The conversion of a ten hectare conventional farmlet in northwest Tasmania to a certified organic intensive vegetable production system over a three year period highlighted weeds as the most challenging management issue. The project objectives were to test and evaluate on a commercial scale, organic production protocols for a range of vegetable crops. Weed management issues were addressed through assessment of weed species present and field evaluation of a range of non-herbicide weeding techniques. Detailed organic weed management protocols are presented for onions (Allium cepa L.), carrots (Daucus carota L.), and broad beans (Vicia faba L.) as examples of non-herbicide weed management in vegetable crops. The field study indicated an increased focus on mechanical weed control methods is essential for organic vegetable cropping if time consuming hand weeding operations are to be minimised or eliminated. Field operator experience in the timing and use of equipment such as flame and brush weeders was shown to be an essential requirement for successful weed management.
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In order to ensure the benefits of weed science are realised through the application of on-ground weed management activities, it is important that there is political, public, and legal support for these management activities. As part of an overall strategic approach to weed management in Tasmania, weed scientists extended their role to developing a scientifically sound weed management law to ensure there were legal requirements for integrated and sustainable weed management operations in the State. The Weed Management Act 1999 places a statutory requirement for assessing the weed risk of plants if they are to be declared weeds under the Act. In addition, simply declaring a species as a weed under law is recognised as being insufficient to ensure action is taken against that weed. Therefore, once a plant species is declared a weed, there is a statutory requirement to develop a scientifically sound weed management plan for that species which not only contains details as to exact actions needed against the weeds, and the legal requirements to undertake those actions, it also details responsibilities for undertaking those actions. Further, the laws require regular review of these plans to ensure they are being implemented appropriately. Finally, both declaration and weed management plan preparation processes are subject to extensive consultation with the general public and provides anyone interested with opportunity to participate in the process. Such laws, as part of a government/community joint strategic approach to weed management, not only lead to a ‘weeds-aware’ society, they provide an atmosphere in which advances in weed science and improved weed management capabilities can be fully realised.
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Act 1999
Physical and herbicide treatments of an estuary infestation of Spartina anglica were compared to determine an optimum treatment for medium to long term control of this estuarine weed. Treatment plots (slash/smother, slash, slash/glyphosate/smother, and glyphosate) were compared with a nil treatment in a randomised complete block design with four replicates. Slashing consisted of cutting the grass to ground level; smothering consisted of covering the grass with a black polyethylene cover; glyphosate treatments consisted of applications of 24g ai/L to the plants. After twelve months, Spartina anglica was harvested from treated plots. Samples were oven dried at 70 degrees Celsius for 48 hours and then weighed. Data was subject to an Analysis of Variance using MINITAB software. The Fischer’s protected Least Significant Difference was calculated at a level of significance of p=0.05. Analysis of results indicated the most effective treatments were slash/smother and slash/glyphosate/smother; these treatments resulted in 97% less biomass than in the nil treatment. As there was no significant difference between these two treatments, it was concluded that the slash/smother treatment was suitable for medium to long term control of rice grass. In practice, this treatment could be combined with follow up smothering and hand removal and would be ideally suited to smaller satellite infestations of Spartina anglica.
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WeedPlan is Tasmania’s first comprehensive plan to manage weeds of State significance in a coordinated and integrated manner. Implemented in 1997, WeedPlan establishes the framework to address existing and potential weed problems that are of significance to primary industry, trade, human welfare, amenity, and biodiversity. WeedPlan’s aim is the more effective use of resources available for weed management thus reducing weed impacts. It closely parallels and complements the National Weed Strategy. This paper outlines WeedPlan and its components, examines outcomes of implementation thus far, and discusses how a strategic planning approach to weed management at a State level as demonstrated by WeedPlan has impacted on approaches to weed management in Tasmania.
