Row orientation to limit weed growth

Technical articles - Centre National d'Agroécologie - Conserwa - Weeds

Field crops Field crops Sowing Row orientation

East-west orientation (left) and north-south (right)

East-west planting is a sowing technique that consists of orienting crop rows in the east-west direction. This technique allows to maximize the shading of weeds by the crop, thus reducing their growth and competition for resources.

Description

East-west planting is particularly effective in regions where the sun is low in the sky during winter, such as in Europe or Australia, because the shadow is maximized. This reduces the amount of light available to weeds, thereby limiting their photosynthesis and growth.

In the photos, it is clear that the light reaching the soil is much less when rows are oriented east-west.

Advantages

Cost

This method is 100% free and requires no material investment. It may require reorganization of sowing if tractor paths are changed.

Impact on weeds

Few studies have quantified the actual impact on weed infestation and competition of this method.

Catherine Boger, in Australia, observed a 51% reduction in weed biomass in a wheat crop and a 37% reduction in barley with east-west row orientation compared to north-south orientation.

The method seems to be especially effective in cereals as it did not yield convincing results for canola or peas.

Impact on light availability

Crops oriented east-west generally intercept more light, resulting in better light competition against weeds. This is especially true for cereals with 28% more light captured by wheat and 18% by barley compared to a north-south orientation.

Notably, thanks to this phenomenon of maximal plant cover and light interception, soil moisture is generally better when this method is practiced.

Impact on yield

Again, significant results are found in cereals where yields are on average 25% higher thanks to this sowing orientation.

Disadvantages

• This planting orientation may not be feasible or may represent a significant loss of time depending on the shape of the field. Indeed, if the plot is rectangular and oriented north-south, sowing along the width is a considerable loss of time and the area of turning tracks is increased.
• We lack scientific and technical data to assess the relevance of this practice, but it does not seem to present glaring disadvantages except for implementation depending on the situation.

Perspectives

Trials are underway by the Centre National d'Agroécologie and numerical data should provide more insight into the method under metropolitan France conditions.

Sources

This article was written by Jasmin Razongles, agronomy engineering student in apprenticeship at the Centre National d'Agroécologie.