Sensor based mechanical weed control in cereals

Post-emergence weed harrowing is a common cultivating method used to control annual weeds in growing cereals and legumes. The whole crop area is cultivated with the harrow with a determined intensity according to the crop- and weed growth stages and the weed density; therefore, selectivity between crop and weeds is highly influential for successful weed harrowing. Weed density, growth stages of crop and weeds and soil resistance to penetration of the harrow-tines are important parameters which determine the harrowing intensity to be applied. A main challenge in weed harrowing is to target the best intensity at the time of harrowing. This requires predictive models that can use the immediate crop and weed responses to harrowing as input variables, also considering soil physical characteristics. Site-specific weed management aims to identify the spatial and temporal variability of weeds and manage them correspondingly.

The general aim of the study was to develop a prototype harrow with an automatic adjustment of the intensity under the approach of site-specific weed management to obtain the highest weed control with the least possible crop damage. The specific objectives of this study were:

1. to determine the efficacy of weed harrowing in cereals through experiments on selectivity in Germany.
2. to study the crop tolerance and crop recovery to burial in soil due to harrowing
3. to study the crop resistance to weed harrowing
4. to assess the contributions to crop yield as a result of controlling weeds by harrowing
5. to assess the soil resistance to harrowing
6. to work out algorithms for automatic adjustment of the harrowing intensity according to

• site-specific soil- and crop variability, and weed abundance assessed before harrowing
• harrowing intensities that produced the highest yield gain in the experiments done during 2007–2009.