Glebelands Market Garden Final Project Report
Site: Glebelands Market Garden
Technical Officer: Delana Davies
Project Title: Evaluating the benefits of the Terrateck wheel hoe with Bio-Discs for weed control in vegetables
Introduction
French horticultural company Terrateck produces a number of specialised tools both manual and machine based. Wheel hoes are a traditional tool of market garden cropping, and the Terrateck version has a recent add-on called Bio-Discs. These are two discs running either side of a crop row, set at a suitable spacing and angle to throw soil inwards and achieve a ‘hilling’, or ridging effect, around the base of the crop.
While the use of discs on machine-mounted cultivators is well known, smaller manual versions have not previously been available. The advantages of burying small weeds (as opposed to uprooting, desiccation or severing) have been overlooked, although the wider issue of mechanical and cultural weed control continues to provoke active discussion. Organically certified systems rely on dry, sunny conditions for effective cultivations to work; burying emergent weeds is a far less weather-sensitive operation. In addition, market pressure to achieve residue-free crops efficiently is unlikely to cease.
The trial was carried out at Glebelands Market Garden – a north-facing site of heavier clay loam soil, located near Cardigan in west Wales.
The Bio-Discs
https://www.terrateck.com/en/houes-pousse-pousse/8-bio-discs.html
The Terrateck wheel hoe follows historic design, with a solid rectangular section steel frame, adjustable height and an offset option, which was employed initially (this proved less efficient than the Glaser hoe design, and so operation reverted to the user pushing from directly behind the wheel hoe). The wheel hoe assembles readily enough (around two hours), and is of solid, durable construction. Once bolted on, the Bio-discs can be spaced apart to suit crop size. However, crop height proved a constraint with subject crops such as leeks or spring onions. At 20cm+, a leek top will bend against the wheel hoe frame, but taller leeks posed a problem.
Trial work
Leek transplants were chosen as the trial crop, as it was possible to have multiple beds for comparison, and existing cultivation for weed removal relies on manual hand- and wheel-hoeing. In addition, their upright habit and slow growth can make weed pressure a labour intensive and costly experience.
The field area used was prepared as usual by contractor ploughing and power harrowing down a clover-dominated ley. Most of the leek beds were subsequently power-harrowed again once – and some twice – immediately before planting. The leek transplants were either raised on-site (early variety), or bought in module form (two later varieties). All were hand-planted – around 10,000 in total.
Alternate triple row beds of 200ft (61m) length were labelled, and two treatments applied, using five beds per treatment:
- Existing practice of hand-hoeing intra-row with stirrup hoes followed by wheel-hoeing between rows, using a Glaser hoe (GH) set up with a stirrup hoe blade followed by cultivating tines
- A single push pass using the Terrateck hoe with Bio-Discs (TBD)
Weeds
The usual range of weed species were present at the site. The most challenging and expensive weed to deal with is the dock, which typically requires manual removal with a light “daisy puller”-type tool or adapted fork. Most other species can be dealt with by a hoe in conventional fashion – that is, severed, desiccated, or dislodged in dry, breezy conditions. All weed species (docks included), can be buried terminally – or at least disrupted – depending on how many days from germination the seed is, and a depth of soil swept over it.
The classic advice to cultivate at ‘white-hair’ stage, when weeds are barely visible, remains important to follow, but weather conditions may lead to delayed weed ‘flushes’, as was the case in this trial. Late in the season with quite mature leeks, there was a volume of late-germinating fat hen and some thistles in all trial rows, despite a clean crop in the very dry earlier-season conditions. The growth rate of some summer weeds like fat hen can be dramatic.
The most difficult weeds to deal with were those germinating intra-row next to the crop; for example, a thin grass blade hard against a leek stem, unhindered by the leafy canopy above.
Results
Weeding operations and data collection were conducted on 8, 15 and 30 June. It was dry and sunny throughout this period, with the last significant rain on 23 May.
