey,   Queensland specifically for 'fluffy' grass seeds. It includes an auger to move   the seed across the bottom of the seed box to the metering box, a rotating   spring (sweeper) to prevent the seed from bridging above the auger, a two, three   or four bladed paddle to push the seed into the metering box and a spiked drum   to meter the seed into the delivery tube (Picture 13). The delivery tube   consists of 7 cm square rubber tube without internal obstructions that would   cause the seed to bridge across the tube. The box can be mounted on a chisel   plough and the seed delivered behind the tines. The seed delivery mechanisms are   driven by a 12 V electric motor through a variable speed gearbox.

Picture 13
Picture 13

Picture 13 (right). Inside the B&S Industries seed box showing the rotating spring (sweeper) to prevent   the seed bridging, the auger and paddle to deliver the seed to the metering box   and the pegs on the cylinder of the seed metering device. The number of blades   on the paddle was varied between two and four in different tests of this seed   box. (Photograph R. Whalley)

While this machine was able to reliably sow M. stipoides seed   without clogging up, the results were unsatisfactory because of uneven   distribution of the seed within the drill rows. Various modifications were   tried, but even distribution of seeds could not be achieved. However, it will   sow an even row of seeds of many other species.

The 'Ausbox' is an all-purpose seed box that was built and manufactured by   Richard Murphy, 'Wollondilly', Coonabarabran, NSW. It is especially designed to   handle a wide range of slick and chaffy seeds. This box consists of a rotating   spirally fluted roller that meters the seed into delivery tubes below the   roller. This is an extremely simple but effective mechanism and the size of the   flutes can be modified for boxes designed for different species (Picture 14).

Picture 14
Picture 14

Picture 14 (right). Inside   the Ausbox showing the fluted roller that delivers seed to an air seeder.   (Photographer R. Whalley)

The Wiedemann/Kelly seed box (Figure 3) was designed to specifically deliver   extremely chaffy seed at a consistent rate. The semi-circular seed box contains   an auger agitator to keep the seed 'tumbling' and a pillar to maintain even   'density of seed' around a pickerwheel that drags the seed out of the box. This   box has also been adapted to sow single rows of seed of Danthonia, Dichanthium, Themeda, Microlaena and Bothriochloa (Picture 15).

Figure 3 (below). The Wiedemann/Kelly   pickerwheel seed box which meters fluffy seeds more evenly than conventional   drum seeders.

Figure 3
Figure 3

Picture 15. The   Wiedemann/Kelly seed box adapted to sow single rows of native grasses, ideal   for sowing seed production areas. (Photograph I. Cole)

Picture 15
Picture 15

Crocodile seeder

The crocodile seeder originated in Queensland and has been successfully used   to sow rough, unprepared sites. It consists of a steel drum with 'shovels'   welded to the round surface (Picture 16 and Picture 17). When the drum is pulled   on an angle, the shovels scoop out a divot of soil leaving a pitted surface with   many small dams to trap and concentrate water. The steel drum is filled with   seed, which falls through holes behind each shovel as it rotates, placing some   seeds in each divot. The size of the divots is governed by the towing angle of   the drum. It is a very robust machine and when pulled by a heavy 4WD or tractor   can be used through light timber.

Picture 16. The   'Crocodile' seeder can be towed behind a 4WD vehicle, comprising a one pass   seeding operation creating a water harvesting pit into which seed is placed.   (Photograph C. Waters)

Picture 16
Picture 16

Picture 17. T.   triandra successfully germinating in pits created by the 'Crocodile'   seeder. (Photograph C. Waters)

Picture 17
Picture 17

Other seeders

Additional ingenious devices for metering fluffy seeds are either available   commercially or have been devised and built. These include rotating brushes to   deliver seeds through suitable-sized holes in a plate, or belt seeders where the   seeds are laid out by hand onto a V-shaped belt which rotates slowly over   rollers, dropping the seeds into a furrow or onto the ground.

