Volunteer potato control in a range of vegetable crops

Mechanical weed control for integrated and organic salad and brassica production

Intelligent thinning for direct drilled salads and vegetables using machine vision

Tillett and Hague Home

Volunteer potato control in a range of vegetable crops (2006 -   )

 Losses resulting from pesticide reviews and customer pressure are reducing selective herbicide options to the point that for some situations there are no products available.  For example, the ’Essential Use’ of post emergence metoxuron (Dosaflo) used to kill potatoes in a wide variety of vegetable crops expired at the end of 2007.  Volunteer potatoes are a particular problem as they are competitive and not very susceptible to mechanical methods.  Furthermore, surviving volunteer potatoes provide a bridge for potato disease, notably blight, which is a concern for potato growers.

In the absence of selective herbicides the targeted application of total herbicides to weed potatoes is an attractive option providing good control with low cost chemicals that have a low environmental impact.  The only available commercial application technique using wipers relies solely on height differential between crop and weed and has important limitations in some circumstances.

 
The aim of this initiative is to develop and demonstrate a computer vision based technology that uses weed detection and targeted application of minimal quantities of a total herbicide (e.g. Glyphosate)  to control volunteer potatoes in a range of vegetable crops particularly in onions and carrots.

Our approach is based on the analyse of video images to locate weeds and control a treatment device probably consisting of a closely spaced array of nozzles.  There are two main technical areas requiring innovation.  These are firstly in the detection and tracking of volunteer potatoes and secondly in the delivery of very highly targeted sprays that achieve good target coverage with little or no off target contamination.  The former is being addressed by THT and the later by our partners in this project The Arable Group’s (TAG) spray unit at Silsoe.

The initial phase of  this work funded by Horticultural Development Council have shown great promise.  Discrimination between live plant material and background been on the basis of colour as developed in earlier projects.  The discriminators of weed from crop that have been investigated include a combination of factors including plant size, shape, height (using optical flow), and position relative to crop rows. 

This project is being conducted under the Horticulture Link Programme with Defra and the Pesticide Safety Directorate as co-sponsors. The project is part funded by the Horticultural Development Council and the British Potato Council and had the following additional industrial partners: Robydome Limited, Garford Farm Machinery , Micron Sprayers, Allium & Brassica Centre, Hypro EU Ltd, Monsanto, Hunterpac Ltd, F B Parrish and Sons, A Findlay.

Diminishing herbicide options, fear of ground water contamination and customer pressure to minimise herbicide use are all pushing the horticultural industry away from reliance on herbicides.  However, product contamination concerns, much of which relate to weeds, necessitate high levels of weed control and have resulted in increasing use of unsustainable hand weeding.

Weeds growing within crop rows are the major problem because they are missed by conventional inter-row mechanical weeding. THT’s imaging and crop row tracking technology applied to inter-row mechanical cultivators improves the situation by reducing the uncultivated within row band through more accurate guidance than can be achieved manually.  However, it is inevitable that some weeds are missed.  In this project we have developed an adaptable, cost-effective technology for mechanically controlling in-row weeds for a wide range of brassica and salad crops.

Our scientific approach to the project was to develop a fast, two dimensional mathematical template matching techniques, (exploiting periodicity within the planting grid), enabling individual crop plants with some spacing variability to be located.  Regular observations of plant position are passed to a tracking algorithm that can follow plant location from a moving vehicle.

A novel shallow cultivation mechanism was also developed. This is synchronised with the plant tracking algorithm enabling weeds to be removed from between crop plants leaving the crop undisturbed.

The sequence of images above shows an experimental cultivator operating above ground on an artificial crop to demonstrate the principle of operation

An experimental implement was constructed based on a standard front mounted Garford vision guided inter-row steerage hoe.  A camera was mounted centrally on the implement looking ahead and down such that the full width of the bed was visible over a length of approximately 2.5m.  Each hydraulically driven rotating disc cultivator was attached to a depth wheel unit mounted on the implement so that cultivation depth could be consistently maintained (normally at approximately 20mm).  The experimental implement had the capacity to take up to five rotating disc units.

   

Results showed that the machine was effective at removing weeds within the row without removing crop plants.  A field trial has shown that a single pass of the machine incorporating intra and inter-row cultivation removes 80% of weeds.

Click on this link to see a 25 second, 6 MB Windows Media File format video the within-row weeding machine in action

This project was sponsored by Defra under the Horticulture Link Programme and was conducted jointly with Warwick HRI who provided the weed science and agronomy expertise. The project was part funded by the  Horticultural Development Council and had the following additional industrial partners: Robydome Limited, Garford Farm Machinery , Edwards Brothers, Robert Montgomery Limited, Allium & Brassica Centre , AGCO

 Intelligent thinning for direct drilled salads and vegetables using machine vision (2007)

 Due to field variability in the process of drilling and germinating seed some high value row crops are sown at a higher density (typically x3) than that which is ultimately desired, and then post emergence, mechanically thinned to the required stand.  The selective thinning process has the objective of leaving the healthiest plants at as close as possible to the optimum spacing.  The intelligence required to make this selection coupled with the accurate mechanical control required has ensured that this process is almost always conducted manually using hand hoes.  There is worldwide interest in reducing difficult repetitive field work due to labour availability, cost and health concerns.

Results from initial experimental work funded by the Douglas Bomford Trust have been encouraging and are illustrated by the photographs below.  The photograph to the left shows lettuce drilled at a nominal spacing of 150mm and prior to thinning.  The photograph on the right is of the same area of crop immediately post automatic thinning to a target spacing of 300mm (with thinned plants removed to aid clarity).

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