The drought conditions were ideal for killing small weeds, but less favourable for steady crop growth. The tilth achieved on the trial area was not ideal, with some lumpy soil over much of the beds due to slightly wet conditions at ploughing, followed by drought. As the Bio-Disc relies on a fine tilth for soil to be readily pushed inward to the crop, the operator’s job was difficult. Subsequent usage on beetroot transplants with a much finer soil tilth made the Bio-Disc a much easier and quicker tool to use.
The Bio-Discs were used to move soil into the base of the leeks for the first cultivation. The second cultivation required additional hand-hoeing to remove weeds too large to bury, and the third resumed with Bio-Disc cultivation only.
No obvious differences were noted in weed density and type or crop yield and growth rate between the two treatments. However, the labour time consumed was measurably different between the two treatments (Table 1).
Table 1: Weeding time and labour costs for five treatment beds, each using the Terrateck wheel hoe with Bio-Discs versus the Glaser hoe and hand-hoeing
|
|
|
TBD |
|
|
GH |
|
|
Date |
8 Jun |
15 Jun |
30 Jun |
8 Jun |
15 Jun |
30 Jun |
|
Weeding time per bed (minutes) |
11.8 |
75.0 |
11.4 |
78.0 |
45.0 |
63.0 |
|
Total treatment weeding time (hours) |
|
8.2 |
|
|
15.5 |
|
|
Labour cost for five beds £* |
|
82 |
|
|
155 |
|
|
Cost saving % |
|
47% less |
|
|
|
|
*Labour costed at £10 per hour
The opportunity to omit a hand-hoeing saves a large amount of time. Any wheeled tool is faster than a manually carried one, as long as it achieves a comparable finish.
Most of the weeds identified on the data sheets following the three weeding operations were either creeping buttercup or grasses tight against the leek shanks. Burying these types of weeds relies on a big enough transplant, and moving enough soil readily into the row. The trial has highlighted the need to consider more careful timing of the planting, and the need to achieve free-flowing soil based on high organic matter levels. This type of soil will always be more forgiving of soil operations when moisture may be higher or lower than optimum.
Following the trial period and rainfall resumption, it proved necessary to Glaser wheel-hoe all the rows. Dormant weed seed amidst mature leeks meant the Bio-Disc tool could not be used due to the crop height conflict at this stage. Having the ability to apply adequate rain gun-type irrigation would have forced greater weed appearance early enough to enable destruction during the three trial cultivations (more tiny weeds are no greater effort to kill).
Crop yield was excellent under both techniques, with a typical leek weight of 400g achieved for early- and middle-season varieties. The over-wintered variety presents a lower average weight with a shorter frame; these results are comparable to previous cropping yields.
Use on other crops
The Terrateck hoe was also assessed on beetroot transplants; it proved very effective, assisted by a fine tilth and easy soil movement into the crop base. The subsequent crop proved exceptionally clean, with a good yield. This hoe would be suitable for any small, transplanted crop, although proponents (notably JM Fortier), enthuse about usage on drilled crops growing in an upright manner, such as rocket or carrots.
Conclusions
This is a valuable tool for the cultivation of upright crops. A sufficiently fine tilth is critical for efficient operation and getting reliable results. The hoe is particularly suited to small- and medium-scale operators with row crops of higher value, but insufficient scale to justify the machinery cost, set-up or training time for tractor-mounted versions. A typical dilemma on small-to-medium farms is whether to get a tractor out and set up the relevant cultivator, or pick up a lower-tech manual tool for more immediate use (but lower efficiency), as the area worked on increases.
Terrateck and other North American manufacturers have manual/rotavator scale finger-weeder options available that can work in conjunction with, or alternately with Bio-Discs to throw soil out and away from the plant base. This might be a tool combination to examine in a future study.
https://www.youtube.com/watch?v=580-nUvehzI
In conclusion, the data suggests that the time savings recorded make the Bio-Discs a cost-effective tool. Over five treatment beds and three weeding operations, use of the Bio-Discs saved 7.3 hours of labour at a cost of £73, compared to the Glaser hoe and hand-hoeing – a 47% reduction in costs. If this is factored into use on other crops, then the Bio-Discs purchase price (<£200 at 2021 prices, wheel hoe not included) could be recouped very quickly.
Adam York, Glebelands Market Garden