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In Tasmania, direct drilled cereal cropping has been adopted by fewer growers compared to other Australian States (ABS, 1996). Experience indicates it is difficult to obtain reliable weed control prior to sowing a cereal crop under Tasmanian conditions unless rates of up to 900 g a.i./ha of glyphosate are used, especially in the higher rainfall areas (>750 mm) Whereas on the mainland, the average glyphosate rate used is 360 g a.i./ha (Dollin et al. 1988). The registered rates for glyphosate use in pre sowing minimum tillage are 360 to 540 g a.i./ha in New South Wales, South Australia, Victoria and Western Australia, yet in Tasmania the registered rates are 540 to 1080 g a.i./ha (Chambers, 1997). This study aimed to determine if increased volume of application could enhance glyphosate efficacy enabling lower doses to be used by Tasmanian farmers. Experiments were established at a high rainfall site (Flowerdale, 1200 mm) and a low rainfall site (Cressy, 670 mm) in Tasmania representing potential cereal cropping districts. Treatments consisted of four rates of glyphosate (180, 360, 540, 720 g a.i./ha) applied in three volumes of water (50, 100, 200 L) at each site. Barley (Hordeum vulgare cv. Franklin) was direct drilled into the experiment sites in autumn. Observations were made every 6 to 8 weeks. Efficacy is expressed in these results as a visual assessment of percentage regrowth cover of clover, grass, and flatweed over a 0.25 m 2 quadrat. At Flowerdale, the efficacy of the lower doses of glyphosate (180 and 360 g a.i./ha) on grass were significantly improved by the higher application volume. The grass component of the treated areas was a clear indicator of treatment efficacy and interactions. The use of 180 g a.i./ha of glyphosate in 200 L ha -1 of water did not differ significantly from 720 g a.i./ha of glyphosate in 200 L ha -1 of water. Low dose efficacy was clearly improved by an increase in application volume. There were no efficacy differences between application volumes when glyphosate was applied at 720 g a.i./ha. At Cressy, the increased dose rates of glyphosate did not significantly improve the efficacy of treatments. The more significant benefits in control were within the lowest dose rate by increasing volume of application from 50 to 100 litres and at the highest dose increasing volume of application from 100 litres to 200 litres of water. The potential to increase glyphosate efficacy through increased application volume was demonstrated at both sites. This water volume effect was more evident at the lower dose rates (180 g a.i./ha and 360 g a.i./ha) and became less evident at the higher dose rates. Although increased dose rate generally showed increased efficacy, the level of significance was much less between 540 g a.i./ha and 720 g a.i./ha, and a lower dose in a higher volume was just as beneficial as a higher dose in a lower volume.
Successful weed management requires a cooperative approach which involves industry, resource managers and the community working in partnership with all levels of government in establishing appropriate legislative, educational and coordination frameworks. Weeds are one of the most serious natural resource degradation issues. Since the human race first became aware of their environment and attempted to cultivate the soil, the battle with pest plants has been ongoing. As technology developed and people and animals became more mobile, plants were transported from their native areas, where natural balances existed, to foreign lands and places where they established themselves as pests. Today pest plants are known as weeds, and everyone knows at least one weed!
In the south-eastern grain belt of Australia, many farmers, although aware of herbicide resistance, are not prepared to take action in regard to herbicide resistance avoidance until the problem actually appears. To tackle this problem nationally a three year extension strategy was run funded by the Grains Research and Development Corporation. Many of the conventional extension methods were employed in this program. A unique, but effective strategy was the introduction of a national herbicide label code based on the mode of action of the different herbicides.
Amaranthus (Amaranthus powellii) in green bean crops reduces crop yields and increases the chances of a processor by-pass due to harvest contamination. Spread is assisted by machinery and livestock such as sheep, presenting this weed as a priority farm hygiene issue. In Tasmania, current attempts at control of A. powellii in established bean crops has been largely unsuccessful. At the core of control difficulties is the lack of a registered selective herbicide strategy to control A. powellii. Screening studies indicated a pre-emergence application of metolachlor at 2880 g/ha followed by a split application of bentazone at 960 g/ha (320 g/ha at A. powellii 2 leaf growth stage, 640 g/ha at A. powellii 4-leaf growth stage) selectively controlled A. powellii in green beans. Acifluorfen applied at 448 g/ha at A. powellii 2-leaf growth stage, or as a split application (224 g/ha at A. powellii 2-leaf, 224 g/ha at A. powellii 4-leaf) also selectively controlled A. powellii in green beans. Improvements in farm hygiene practices were considered critical in reducing the spread of A. powellii in the first instance.
