Weeds and Soil Health

 Rather than talk about a specific weed I thought it would be worthwhile to explore the underlying cause for weed establishment in pastures- unhealthy soils. Soil science is a complex subject and I'm more of a novice than an expert in the field yet what I'm learning through working as a Landcare Officer is the fundamental role soil health has in farming systems-particularly its role in supporting or suppressing undesirable plants, a.k.a weeds, therefore it's a topic I cant ignore and nor would I want to.  It's commonly believed that healthy soils support weeds and desirable pasture species equally well.  However it's quite the contrary, in the same way that an insect infestation indicates unhealthy plants with a nutritional imbalance, a weed infestation indicates that something's not right with the soil which in turn suppresses the growth of high producing pasture species and provides an environment favoured by weeds (Shepherd G. 2009).

 

In determining what's not right with the soil its physical, chemical and biological components need to be properly assessed.  If thistles are your annoyance, a soil assessment may discover that the soil is deficient in the trace element Calcium and bacteria and high in Potassium and Sulphur-a profile typical of supporting thistles. An infestation of thistles would suggest soil conditions and fertility, (status of soil with respect to the amount and availability of elements to plants necessary for plant growth i.e. calcium, magnesium, potassium and sodium) are inadequate to maintain a complete, vigorous pasture cover. Competitive suppression by vigorous pasture growth plays a major role in preventing weed establishment. Once the underlying soil deficiency is known appropriate action can be taken i.e. the application of liquid calcium incorporating a form of organic carbon along with the addition of fertiliser with the right trace elements to help alter the soil environment in such a way that weeds don't want to grow.

 

Changing the soil environment can successfully deal with any weed problem and provides for a more effective long term solution than the use of herbicides. However when faced with the initial problem of weeds, the incorporation of herbicides into a solution containing a pH modifier with ammonium humate, can provide good weed control. A mixture such as this enables the amount of herbicide used to be reduced by 25-35%, helping to buffer the effect of herbicide on soil life. Regular use of herbicides has a negative impact on soil microbes which are responsible for maintaining the nutrient balance and availability in the soil. The underlying message of this article is that whilst using chemical herbicides provides a quick-kill it only addresses the symptoms and does nothing to rectify the underlying cause.

 

LOCAL TRAINING IN SOIL HEALTH:

As part of the Targeted Land Stewardship program, the South Gippsland and Bass Coast Landcare Networks are running a series of courses on soil health in 2011. Two courses, Vital Soils 1 and Healthy Soils, Sustainable Farms are afforded to cater for primary producers and hobby farmers alike. Vital Soils 1, delivered by Sonia Lee is a 4 day training course delivered in the classroom and the field teaching an integrated, regenerative approach to soil management (Poowong July 2011). Healthy Soil, Sustainable Farms, delivered by Chris Alenson is a 3 day training course looking at soil health and fertility (Bunyip June 2011). To find out more or to RSVP (essential) please contact project officer Kathleen Bartlett on 5662 5759 or email kathleenb@wgcma.vi.gov.au

REFERENCES AND ADDITIONAL RESOURCES:

Baxter, M.N.  2001. Know Your Soils Agriculture Victoria- Bendigo. Centre for Land Protection Research. Part 1, 2 and 3.

Shepherd, T.G. 2009. Visual Soil Assessment. Volume 1. Field guide for pastoral grazing and cropping on flat to rolling country. Second edition. Horizons Regional Council, Palmerston North. 119p

 

INTERNET RESOURCES:

Target 10 online www.target10.com.au. Follow the prompts to Manuals, Soils and Fertilisers.

The Department of Primary Industries www.new.dpi.vic.gov.au. Type Soil Fertility into the search bar and follow the link.

 

Agapanthus- time to remove seed heads

Agapanthus- you great us in summer with your friendly ball shaped flowers, you don't need much attention or care you just grow and grow. Come mid summer your flowers start to fade and your once attractive features are replaced with dull looking seed heads. Then you persevere throughout autumn and into winter with your long strappy leaves unscathed by drought or light frosts only to shoot up yet another blue pom pom come next summer.

If you enjoy the sight of agapanthus in flower lining the driveway or the low maintenance function that they provide then that's fair enough (I know I do!). However there are things to consider when it comes to this plants ability to readily spread. Each agapanthus plant is able to produce 2,400 seeds on average- these are then spread by water, wind or dumped garden waste. Aside from seed production, the primary method of spread in Victoria is vegetative means i.e. they multiply by themselves in clumps. A plant with such qualities, (in many cases and for obvious reasons) has the tendency to wonder beyond the drive way.

To avoid the problem of unwanted spread there are a couple of things that can be done. Firstly- to avoid the problem of seeds spreading, (whilst still be able to enjoying the plant in full bloom) cut off the seed heads once the plant has finished flowering (roughly now!). Secondly-plants in unwanted areas can be dug out, keeping in mind that all the underground roots (rhizomes) must be removed and disposed of appropriately. Any rhizomes left in the ground will regrow- even plants left lying upside down on the surface may take root and regrow, therefore correct disposal is important. The root system is fairly shallow meaning that plants can be peeled over and up-ended with less effort than one might expect.

If left uncontrolled in natural ecosystems- such as woodlands or grassy woodlands, agapanthus will become established and outcompete native vegetation forming a dense monoculture. Action on your property helps to keep our natural areas free from weed threat so that they can be enjoyed by all. So while the sun shining-now is the perfect time to get out in the garden- remove those seed heads and do your bit for the environment!

