Broadleaf Dock

A recent visit to a farm, (that rears dairy calves) in South Gippsland has prompted me to talk about dock. Several paddocks on the farm were thick with broadleaf dock (Rumex obtusifolius), whilst out on a paddock the farmer asked "why is it growing with such vigour?" and "How can I get it under control without relying on herbicide?"

 

To address the first question one needs to try and understand what that plant is telling us. Docks are a perennial herb with a thick taproot. Plants with taproots are typically found in areas of poor drainage- the plant is trying to correct this problem by penetrating deep into the subsoil to improve drainage and aeration. Why might drainage be poor you ask- In pastures, calcium is a mineral removed in great quantities with the least return in the manure. Calcium is the element which, among other things, causes soil particles to move apart for good aeration and drainage. Soils deficient in calcium are in effect prone to water logging. Therefore even before doing a soil assessment or test we can assume that calcium may be deficient and that drainage is poor. High stocking rates may be another factor for compaction and subsequent poor drainage however the farmer indicated that stocking rates were fairly low and that they haven't even been stocked recently given the amount of water on the place.

Delving deeper, (quite literally!) a soil core sample was taken so that a quick visual assessment of the soils biotic and physical qualities could be made. It was obvious from the sample taken that the soil lacked diversity of microfauna with only earth worms present. A cockchafer grub was also found in the sample. Cockchafers are common pasture pests in Gippsland, affecting shallow rooted pasture species, having minimal impact on deep-rooted plants such as lucerne, cocksfoot, phalaris and dock for that matter. The extent and severity of damage caused by cockchafers varies markedly from year to year and from one property to the next. The main indicators of their presence can be found during a dry spell after the autumn break, when dead pasture is found among areas of green. Dead pasture, unless re-sowed, provides a perfect home for a new dock plant or another broadleaf plant such as capeweed. Perhaps this is another factor contributing to the growth of dock throughout the paddock. Looking at the grass in the sample, (namely the roots) it's clear that they are confined to the top few cm's of soil- yet another indicator that oxygen is poor lower down.

Following the visual assessment a *soil test was taken for chemical analysis. Results of the test found that, as suspected, the available calcium was slightly low. It also revealed that the available potash exceeded the available phosphate- this is characteristic of soil favoured by broadleaf weeds. Available nitrogen was low, (6.1ppm, desired level=26ppm). Nitrogen is the one nutrient that can be hard to manage as it's readily lost through leaching. Soil bacteria play a critical role in converting the nitrogen into amino acids- in this form it is not likely to leach.  The soil test didn't test for the present of soil bacteria yet if it did there would be affair chance they would be in insufficient numbers.

With all the above in mind – finding an answer to the second question can seem overwhelming! I'm not an agronomist- and I don't intent to give specific advice as such- rather I've put together a list of useful resources below that can help you build a picture of ways to correct your specific weed problems.

Remember- you can spray pasture weeds with herbicide until the cows come home yet correcting the health of the soil should be the aim of the game.

McCaman J.L. 1994. Weeds and Why They Grow. Acres Australia www.acresaustralia.com.au

 Department of Primary Industries, Victoria information on soil relevant to agriculture; http://new.dpi.vic.gov.au/agriculture/farming-management/soil-water

Department of Primary Industries, Victoria information on the Red headed cockchafer

http://new.dpi.vic.gov.au/agriculture/pests-diseases-and-weeds/pest-insects/ag1358-the-redheaded-pasture-cockchafer

Primary Industries, NSW information on fertilisers and soil improvement http://www.dpi.nsw.gov.au/agriculture/resources/soils/improvement

*It should be said that a plant tissue test is the preferred method for diagnosing trace element status of a pasture rather than a soil test but for the purposes of this exercise a soil test was taken.

Bridal Creeper: Be part of a program to reduce its spread!

Bridal creeper (Asparagus asparagoides) is a perennial climber growing to 3m tall with a tuberous root system growing rapidly in autumn/winter (NOW) dying back to the roots over summer.  The glossy leaves are a distinct bright green colour and 3cm long. Flowers are small and greenish to white hanging on stalks singly or in pairs along branchlets. Fruits are small red berries, 6-10 mm in diameter with up to 9 black, shiny seeds within when ripe.  Bridal creeper is a Weed of National Significance as it readily invades disturbed and undisturbed vegetation across a wide range of habitats.

