Homemade Interplant Weeding Broom – The Vibrating Weeding Broom (VWB)
Takao Furuno, Aigamo Family, Furuno Farm, Fukuoka Prefecture, Japan○○

Easy early interplant (not just inter-row) weeding by hawking*Can you weed a 100 m row of vegetables or upland field rice plants in one minute?

* As the weeding “broom” is based on a Japanese-style broom, called a hawki, this method has been named “hawking”.

Takao Furuno

Vibrating weeding broom with four broom units in series.

Top: Cabbage hawking. Hawking with cabbages is easy because they are transplanted.
Right: First hawking with Japanese daikon (while radish)1. Is interplant weeding one of the bottlenecks of organic farming?
As in Fig. 1, crops (rice, wheat and other cereal grains, soybeans, maize, vegetables) are often planted
in rows and the space between the rows is called the inter-row space. The spaces in between the crop
plants in a row are called interplant spaces.
Figure 1. Inter-row and interplant spaces.
Inter-row weeding is called intertillage weeding. Since there areno crops growing in this space, weeding can be carried out
quickly and moving forward (or backward) continuously with ahoe or other hand tool, or a machine. Mechanization is possible.
On the other hand, in the interplant spaces, the weeds and thecrops are close to one another, so it would seem to be difficult toeliminate only the weeds by moving forward continuously with amachine without harming the crop. For nearly 40 years as anorganic farmer I was convinced that “mechanization of interplant
space weeding cannot be easily done” and quietly continued to
weed between the plants using my hands or a triangular hoe.
There are probably many farmers around the world who think anddo the same, and this may be “common sense” in farming.
In 2016, however, after a long period of trial and error, I quite bychance tried out a “vibrating weeding broom” that uses a rakewith thin, spring steel wires and was able to carry out continuous(down the row) early interplant weeding without damaging thecrop. My conviction of 40 years melted away in an instant.
Weeding using the vibrating weeding broom (VWB) I named hawking after the Japanese-style broom,
called a hawki.
Video clips of hawking taken with a smartphone have been posted on a dropbox website.(1) You will
understand instantly how this elegantly simple mechanism works.

2. The VWB is handmade
When I talk about the VWB, someone always asks, “Where can I buy it?” I made the VWB myself bybuying this kind of rake (with the thin spring steel wires) at a store. I also recommend you make yourown handmade VWB. Making it yourself will help you understand how it works and you will also beable to improve it by adding on your own ideas. This is known as “technological self-sufficiency.”
The rakes use stiff spring steel wires which radiate out in a fan-like manner. Looking at the shape ofthe broom, many people think that not only the weeds but also the vegetables will be uprooted. First
widen the space between the steel wires on one of the rakes and try hawking an appropriately sized
vegetable. You should see a “very convenient truth.”Figure 2. Overview of the VWB
DIY stores sell different kinds of rakes, but the ones
I am using are have spring steel wires that are
angled down at the end, this part being about 12cm
long (AB in Fig. 2), and the main part of the wire
(BC in Fig. 2) being about 35cm long.
Of course, it is possible to use one rake, but theweeding effectiveness improves significantly if
three or more are used in series. As in Fig. 2, I use
four rakes held together in series.
As you can see in Fig. 2, the wires jut out toward
the left when seen from the handle and some of thewires are cut off with wire clippers to leave only
six on each rake. For the reason why the wires are
made to jut out to the left of the handle, please see
the explanation of the mechanism in section 3.
The handles on each rake, except for one, are cut
off at a length of around 60cm. The distance
between the tips of the wires on each rake in theseries is about 12cm (m in Fig. 2). Using cardboard
as packing material, fix the four handles firmly inplace using duct (waterproof) tape, as seen on the left in the photo.

The distance between the wires on each of the rakes isadjusted to about 6cm. The rakes usually come with ametal tool for adjusting this distance (B in Fig. 3). Thisadjustment is very important. If it is not just right, thevibration does not work correctly.
The final stage is to try hawking a plot of soil that has
no weeds or grass. Look at the shape of the track toensure that the wires are moving correctly, and adjust
them while looking to see how they interact together (see (3) in Structure of the Multi-rake Broom on
page 6 for more info). You can also adjust the angles of the wires on each of the rakes so that the wiretips are all on the same plane (i.e. they all touch the ground at the same time). The explanation may
sound difficult, but it’s actually very easy to do.