Experiments were conducted between 1988 and 1990 at Elliott, Cressy, and Ross in Tasmania, Australia using three cultivars (Yandee, Geebung, and 75A329) of narrow-leafed lupin (Lupinus angustifolius). The purpose of these experiments was to examine narrow-leafed lupin growth and development in Tasmania in relation to specific environmental factors. These factors were related to growth and development measurements. It was hoped to use these realtionships in a simple crop model suitable for assessing sites for the commercial production of lupins. Preliminary experiments in 1988 examined the lupin cultivars for agronomic suitability in Tasmania. Increased grain yield was a function of more pods/m2 rather than increased pods /plant. This suggested that lower yields of the indeterminate line 75A329 could be compensated for by a higher plant density than in the indeterminate cultivars. Lupins responded to a higher rainfall and extended growing season at Elliott thus outyielding crops at Cressy and Ross. Detailed field experiments were conducted in 1989 and 1990 at Elliott and Cressy. Lupin crops developed very slowly in the first 8-10 weeks, and then grew rapidly after flowering was initiated. It appeared floral initiation was a function of higher temperatures and longer days in Yandee and 75A329 with further responses to vernalisation in Geebung. Plant density significantly affected grain yield . 75A329 showed the largest yield responses to increased plant density. Although increased plant density resulted in increased laef area, leaf senescence took place earlier in the highest density crops probably due to competitive effects. Optimum density for the indeterminate cultivars was 40 plants/m2. It may be higher for determinate cultivars. Low density crops were able to utilise their leaf area for light interception more eficiently than high density crops. In the latter, branches and leaves were pushed more towards vertical rather than horizontal thus less leaf area was presented to intercept light. The study established that early sowing of lupins in tasmania allows more time to grow and develop and yield more grain. a direct relationship was established between increased total dry matter and increased grain yield. The model developed in this study used thermal time as its only external factor to determine L, intercepted radiation (%), and total dry matter (kg/ha) during crop growth. From the predicted figure for total dry matter accumulated by harvest time, an estimate of potential grain yield could be made for that crop. This study demonstrated the principle of collecting agronomic data and, guided by basic plant physiological principles and mathematical procedures, assembling simple sub-models that when linked can approximate a particular aspect of crop growth.
Wild poppy species
(Papaver dubium, P. hybridum, P. rhoeas, P. setigerum, and P. argemone)
are a weed threat to the commercial oil poppy industry in Tasmania, Australia.
Data on the germination characteristics of wild poppies as weeds of oil
poppy crops were collected in field, laboratory and glasshouse based experiments.
An indication on relative occurrence and distribution of the wild poppy
species was also obtained. P. dubium and P. hybridum were
found to be the most widespread wild poppy species in Tasmania with P.
dubium commonly occurring at very high infestations. P. rhoeas,
although uncommon, occured in isolated heavy infestations and was an aggresive
competitor. P. setigerum and P. argemone were the least common.
Comparitive field studies were made of the wild poppy species in oil poppy
crops. Emergence counts were made over a full growing season across five
different crops. P. dubium, P. rhoeas, and P. setigerum
showed emergence profiles most similar to P. somniferum. Laboratory studies
using solutions of Polyethylene glycol (PEG 6000) indicated P. rhoeas
had a moisture/germination response most similar to P. somniferum.
Glasshouse studies were
conducted to determine
if germination potential was effected by depth of seed in soil. The germination
of each of the wild poppy species, except P. argemone, was not significantly
effected by soil depths up to 200mm. The comparative emergence and germination
profiles of each of the wild poppy species studied, along with an indication
of their relative occurrence in Tasmania will be used to modify existing
oil poppy cultural practices to decrease the weed threat of wild poppy
species to oil poppy crops.