Sowing seeds of native grasses in drill rows is appropriate for the   establishment of stands for seed production (see Section 6) but is not   necessary for many purposes, such as for re-vegetation following mining. Many   such situations involve sowing in areas where the substrate includes numerous   rocks and stones and drilling equipment is easily damaged. A far better approach   under these circumstances is to broadcast the seed and either cover lightly   using chains or harrows, or simply rely on the ancillary structures to ensure   that at least some seeds end up in safe sites. Seed broadcasting can be done   using the seed boxes described above with the seed delivery tubes swinging free   to broadcast the seed or using equipment specifically designed for the purpose.

A hydro/pneumatic seeder has been developed by John Stafford (Vegetation   Management Services, Lenswood, South Australia). This machine attempts to reduce   the weed problems associated with broadcasting seed by adopting the principles   of row-crop management. This machine consists of three major components. A pilot   spray enabling initial marking of strips, the seed drill which sows seed in a   liquid polymer suspension, and a mid-row sprayer which allows inter-row weed   control (Picture 18).

Picture 18 (right). The   hydro/pneumatic seeder sowing Chloris truncata seed into open cuts made   in the fallow strips that were created and maintained by a previous application   of gylphosate. (Photograph J. Stafford)

Picture 18
Picture 18

Seed blowers

Two seeders designed and built by NSW Agriculture, have been developed to   provide low cost seeding equipment, which can easily be built in a farm   workshop. The 'cranny seeder' (Picture 19) is designed to place seed in suitable   micro-sites in the landscape. Placing seed into log mounds or fallen timber has   been used as a successful establishment technique in low rainfall areas. These   sites concentrate nutrients and moisture and protect new seedlings from drying   out and stock grazing. The Cranny seeder is mounted on a 4WD vehicle and seed is   blown through a hand-held wand into suitable micro-sites while driving through a   paddock. A second seeder, the 'dribble seeder' (Picture 20) is designed to   spread a small amount of seed over a large area. It is mounted on a 4WD vehicle   or ATV and delivers a slow trickle of seed in front of a tyre as it travels   through a paddock. The dribble seeder could be used when travelling through a   paddock to muster or check stock, so would not be an extra job for a landholder.   The effectiveness of these techniques has not been tested, but they are more   likely to work in moist conditions.

Picture 19. The NSW   Agriculture 'cranny seeder' blows seed into suitable micro-sites like log mounds   to assist establishment and causes no soil disturbance. (Photograph C. Waters)

Picture 19
Picture 19

Picture 20. The NSW   Agriculture 'dribble seeder' can be mounted on an ATV to sow seed over a large   area while doing other jobs. This picture shows the paddle auger that slowly   dribbles the seed. This technique has not yet been evaluated, however it is   expected to be most successful under moist soil conditions. (Photograph C.   Waters)

Picture 20
Picture 20

Air seeders

Gil Fletcher of Land Reclamation Services Pty Ltd in Emerald, Queensland, has   designed and built an air seeder which will broadcast fluffy or awned native   grass seeds without bridging or clogging (Picture 21). Essentially, this   equipment consists of a conical hopper with a metering valve at the bottom   comprising a disc on top of an open tube through which a suction is created   using a sawdust extraction fan. Various stirring arms prevent the seed from   bridging within the hopper. The seed-air mixture is then delivered through   flexible hoses to a boom with three or four outlets so that the seed is   delivered behind the machine. An additional hopper and more conventional seed   metering device can be attached to deliver smooth seeds such as those of shrubs   or trees, into the air stream. This equipment will also handle grass material   containing a large quantity of straw provided it has been passed through a chaff   cutter.