3. Mechanism of Interplant Weeding Using the VWB
In interplant weeding, where the crop and the weeds are close together, we firstly look for differencesin the two that can be exploited and then think up a technology(1) Differences in roots
In the paddy fields where I rotate crops, the crops germinate about two weeks after sowing. At about
the same time, the sprouts of a great variety of early weeds, including shortawn foxtail (Alopecurusaequalis), green foxtail (or bristle-grass, a species of annual grass, Setaria viridis), Japanese barnyard
millet (Echinochloa esculenta (A. Braun) H. Scholz (1992)), chickweed (or stitchwort, Stellaria sp.),
shepherd's purse (or shepherd's pouch, Capsella bursa-pastoris), lamb's quarters (Chenopodium
album), buttercup (Ranunculus japonicus) and others show above the surface of the soil to form agreen carpet over the whole paddy field if you just leave them as they are.
There are, of course, exceptions, but these early weeds are like the Weeds (1) and (2) in Fig. 3, whosethin roots spread out just under the surface of the soil. A typical example is Japanese barnyard millet.
The Japanese barnyard millet and the rice plant have very similar appearances aboveground, but havedifferent types of roots.
Weed (3) in Fig. 3 is one that has just sprouted from a shallow point beneath the surface of the soil andhas not yet sent out any roots. Weed (4) is one that has just sprouted by sending up a mesocotyl fromsome distance below the surface of the soil and has almost no roots.

Thus, although there are exceptions, almost all early-stage weeds have thin roots that spread out justbelow the surface of the soil or have almost no roots at all.

Figure 3. Difference in the roots of early-stage weeds and crops
Weeds:
Weed (1) Roots spray out just below soil surface
Weed (2) Shoot out a mesocotyl and roots spray out just below soil surface
Weed (3) Has sprouted but not yet sent out roots
Weed (4) Has shot out a mesocotyl and sprouted but not yet sent out roots
In contrast, crop plants such as rice, cereal grains, soybeans, vegetables, and so on, compared withweeds, have strong roots which have spread firmly and penetrated down to a deeper level (around 3cm). This early-stage dissimilarity has a time limit, but is vitally important. Hawking is a techniquethat has been assembled by recognizing the importance of this dissimilarity in roots.
(2) Movement of the wires
Vertical vibration
As you pull the VWB along the ground, as in A in Fig. 3, the tip of the VWB wire pierces the soil
under the roots of the weed at an acute angle, like a hoe, catching onto the roots and pulling them
upward, pulling the whole weed out of the ground. It then drops the weed on the surface of the soil,
where it withers and dies.
By combination of the wire’s own weight and the power used to pull the broom, the tip of the wire isalways forced to pierce the soil at an acute angle, but as it pierces deeper it meets with the resistanceof the soil it is pushed back, but then returns to the original position due to the force of repulsion in thestiff spring steel wire. Thus the tip of the wire vibrates vertically, piercing the soil at almost the same
depth (1 to 2 cm) as the broom moves forward.
At the same time, as in Fig. 3, the crop plants, whose roots have sunk a bit deeper than those of theweeds, since the tip of the wire does not reach down far enough, the crop plants are not pulled out of
the soil.
Even if the tip of the wire does reach the roots of a crop plant, since the roots of the plant are strong it
will not be easily pulled out of the soil as the weeds are.
Horizontal vibration
What happens with weeds like Weeds (3) and (4) in Fig. 3 that have not yet developed roots that the
tip of the wire can catch on to immediately after sprouting? These will be weeded by the horizontal
vibrating motion of the wires. Fig. 2 shows the overall view of a VWB with four rakes in series.
Grasping the handles R and S, if you pull the VWB over the crop plants, i.e. perform interplant weeding,each of the wires, spread out like a fan, pierce the ground at an acute angle, and due to the resistanceof the soil and the springiness of the steel wire will oscillate (vibrate) horizontally violently and noisily,stirring up the soil as they go.
The result of this is that the Weeds (3) and (4) in Fig. 3, the weeds that have not yet developed any
significant roots, will be moved around with the soil, their roots (if any) and mesocotyl being severed,and will dry out, be buried, wither and die.
In the video clips mentioned above, there is a slow-motion clip. Looking at this clip, you will noticethat wires further up the backbone away from the handle of the VWB (“l” in Fig. 2) show a greater
horizontal vibrating motion, stirring up the soil and weeds very well. As in Fig. 2, the wires are madeto jut out to the left of the overall VWB in order to make good use of this special property of the fanlike arrangement of the wires.
At first, I carried out hawking with the rakes arranged symmetrically with respect to the backbone of
the VWB. When I did that, the central wires located just under the backbone hardly showed any
horizontal vibrations at all and weeds remained for a certain interval on both sides of the wires.
(3) Structure of the Multi-rake Broom
Why, as in the photo and Fig. 2, does the VWB use four rakes?
Naturally, the smaller the distance between the wires, the more effective we would expect the weeding
to be, but in fact things are not that simple. This is because the crop plant’s leaves and stems become