Narrow-leafed lupin cultivars, Yandee, Geebung, and 75A329 can all be successfully cultivated for grain in Tasmania. Field experiments to examine yield responses to density were conducted in 1989 and 1990 at Elliott (North West Tasmania) and Cressy (Midlands). Seeding rates were used to approximate target plant densities 10, 20, 40, 80, and 160 plants/m2 in 1989 and 10, 40, and 160 plants/m2 in 1990. At harvest, all pods were removed, the number of pods and pods/plant counted, and grain yield/ha calculated. Poorer plant growth at Elliott resulted in failure to reach an optimum density for yield, whereas at Cressy under better growth conditions, yield peaked at approximately 40 plants/m2. Due to the determinate characteristic of cv. 75A329, a much higher plant density may be required as it did not reach its maximum yield in any of the experiments. The plant density/grain yield data collected in 1989 was used to derive a set of regression equations (second order) to quantify the responses of yield to plant density in these environments.
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The Port Sorell Landcare Group with assistance from the Department of Primary Industry and Fisheries has been assessing a range of techniques with potential to contain isolated outbreaks of Spartina in the Rubicon estuary in the north of Tasmania. The data being collected will include biomass measurement and shoot regrowth counts. Preliminary findings, based on observations, are that a technique called slash/smother was effective. The technique involved the slashing of Spartina to a height of 10 cm in the spring, and laying black plastic sheeting on the slashed Spartina. The plastic was secured by placing chicken wire over the top and staking both wire and plastic to the mud substrate with sprung wire pegs. The plastic was left over the spring/summer period before being removed. Other techniques studied involved the use of glyphosate and oxygenated bleach. Trial work will continue in 1995/96 with methodology based on the findings of this year's study.
Weed mapping is a critical component in the development and monitoring of successful and economically sound weed management strategies. Interest in mapping weeds has increased rapidly within Tasmania over the last two years and has come mainly from the Landcare movement. Several groups are operating in Tasmania who have developed or adapted some form of weed mapping activity.
Farm weed mapping- This is presented as an example of a 'low-tech' weed mapping technique. The system is based on field notebook records and weed distributions recorded on plastic overlays on top of a 1:6000 aerial photograph of the farmer's property. This technique is easily adapted by Landcare groups to mapping weeds in a catchment by replacing the photograph with a 1:25000 base map.
GPS/GIS-This is the 'high-tech' approach based on the sue of a GPS unit to record infestations of weeds. Pilot studies to develop a methodology have been undertaken in Tasmania using gorse (Ulex europaeus) and serrated tussock (Nasella trichotoma) as target weeds.
Interest in weed mapping in Tasmania resulted in the convening of a weed mapping workshop at Launceston where the Tasmanian Weed Mapping Network (TWMN) was formed. TWMN is composed of people involved, or interested, in recording the occurrence and distribution of weeds throughout the State. Its main purposes are:
- To develop and promote consistent state wide weed mapping guidelines
- To serve as a communication channel for network members
- To provide advice on standard weed mapping techniques to individuals and groups
No Abstract
This project was designed to develop a method of weed mapping for growers to use on their farms to assist them in developing improved weed management techniques that make maximum use of improved crop rotations, and require minimum herbicide inputs. It also aimed to analyse current pyrethrum-inclusive crop rotations to identify if a particular rotation had any significant effect on either an increase or a decrease in specific weed species occurring in pyrethrum crops. The project was conducted within the framework of 'systems thinking', a way of looking at, learning about, and understanding complex situations.
A survey of DPIF staff, growers, vegetable processors and agricultural consultants provided information on amaranth occurrence in Tasmania. These groups see Powell's amaranth, Amaranthus powellii, as the major amaranth weed problem with redroot amaranth, A. retroflexus, as a minor problem. The most serious occurrence of Powell's amaranth was in green bean and summer brassica crops grown on Tasmania's north-west coast. In southern Tasmania, Powell's amaranth was reported as a minor problem. The north-east and central regions of Tasmania did not have any major problems with amaranth but recognsied it as a potential weed problem. The main form of amaranth seed transmission in the north-west of the state was thought to be via harvesting equipment and other farm machinery. A number of strategies, including inter-farm hygiene are being considered by the DPIF to control Powell's amaranth in green bean and summer brassica crops.
