Construcción de Categorías desde la Guía 34

N. trichotoma biomass was reduced on trial plots in early summer (January), prior to thatching by slashing the sward to 80 mm length. This was followed by herbicide control of regrowth using glyphosate or atrazine at label

recommended dilutions, applied at 770 ml/m-2

in autumn or winter. Note: Subsequent monitoring in 1997 of the year 3 trial plots established in 1995-96 suggest that the late autumn (May) herbicide application and associated treatment accession dates (thatching in July and thatch removal in October) make up the optimum treatment process (C. Hocking 1997, pers. comm.).

Seed content and germinability

Laboratory-based assessment of seed content and germinability revealed a

dormancy operating on T. triandra seed germination. The assessments showed

an increase over time of both available (free) seed, and germination rates. Data from laboratory-based assessment of seed was used to determine rates of germinability occurring in the field. It was revealed that conversion into seedlings in the field were averaging a rate of 15% of the available germinable seed being applied to plots. Data from these trials also showed variation of seed availability and germinability from hay within, and between sites.

Optimum T. Triandra establishment and thatch rates

Both the 1994 - 95 and 1995 - 96 trials which showed establishment rates of 30 to 40 T. triandra plants m-2

provided the optimum seedling densities. In order to achieve 30.0 plants m-2, and using a modifier of 15% conversion into seedlings in the field of germinable seed (see above) a minimum of 200 available germinable seeds m-2

should be applied in seed-bearing thatch.

Thatching and thatch removal

The seed content of hay was used to select which wool bales of hay were used on the 1995 - 96 trials. Homogenising the hay used was critical in equalising seed content across all thatch treatments. This is proposed as necessary in any

patchiness in seedling establishment (too many seedlings in some areas and not enough in others). Either burn or manual removal of hay in late spring or early summer produced satisfactory (>30 plants m-2

) rates of T. triandra establishment.

6.2 Transferability of results

The work reported in this thesis has resulted in techniques for removing N.

trichotoma from T. triandra-dominated grassland remnants and replacing this with T. triandra at St Albans, Victoria. The consistency of results over the three years of research suggest that the methods are reliable in the context of the site and conditions of this research. Caution is urged in the appropriation of the findings of this research to other sites and other target weed species. It is proposed that the methodology produced by this research be assessed and modified as required before use on other sites and other target species.

6.3 Setting up trials as a first step to management

This research has produced an effective method for replacing N. trichotoma with

T. triandra on western basalt soils on a site sixteen kilometres north-west of Melbourne. It is proposed this methodology could be used as a basis for further development of methods for:

1. The management of N. trichotoma, a noxious weed of south-east Australia on

non-ploughable or marginal farmland, roadsides, rail corridors, firebreaks and other related land,

2. The conservation management of remnant T. triandra- dominated western

basalt plains grassland.

However, before this management tool can be applied with any confidence in the predictability of results further site specific trialing of the methodology should be carried out. It is recommended the following four treatment regimes be trialed before selecting methods for broad-scale site treatment (Tables 4, 5, 6, and 7).

Table 4

Treatment 1

• January Slashtarget N. trichotoma weed sward • At the optimum time prior to full seed

dehiscence (generally mid - late summer)

Harvest and securely store seed-bearing T. triandra hay • February Treat N. trichotoma regrowth with atrazine

• March - April Assess seed availability/germinability in T. triandra hay (see 3. Harvesting and assessing Themeda triandra seed-bearing hay for revegetation)

• May Apply seed-bearing T. triandra thatch with appropriate volume to achieve = 30 plants/m-2_{. Adjust thatch volume to provide highest possibility of} achieving =30.0 T. triandra plants/m-2 _{(see T. triandra germination rates} in the field, in 5.4.5 Field germination rates)

• July Burn removal of thatch

Table 5

Treatment 2

TIME ACTION

• January Slashtarget N. trichotoma weed sward • At the optimum time prior to full seed

dehiscence (generally mid - late summer)

Harvest and securely store seed-bearing T. triandra hay • July Treat N. trichotoma regrowth with atrazine

• August - September Assess seed availability/germinability in T. triandra hay (see 3. Harvesting and assessing Themeda triandra seed-bearing hay for revegetation)

• October Apply seed-bearing T. triandra thatch at appropriate volume to achieve =30 plants m-2_{. Adjust thatch volume to provide highest possibility of} achieving =30.0 T. triandra plants m-2 _{(see T. triandra germination rates} in the field, in 5.4.5 Field germination rates)

• December Manually remove thatch

Table 6

Treatment 3

TIME ACTION

• January Slashtarget N. trichotoma weed sward • At the optimum time prior to full seed

dehiscence (generally mid - late summer)

Harvest and securely store seed-bearing T. triandra hay • July Treat N. trichotoma regrowth with atrazine

• August - September Assess seed availability/germinability in T. triandra hay (see 3. Harvesting and assessing Themeda triandra seed-bearing hay for revegetation)

• October Apply seed-bearing T. triandra thatch with appropriate volume to achieve =30 plants m-2_{. Adjust thatch volume to provide highest possibility of} achieving =30.0 T. triandra plants m-2 _{(see T. triandra germination rates} in the field, in 5.4.5 Field germination rates)

Table 7

Treatment 4

TIME ACTION

• January Slashtarget N. trichotoma weed sward • At the optimum time prior to full seed

dehiscence (generally mid - late summer)

Harvest and securely store seed-bearing T. triandra hay • May Treat N. trichotoma regrowth with glyphosate

• May - June Assess seed availability/germinability in T. triandra hay (see 3. Harvesting and assessing Themeda triandra seed-bearing hay for revegetation)

• July Apply seed-bearing T. triandra thatch with appropriate volume to achieve =30 plants m-2_{. Adjust thatch volume to provide highest possibility of} achieving =30.0 T. triandra plants m-2 _{(see T. triandra germination rates} in the field, in 5.4.5 Field germination rates)

• October Burn removal of thatch

Trial structure

The following procedures are recommended when establishing field trials:

• A block area is recommended to be established at the trial site with

randomised sets of quadrats established within the block,

• Quadrats should be a minimum area of 1.0 m-2 with a perimeter buffer zone

external to each quadrat to minimise ‘edge effect’ biases,

• Each treatment plus control should have a minimum of six replicates,

• If possible data should be collected at monthly accessions, or at a minimum

of two-monthly accessions for at least twelve months after final treatments,

• Data collected is recommended to be simply a recording of the species and

their number present at each accession. Plants should not be removed, and should be recounted if still present at each assessment time. This should provide data regarding fluctuations in species present and their numbers over time.