sandwiched between the wires, which will also pull along rice straw and clumps of soil, or push over,
rip out or bury the crop plants. In contrast, if the distance between the wires is too large, some weeds
will remain in the soil after you have carried out the hawking with the VWB.
It is the multi-rake broom structure that resolves this problem. As in Fig. 2, there are four rakes inseries and the distance between the wires is set at 6cm. Since the early-growth vegetables are small,they easily pass through the 6cm interval, and they are not pulled out by the roots, as mentioned earlier.
However, since the wires of each of the rakes are aligned so that they are offset from each other (i.e.
are not following on from one to the next in a straight line), from the viewpoint of the weeds, whichhave shallow roots, this is the same as having a gap between the wires of 6cm divided by 4 = 1.5cm.
Moreover, the horizontal vibrations of the wires further decrease this 1.5cm gap, pulling out andpushing aside the weeds, giving a very satisfactory weeding effect.
This can be easily seen by looking at the slow-motion video clip. As the interplant weeding is carriedout, each of the wires does a “Munroe walk,” working together as a team.

4. Practical Hawking
The mechanism of hawking differs from all conventional weeding techniques and still requires somethinking and tweaking. The technique is still at the trial-and-error testing stage, and I will set out herea few of the points I have noticed.
(1) Plowing
Plowing carried out before sowing or transplanting of the crop plants is carried out carefully to breakthe soil up into fine particles so that the weeds do not survive. If quite large weeds are remaining at
this stage, they cannot be dealt with by hawking.
However, it is not necessary to break up all the soil in the ridges and furrows into fine particles. I justtake care to break up finely the surface layer of the ridges to a depth of 1 to 2cm.
(2) Appropriate crops
Grains such as rice directly sown into dry fields, wheat and other cereal grains, soybeans, maize andso on have large seeds, robust and flexible leaves and stems and sturdy roots and are therefore theeasiest crops to use hawking on. Interplant weeding by hawking is also very easily carried out on
potatoes and the yam eddoe (Colocasia esculenta (L.) Schott) at the early stage.
However, these crops are generally cultivated using land-extensive methods. For larger areas, it will
be necessary to mechanize hawking. Since around 2007, I have been collaborating with thedevelopment division of the Fukuoka agricultural machinery maker Orec to develop a weedingmachine for dry fields. Since February 2016, after much creative activity, we have started work on themechanization of hawking.
We found that, among sown vegetables, hawking works well with the daikon radish, white turnip,
Japanese mustard spinach (Brassica rapa var. perviridis), spinach, edible chrysanthemum(Chrysanthemum coronarium), potherb mustard (Brassica rapa var. nipposinica), burdock and others.
However, if the leaves and stems are pulled too much, branched roots occurred in burdock and thewhite turnip became an oval shape. It is therefore especially important when trying out hawking tolook with your own eyes, think about what is happening and make your own judgements.
Among the transplanted vegetables, hawking was found to work well with cabbage, lettuce, takana(Brassica juncea var. integrifolia), katsuona, onion, kujo leek, chives and others. I’m sure there areother vegetables that hawking will work well with.
In general, as transplanted vegetables have firm roots that go deep into the soil, once they get settled
into the soil, hawking is a very suitable technique for weeding.
In contrast, it was surprisingly difficult to use hawking with Chinese cabbage and carrots. I intend to
take up the challenge with these crops again this year.
(3) Timing
There’s no simple answer to the question “What’s the right time to carry out hawking?” I simply lookat the condition of the crops and weeds and make a judgment based on what I see. You’ll soon find out
if you give it a try. In general, when the crop plants have reached a certain size and the weeds are justbeginning to sprout is a good time. In reality, however, the weeds sometimes sprout and grow before
the crop plants do. In this case, I carry out inter-row hawking before doing interplant hawking. This isbecause when the soil on both sides of the crop row is soft and loose it is easier to carry out interplant
hawking.
Once the weeds exceed 3 to 5cm in height, the roots are generally quite strong and it becomes difficult
to remove them by hawking.
(4) Thinking about weeding
In contrast to conventional weeding methods, the weeding is not perfectly completed by carrying out
hawking just once. During repetition of hawking a number of times, the vibration of the wires makes
the soil soft and loose, fewer weeds are seen and it becomes more difficult for them to grow.