No Abstract
Potatoes in onion crops are a headache, but more than that, volunteer potatoes in onion crops, from sowing onions after potatoes decreases onion yields, and bulb quality and increases operating costs. Volunteer potatoes at a density of four plants/m2 in onion crops which are common in Tasmania, can reduce onion yields by up to 75%. Overseas research has shown fluroxypyr (Starane) in conjunction with other herbicides will control volunteer potato plants selectively in onion crops. In Tasmania, the DPIF first examined fluroxypyr along with other herbicides in 1988 for their potential efficacy to control volunteer potatoes. Further trial work in subsequent years examined the tolerance of onion plants to fluroxypyr application at different stages of onion and potato plant growth, and different application rates.
Fluroxypyr (methyl hepyl ester) applied sequentially, (300 g + 300 g and 225 g + 225 g a.i./ha, each 21 days apart), to potato plants in conjunction with other commercial onion herbicides significantly (P=0.01) reduced viable tuber number when applied at either tuber initiation or flowering, but not earlier than tuber initiation. Daughter tuber numbers from potato plants originating from mother tubers 50 g to 100 g were significantly (P= 0.01) reduced by fluroxypyr. Fluroxypyr applied to autumn sown onions at the above rates significantly (P= 0.05) decreased onion yield when applied at the five leaf stage of crop growth. Fluroxypyr did not significantly reduce total yield of spring-sown onions at any growth stage.
The growth of volunteer, or weed, potatoes in onion crops sown in rotation after potatoes depresses onion yields, decreases bulb quality, and increases operating costs. Current chemical control measures use repeated applications mainly of contact herbicides e.g. oxyfluorfen. In some cases, volunteer potatoes are hand pulled at costs between $80 and $240 per hectare. a further problem is the production of viable daughter tubers that sustain the volunteer potatoes for several seasons. This interferes with clean crop rotations as the carry-over volunteers are a source of pests and disease for future potato crops. Overseas work has shown the effectiveness of fluroxypyr, used in sequential applications with other herbicides, to control volunteer potatoes in onion crops. Fluroxypyr is a translocated herbicide not currently registered for use in onions in Australia. The aims of this experiment were to:
- Establish if autumn and spring sown onions are susceptible to combinations of fluroxypyr and some commercially used onion herbicides
- Select the most effective control strategy to control volunteer potatoes in onion crops, and reduce the yield and viability of the volunteer potato daughter tubers.
Maintaining soil health and nutrition is fundamental to the establishment of a sustainable organic production system. A four year project was undertaken in Tasmania to test and evaluate on an intensive commercial scale, organic vegetable crop production protocols. In addition to data on production, costs, yields, and market premiums, a soil health monitoring program was included in the project. The purpose was to assess and measure the effects of organic production activities on soil health. Soil health was measured in terms of physical soil structure, available nutrients, organic carbon, soil pH, and balance of beneficial soil flora and fauna. After three years of organic production, soil measurements indicated:
- Physical soil structural
improvements were still required.
- Soil organic carbon
was stable but less than desirable.
- Soil nitrogen decreased
depending on cropping history.
- Minimal change to
available phosphorous (P) and potassium (K) levels.
- Minimal change to
soil pH.
- Increased levels
of bacterial and fungal biomass compared with a conventionally managed
site.
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The Weed Management Act 1999 is a modern piece of legislation that for the first time directly underpins a strategic approach to integrated and coordinated weed management in Tasmania. The legislative model was first discussed in WeedPlan, Tasmania's Weed Management Strategy, in 1996 following extensive public comment on weed management issues in Tasmania. A core component of WeedPlan is the importance of community weed management in delivering on strategic weed management objectives. This Act requires a plant to have its weed risk objectively assessed prior to a proposed declaration. In addition, to ensure action is taken to control a declared weed, there is a statutory requirement to produce a management plan that details roles and responsibilities and specifies restrictions and measures required in respect of the weed. Both these processes involve a significant consultation phase, which allows the community to participate in their development. The Weed Management Act 1999 promotes a government/community partnership approach to weed management, which will result in greater support for its implementation and advance weed management in Tasmania.
