Weed control - latest chemical and non-chemical options for the production sector

We understand that weeds are just plants growing in the wrong place but they mean so much more to growers.

Reason Farms: Micron Spraydome units used for weed control in California orchards - image: Micron Group
Reason Farms: Micron Spraydome units used for weed control in California orchards - image: Micron Group

Whether you are growing trees and shrubs, fruit or vegetables, weeds will rob a crop of water and nutrients, so delaying maturity and lowering yields.

Let the weeds grow and they can reduce light levels to seedlings and young plants. They can harbour pests and diseases that could lower crop quality, or even decimate it. Weeds may also pose a problem at harvest, leading to produce being downgraded or, worse, being unsaleable.

Weeds can seriously hinder our ability to green the environment and feed the ever increasing population. In addition, they damage the bottom line - profit margins can be squeezed and there is the threat of making a loss. As we lose more land to housing, solar farms and storage and distribution centres, the area for growing is less and production will have to intensify. Weeds must be controlled.

Field preparation

Clearly a clean start is a wise approach and thorough field preparation can go a long way to achieving this. The problem is then how to keep it clean. Weeding by hand is far too costly and any cultural techniques must be practised with care to avoid damaging soil structure and causing erosion. Some cultural techniques also carry the risk of increasing weed populations if the roots of perennials are chopped.

Chemical herbicides have been the solution for decades but concerns over human and environmental safety as well as problems of resistance have led to the number of herbicides being reduced. Indeed, recent legislative and regulatory pressures, mainly through the EU's Pesticides Framework Directive, Sustainable Use Directive, Pesticides Authorisation Regulation and the Groundwater Directive, have severely reduced the choice of product available to growers.

Concerns over the potential loss of glyphosate have been abated for the moment by the granting of a temporary authorisation for a further 18 months. Hopefully new chemicals will be developed and brought to market, but to safeguard those chemicals still available greater care will be required in planning weed control, particularly in the selection and application of product. Of course, integrated approaches to weed control should be given greater consideration.

Living mulches have advantages in that they reduce soil erosion, increase organic matter in the soil and can reduce temperature fluctuations while doing the all-important job of suppressing weeds. But depending on the type used, living mulches can compete with crops, may attract pests and diseases and in most cases will need some form of maintenance.

Weed brushes and flame guns continue to find employment in the task of controlling weed growth but restrictions on herbicide availability and usage are helping to drive a new market. We are seeing innovative developments in non-herbicide weed-control methods that use steam, hot water and even electricity.

These units have an additional advantage over chemical herbicides in that many have a wide operating window, being safe to use in windy conditions and on wet ground. Some require little or no training in their usage and need no certification, although health and safety implications must be considered.

Thermal technology

Since 2010 Weedingtech's Foamstream, the system of controlling weeds by harnessing the power of thermal technology through the application of hot water and foam, has found a home in the amenity and water industries.

Using 100 per cent hot water, the Cardley-Wave system for weed removal works by blasting the cellular structure of the weeds and so prevents growth above ground, eventually exhausting the root. Applications are as wide ranging as motorways to cemeteries and other amenity areas.

Ubiqutek is pioneering the use of electricity as an alternative weed-control method, organically killing the stems and roots of all weeds, including woody and deep-rooted ones, and so reducing reliance on chemical herbicides.

Based in the Midlands, Ubiqutek has a professional hand weeder, the Ubiqutek Touch. This unit can be mounted onto a utility vehicle and uses electricity to boil weeds from tip to root, turning any water content into steam and leaving the surrounding plants and the soil unharmed.

The Ubiqutek Touch is powered by a diesel engine and uses around 15 litres of fuel per day. It has a 25m umbilical cable with optional extensions and is suited to horticultural use including by growers and grounds or landscape maintenance staff. Biometric access restricts use to trained operatives.

Further innovation and development of these and other methods of weed control will bring down costs in the future, but for the time being at least many growers will continue to rely on chemical herbicides as an effective, time-saving and cost-efficient means of controlling weeds. Using the right applicator can reduce costs further by using less chemical, as Reason Farms partner John Amarel found.