By carrying out hawking intensively two or three times when the crop plants have reached a certain
size eliminates weeds well. If the interval between hawking sessions is too long, the weeds will becomelarger and much more difficult to remove by hawking with the VWB.
I am currently conducting an observation survey on how many weeks pass before weeds appear after
hawking.
(5) Soil condition
As a rule, hawking should be carried out when the soil is dry. The soil will then become soft and loose
and the weeding effect will be better.
With some types of soils, however, when the soil is very dry it will be too hard for the tips of the wired
to penetrate in some places. In these cases, it is probably effective to carry out hawking after rain has
fallen and the surface of the soil is a little softer.
(6) Causes of crop damage and avoidance measures
1) The crop plants are still small and the roots are not yet well developed  Wait.
2) The wire tips pierce too deeply  Adjust the angle of the wires and the weight of the VWB.
3) The wire tips do not pierce the soil and pass over the leaves of the crop plants  Adjust the angleof the wires and/or lower the handle when pulling the VWB.
4) The crop plants are injured just by contact with the wires. This mainly occurs in the morning with
lettuce when the leaves are a little stiff after absorbing a lot of water.  In the afternoon, when thetemperature has risen and the leaves are wilting a little from the sun and wind, hawking can be carriedout by increasing the interval between the wires and passing slowly down the row. It is also possible
to fix some sponge rubber on the wires to prevent leaf damage.
5) Lumps of soil and straw get caught between the wires, causing the crop plants to get pushed over
 Increase the interval between the wires. Carry out more careful plowing.
6) The crop plants become covered in soil  The crop plants are too small; wait a while. Increase theinterval between the wires and pass down the row more slowly.
5. Characteristics of the VWB
I’m an organic farmer, not a researcher, but I think the VWB has the following four special
characteristics.
(1) The soil is pierced at an acute angle.
The rakes from which the VWB derive pierce the soil at an obtuse angle, as seen in Fig. 4.
With the acute angle, the resistance of the soil is greater, and the spring steel wires catch on to theweeds, lifting them up out of the ground as the wires vibrate strongly both horizontally and vertically
due to the properties of the spring steel wire.
Figure 4. Difference between the VWB and conventional spring steel wire weeding machines
In contrast, the spring steel wire weedingmachines produced by British and Japanesemakers that I have seen in books, manuals,
video clips or practical demonstrations, as in Fig.
4, have the tips of the spring steel wires(sometimes known as “tines”) make an obtuse
angle with the ground surface, seemingly
stroking the soil. This is perhaps a different wayof thinking about the weeding mechanism.
(2) The VWB is a specialized interplant weeder
The VWB focusses on the interplant space to carry out aggressive interplant weeding.
(3) Requires less labor and strength, and is fast
To perform interplant weeding of 100 m of vegetables with a triangular hoe or by hand will take you
two hours. If the conditions are right, carrying out hawking over 100 m will take you one minute.
Check out the video clip!
(4) Pocketbook-friendly appropriate technology
A rake will set you back 980 yen ($11) in the Japanese DIY store. This is appropriate and simple
technology that is cheap and can be handmade by Asian farmers. My Indian friend said, “We don’t
have this kind of rake in India, but we can make the VWB with bicycle spokes.” Bicycles are seen allover the world.
I wrote about “characteristics,” but actually this is the kind of simple technology that many people allover the world have worked to produce throughout the long history of humanity.

