Buddingh finger weeder in pickling cucumbers
Buddingh finger weeder in pickling cucumbers.
Buddingh finger weeder in pickling cucumbers.


Hiniker ridge tiller cultivator in maize
Hiniker ridge tiller cultivator in maize.
Hiniker ridge tiller cultivator in maize.


Rotary hoe in soybean
Rotary hoe in soybean.
Rotary hoe in soybean.


Introduction to
mechanical weed control

By Daniel C. Cloutier Contact information:

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Weeds are plants that are considered undesirable in a crop at a given time. Weeds are harmful for a number of reasons. They reduce crop yields, interfere with the harvest, support pathogens and insect pests and contaminate seeds.

Weed control is as old as farming itself. However, progress in mechanized weed management did not begin until the early eighteenth century, when Jethro Tull invented a seed planter for row crops, which allowed weeds between the rows to be killed by cultivation.

Physical control was the main method used against weeds until herbicides appeared in the mid-twentieth century (Wicks et al. 1995). Mechanical weed control is a proven technique and kept fields free of weeds long before the advent of herbicides. This technique has experienced somewhat of a rebirth in the last few years. The objective of this chapter is to present the principles behind mechanical weeding and to give some examples to illustrate them.

Before the advent of herbicides, mechanical methods of weed control were used successfully for several centuries. Cultivator technology continued to evolve even after the development of herbicides, and these implements are efficient and versatile. In some cases, they are the only weed control tools available and they are often a cost-effective alternative to herbicides.

Cultivators are agricultural implements that require careful adjustment to ensure optimal performance. To kill a maximum number of weeds, cultivators should be operated as close to crop rows as possible without injuring the crop. The effective use of cultivators requires a fair amount of experience and careful observation, which may explain why research teams arrive at widely varying conclusions in similar situations.

The effectiveness of cultivation is directly influenced by cultivation depth and degree of soil moisture. Cultivation that is too shallow may spare weeds and cultivation that is too deep increases the risk of crop damage. Working depth can be adjusted by means of wheels attached to the frame or the three-point hitch. The use of weights and reduction of tractor speed can also increase the operating depth. Cultivating when the soil is too wet leads to clod formation and may not destroy weeds. The optimal level of soil moisture depends on the cultivator type, with rotary hoes and harrows being best suited to moist soils.

In general, two types of cultivators are required for effective weed control: one at pre-emergence or early post-emergence and a second later in the season. The vulnerability of crops to damage depends on their growth stage. For example, legumes are most vulnerable at the hook stage, when cultivation can reduce yield. In Quebec, two to seven cultivations are usually carried out, depending on the crop and the degree of weed infestation. Tractor speeds range from 3 km/h to 20 km/h depending on the cultivator type and the growth stage of the crop.

Cultivation is not only effective in controlling weeds; it also benefits the crop by breaking up the surface crust, aerating the soil, stimulating the activity of soil microflora, reducing the evaporation of soil moisture and facilitating the infiltration of rainwater.

Cultivator selection is only one component of an effective weed control program. Technical mastery of the cultivator is critical, as is weeding at the appropriate growth stage of the weeds and the crop. Delaying treatment for a few days may significantly reduce the effectiveness of a cultivation operation. The timing of treatment is probably more critical in successful weed control than the choice of cultivator.