Brassicas limited in weed control

This article discusses the limitations of using brassica cover crops for weed control. A brief overview of the role of cover crops is provided, followed by a short review of research looking at brassica cover crops

Overview of organic agriculture

The acquisition of food, textiles and other resources from plants and animals has been a major concern for human societies, from the earliest days as hunter-gathers, through pastoral and swidden phases, to agrarian societies, with an associated trend away from nomadic to sedentary lifestyles. Yet as agricultural production intensified and expanded, the negative effects on the underlying resource base have also increased. The history of environmental damage caused by agriculture is well documented; impacts include air pollution from greenhouse gases such as carbon dioxide, methane, nitrous oxide; land degradation as a result of clearing, cultivation of sloping land and salinity; water pollution from fertilisers, pesticides, overuse and wetland draining; and the loss of biological and ecological diversity (Norse and Tschirley 2003). In the area of conventional weed science, for example, considerable attention has been placed on herbicides but this has not achieved a long-term decline in agricultural weed populations. Instead, farmers have become dependant on herbicides as widespread resistance in a range of weed species has emerged (Gill 2002)

Organic agriculture: opportunities and challenges

The organic movement may have gained a place in the spotlight of the mainstream media now, but it has not been like that for long. Since the 1950s, organic farmers operating at a grass roots level have devised, tested and shared production methods. They have codified a set of ideals into a pioneering best practice agricultural management system that addresses multiple community values. Niche markets have gradually been created, commonly based on trust and goodwill (formal certification did not begin until the 1960s and 1970s), and often using novel direct marketing strategies such as box schemes and community supported agriculture. After many years of consumers having to hunt around for their organic produce from several suppliers, perhaps directly from the farmer, the task is now a lot easier with specialist food shops and organic shelf space in supermarkets, in the industrialised world at least. Global links have been forged in all continents as organic agriculture has been seen to be an effective rural development option

Investigation of management practices and economic viability of vineyards for organic wine production

This paper reports the findings of two components of a research investigating the viability of organic wine grape production. Firstly the results of a survey of Australian organic wine grape growers’ management practices and secondly the first year findings of an experimental organic vineyard compared to an associated conventional vineyard. The survey found a heavy reliance on sulphur and copper sprays for powdery and downy mildew control. The experimental vineyard showed similar yields to conventional growing and in many cases higher sugar, though some increase in botrytis in organic Shiraz

Brassica cover crops for weed control in organic vegetable production

Cover crops (or green manures) are commonly used by organic vegetable growers for soil fertility building and other benefits including weed control. Brassica crops have been reported to control weeds in subsequent crops, usually attributed to the allelopathic effects of glucosinolates (GSL) in the brassica residues, although the effects are inconsistent. New brassica varieties with high GSL levels (Brassica juncea cv. Fumus and Raphanus sativus cv. Weedcheck) were tested in combination with mechanical weed control and another locally grown forage crop (Lolium multiflorum cv. Conquest) for their effects on weed growth during the pre-crop phase and subsequent weed and lettuce growth during the in-crop phase. The cover crops and bare fallow controlled weeds effectively during the pre-crop phase, but did not affect weed and lettuce growth in the following in-crop phase. The cover crops provided better on-going weed control than the bare fallow. Reducing the delay between the pre- and in-crop phases from four weeks to one day did not affect weed and lettuce growth. Weed control was closely related to the amount of light reduction by the cover crops, while competition for nutrients and water appeared to be less important in weed suppression by the cover crops. The use of cover crops requires careful selection of appropriate varieties, attention to good cover crop husbandry (particularly establishment) and an awareness of prevailing weed seed bank levels

Improving competitive ability of chickpea with sowthistle

An experiment was conducted to examine the extent of root and canopy interference of chickpea (Cicer arietinum L.) with sowthistle (Sonchus oleraceus L.). Sowthistle was surrounded with either two or eight chickpea plants. There were different types of competition: no competition, shoot competition, root competition and full competition (root and shoot). The performance of sowthistle grown in full competition with two chickpea plants was the same as that grown with root competition only. Also, there were no significant differences between sowthistle grown with chickpea canopy shade and the control, where there was no competition. On the other hand sowthistle grown with eight neighbours was significantly suppressed in full, canopy or root competition

Australian Organic Market Report 2010

This is the second report the Biological Farmers of Australia has commissioned to help industry bench mark the growth and health of its sectors. This report - another significant milestone in the two decade plus history of the rapidly developing Australian certified organic sector - builds the information base for industry to benchmark production and market value against past and current claims and estimates and will enable monitoring of future growth of the certified organic market in Australia and its farming and production base. In an industry characterised by operational diversity, this report allows for performance assessment by sector. The next publication in this series is planned in 2012 (biennial since the inaugural report in 2008) as a means of providing the wider industry with invaluable and realistic market information

Australian Organic Market Report 2008

Being four years since the publication of a similar research document, the Australian Organic Market Report (AOMR) 2008 is a landmark report for the organic industry. The report will be invaluable for monitoring and planning the industry development during a period of high growth. Delivering consistent data for benchmarking growth across the various sectors of the industry, it will be a key tool for decision making by organic producers and marketers, along with interested parties such as government and media, in assisting in understanding the nature, size and development of the organic industry in Australia. Supply chain development has been hindered over many years by a lack of basic information about volumes, seasonality, continuity and quality, not only making it difficult for potentially new members of industry to feel confident about investing in organic, however also likely to cause overseas buyers to look for other countries with more comprehensive industry information. The report is an important base research document required by any growing industry. It has been commissioned by Biological Farmers of Australia (BFA), and has been carried out independently by the University of New England’s Organic Research Group. The report has the financial support of major sponsor Westpac Bank, all State Governments in Australia as well as many dedicated industry businesses

A Unification of Models of Tethered Satellites

In this paper, different conservative models of tethered satellites are related mathematically, and it is established in what limit they may provide useful insight into the underlying dynamics. An infinite dimensional model is linked to a finite dimensional model, the slack-spring model, through a conjecture on the singular perturbation of tether thickness. The slack-spring model is then naturally related to a billiard model in the limit of an inextensible spring. Next, the motion of a dumbbell model, which is lowest in the hierarchy of models, is identified within the motion of the billiard model through a theorem on the existence of invariant curves by exploiting Moser's twist map theorem. Finally, numerical computations provide insight into the dynamics of the billiard model