Desk study on the control of weeds in organic arable and horticultural production systems OF0152

The Ministry is seeking to encourage an expansion of organic farming with a research programme to provide information of benefit to organic farmers and to policy makers. The lack of a reliable and effective weed control system that does not rely on herbicides, has been highlighted as the major problem in limiting the growth of organic farming in the UK. Studies have been made that are aimed specifically at developing organic weed control techniques. There has also been work on non-chemical methods for dealing with weeds in conventional systems. Research in weed biology, population dynamics, and competition modelling from conventional systems also provide valuable information for improving weed control strategies. In addition, research into novel and improved methods of plant husbandry, plant breeding, and the application of new technology in guidance systems etc., can also make a contribution to providing better weed control in organic and conventional systems. However, because of the diverse nature of the research it is not easy to assess the current state of the art for weed control in organic farming systems. The main objective of the present project was to identify and collate the relevant R&D that has been carried out and published on weed control in organic arable and horticultural production systems. The study was also intended to define the current state of the art in non chemical weed control, allowing recommendations to be made for future research work

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

A Dynamic Optimisation Model of Weed Control

It is argued in this paper that static approaches to weed management, where the benefits and costs are only considered within a single season, are inappropriate for assessing the economic benefits of weed control technologies. There are carryover effects from weed management as weeds that escape control in one season may reproduce and replenish weed populations in following seasons. Consequently, it is appropriate to view weed control in the context of a resource management problem where the goal is to determine the optimal inter-temporal level of weed control that maximises economic benefits over some pre-determined period of time. A dynamic optimisation model for weed control is presented. Using the tools of comparative static analysis and Pontryagin's maximum principle, the conditions for optimal input use (ie weed control) are compared for static and dynamic situations. It is shown that a higher level of input use for a given weed population is optimal using a dynamic framework than would be derived under a static framework. The analysis is further extended by the incorporation of uncertainty and shows that the optimal level of weed control is also affected by uncertainty in herbicide efficacy and the survival of weed seeds produced. A case study of the optimal long-term management under deterministic and stochastic conditions of an annual cropping weed, Avena fatua, is presented.weed control, resource economics, optimal control, dynamic programming, wild oats, Farm Management,

Combining physical and cultural weed control with biological methods – prospects for integrated non-chemical weed management strategies

The paper deals with the possibilities of combining physical weed control with biological weed control

Competitiveness of winter wheat stands against weeds: Effects of cultivar choice, row width and drilling direction

The need for competitive crop stands can be regarded as a basic requirement for weed control, potentially reducing the need for direct control measures. One way the crop may suppress weed growth is by the restriction of light through crop shading. As part of the EU-project ²Strategies of weed control in Organic Farming² (WECOF) trials with winter wheat were carried out to evaluate the potential of wheat shading ability as a weed control measure. Factors included were cultivar, row width and drilling direction. Results of the first experimental year are presented

Barley Weed Control Trial

Demand for local, organic grains has been increasing in recent years as businesses such as flour mills, malt houses, and bakeries have grown and developed business models to include a higher proportion of local ingredients in their products. The organic grains industry requires the use of innovative strategies to control weeds and address disease issues to grow grains in the most efficient manner. In 2017, the University of Vermont Extension Northwest Crops and Soils Program conducted the second year of a trial to evaluate the impact of row spacing and cultivation on weed pressure and barley yield and quality

Vision-based weed identification with farm robots

Robots in agriculture offer new opportunities for real time weed identification and quick removal operations. Weed identification and control remains one of the most challenging task in agriculture, particularly in organic agriculture practices. Considering environmental impacts and food quality, the excess use of chemicals in agriculture for controlling weeds and diseases is decreasing. The cost of herbercides and their field applications must be optimized. As an alternative, a smart weed identification technique followed by the mechanical and thermal weed control can fulfill the organic farmers’ expectations. The smart identification technique works on the concept of ‘shape matching’ and ‘active shape modeling’ of plant and weed leafs. The automated weed detection and control system consists of three major tools. Such as: i) eXcite multispectral camera, ii) LTI image processing library and iii) Hortibot robotic vehicle. The components are combined in Linux interface environment in the eXcite camera associate PC. The laboratory experiments for active shape matching have shown interesting results which will be further enhanced to develop the automated weed detection system. The Hortibot robot will be mounted with the camera unit in the front-end and the mechanical weed remover in the rear-end. The system will be upgraded for intense commercial applications in maize and other row crops

Flax Weed Control Trial

Flax (Linum usitatissimum L.) is a multi-purpose crop grown for its fiber, oil (linseed oil), and meal. The majority of production occurs in the Dakotas, Minnesota, and Montana. Recently there has been interest in growing flax in the northeast, both for human consumption and for animal feed, for its high levels of heart-healthy omega-3 fatty acids. Flax is a spring annual that is usually planted as early as the ground can be worked. However, one of the main challenges to successfully growing flax is weed control. Flax plants compete poorly with fast growing weeds due to its relatively short height (between 12 and 36 inches when mature) and tiny leaves. This trial was initiated to see if management, including different row spacing and cultivation, would reduce weed density in flax and improve yields

Tolerance to weed harrowing in spring barley genotypes

Controlling weeds in spring cereals grown under organic conditions is mostly done by post emergence weed harrowing, where spring tines of the weed harrow control weeds by uprooting and/or covering small weeds plants with soil. In situations with relatively large weed plants and relatively small crop plants, there are increased risks for crop damages by soil coverage or other mechanical damages of the crop leaves. These damages are increasing with increasing weed control intensity, and are resulting in reduced crop growth immediately after weed harrowing. There are risks that the reduced growth reduces final crop yield too. However, there is some evidence that there are varietal differences in the tolerance to weed harrowing. The aim of this study was to estimate the damages by weed harrowing in four pure genotypes and three two- or one three-component mixtures of spring barley, and to analyze if there were differences in tolerance to weed harrowing between the genotypes and mixtures. Results from a two-year field study showed that there were varietal differences in the tolerance to mechanical weed control in the immediate effect as well as the short term effect, however there were marked differences in the immediate and short term effect between the two years. Regarding the long term effect of weed harrowing on yield, there were no significant differences in 2003 but in 2004, Brazil and the three component mixture suffered significantly from weed harrowing while Modena, Otira and Modena+Orthega mixture, seems to benefit from weed harrowing. The reason for these differences is probably due to differences in growth habit at the time for weed harrowing

Barley Weed Control Trial

Demand for local, organic grains has been increasing in recent years as businesses such as flour mills, malt houses, and bakeries have grown and developed business models to include a higher proportion of local ingredients in their products. While acreage has increased in recent years, the organic grains industry requires the use of innovative strategies to control weeds and address disease issues to grow grains in the most efficient manner. In 2016, the University of Vermont Extension Northwest Crops and Soils Program evaluated barley grown in with different row spacing combined with cultivation to assess the weed control potential of these new seeding strategies