 

Kate

Yellow-flowering herbaceous plants; Senecios The Good and the Bad

Senecio species are possibly the largest genus of flowering plants with roughly 1500 species, of which approximately 50 are native to Australia (Richardson et al 2007).  A well known specie of Senecio in South Gippsland is Ragwort (Senecio jacobaea). Senecios are distinguished by having yellow flowers and alternately rranged leaves that often have stem-clasping ear-shaped lobes at their bases. Known to colonise disturbed areas and germinate quickly following bush-fires, Senecios are pioneering plants. In the scheme of a plant community, Senecios are understory plants with some species becoming invasive under ideal conditions. 

With so many types of Senecio, correct identification can be difficult. Provided you have a sample of parts of the plant; leaves, flowers etc. below can be used as a guide to at least identify the 'bad' from the 'good'.

The Bad guys

Number of introduced species of Senecio in Victoria? There are roughly 5 exotic/introduced species of Senecio in Victoria.

What are some of the ones that are found/could be found in South Gippsland?

Ragwort (Senecio jacobaea) is a major pasture weed in South Gippsland. Cattle selectively avoid grazing it so it proliferates. Poisonous to grazing mammals, both fresh and when dried in hay or chaff, ragwort causes liver damage, leading to photosensitisation, jaundice, wasting and sometimes death. 

Fireweed (Senecio madagascariensis). There are *no recorded infestations of Fireweed in the South Gippsland region, (*at the time of publication) however the growing conditions are suitable for a potential outbreak. Fireweed, like ragwort, is toxic to stock and has the potential to out compete desirable pasture grasses.  This plant is a Victorian Weed Alert Weed see Department of Primary Industries Weed Alert Fact Sheet; Fireweed (Senecio madagascariensis)

African daisy (Senecio pterophorus). Found in the Port Phillip region, African daisy as with ragwort and fireweed can cause heavy losses in agricultural productivity (being toxic to stock, avoided by cattle and costly to control).  African daisy grows in a variety of situations from well-drained hillsides to semi-waterlogged gullies making it a threat to near by West Gippsland. For identification and control see the Landcare Note; African daisy (Senecio pterophorus)

 

The Good guys

Number of Senecio species native to Victoria? 50, (too many to mention!) 16 of these species can be found in the Melbourne area alone (Gray et al 2006).

What are some of the common natives found/could be found in South Gippsland?

Firewheel groundsel (Senecio linearifolius) can be found in wet and damp forests in higher hills and gullies.  The plant has sharply-toothed, long leaves that are dark green in colour growing to 150mm long (the leaves of ragwort are 35cm long). Flowerheads are small with 5 petals (ragwort has 12-15 petals).

Rough Fireweed (Senecio hispidulus var. hispidulus) can be found in grasslands, dry and valley forests, coastal banksia woodland and tea tree heath. The plant has toothed to –lobed, long to egg shaped leaves growing to 60mm. Image of Rough Fireweed 

Cotton fireweed (Senecio quadridentatus) is the most common and widespread Senecio species, found in riparian scrub, dry and valley forests and tea-tree heath.  The plant has narrow, pointed leaves to 100mm long, becoming smaller up the stem.  

 

If the above doesn't get you to a clear point of identification, (this is likely-considering there are so many species!) then there's some great reference material to help you discover exactly which Senecio you're dealing with. See below for details.

 

References  

Introduced Senecio information;

Richardson F.J., Richardson R.G. and Shepherd R.C.H. (2007). Weeds of the South-East an Identification Guide for Australia. R.G and F.J, Victoria

 

Native Senecio information;

Australian Plant Society Maroondah (2001). Flora of Melbourne. 3^RD Edition.  Hyland House, Melbourne

 

Kate

Holly (Ilex aquifolium); a Naughty not Nice bush invader

With its glossy dark green leaves and scarlet red berries its no wonder European culture has long associated holly with Christmas time. Native to Europe, holly was introduced to Australia for ornamental use (Muyt 2001) and has now become a familiar foe in areas with cool, moist climates- including southern Victoria and Tasmania among other places.

 

Holly prefers fertile, deep, friable, moist and well drained soils- like those found within the Strzelecki Ranges. Plants are typically dormant in cooler areas over winter however they may continue to grow during mild winters and in warmer locations. Small white flowers are produced in late spring to early summer with red fruit developing over autumn- winter on female plants. On any given plant, some leaves have sharp triangular spines along the leaf edge while others are spineless.

 

The plant is of primary concern due to its impact on recreation and native vegetation. Holly forms dense thickets, (if left uncontrolled) restricting access to people and vehicles in remote areas or along poorly maintained tracks. The berries and leaves of holly are toxic to people, especially children. Reported symptoms include nausea, vomiting, diarrhoea, collapsing and unconsciousness (the fruit is not considered fatal) (Sheperd 2004). In a damp or wet forest environment, those areas once occupied by tall native shrubs will become dominated by holly creating a poor shrub layer. In turn impacting upon the lower layers of vegetation i.e. herbs and ground cover plants and preventing natural regeneration. Another feature which puts this plant on the naughty not nice list is that it provides a food source and shelter for pest animals. The berries are to some extent eaten by foxes (Garcia, Martines & Obeso 2007) as well as browsed by goats and deer (Obeso 1997).

 

To control holly seedlings and plants less than 1 metre tall can be dug out. Tops are prone to break away when pulled so if roots remain they should be dug out. All removed material should be disposed of appropriately, Larger plants can be controlled using the cut and paint or drill and fill methods. If using herbicide, treat the plant in spring- early summer when the plants are actively growing. Priority for initial treatment should be given to fruit-bearing female plants. For further information on the identification or control of holly please contact Kate Williams, South Gippsland Landcare Network Project Officer on (03) 5662 5759 or email katew@wgcma.vic.gov.au.

 

Kate