Deferred grazing improves soft spinifex association

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Journal of the Department of Agriculture, Journal of the Department of Agriculture, Western Australia, Series 4 Western Australia, Series 4

Volume 10

Number 11 November, 1969 Article 8

1-1-1969

Deferred grazing improves soft spinifex association Deferred grazing improves soft spinifex association

H Suijdendorp

Follow this and additional works at: https://library.dpird.wa.gov.au/journal_agriculture4

Part of the Agronomy and Crop Sciences Commons, Plant Pathology Commons, and the Sheep and Goat Science Commons

Recommended Citation Recommended Citation

Suijdendorp, H (1969) "Deferred grazing improves soft spinifex association," Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 10: No. 11, Article 8.

Available at: https://library.dpird.wa.gov.au/journal_agriculture4/vol10/iss11/8

This article is brought to you for free and open access by the Agriculture at Digital Library. It has been accepted for inclusion in Journal of the Department of Agriculture, Western Australia, Series 4 by an authorized administrator of Digital Library. For more information, please contact [email protected].

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RESULTS FROM //

RECENT RESEA RCH // « technical report

DEFERRED GRAZING IMPROVES SOFT SPINIFEX ASSOCIATION

By H. Suijdendorp

T H E Pastoral region in Western Australia where T r i o d i a pungens (soft spinifex) makes up most of t h e vegetation, covers an area of about 1 7 , 0 0 0 square miles in the Forrest and De Grey pastoral areas.

O n the deeper granitic sands in much of the region, plant associ- ations revert to a pure stand of soft spinifex after about five or six years' grazing. It is common practice to burn at this stage, to encourage the re-establishment of other species and the production of palatable spinifex regrowth.

Winter burns near the coast do not kill mature spinifex. As a result, although spinifex regrowth is encouraged, other

species do not become estab- lished. Summer fires however kill the mature spinifex tus- socks and allow the appearance of other species such as Chry- sopogon latifolius (weeping grass), Neurachne clementii,

Eragrostis eriopoda (woolly butt) and Eriachne dbtusa.

With continuous grazing during the growing season the more palatable and nutritious species are reduced in vigour and cannot compete with soft spinifex. The result is that spinifex again becomes dominant after a few years.

The study reported here examined a method of pre- venting spinifex domination by combining deferred grazing management with summer burning.

Method

Stock and management In November, 1953, a 24-acre spinifex site on Abydos Re- search Station was vermin fenced and subdivided into two 12-acre paddocks. One of these paddocks was further subdivided into 12 one-acre paddocks. Between 1953 and 1956

L e f t — c o n t i n u o u s l y grazed t r e a t m e n t showing spinifex as d o m i n a n t plant.

R i g h t — d e f e r r e d g r a z i n g t r e a t m e n t w i t h woolly b u t t as main species 487

the 12-acre paddock was continually grazed by four sheep while another four sheep were used to rotationally graze the one-acre paddocks. Sheep in the rotationally grazed treatment were shifted each fort- night.

At the end of 1956 the stock- ing rate in each treatment was reduced to one sheep per four acres but the grazing management remained the same.

Burning and management Each November an area of about two acres was burnt on both the continuously grazed and rotationally grazed treat- ments. Sheep on the rotationally grazed treatment were then excluded from burnt paddocks until seedling establishment after the summer rains. Sheep on the continuously grazed treatment had access to the burnt area at all times.

Results

At the beginning of the study both treatment areas were covered by a closed community of soft spinifex and had not been grazed by anything but kangaroos since 1945.

The results for burnt areas on the continually grazed treatment (Figure 1) indicate that re-vegetation by non- spinifex species was limited.

Palatable perennials a n d annuals did not survive for long after germination and were replaced by unpalatable species such as Cassia notabilis (cockroach bush). As a result ground cover on the continuously grazed treatment diminished annually. In very good seasons a flush of annuals on some areas allowed the

Journal of Agriculture, Vol 10 No 11, 1969

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sheep to produce some wool but in light seasons forage production was low.

On the rotationally grazed treatment, deferring grazing on the burnt plots allowed grasses other than soft spinifex to show a gradual increase over successive burning cycles.

Unexpectedly, after the third fire, grasses such as Eragrostis and Aristida species increased so rapidly that the soft spinifex was kept at a low density.

In 1967, the total ground cover was 47.8 per cent. (Figure 2), higher than at any time during the study. The photo compares this ground cover with that of a continuously grazed area.

Discussion

The results indicate that soft spinifex is unlikely to regain dominance when a deferred grazing system is associated with summer burning. The resulting change in plant as- sociations is towards grasses which produce a large quantity of nutritious forage during the wet season. However, such vegetation will not support sheep during the long dry periods. During the dry the sheep will need to be moved to spinifex paddocks for grazing.

On some stations (e.g., Boo- darie station in a 100 sq. mile paddock) the suppression of soft spinifex as the dominant species has been achieved on deeper soils after the second fire.

It appears that soft spinifex is the climax community only on shallow soils associated with granitic outcrops and granitic hills. On deeper soils it may be simply an invader which can be controlled by deferred grazing in association with November burning.

• SOFT S P I N I F E X A OTHER SPECIES

5 8 | 5 9 FIRE

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1954 55 56 57

Figure 1.—Effect of continuous grazing on a soft spinifex association l 1 r 61 62 63164 65 66 67

FIRE

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•SOFT SPINIFEX AOTHER SPECIES

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1954 55 56 57 58 I 59 60 61 62 63 '64 65 66 67 FIRE FIRE Figure 2.—Effect of deferred grazing on a soft spinifex association The increase in " other species " in the last cycle was due to the appearance of Psoralia spp. These were unpalatable on first appearance but were eventually severely grazed.

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