General
In future mechanical weed control will become more important for vegetable crops. Especially in smaller crops less herbicides are available. New herbicides will only sporadically obtain authorization.
Many opportunities to control weeds between the rows are available and successfully deployed. Intra-row weeders like finger and torsion weeders are capable to control most of the weeds in the row. There are also a number of intelligent inter-row weeders with sensors and intra-row hoes on the market. The projects ‘Growing with Future’ (Telen met Toekomst) and ‘Sustainable Farming Starts with You’ (Duurzaam Telen Begint bij Jou) places a lot of emphasis on using these techniques.
Control in the crop row (without sensors) by:
The Torsion Weeder:
The two spring teeth on both sides of the crop row uproot the weeds.
Two diameters are available: 7 and 9 mm. The soil and crop determine the preference. Usually 9 mm will suffice.
Torsion weeder in maize
Finger Weeder:
Finger weeders are available in different sizes (diameter 25 - 100 cm). A small diameter is preferable for instance in onions and a bigger one in arboriculture. Most finger weeders are made of plastic instead of rubber. Especially the soft types can be used in sensitive crops and light soils. The somewhat harder types in robust crops and heavier soils. The hardness largely determines the result.
Finger weeders in all shapes and sizes.
Both weeders touch the crop. When the weeders are used well the damage is negligible. The risk that the operations will increase the incidence of diseases is small. In addition, the risk of some plant loss is present. The yield loss is acceptable.
Finger weeder use in onions is possible
Control in the crop row (with sensors)
In recent years a lot of work has been carried out reprarding weed control in crop rows with sensors (light sensors and cameras). These sensors determine the location of the crop plants after which one or two hoes per row control the weeds between the crop plants. Machines that currently are available are:
The Radis (France):
This machine works with light sensors that determine the plant location (the plant should be bigger than the weeds). The hoes are guided in and out the row by pneumatic techniques. Applied Plant Research (WUR) has adjusted the machine, by which the capacity has increased. Also now two hoes are used per crop row.
Radis (new model)
The Robocrob inrow weeder (England):
This tool uses a camera per 3-4 rows. The camera locates the location of the plant. The weed control in a row takes place with a disc. It has a cutout, which is steered around the crop plant with the aid of hydraulics.
The Robovator (Denmark):
The plant location is again determined by a camera. These intra-row hoe works with one camera per crop row. Two hoes, which hydraulically are directed in and out of the row, control the weeds in the row. The camera is also used to follow the crop rows.
Crop adaptation
To use intra-row weeders in some crops may require adjustment of the crop production. One example is the seeding of onions in clusters.
Optimization weed control
Mechanical weed control in the row can be optimized. Steering systems with or without camera follow the crop rows. Also more and more RTK-GPS is used. RTK-GPS makes it possible to hoe precisely. By sowing with RTK-GPS followed by hoeing one can work more accurately and hoe only a few centimeters from the row.
RTK-GPS with both tractor and machine steering systems is preferred.
Because the tractor and the machine neatly follow the crop rows the driver can keep a close eye on the hoeing.
Mechanical weed control does not start with the first hoe or harrow application, but at ploughing. Ten golden rules to optimize the effect of mechanical weed control:
1. Make sure the field lays flat. This makes depth adjustment of hoes easier.
2. Appropriate adjustment of sowing and planting machine is very important. A fixed and equal distance between the rows and a uniform depth of sowing and planting improves the result.
3. Tune the working width of the used machines. This prevents problems with the connection between rows and adjustment of hoes in tractor tracks.
4. Start early with controlling weeds. Small weeds can be controlled much easier than larger weeds.
5. Hoe and harrow as shallow as possible and carry out the subsequent
operations at the same depth. This prevents germination of new weed seeds from deeper layers.
6. Make sure that the weeds and the weed roots loosen from the soil. This can be improved by placing harrow teeth behind the hoes. This can prevent re-growth of the weeds.
7. Try to hoe as close as possible to the crop row. Every centimeter hoed more between the rows results in less weeds. Modern
steering systems such as cameras and RTK-GPS are good tools to make this possible.
8. If possible, use the new intra-row weeders, like finger and torsion weeders or one of the newest weeders with plant recognition in combination with hoeing in the row.
9. Do not wait too long with a weed controlling application after a rainy period. Start before the soil becomes too hard for a good intrusion of hoes and other weeding equipment. Especially a requirement for heavy loam and clay soils.
10. Use hill up hoeing in crops that have grown large. Small weeds are covered with 3-4 cm soil. This coverage provides adequate weed control.
This article is written by a researcher of Applied Plant Research (WUR) as output for the project ‘Growing with future’ (Telen met toekomst). And is the result of years of research into the possibilities of mechanical weed control in several crops