Micron Spraydomes

Reason Farms grows prunes, walnuts and almonds in 1,400 acres of orchards near Yuba City in the Sacramento Valley, California, USA. Over the past few years Amarel has purchased six Micron Spraydome 1200 and four Spraydome 600 sprayers plus, most recently, an adjustable-width Micron Spraydome 3049 for controlling weeds throughout the orchards.

"Consistent droplet size and higher weedkiller concentrations per drop were two major factors we considered when purchasing the machines and the Spraydome range met our requirements on both counts," says Amarel. "The sprayers are easy to operate and maintain, and their user-friendly design allows our operators to easily solve any issues that arise in the field with just a few tools."

Prior to acquiring the sprayers, Reason Farms was concerned about the high costs of herbicides. The sprayers have helped address this issue. Amarel adds: "With Spraydomes, we have managed to significantly reduce the expenditure while maintaining total control of the weeds."

The Spraydome range utilises Micron's Controlled Droplet Application (CDA) technology, which provides even droplet distribution and product coverage over the target area.

The sprayers' shielded design and the breakaway mechanism on the smaller units enable weeds to be controlled around the base of trees without causing damage. The shields also allow continued spraying in breezy conditions when unshielded applicators are likely to need to cease operation until more favourable conditions return.

Amarel also reports a saving in time and labour. "We can cover more acres in a day and don't need to stop and fill up the spray tank so often," he says. Micron Group is based in Bromyard, Herefordshire. The company recently launched a Varidome band sprayer for salad onions and Varidome S3 Hybrid for work in asparagus.

Latest introductions

Sprayer manufacturers appear to have confidence in a future that involves the use of chemical herbicides and pesticides. The Cereals 2016 show in Cambridgeshire last month (15-16 June) witnessed a host of sprayer introductions, from self-propelled through trailed and mounted to the smaller backpack units for localised applications. But the question for many growers of nursery stock, fruit and vegetables will remain: "What can we apply?"

New sprayers and associated devices available from major manufacturers

Xenis from Berthoud is a mounted sprayer offering tank capacities of 800, 1,000 or 1,200 litres. A 1,500 model is expected later this year.

The latest sprayer from Kuhn Farm Machinery is a new 3,000-litre trailed unit. The Lexis 3000 can be specified with booms from 18m to 24m, with either the Trapezia or Equilibra suspension system to maintain a stable height of spray.

Completing Team Sprayers' range of trailed crop sprayers, the new Leader 4 is offered with tanks from 3,000 litres to 5,000 litres and booms from 21m to 30m.

Built specifically for the JCB 4220 tractor, the latest demount sprayer from Landquip is available in spray widths from 20m to 30m, with the aluminium boom folding to a narrow transport width of 2.45m. The sprayer also features a linkage-mounted, easy-clean 30-litre induction bowl.

Designed for large growers and contractors, Knight Farm Machinery's new 4D boom suspension system includes boom levelling system Distance Control II with extra sensing elements that ensure the boom automatically maintains the optimum height above the crop or ground.

David King Electronics offers up-to-date technology solutions for retrofitting to simple or complex trailed, mounted and self-propelled sprayers. Products range from the Spraylight terminal providing up to seven boom sections with a main switch enabling start of work at the touch of a button, to next-generation GPS guidance systems.

Precision guidance, auto steering, application rate control, mapping, variable rate application, automatic boom section control and wireless data transfer have been integrated into a single convenient package by TeeJet Technologies to help growers maximise productivity. TeeJet has also introduced the Matrix 430 easy-to-use Global Navigation Satellite System for a wide range of field applications including spraying, spreading, tillage and seeding.

New from John Deere are two high-end options for the M700 and M900 Series trailed sprayers - a total of six models with tanks from 2,400 to 6,200 litres and 18-40m booms. The options are the BoomTrac automatic levelling and height control and LED field lighting. At Cereals 2016 John Deere also showed the R4050i self-propelled sprayer with 5,000-litre tank and lightweight carbon-fibre boom, but it is not scheduled for production until 2018.

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