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The development of community action against weeds throughout Tasmania over the last five years has led to the development and implementation of weed management strategies by local communities.These strategies are underpinned by WeedPlan, the Tasmanian Weed Management Strategy. Community Weed Management strategies play a key role in the fight against weeds in Tasmania by harnessing community input into strategically addressing weeds of regional (and often State) priority. The strategies recognise that weeds affect everyone and are not just a problem for farmers or government. The message that weeds affect all members of the community is promoted in order to encourage the community to take ownership of local weeds problems. This paper provides an overview of the development and operation of Tasmania’s Community Weed Management groups and highlights the benefits of gathering together stakeholders, governments and the general public to plan and im-plement a coordinated, strategic approach to weed management.
The development of the Tasmanian State weed strategy ‘Weedplan’ and recent incursions by potential pest plants has highlighted opportunities to increase the rate of early detection and the need to develop a clearly defined response protocol. New pest plant species recently (< 5 years) detected in Tasmania have included Alternanthera philoxeroides, Amaranthus spinosus, Amaranthus albus, Cyperus rotundus, Kochia scoparia, Myrsiphyllum asparagoides, Cuscuta suaveolens, Adonis microcarpa and Teucrium scorodonia. The past approach to the detection of recently introduced species has been adhoc and informal with only one of the above species A. philoxeroides, having been detected through a formalised surveillance program. The establishment of a surveillance network and the development of a re-sponseprotocol is discussed.
Alligator weed, Alternanthera philoxeroides, is considered to be one of the greatest threats to rivers, irrigation schemes and wetland habitats in the world. The pest status of alligator weed in waterways results from prolific growth that reduces recreational use of water, alters aquatic ecology and displaces desirable plant species. It blocks rivers, streams and drains causing sedimentation and flooding problems and provides habitats for disease vectors and insect pests (Julien et al. 1979). Unlike other aquatic weeds, alligator weed can grow vigorously in terrestrial situations. In 1996 alligator weed was found growing in a Brisbane suburban garden. Further investigations indicated it was being propagated in gardens around Australia by some ethnic groups who were mistakenly growing it as a vegetable plant native to their own country. An investigation into the potential occurrence of alligator weed in Tasmania was initiated in November 1997. Expertise was sought from the Keith Turnbull Research Institute in Victoria, who were undertaking their own management program, and it was determined that alligator weed was likely to be growing in Tasmania. A taskforce was established, which included representatives from the Sri Lankan community and Office of Multicultural and Ethnic Affairs. The major role of the taskforce was to develop and implement a strategic plan for the eradication of alligator weed in Tasmania. The main priorities of the plan were to identify the problem, develop a targeted public awareness campaign and to put in place a management plan that identified actions for control and an ongoing monitoring program. The awareness and education program that followed resulted in the confirmation of two garden infestations and a potted plant of alligator weed. To assist in determining the location and eradication of all plantings of alligator weed a replacement species program was implemented. This program parallelled with what was taking place in Victoria with the same replacement species, lesser joyweed, Alternanthera denticulata, being adopted. This species was chosen due to its favourable taste and food value and it was also native to Tasmania. It has been adopted by the Sri Lankan community as an acceptable alternative to alligator weed. This successful program is an example of State governments and local community groups working together in cooperation to achieve a solution that is acceptable for everyone concerned. It also highlights the benefits of collaboration, consultation and an emphasis on a sensitive approach when dealing with weed issues of a cross cultural nature.
No Abstract
In the south eastern wheat belt of New South Wales, many farmers, although aware of herbicide resistance, are not prepared to take action in regard to herbicide resistance avoidance until the problem actually appears. To tackle this problem nationally a three year extension strategy has been established. Many of the conventional extension methods have been adopted in this program and perhaps the most significant and hopefully useful strategy is the introduction of a national herbicide label code based on the herbicide's mode of action.
Throughout the cropping regions of Australia both the number of species of herbicide resistant weeds and the area affected have been increasing. Despite a greater understanding of the cause of herbicide resistance very few growers, unless actually faced with resistant weeds, were found to change their cropping practices to prevent the problem from occurring. The aim of the project was to increase the adoption of management strategies that minimise the risk of developing herbicide resistant weed populations.
