Jua Kali Intermediate Technology

Weeding and Weeding Tools PDF Print E-mail
Weeding and Weeding Tools

Introduction: Weeds cause greater reduction in potential yields than any other single factor by their competition for light, nutrient and water with the crop the farmer is trying to grow. This is particularly true at the small scale level where to tools available, such as the machete, are intended to be for multipurpose use rather than for weeding.

It is often traditional to start weeding when the weed canopy covers the whole area. At present most weeds are removed by mechanical means but the rate and type of work of the existing tools is both slow and tends to loosen the soil thus allowing valuable moisture to escape. In any one area weeds develop at the same time so the hand labour is limited to those who normally work on that area and where extra casual labour is available the cost is high in relation to the daily output. The net result is that some weeds are able to seed before they can be removed and the weed seed reservoir in the soil increases thus compounding the problem. The work of weeding is normally carried out by women and young persons and is very tedious but necessary in terms of the number of hours and days needed. The relief from the competition comes when the crop canopy is sufficiently large for its competition to prevent further germination.

Theory for improved weed control
Annual weeds are frequently the most troublesome due to the large numbers of seeds they produce on a short growth period. Rains cause both the weeds and crop to geminate but generally the crop emerges over a short period of time than different weeds which appear over a longer period. Weeding should start immediately the rows of the emerging crop can be identified. At this stage the emerged weed seedlings will be at the two to three leaf stage while many others will have geminated but not yet emerged.

Experience has shown that weeding the whole area can control by both the emerged seedlings and those which have germinated but not yet emerged and this control will last for 2-3 weeks which allows the crop canopy to develop thus inhibiting further weed germination.

Practices for improved weed control
The techniques used should combine weed control with moisture conservation and the minimum energy input. The best technique is the passage of a thin blade inclined horizontally through the soil at a depth of about 10 mm. The soil and weeds are raised and flow over the blade back to the soil where the weeds lie on the surface and desiccate due to the effects of sun and wind. If there is a surface crust this will be broken to form a mulch to cover or seal any cracks and reduce moisture loss. 

The tools described below have been designed to raise seedling weeds with the minimum energy input and at higher rates of work than normally found.

The growing of crops in rows greatly facilitates weeding and two designs of tool are needed for weed control. One for weeding the long spaces between the rows and the other to remove the weeds between each plant along the row.

Weeding between the plants: Seeds should be planted at as constant spacing as possible the distance being according to recommended agronomic practice.  The width of the tool should be less than the crop space to reduce the chances of damage and allow error in planting distance.

The width of the hand weeder for between-the-plants will depend on the crop but widths of 100 or 120 mm have been found appropriate.

The shape of blade may vary but the types shown here have been developed from practical experience to give the best performance.

Hand hoes

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Handle length: The weeder can be used with a short or long handle – each has advantages and limitations. A short handle requires the user to bend the back but it can be used by one hand while the other can move the plant to allow more accurate work especially along-the-row while the long handle is better between-the-rows except if the soil surface is hard when more energy is needed to penetrate the surface.

Wheel Hoes
The area between the rows has no plants so a higher rate of weeding can be practiced and the wheel hoe has been developed to accomplish this. A wheel is used to control the depth and the ‘V’ shaped blade with sharp tip enters hard soils.

In use, the tool is pushed backwards and forwards advancing in small increments of about 200 mm depending on the conditions. When pulled backwards the weeds wrapped round the blades are cleaned off leaving it ready to raise more weeds.

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This model is designed for crops in row widths of 300 mm and is 230 mm wide to avoid variations which occur naturally even when using a guide string when planting.

The side plates holding the blades also indicate to the operator the cutting width as the ends of the blade are not easily seen under the soil surface. An ‘A’ blade version and a specialised offset twin wheel version have been evaluated but not pursued.   

Drawing of Hand Weeder  

The drawing of the hand weeder is for a width of 100 mm but can easily be 120 mm. The blade material will depend n local availability but the thinner the less the energy needed and the better the penetration.
Attachments:
FileDescriptionFile size
Download this file (Hand Hoes Nov 08.pdf)Hand HoePlans for the hand hoe13 Kb
 
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