Picture 21. Air   seeder designed and built by Gil Fletcher of Land Reclamation Services, Emerald,   QLD. The petrol motor powers a sawdust extractor fan and a stirring disk and   valve powered by a 12 V motor meter the seed from the bottom of the large hopper   into the air stream. The smaller hopper on the right has a more conventional   seed metering device, also powered by a 12 V electric motor to deliver smooth   seed into the air stream. (Photograph D. Munnich)

Picture 21
Picture 21

Another seeder that is suitable for cleared land has been built by Rosedale   Engineering at Gulgong. The 'Germinator' uses components from broad-acre farming   machinery and is designed to cultivate the seeding row, place the seed close to   the surface and cover it with a press wheel. The seed is metered from an   'Ausbox' seed box and delivered to the tines with an air system. The Germinator   has worked quite successfully, although some problems with seed blockages have   occurred. Modifications have been made to the seeder by NSW Agriculture and DLWC   which have improved its performance (Picture 22).

Picture 22. The   'Germinator', built by Rosedale Engineering at Gulgong, is a modified air seeder   designed to direct drill native grass seed. The 'Ausbox' employs a fluted roller   as an effective seed metering device. The air seeder system distributes the seed   with minimal blockages and surface sowing boots place the seed at or very near   the soil surface. (Photograph C. Waters)

Picture 22
Picture 22

Hydromulching

Hydromulching involves putting seed, dye coloured wood pulp and perhaps some   fertiliser into a water-filled tank and spraying the agitated mixture on top of   the soil via a 50 mm diameter hose. Ideally, the mulch should be about 20 mm   thick on the soil surface to provide a stable surface for seed germination and   provide some control of the germination of small seeded weeds beneath it. The   agitation of the cellulose fibre in the tank and the large diameter delivery   tube mean that virtually any native grass seed can be evenly sown using this   equipment (Picture 23).

Picture 23
Picture 23

Picture 23 (above). Hydromulched area beside the   Armidale Bypass eight days after treatment. Note the sparse cover of the mulch   and the M. stipoides seeds. (Photograph R. Whalley)

Use of other mulches

Satisfactory emergence can be obtained by covering surface sown seed with a   variety of mulches where a high-density stand is required. Mulch depths of about   20 mm are satisfactory for friable mulches, which do not impede the seedling   emergence for relatively large seeded species such as M. stipoides.   Thinner layers of mulch should be used for smaller seeded species.

The most satisfactory mulches appear to be mulched eucalypt, sheep manure or   wood pulp as used in a hydromulcher. Because M. stipoides is more   abundant on acid soils, mulches which tend to make the soil more acid are likely   to give it and similar species a competitive advantage over weeds.

Forage harvesting and spreading

Harvesting the whole plant using either hand labour or a forage harvester   when most of the seed is ripe and immediately spreading the harvested material   on the site to be sown is a technique which has been found to be successful for   some species, particularly T. triandra. A slightly different technique   is to harvest groups of spikelets (Spikelet - Consists of one or more florets and is the basic unit of the inflorescence in grasses) of T. triandra using a suitably adjusted brush harvester and spread   them directly on to the soil surface. This approach has been used successfully   to replace serrated tussock (Nassella trichotoma) on the St. Albans   campus of the Victorian University of Technology.

The procedure as used by the Native Grass Resources Group Inc. in South   Australia, involves harvesting the whole T. triandra plants when the   black awns of the fertile spikelets become apparent in December or January. The   harvested material is immediately spread on the area to be planted and left for   the next nine months. During this time, the dispersal units fall and the hygroscopically (Hygroscopic - Responds (twists or opens) to moisture changes) active awns (Awn - An elongated bristle-like appendage attached to the apex, back or base of the glume, lemma or palea) position the fertile spikelets in suitable microsites at or below the soil   surface. In the following September/October, spraying with a herbicide of the   triazine group kills all the perennial or annual weed growth. After this weed   growth has dried, it is burnt to expose a bare, moist, undisturbed soil. A rise   in soil temperature to about 25°C will stimulate the T. triandra germination within seven to ten days.

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