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Field experiments were conducted at three sites on basaltic krasnozems to examine cadmium (Cd) responses of Russet Burbank potatoes to different rates of broadcast lime and banded phosphorous (P). Double superphosphate (DSP, containing 15 and 90 mg Cd kg-1) and triple superphosphate (TSP, 12 mg Cd kg-1) were the sources of P. In a fourth experiment, lime was banded with basal fertiliser. Despite producing a range of topsoil pH (1:5 H2O) of 5.2 to 7.1, broadcast lime had no effect on tuber Cd concentrations. Lime had no effect when banded with the basal fertiliser, and the practice did not adversely affect yields. With broadcast lime, Cd availability from the fertiliser band may have been unaffected. However there were also no lime x P interactions at any site, suggesting that lime also had no effect on the availability of Cd in the soil. It is possible that Tasmanian krasnozems, with their high organic matter and iron oxide content, restrict the availability of Cd in the soil such that pH change exerts little net influence on Cd availability. Increasing amounts of Cd applied in P fertiliser increased tuber Cd concentrations significantly, but increases were less per unit of P than those found previously when TSP with 151 mg Cd kg-1 was used.
Separate field experiments were conducted with Russet Burbank and Kennebec potatoes on a basaltic krasnozem where tuber cadmium (Cd) responses were examined over three rates of banded phosphorous (P), supplied as double superphosphate (DSP) containing either 15 or 90 mg Cd kg-1. In both cultivars, tuber Cd concentrations increased with rate of DSP. This response was due more to the amount of P supplied in the DSP than the amount of Cd supplied in the DSP and may be a result of banded P encouraging root proliferation in the fertilizer band. Even with DSP at 15 mg Cd kg-1, Cd additions at rates of DSP needed for high yields were 6-20 times higher than corresponding rates of Cd removal in tubers. Examination of data from all studies of Cd in Russet Burbank on Tasmanian krasnozems showed a significant relationship between petiole and tuber Cd concentrations, but the estimation of a petiole concentration associated with the critical tuber Cd concentration in Australia was subject to unacceptable uncertainty due to variation between sites.
Potatoes as a weed problem is becoming more wide spread in Britain, Europe, North America, New Zealand,and Australia. Beattie attributes this increase in Tasmania to the change of cultivar from Kennebec to Russet Burbannk having an extended dormancy and producing more tubers. In Europe, Askew lists the intensified potato production, increased mechanical harvesting, milder winters and new cultivars as reasons for the presence of volunteer potatoes. Volunteer potatoes have been identified as problems in green beans, sweet corn, broccoli, carrots, onions, poppies, sugar beet, dried and vining peas, faba, and phaseolas beans, canola, cereals and herbage seed crops. Both the density and time of removal of volunteer potatoes have been shown to affect the crop response. Densities of four tubers per square metre gave crop supression if removal was not achieved within one month of crop establishment. Densities exceeding four tubers per square metre are common with up to 50 tubers per square metre being recorded. Hill has shown the importance of volunteer potatoes as a source of infestation of the potato moth. With the moth, migrating from volunteer potato paddocks to commercial paddocks mainly at the senescence of commercial crops. Various control methods have been used to address the volunteer problem including using cultivation and frost, grazing, mechanical methods, and chemicals. Chemicals have been used in three ways to reduce volunteers. Chemicals have been used in three ways to reduce volunteers:
- Sprout inhibitors such as maleic hydrazide and chlorpropham
- Soil fumigation using methyl bromide and ethyl dibromide
- Use of herbicides.
Note: Citations have been removed from this Abstract.
The dairy industry in north-west Tasmania currently relies on white clover and ryegrass for long term pastures. White clover lacks persistence on krasnozem soils where the dry period in summer is exacerbated by the low water holding capacity of these soils. As part of the strategy to overcome this problem, a programme of introduction and evaluation of perennial legumes (other than white clover) has been supported by the Dairy Research Council.
- A large number of articles for magazines,
industry newsletters, and newspapers from 1987 to present.