Left uncontrolled, it can have significant impacts to natural ecosystems. The plant can dominate ground flora forming dense curtains that smother shrubs and the lower canopy of trees. Bridal creeper is not considered an agricultural weed as it is palatable to stock and reproduction is greatly inhibited by herbivores. Bridal creeper has a number of features which make it difficult to control – its tuber reserves provide a buffer against adverse seasons, it has a wide germination range and, as mentioned above, it can invade undisturbed areas. On the up side - bridal creeper has a short-lived seedbank and seed production only occurs in early emerging stems.

With this in mind, preventing invasion in the first place and being vigilant in controlling new outbreaks really is the best line of defence. Typically new outbreaks occur underneath tall trees where seeds have been spread by birds, monitor these areas for potential outbreaks. All underground tubers need to be removed in order for manual removal to be fully effective. Tubers can grow at some depth under the soil therefore using a small mattock to get leverage is the best way to go.  All removed material should be double bagged and disposed of appropriately.  Removed tubers have been shown to survive even with out light for 2 years- therefore correct disposal is important.

If you have noticed Bridal creeper on your property, please contact Kate Williams, Landcare Project Officer at the South Gippsland Landcare Network on (03) 5662 5759 or email katew@wgcma.vic.gov.au.  The Network is managing a control project along the Gippsland coast from Phillip Island to Port Albert, (where it is known to exist) in partnership with a range of stakeholders and financial assistance is available until July this year. This project is supported by Coastcare Victoria Community Grants- a joint program delivered in partnership between the Australian Government's Caring for Our Country and the Department of Sustainability and Environments Coast Action/Coastcare program.

FREE Field Days on Alternatives to Chemical Control April 19th & 21st

FREE Field Days on Alternatives to Chemical Control April 19^th & 21^st

The rising cost of chemicals combined with uncertainty about safety and a desire to manage land in a more sustainable way prompts many people to consider alternatives to herbicide. Depending on the situation though, for any type of weed control it is usually a combination of controls that will be the most efficient way to deal with the problem. A good example is Gorse control where large infestations are mechanically mulched and the resultant regrowth is treated by chemicals and any new seedlings can be removed by hand over time. Mechanical control, being the most obvious method of non-chemical weed control, is not covered in this article. Some of the alternatives and a brief description of each method are described below.

 

Flame weeding. Uses an LP gas fired burner-either a direct flame or infrared burner. Weeds are not 'burnt' but lose the ability to move moisture and carry on photosynthesis causing the plant to wither and die within one to three days. Small plants are more susceptible to heat than more mature growth, therefore flame weeding works best when the weeds are small-typically less than 5cm high. Further info on flame weeders www.gameco.com.au

or www.elgas.com.au/for-business/flame-weeding

Steam weeding. Generally steam weeders require significant energy inputs to heat the water and they can require significant amounts of water. Suitable for Forestry, Fruit & Vegetable growers, Vineyards & similar, Road Authorities Shires and City Councils etc. Further info on steam weeders

www.acaengineering.com.au

BioWeed™ Herbicide. Used in agriculture, horticulture and by municipalities. Spot spraying and selective broad acre spraying of blackberry, gorse, ragwort, patterson's curse, thistles and other invasive weed species. BioWeed™ Herbicide works by desiccation of the cell walls of all contacted plant and seed tissue. On contacting living plant or seed tissue it quickly penetrates and disrupts normal membrane permeability and cellular physiology. Sprayed weed leaf tissue becomes dehydrated, creating a quick, visual browning effect within 1 to 12 hours of application. BioWeed™ Herbicide is a certified organic input. Further info on BioWeed™ Herbicide

www.certifiedorganics.info

To find out more on alternative control, The South Gippsland Community Task Force (CWT) in partnership with the Victorian Blackberry Taskforce is hosting two free sessions focusing on alternative blackberry control. Come along to one of the two days and learn from industry experts and real life examples of how blackberry has and can be controlled using alternative methods such as the BioWeed™ Herbicide. The field days are to be held on Tuesday April 19^th at the Mirboo North Football Club rooms and Thursday April 21^st at the Foster Memorial Arts Centre 10am – 2.00pm (lunch included). Everyone welcome. RSVP essential for catering purposes to South Gippsland Landcare Network (03) 5662 5759 or email

katew@wgcma.vic.gov.au

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.