6. The Relationship between Hawking and Integrated Duck and Rice Farming (IRDF)
During hawking, the spring steel wires vibrate vertically and horizontally. In a paddy field, the aigamo
ducks’ feet also move horizontally and vertically in the water. The oscillating movement is the same,the only difference being whether it is in a dry or wet field.

I have been working on the systemization of Integrated Duck and Rice Farming (IRDF) since 1988.
The aigamo have now come to swim in paddy fields all over Asia. Since 2003, I have endeavored to
combine direct sowing of rice in dry fields with the use of aigamo. Here, the most pressing issue was
the weeding of dry fields, since the rice and Japanese barnyard millet sprout at the same time. Interrow weeding was completely resolved by use of the spiral rotor developed by Orec. However, theinterplant weeding was a difficult problem.
After many twists and turns, in February 2016 I just happened to notice a spring steel wire rake in mystoreroom. After trying out interplant weeding of wheat with the rake, developments simply took offfrom there. In May, I tested the rake by attempting interplant weeding with rice sown directly into a
dry field. This helped to raise the precision of interplant weeding to a completely new level.
In September, I carried out hawking trials with various kinds of fall and winter vegetables. These trials
turned out so well that even I was surprised. In contrast to rice, vegetables have soft leaves which
spread out and have differing shapes according to the type of vegetable. I thus tried out the multi-rake
structure.
Then, in May 2017, on the basis of the experience gained using the multi-rake structure with vegetables,
I tried out the new VWB on directly sown dry
field rice. The results were excellent. The
Japanesebarnyard
milletdecreased
dramatically. At present (June 2017), water
has now been released into the fields and theaigamo are having fun swimming around in
the field, making the water sparkle. I think thework of organic farming is really interesting –even the mistakes.
June 2017(1) Description of the video clips accessible at:https://www.dropbox.com/sh/qojbik0cifz3gau/AABFqf3yXFpHDrxyovzES5-ta?dl=0
26.mov - Interplant weeding for turnips. The weed plant is the tough Japanese buttercup.
35.mov - Green pak choi – easy hawking without damaging the vegetable leaves. The wires do the‘Munroe walk’.
42.mov - Early interplant weeding with onions.
54.mov - As cabbages are transplanted, hawking can be performed easily at an early stage. Note themovements of the wires and the cabbages.

1.mov - Comparison of weeding speed for triangular hoe and hawking.
38.mov - When the soil is hard, first carry out inter-row hawking to soften up the soil, then do theinterplant hawking. Or, do the hawking after the surface of the soil has become soft after rain.
43.mov - Hawking on rice sown directly into a dry field. Hawking is easy to do with grains or beans
such as rice, cereal grains, soybeans, adzuki beans, maize, etc. We are developing mechanizedhawking for these land-extensive crops.
* This article was originally published in Japanese in: Tsuchi to Kenko (Soil and Health – journal of
the Japan Organic Agriculture Association), July 2017 (#475). Pp. 16-22---------Aigamo Family, Furuno Farm
A hundred varieties of crops by organic farming
Website: http://aigamokazoku.com (Japanese)∙
Integrated Duck and Rice Farming (IRDF): 7.3 ha∙
Various vegetables: 3 ha∙
Wheat: 2 ha∙Natural egg-laying chickens: 300∙
Aigamo duck chicks: 4000 (1,400 used by the farm, the remainder are sold)∙A variety of processed products from the agricultural produce.
Inquiries: 090-2856-7995
e-mail: furuno@d4.dion.ne.jp824 Jumei, Keisen Town, Kaho Gun, Fukuoka Prefecture, JAPAN 820-0603----------